Plumbylene

Last updated
Plumbylenes, R2Pb Plumbylene structure.svg
Plumbylenes, R2Pb

Plumbylenes (or plumbylidenes) are divalent organolead(II) analogues of carbenes, with the general chemical formula, R2Pb, where R denotes a substituent. Plumbylenes possess 6 electrons in their valence shell, and are considered open shell species.

Contents

The first plumbylene reported was the dialkylplumbylene, [(Me3Si)2CH]2Pb, which was synthesized by Michael F. Lappert et al in 1973. [1]

Plumbylenes may be further classified into carbon-substituted plumbylenes, plumbylenes stabilized by a group 15 or 16 element, and monohalogenated plumbylenes (RPbX). [2]

Synthesis

Plumbylenes can generally be synthesized via the transmetallation of PbX2 (where X denotes halogen) with an organolithium (RLi) or Grignard reagent (RMgX). [2] The first reported plumbylene, [((CH3)3Si)2CH]2Pb, was synthesized by Michael F. Lappert et al by transmetallation of PbCl2 with [((CH3)3Si)2CH]Li. [1] The addition of equimolar RLi to PbX2 produces the monohalogenated plumbylene (RPbX); addition of 2 equivalents leads to disubstituted plumbylene (R2Pb). [3] Adding an organolithium or Grignard reagent with a different organic substituent (i.e. R’Li/R’MgX) from RPbX leads to the synthesis of heteroleptic plumbylenes (RR’Pb). [3] Dialkyl-, [1] diaryl-, [4] diamido-, [5] dithioplumbylenes, [3] and monohalogenated plumbyelenes [3] have been successfully synthesized this way.

General synthesis of plumbylenes via transmetallation General synthesis of plumbylenes.png
General synthesis of plumbylenes via transmetallation

Transmetallation with [((CH3)3Si)2N]2Pb as the Pb(II) precursor has also been used to synthesize diarylplumbylenes, [6] disilylplumbylenes, [7] and saturated N-heterocyclic plumbylenes. [8]

Synthesis of various plumbylenes via transmetallation from [((CH3)3Si)2N]2Pb Plumbylene Synthesis transmetallation.png
Synthesis of various plumbylenes via transmetallation from [((CH3)3Si)2N]2Pb

Alternatively, plumbylenes may be synthesized from the reductive dehalogenation of tetravalent organolead compounds (R2PbX2). [6]

Synthesis of plumbylenes via reductive dehalogenation of tetravalent organolead compounds Plumbylene Synthesis reductive dehalogenation.png
Synthesis of plumbylenes via reductive dehalogenation of tetravalent organolead compounds

Structure and bonding

Key valence orbitals of Pb in plumbylenes: the 6s lone pair and vacant 6p Key valence orbitals of Pb in plumbylenes the 6s lone pair and vacant 6p.svg
Key valence orbitals of Pb in plumbylenes: the 6s lone pair and vacant 6p

The key aspects of bonding and reactivity in plumbylenes are dictated by the inert pair effect, whereby the combination of a widening s–p orbital energy gap as a trend down the group 14 elements and a strong relativistic contraction of the 6s orbital lead to a limited degree of sp hybridization and the 6s orbital being deep in energy and inert. [9] Consequently, plumbylenes exclusively have a singlet spin state due to the large singlet–triplet energy gap, and tend to exist in an equilibrium between monomeric and dimeric forms in solution. [9] This is in contrast to carbenes, which often have a triplet ground state and readily dimerize to form alkenes.

In dimethyllead, (CH3)2Pb, the Pb–C bond length is 2.267 Å and the C–Pb–C bond angle is 93.02°; the singlet–triplet gap is 36.99 kcal mol−1. [10] [ verification needed ]

Dimethyllead, (CH3)2Pb, and diphenyllead, (C6H5)2Pb Dimethyllead diphenyllead.png
Dimethyllead, (CH3)2Pb, and diphenyllead, (C6H5)2Pb

Diphenyllead, (C6H5)2Pb was computed with GAMESS at the B3PW91 level of theory using the basis sets 6-311+G(2df,p) for C and H and def2-svp for Pb with the ECP60MDF pseudopotential, in an adapted procedure (which uses the cc-pVTZ basis set for Pb instead). [11] The molecular orbitals (MOs) (visualized using Chimera [12] ) and natural bond orbitals (NBOs) (visualized using multiwfn [13] ) generated are produced below, and qualitatively identical to the literature. [11] As expected, the HOMO is 6s-dominated, and the LUMO is 6p-dominated. The NBOs are of the 6s lone pair and vacant 6p orbital respectively.

Plumbylene diphenyllead HOMO.png
HOMO
Plumbylene diphenyllead LUMO.png
LUMO
Diphenyllead NBO 6s lone pair.png
NBO 6s lone pair
Diphenyllead NBO vacant 6p.png
NBO 6p vacant orbital
Molecular orbitals (MOs) and natural bond orbitals (NBOs) of diphenyllead

The Pb–C bond distance was found to be 2.303 Å and the C–Pb–C angle 105.7°. Notwithstanding the different levels of theory, the larger bond angle for (C6H5)2Pb compared to (CH3)2Pb can be rationalized by the greater repulsion between the sterically bulkier phenyl groups relative to methyl groups.

Atoms in molecules (AIM) topology analysis revealed critical points in (C6H5)2Pb, and is consistent with the literature.[ clarification needed ] [11]

AIM molecular graph of diphenyllead. Green points indicate (3, +3) critical points; orange, (3, -1); and purple, (3, -3). Diphenyllead plumbylene AIM molecular graph.png
AIM molecular graph of diphenyllead. Green points indicate (3, +3) critical points; orange, (3, -1); and purple, (3, -3).

Plumbylenes occur as reactive intermediates in the formation of tetravalent plumbanes (R4Pb). [14] Although the inert pair effect suggests the divalent state should be thermodynamically more stable than the tetravalent state, in the absence of stabilizing substituents, plumbylenes are sensitive to heat and light, [15] and tend to undergo polymerization and disproportionation, forming elemental lead in the process. [14] [15]

Plumbylenes can be stabilized as monomers by the use of sterically bulky ligands (kinetic stabilization) or heteroatom-containing substituents that can donate electron density into the vacant 6p orbital (thermodynamic stabilization). [2]

Dimerization

Equilibrium between plumbylenes (monomer) and diplumbenes (dimer) in solution Plumbylene dimerization.png
Equilibrium between plumbylenes (monomer) and diplumbenes (dimer) in solution

Plumbylenes are able to undergo dimerization in two ways: either through the formation of a Pb=Pb double bond to form a formal diplumbene, or through bridging halide interactions. [2] Unhalogenated plumbylenes tend to exist in an equilibrium between the monomeric and dimeric form in solution, and, due to the low dimerization energy, as either monomers or dimers in the solid state, depending on the steric bulk of substituents. [2] [9] [16] [17] However, increasing the steric bulk of lead-bound substituents can prevent the close association of plumbylene molecules and allow the plumbylene to exist exclusively as monomers in solution [18] or even in the solid state. [3] [17]

The driving force for dimerization in general arises from the Lewis amphoteric nature of plumbylenes, which possess a Lewis acidic vacant 6p orbital and a weakly Lewis basic 6s lone pair, which can act as electron acceptor and donor orbitals respectively. [7] [11]

Valence bonding diagram showing donation of 6s lone pairs of Pb into vacant 6p orbital of adjacent Pb in diplumbene Valence bonding diagram showing donation of 6s lone pairs of Pb into vacant 6p orbital of adjacent Pb in diplumbene.png
Valence bonding diagram showing donation of 6s lone pairs of Pb into vacant 6p orbital of adjacent Pb in diplumbene

These diplumbenes possess a trans-bent structure similar to that in lighter, non-carbon congeners (disilenes, digermylenes, distannylenes). [9] The observed Pb–Pb bond lengths in diplumbenes (2.90 – 3.53 Å) have been found to typically be longer than those in tetravalent diplumbanes R3PbPbR3 (2.84 – 2.97 Å). [17] This, together with the low computed dimerization energy (energy released from the formation of dimers from monomers) of 24 kJ mol−1 for Pb2H4, [19] indicates weak multiple bonding. This counterintuitive result is due to the pair of 6s-6p donor-acceptor interactions representing the Pb=Pb double bond in diplumbenes being less energetically favourable compared to the overlap of spn orbitals (with a higher degree of hybridization than in diplumbenes) in the Pb–Pb single bond in diplumbanes. [17]

In monohalogenated plumbylenes, the halogen atom on one plumbylene is able to donate a lone pair into the vacant 6p orbital of the lead atom on a separate plumbylene in a bridging mode. Monohalogenated plumbylenes have been found to generally exist as monomers in solution and dimers in the solid state, but, again, sufficiently bulky substituents on lead can sterically block this dimerization mode. [2]

Due to decreasing dimerization energy down Group 14, while monohalogenated stannylenes and plumbylenes dimerize via the halogen-bridging mode, monohalogenated silylenes and germylenes tend to dimerize via the abovementioned multiply-bonded mode instead. [2]

Equilibrium between monomers and halogen-bridged dimers in monohalogenated plumbylenes Equilibrium between monomers and halogen-bridged dimers in monohalogenated plumbylenes.png
Equilibrium between monomers and halogen-bridged dimers in monohalogenated plumbylenes

In a recent study, an N-heterocyclic plumbylene was shown to undergo dimerization leading to C–H activation, existing in solution in an equilibrium between the monomer and a dimer resulting from cleavage of an aryl C–H bond and formation of Pb–C and N–H bonds. [20] DFT studies proposed that the reaction occurred via electrophilic substitution at the arene of one plumbylene by the lead atom of another, and involves concerted Pb–C and N–H bond formation instead of insertion of Pb into the C–H bond. [20]

Stabilizing intramolecular interactions with substituents bearing lone pairs

Plumbylenes may be stabilized by electron donation into the vacant orbital of the lead atom. The two common intramolecular modes are resonance from a lone pair on the atom directly attached to the lead or by coordination from a Lewis base elsewhere in the molecule. [21]

For example, Group 15 or 16 elements directly adjacent to Pb donate a lone pair in manner similar to their stabilizing effect on Fisher carbenes. [2] [4] [22] [23] Common examples of more remote electron-donors include nitrogen atoms that can lead to a six-memberd ring by bonding to the lead. [21] Even a fluorine atom on a remote trifluoromethyl group has been seen forming a coordination to lead in [2,4,6-(CF3)3C6H2]2Pb. [24]

(a) Valence orbital diagram showing the donation of a lone pair on heteroatom E to the vacant 6p orbital of adjacent Pb. (b) Examples of heteroatom-stabilized plumbylenes (a) Valence orbital diagram showing the donation of a lone pair on heteroatom E to the vacant 6p orbital of adjacent Pb.png
(a) Valence orbital diagram showing the donation of a lone pair on heteroatom E to the vacant 6p orbital of adjacent Pb. (b) Examples of heteroatom-stabilized plumbylenes
Example of plumbylene stabilized by lone pair donation from heteratom in side-arm of substituent (2).png
(2,4,6-(CF3)3C6H2)2Pb skeletal.png
(2,4,6-(CF3)3C6H2)2Pb X-ray.png
(From left) Example of plumbylene stabilized by lone pair donation from heteratom in side-arm of substituent; [2,4,6-(CF3)3C6H2]2Pb and its X-ray structure showing donation of lone pairs on F atoms in substituents to Pb atom (highlighted with red dashed lines)

Agostic interactions

Agostic interactions have also been shown to stabilize plumbylenes. DFT computations on the compounds [(R(CH3)2Si){(CH3)2P(BH3)}CH]2Pb (R = Me or Ph) found that agostic interactions between bonding B–H orbitals and the vacant 6p orbital lowered the energy of the molecule by ca. 38 kcal mol−1; this was supported by X-ray crystal structures showing the favourable positioning of said B–H bonds in proximity of Pb. [25]

Agostic interactions between B-H bonds and vacant 6p orbital of Pb (2).png
Plumbylene agostic front view2.png
Plumbylene agostic top view2.png
(From left) Examples of plumbylenes exhibiting agostic bonding between B–H bonds and vacant 6p orbital of Pb; front and top views of X-ray crystal structure of [((CH3)3Si){(CH3)3P(BH3)}CH]2Pb. Agostic interactions are highlighted with red dashed lines in the front view; the axis of interactions is indicated with a red dot in the top view.

Reactivity

As previously mentioned, unstabilized plumbylenes are prone to polymerization and disproportionation, and plumbylenes without bulky substituents tend to dimerize in one of two modes. Below, the reactions of stabilized plumbylenes (at least at the temperatures at which they were studied) are listed.

Lewis acid-base adduct formation

Plumbylenes are Lewis acidic via the vacant 6p orbital and tend to form adducts with Lewis bases, such as trimethylamine N-oxide (Me3NO), [26] 1-azidoadamantane (AdN3), [27] and mesityl azide (MesN3). [26] In contrast, the reaction between stannylenes and Me3NO produces the corresponding distannoxane (from oxidation of Sn(II) to Sn(IV)) instead of the Lewis adduct, which can be attributed to tin being a period above Pb, experiencing the inert pair effect to a lesser degree and hence having a higher susceptibility to oxidation. [28]

In the case of AdN3, the terminal N of the azidoadamantane binds to the plumbylene via a bridging mode between the Lewis acidic Pb and the Lewis basic P atom; [27] in the case of MesN3, the azide evolves N2 to form a nitrene, which then inserts into a C-H bond of an arene substituent and coordinates to Pb as a Lewis base. [26]

Reaction of plumbylenes with various Lewis bases Reaction of plumbylenes with various Lewis bases.png
Reaction of plumbylenes with various Lewis bases

Insertion

Similar to carbenes [29] and other Group 14 congeners, [2] plumbylenes have been shown to undergo insertion reactions, specifically into C–X (X = Br, I) and Group 16 E–E (E = S, Se) bonds. [6]

Insertion reactions of R2Pb with R'-X (X = Br, I), R'-E-E-R' (E = S, Se) and S8 Insertion reactions of plumbylenes.png
Insertion reactions of R2Pb with R'–X (X = Br, I), R'–E–E–R' (E = S, Se) and S8

Insertions into lead-substituent bonds can also occur.27 In the examples below, insertion is accompanied by intramolecular rearrangement to place more electron-donating heteroatoms next to the electron-deficient lead.27

Insertion of an alkylazide and an isocyanate into [(Si(CH3)3)3Si]2Pb Insertion of an alkylazide and an isocyanate into ((Si(CH3)3)3Si)2Pb.png
Insertion of an alkylazide and an isocyanate into [(Si(CH3)3)3Si]2Pb

Transmetallation

Plumbylenes are known to undergo nucleophilic substitution with organometallic reagents to form transmetallated products.28 In an unusual example, the use of TlPF6, bearing the weakly coordinating anion PF6−, led to the formation of crystals of an oligonuclear lead compound with a chain structure upon work-up, highlighting the interesting reactivity of plumbylenes.28

Transmetallation between a plumbylene and various organometallic reagents (top) and the formation of an unusual oligomeric chain compound (bottom) Transmetallation between a plumbylene and various organometallic reagents (top) and the formation of an unusual oligomeric chain compound.png
Transmetallation between a plumbylene and various organometallic reagents (top) and the formation of an unusual oligomeric chain compound (bottom)

In addition, plumbylenes can also undergo metathesis with group 13 E(CH3)3 (E = Al, Ga) compounds. [18]

Metathesis reaction between R2Pb and E(CH3)3 (E = Al, Ga). In this example, the plumbylene formed dimerizes into a diplumbene Metathesis reactions of plumbylenes.png
Metathesis reaction between R2Pb and E(CH3)3 (E = Al, Ga). In this example, the plumbylene formed dimerizes into a diplumbene

Plumbylenes bearing different substituents can also undergo transmetallation and exchange substituents, with the driving force being the relief of steric strain and the low Pb-C bond dissociation energy. [30]

Transmetallation reaction between R2Pb and R'2Pb Transmetallation reactions of plumbylenes.png
Transmetallation reaction between R2Pb and R’2Pb

Applications

Synergic s-donor-s-acceptor interactions of PbCl2 with Pt(PCy3)2 Synergic s-donor-s-acceptor interactions of plumbylene with Pt(PCy3)2.png
Synergic σ-donor-σ-acceptor interactions of PbCl2 with Pt(PCy3)2

Plumbylenes can be used as concurrent σ-donor-σ-acceptor ligands to metal complexes, functioning as σ-donor via its filled 6s orbital and σ-acceptor via its empty 6p orbital.

Room temperature-stable plumbylenes have also been suggested as precursors in chemical vapour deposition (CVD) and atomic layer deposition (ALD) of lead-containing materials. [31] Dithioplumbylenes and dialkoxyplumbylenes may be useful as precursors for preparing the semiconductor material lead sulphide and piezoelectric PZT respectively. [32]

Related Research Articles

In organic chemistry, a carbene is a molecule containing a neutral carbon atom with a valence of two and two unshared valence electrons. The general formula is R−:C−R' or R=C: where the R represents substituents or hydrogen atoms.

A transition metal carbene complex is an organometallic compound featuring a divalent organic ligand. The divalent organic ligand coordinated to the metal center is called a carbene. Carbene complexes for almost all transition metals have been reported. Many methods for synthesizing them and reactions utilizing them have been reported. The term carbene ligand is a formalism since many are not derived from carbenes and almost none exhibit the reactivity characteristic of carbenes. Described often as M=CR2, they represent a class of organic ligands intermediate between alkyls (−CR3) and carbynes (≡CR). They feature in some catalytic reactions, especially alkene metathesis, and are of value in the preparation of some fine chemicals.

<span class="mw-page-title-main">Persistent carbene</span> Type of carbene demonstrating particular stability

A persistent carbene (also known as stable carbene) is a type of carbene demonstrating particular stability. The best-known examples and by far largest subgroup are the N-heterocyclic carbenes (NHC) (sometimes called Arduengo carbenes), for example diaminocarbenes with the general formula (R2N)2C:, where the four R moieties are typically alkyl and aryl groups. The groups can be linked to give heterocyclic carbenes, such as those derived from imidazole, imidazoline, thiazole or triazole.

Organogermanium chemistry is the science of chemical species containing one or more C–Ge bonds. Germanium shares group 14 in the periodic table with carbon, silicon, tin and lead. Historically, organogermanes are considered as nucleophiles and the reactivity of them is between that of organosilicon and organotin compounds. Some organogermanes have enhanced reactivity compared with their organosilicon and organoboron analogues in some cross-coupling reactions.

<span class="mw-page-title-main">Organolead chemistry</span>

Organolead chemistry is the scientific study of the synthesis and properties of organolead compounds, which are organometallic compounds containing a chemical bond between carbon and lead. The first organolead compound was hexaethyldilead (Pb2(C2H5)6), first synthesized in 1858. Sharing the same group with carbon, lead is tetravalent.

Carbene analogs in chemistry are carbenes with the carbon atom replaced by another chemical element. Just as regular carbenes they appear in chemical reactions as reactive intermediates and with special precautions they can be stabilized and isolated as chemical compounds. Carbenes have some practical utility in organic synthesis but carbene analogs are mostly laboratory curiosities only investigated in academia. Carbene analogs are known for elements of group 13, group 14, group 15 and group 16.

<span class="mw-page-title-main">Germylene</span> Class of germanium (II) compounds

Germylenes are a class of germanium(II) compounds with the general formula :GeR2. They are heavier carbene analogs. However, unlike carbenes, whose ground state can be either singlet or triplet depending on the substituents, germylenes have exclusively a singlet ground state. Unprotected carbene analogs, including germylenes, has a dimerization nature. Free germylenes can be isolated under the stabilization of steric hindrance or electron donation. The synthesis of first stable free dialkyl germylene was reported by Jutzi, et al in 1991.

<span class="mw-page-title-main">Stereoelectronic effect</span> Affect on molecular properties due to spatial arrangement of electron orbitals

In chemistry, primarily organic and computational chemistry, a stereoelectronic effect is an effect on molecular geometry, reactivity, or physical properties due to spatial relationships in the molecules' electronic structure, in particular the interaction between atomic and/or molecular orbitals. Phrased differently, stereoelectronic effects can also be defined as the geometric constraints placed on the ground and/or transition states of molecules that arise from considerations of orbital overlap. Thus, a stereoelectronic effect explains a particular molecular property or reactivity by invoking stabilizing or destabilizing interactions that depend on the relative orientations of electrons in space.

<span class="mw-page-title-main">Activation of cyclopropanes by transition metals</span>

In organometallic chemistry, the activation of cyclopropanes by transition metals is a research theme with implications for organic synthesis and homogeneous catalysis. Being highly strained, cyclopropanes are prone to oxidative addition to transition metal complexes. The resulting metallacycles are susceptible to a variety of reactions. These reactions are rare examples of C-C bond activation. The rarity of C-C activation processes has been attributed to Steric effects that protect C-C bonds. Furthermore, the directionality of C-C bonds as compared to C-H bonds makes orbital interaction with transition metals less favorable. Thermodynamically, C-C bond activation is more favored than C-H bond activation as the strength of a typical C-C bond is around 90 kcal per mole while the strength of a typical unactivated C-H bond is around 104 kcal per mole.

<span class="mw-page-title-main">Cyclic alkyl amino carbenes</span> Family of chemical compounds

In chemistry, cyclic(alkyl)(amino)carbenes (CAACs) are a family of stable singlet carbene ligands developed by the research group of Guy Bertrand in 2005 at UC Riverside. In marked contrast with the popular N-heterocyclic carbenes (NHCs) which possess two "amino" substituents adjacent to the carbene center, CAACs possess one "amino" substituent and an sp3 carbon atom "alkyl". This specific configuration makes the CAACs very good σ-donors and π-acceptors when compared to NHCs. Moreover the reduced heteroatom stabilization of the carbene center in CAACs versus NHCs also gives rise to a smaller ΔEST.

<span class="mw-page-title-main">Stannylene</span> Class of organotin(II) compounds

Stannylenes (R2Sn:) are a class of organotin(II) compounds that are analogues of carbene. Unlike carbene, which usually has a triplet ground state, stannylenes have a singlet ground state since valence orbitals of tin (Sn) have less tendency to form hybrid orbitals and thus the electrons in 5s orbital are still paired up. Free stannylenes are stabilized by steric protection. Adducts with Lewis bases are also known.

<span class="mw-page-title-main">Diphosphagermylene</span> Class of compounds

Diphosphagermylenes are a class of compounds containing a divalent germanium atom bound to two phosphorus atoms. While these compounds resemble diamidocarbenes, such as N-heterocyclic carbenes (NHC), diphosphagermylenes display bonding characteristics distinct from those of diamidocarbenes. In contrast to NHC compounds, in which there is effective N-C p(π)-p(π) overlap between the lone pairs of planar nitrogens and an empty p-orbital of a carbene, systems containing P-Ge p(π)-p(π) overlap are rare. Until 2014, the geometry of phosphorus atoms in all previously reported diphosphatetrylenes are pyramidal, with minimal P-Ge p(π)-p(π) interaction. It has been suggested that the lack of p(π)-p(π) in Ge-P bonds is due to the high energetic barrier associated with achieving a planar configuration at phosphorus, which would allow for efficient p(π)-p(π) overlap between the phosphorus lone pair and the empty P orbital of Ge. The resulting lack of π stabilization contributes to the difficulty associated with isolating diphosphagermylene and the Ge-P double bonds. However, utilization of sterically encumbering phosphorus centers has allowed for the isolation of diphosphagermylenes with a planar phosphorus center with a significant P-Ge p(π)-p(π) interaction.

A Fischer carbene is a type of transition metal carbene complex, which is an organometallic compound containing a divalent organic ligand. In a Fischer carbene, the carbene ligand is a σ-donor π-acceptor ligand. Because π-backdonation from the metal centre is generally weak, the carbene carbon is electrophilic.

Dispersion stabilized molecules are molecules where the London dispersion force (LDF), a non-covalent attractive force between atoms and molecules, plays a significant role in promoting the molecule's stability. Distinct from steric hindrance, dispersion stabilization has only recently been considered in depth by organic and inorganic chemists after earlier gaining prominence in protein science and supramolecular chemistry. Although usually weaker than covalent bonding and other forms of non-covalent interactions like hydrogen bonding, dispersion forces are known to be a significant if not dominating stabilizing force in certain organic, inorganic, and main group molecules, stabilizing otherwise reactive moieties and exotic bonding.

<span class="mw-page-title-main">Carbones</span> Class of molecules

Carbones are a class of molecules containing a carbon atom in the 1D excited state with a formal oxidation state of zero where all four valence electrons exist as unbonded lone pairs. These carbon-based compounds are of the formula CL2 where L is a strongly σ-donating ligand, typically a phosphine (carbodiphosphoranes) or a N-heterocyclic carbene/NHC (carbodicarbenes), that stabilises the central carbon atom through donor-acceptor bonds. Carbones possess high-energy orbitals with both σ- and π-symmetry, making them strong Lewis bases and strong π-backdonor substituents. Carbones possess high proton affinities and are strong nucleophiles which allows them to function as ligands in a variety of main group and transition metal complexes. Carbone-coordinated elements also exhibit a variety of different reactivities and catalyse various organic and main group reactions.  

<span class="mw-page-title-main">Organoberyllium chemistry</span> Organoberyllium Complex in Main Group Chemistry

Organoberyllium chemistry involves the synthesis and properties of organometallic compounds featuring the group 2 alkaline earth metal beryllium (Be). The area remains understudied, relative to the chemistry of other main-group elements, because although metallic beryllium is relatively unreactive, its dust causes berylliosis and compounds are toxic. Organoberyllium compounds are typically prepared by transmetallation or alkylation of beryllium chloride.

<i>m</i>-Terphenyl Organic ligand

m-Terphenyls (also known as meta-terphenyls, meta-diphenylbenzenes, or meta-triphenyls) are organic molecules composed of two phenyl groups bonded to a benzene ring in the one and three positions. The simplest formula is C18H14, but many different substituents can be added to create a diverse class of molecules. Due to the extensive pi-conjugated system, the molecule it has a range of optical properties and because of its size, it is used to control the sterics in reactions with metals and main group elements. This is because of the disubstituted phenyl rings, which create a pocket for molecules and elements to bond without being connected to anything else. It is a popular choice in ligand, and the most chosen amongst the terphenyls because of its benefits in regards to sterics. Although many commercial methods exist to create m-terphenyl compounds, they can also be found naturally in plants such as mulberry trees.

<span class="mw-page-title-main">Diphosphadiboretanes</span> Chemical compound

1,3-Diphospha-2,4-diboretanes, or B2P2, is a class of 4-member cyclic compounds of alternating boron and phosphorus atoms. They are often found as dimers during the synthesis of boraphosphenes (RB=PR'). Compounds can exhibit localized singlet diradical character (diradicaloid) between the boron atoms in the solution and solid state.

<span class="mw-page-title-main">Bismuthinidene</span> Class of organobismuth compounds

Bismuthinidenes are a class of organobismuth compounds, analogous to carbenes. These compounds have the general form R-Bi, with two lone pairs of electrons on the central bismuth(I) atom. Due to the unusually low valency and oxidation state of +1, most bismuthinidenes are reactive and unstable, though in recent decades, both transition metals and polydentate chelating Lewis base ligands have been employed to stabilize the low-valent bismuth(I) center through steric protection and π donation either in solution or in crystal structures. Lewis base-stabilized bismuthinidenes adopt a singlet ground state with an inert lone pair of electrons in the 6s orbital. A second lone pair in a 6p orbital and a single empty 6p orbital make Lewis base-stabilized bismuthinidenes ambiphilic.

Gallylenes are a class of gallium species which are electronically neutral and in the +1-oxidation state. This broad definition may include many gallium species, such as oligomeric gallium compounds in which the gallium atoms are coordinated to each other, but these classes of compounds are often referred to as gallanes. In recent literature, the term gallylene has mostly been reserved for low valent gallium species which may have a lone pair, analogous to NHC's or terminal borylenes. They are compounds of academic interest because of their distinctive electronic properties which have been achieved for higher main group elements such as borylenes and carbenes.

References

  1. 1 2 3 Davidson, Peter J.; Lappert, Michael F. (1973). "Stabilisation of metals in a low co-ordinative environment using the bis(trimethylsilyl)methyl ligand; coloured SnII and PbII alkyls, M[CH(SiMe3)2]2". Journal of the Chemical Society, Chemical Communications . 1973 (9): 317a. doi:10.1039/C3973000317A. ISSN   0022-4936.
  2. 1 2 3 4 5 6 7 8 9 Mizuhata, Yoshiyuki; Sasamori, Takahiro; Tokitoh, Norihiro (2009). "Stable Heavier Carbene Analogues". Chemical Reviews . 109 (8): 3479–3511. doi:10.1021/cr900093s. ISSN   0009-2665. PMID   19630390.
  3. 1 2 3 4 5 Pu, Lihung; Twamley, Brendan; Power, Philip P. (2000). "Terphenyl Ligand Stabilized Lead(II) Derivatives of Simple Organic Groups: Characterization of Pb(R)C6H3-2,6-Trip2 (R = Me, t-Bu, or Ph; Trip = C6H2-2,4,6-i-Pr3),{Pb(μ-Br)C6H3-2,6-Trip2}2, py·Pb(Br)C6H3-2,6-Trip2 (py = Pyridine), and the Bridged Plumbylyne Complex [{W(CO)4}2(μ-Br)(μ-PbC6H3-2,6-Trip2)]". Organometallics . 19 (15): 2874–2881. doi:10.1021/om0001624. ISSN   0276-7333.
  4. 1 2 Harris, David H.; Lappert, Michael F. (1974). "Monomeric, volatile bivalent amides of group IVB elements, M(NR12)2and M(NR1R2)2 (M = Ge, Sn, or Pb; R1 = Me3Si, R2 = Me3C)". Journal of the Chemical Society, Chemical Communications . 1974 (21): 895–896. doi:10.1039/C39740000895. ISSN   0022-4936.
  5. ↑ Hitchcock, Peter B.; Lappert, Michael F.; Samways, Barry J.; Weinberg, Erica L. (1983). "Metal (Li, GeII, GeIII, SnII, and PbII) 2,6-dialkylbenzenethiolates; X-ray crystal structures of Sn(SAr)2 (Ar = C6H2But3-2,4,6) and [M(SAr')2]3 (M = Sn or Pb, Ar' = C6H3Pri2-2,6)". Journal of the Chemical Society, Chemical Communications . 1983 (24): 1492–1494. doi:10.1039/C39830001492. ISSN   0022-4936.
  6. 1 2 3 Kano, Naokazu; Shibata, Kazusato; Tokitoh, Norihiro; Okazaki, Renji (1999). "Synthesis, Structure, and Reactivity of Kinetically Stabilized Divalent Organolead Compounds (Plumbylenes)". Organometallics . 18 (16): 2999–3007. doi:10.1021/om990188z. ISSN   0276-7333.
  7. 1 2 Klinkhammer, Karl Wihelm; Schwarz, Wolfgang (1995). "Bis(hypersilyl)tin and Bis(hypersilyl)lead, Two Electron-Rich Carbene Homologs". Angewandte Chemie International Edition in English . 34 (12): 1334–1336. doi:10.1002/anie.199513341. ISSN   0570-0833.
  8. ↑ Charmant, Jonathan P. H.; Haddow, Mairi F.; Hahn, F. Ekkehardt; Heitmann, Dennis; Fröhlich, Roland; Mansell, Stephen M.; Russell, Christopher A.; Wass, Duncan F. (2008). "Syntheses and molecular structures of some saturated N-heterocyclic plumbylenes". Dalton Transactions . 2008 (43): 6055–6059. doi:10.1039/B808717B. ISSN   1477-9226. PMID   19082063.
  9. 1 2 3 4 Fischer, Roland C.; Power, Philip P. (2010). "π-Bonding and the Lone Pair Effect in Multiple Bonds Involving Heavier Main Group Elements: Developments in the New Millennium". Chemical Reviews . 110 (7): 3877–3923. doi:10.1021/cr100133q. ISSN   0009-2665. PMID   20672858.
  10. ↑ Su, Ming-Der (2004). "Theoretical Study on the Reactivities of Stannylene and Plumbylene and the Origin of their Activation Barriers". Chemistry: A European Journal . 10 (23): 6073–6084. doi:10.1002/chem.200400413. ISSN   1521-3765. PMID   15515104.
  11. 1 2 3 4 Olaru, Marian; Duvinage, Daniel; Lork, Enno; Mebs, Stefan; Beckmann, Jens (2018). "Heavy Carbene Analogues: Donor-Free Bismuthenium and Stibenium Ions". Angewandte Chemie International Edition . 57 (32): 10080–10084. doi:10.1002/anie.201803160. ISSN   1433-7851. PMID   29644767.
  12. ↑ Pettersen, Eric F.; Goddard, Thomas D.; Huang, Conrad C.; Couch, Gregory S.; Greenblatt, Daniel M.; Meng, Elaine C.; Ferrin, Thomas E. (2004). "UCSF Chimera—A visualization system for exploratory research and analysis". Journal of Computational Chemistry . 25 (13): 1605–1612. CiteSeerX   10.1.1.456.9442 . doi:10.1002/jcc.20084. ISSN   0192-8651. PMID   15264254. S2CID   8747218.
  13. ↑ Lu, Tian; Chen, Feiwu (2012). "Multiwfn: A multifunctional wavefunction analyzer". Journal of Computational Chemistry . 33 (5): 580–592. doi:10.1002/jcc.22885. ISSN   1096-987X. PMID   22162017. S2CID   13508697.
  14. 1 2 Tokitoh, Norihiro; Ando, Wataru (2003). "Silylenes (and Germylenes, Stannylenes, Plumbylenes)". In Moss, Robert A.; Platz, Matthew S.; Jones, Maitland (eds.). Reactive Intermediate Chemistry. John Wiley & Sons. pp. 651–715. doi:10.1002/0471721492.ch14. ISBN   9780471233244.
  15. 1 2 Weidenbruch, Manfred (2003). "From a Cyclotrisilane to a Cyclotriplumbane: Low Coordination and Multiple Bonding in Group 14 Chemistry". Organometallics . 22 (22): 4348–4360. doi:10.1021/om034085z. ISSN   0276-7333.
  16. ↑ Stürmann, Martin; Saak, Wolfgang; Marsmann, Heinrich; Weidenbruch, Manfred (1999). "Tetrakis(2,4,6-triisopropylphenyl)diplumbene: A Molecule with a Lead–Lead Double Bond". Angewandte Chemie International Edition . 38 (1–2): 187–189. doi:10.1002/(sici)1521-3773(19990115)38:1/2<187::aid-anie187>3.0.co;2-2. ISSN   1521-3773.
  17. 1 2 3 4 Hino, Shirley; Olmstead, Marilyn; Phillips, Andrew D.; Wright, Robert J.; Power, Philip P. (2004). "Terphenyl Ligand Stabilized Lead(II) Derivatives: Steric Effects and Lead−Lead Bonding in Diplumbenes". Inorganic Chemistry . 43 (23): 7346–7352. doi:10.1021/ic049174y. ISSN   0020-1669. PMID   15530084.
  18. 1 2 Erickson, Jeremy D.; Fettinger, James C.; Power, Philip P. (2015). "Reaction of a Germylene, Stannylene, or Plumbylene with Trimethylaluminum and Trimethylgallium: Insertion into Al–C or Ga–C Bonds, a Reversible Metal–Carbon Insertion Equilibrium, and a New Route to Diplumbenes". Inorganic Chemistry . 54 (4): 1940–1948. doi:10.1021/ic502824w. ISSN   0020-1669. PMID   25629212.
  19. ↑ Klinkhammer, Karl W.; Fässler, Thomas F.; Grützmacher, Hansjörg (1998). "The Formation of Heteroleptic Carbene Homologues by Ligand Exchange— Synthesis of the First Plumbanediyl Dimer". Angewandte Chemie International Edition . 37 (1–2): 124–126. doi:10.1002/(sici)1521-3773(19980202)37:1/2<124::aid-anie124>3.0.co;2-c. ISSN   1521-3773.
  20. 1 2 Guthardt, Robin; Oetzel, Jan; Schweizer, Julia I.; Bruhn, Clemens; Langer, Robert; Maurer, Martin; Vícha, Jan; Shestakova, Pavletta; Holthausen, Max C.; Siemeling, Ulrich (2019). "Reactive Dimerization of an N-heterocyclic Plumbylene: C–H Activation with PbII". Angewandte Chemie . 131 (5): 1401–1405. doi:10.1002/ange.201811559. ISSN   0044-8249.
  21. 1 2 Barrau, Jacques; Rima, Ghassoub; El-Amraoui, Tajani (1998). "Stable divalent heteroleptic species ArO(X)M [Ar = 2,4,6-Tris(dimethylaminomethyl)phenyl-, M = Ge, Sn, Pb]". Journal of Organometallic Chemistry . 561 (1–2): 167–174. doi:10.1016/S0022-328X(98)00552-X. ISSN   0022-328X.
  22. ↑ Hahn, F. Ekkehardt; Heitmann, Dennis; Pape, Tania (2008). "Synthesis and Characterization of Stable N-Heterocyclic Plumbylenes". European Journal of Inorganic Chemistry . 2008 (7): 1039–1041. doi:10.1002/ejic.200701260. ISSN   1434-1948.
  23. ↑ Yao, Shenglai; Block, Stefan; Brym, Markus; Driess, Matthias (2007). "A new type of heteroleptic complex of divalent lead and synthesis of the P-plumbyleniophosphasilene, R2Si=P–Pb(L): (L = β-diketiminate)". Chemical Communications . 2007 (37): 3844–3846. doi:10.1039/B710888E. ISSN   1359-7345. PMID   18217666.
  24. ↑ Brooker, Sally; Buijink, Jan-Karel; Edelmann, Frank T. (1991). "Synthesis, structure, and reactivity of the first stable diaryllead(II) compound". Organometallics . 10: 25–26. doi:10.1021/om00047a014.
  25. ↑ Izod, Keith; Wills, Corinne; Clegg, William; Harrington, Ross W. (2009). "Acyclic Dialkylstannylene and -Plumbylene Compounds That Are Monomeric in the Solid State". Organometallics . 28 (19): 5661–5668. doi:10.1021/om900614q. ISSN   0276-7333.
  26. 1 2 3 Janes, Trevor; Zatsepin, Pavel; Song, Datong (2017). "Reactivity of heavy carbene analogues towards oxidants: A redox active ligand-enabled isolation of a paramagnetic stannylene". Chemical Communications . 53 (21): 3090–3093. doi:10.1039/C7CC00837F. ISSN   1359-7345. PMID   28243651.
  27. 1 2 Schneider, Julia; Krebs, Kilian M.; Freitag, Sarah; Eichele, Klaus; Schubert, Hartmut; Wesemann, Lars (2016). "Intramolecular Tetrylene Lewis Adducts: Synthesis and Reactivity". Chemistry: A European Journal . 22 (28): 9812–9826. doi:10.1002/chem.201601224. ISSN   0947-6539. PMID   27273819.
  28. ↑ Johnson, Brian P.; Almstätter, Stefan; Dielmann, Fabian; Bodensteiner, Michael; Scheer, Manfred (2010). "Synthesis and Reactivity of Low-Valent Group 14 Element Compounds". Zeitschrift für Anorganische und Allgemeine Chemie . 636 (7): 1275–1285. doi:10.1002/zaac.201000029. ISSN   0044-2313.
  29. ↑ Dötz, Karl Heinz (1984). "Carbene Complexes in Organic Synthesis [New Synthetic Methods (47)]". Angewandte Chemie International Edition in English . 23 (8): 587–608. doi:10.1002/anie.198405871. ISSN   0570-0833.
  30. ↑ Stürmann, Martin; Weidenbruch, Manfred; Klinkhammer, Karl W.; Lissner, Falk; Marsmann, Heinrich (1998). "New Plumbylenes and a Plumbylene Dimer with a Short Lead−Lead Separation". Organometallics . 17 (20): 4425–4428. doi:10.1021/om9804475. ISSN   0276-7333.
  31. ↑ Bačić, Goran; Zanders, David; Mallick, Bert; Devi, Anjana; Barry, Seán T. (2018). "Designing Stability into Thermally Reactive Plumbylenes". Inorganic Chemistry . 57 (14): 8218–8226. doi:10.1021/acs.inorgchem.8b00719. ISSN   0020-1669. PMID   29943579. S2CID   49410374.
  32. ↑ Rekken, Brian D.; Brown, Thomas M.; Olmstead, Marilyn M.; Fettinger, James C.; Power, Philip P. (2013). "Stable Plumbylene Dichalcogenolate Monomers with Large Differences in Their Interligand Angles and the Synthesis and Characterization of a Monothiolato Pb(II) Bromide and Lithium Trithiolato Plumbate". Inorganic Chemistry . 52 (6): 3054–3062. doi:10.1021/ic302513c. ISSN   0020-1669. PMID   23441916.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.