In chemistry, a transition metal chloride complex is a coordination complex that consists of a transition metal coordinated to one or more chloride ligand. The class of complexes is extensive. [1]
Halides are X-type ligands in coordination chemistry. They are both σ- and π-donors. Chloride is commonly found as both a terminal ligand and a bridging ligand. The halide ligands are weak field ligands. Due to a smaller crystal field splitting energy, the homoleptic halide complexes of the first transition series are all high spin. Only [CrCl6]3− is exchange inert.
Homoleptic metal halide complexes are known with several stoichiometries, but the main ones are the hexahalometallates and the tetrahalometallates. The hexahalides adopt octahedral coordination geometry, whereas the tetrahalides are usually tetrahedral. Square planar tetrahalides are known for Pd(II), Pt(II), and Au(III). Examples with 2- and 3-coordination are common for Au(I), Cu(I), and Ag(I).
Due to the presence of filled pπ orbitals, halide ligands on transition metals are able to reinforce π-backbonding onto a π-acid. They are also known to labilize cis-ligands. [2] [3]
Homoleptic complexes (complexes with only chloride ligands) are often common reagents. Almost all examples are anions.
Complex | colour | electron config. | structure | geometry | comments |
---|---|---|---|---|---|
TiCl4 | colourless | (t2g)0 | tetrahedral | ||
[Ti2Cl9]− | white/colourless | d0d0 | face-sharing bioctahedron | Ti-Cl(terminal) = 2.23 Å, 2.45 (terminal) (N(PCl3)2)+ salt) [4] | |
[Ti2Cl9]3- | orange | (t2g)1(t2g)1 | face-sharing bioctahedron | Ti-Ti =3.22 Å Ti-C1(terminal) = 2.32-2.35 Å, Ti-Cl(bridge) = 2.42-2.55 Å ((NEt4+)3)3 salt) [5] | |
[Ti2Cl10]2− | colourless | d0d0 | bioctahedral | ||
[Ti3Cl12]3- | green | (t2g)1(t2g)1(t2g)1 | face-sharing trioctahedron | Ti-Ti = 3.19, 3.10 Å (terminal) Ti-C1(terminal) = 2.36 Å (terminal), Ti-Cl(bridge) = 2.50 Å ((PPh4+)3)3 salt) [6] | |
[TiCl6]2− | yellow | d0 | octahedral | PPh4+ salt Ti-Cl = 2.33 Å [7] | |
VCl4 | red | (t2g)1 | tetrahedral | V1−Cl = 2.29 Å | |
V2Cl10 | violet | (t2g)0 | edge-shared bioctahedron | V1−Cl(bridging) = 2.48 Å V1−Cl(terminal) = 2.16-2.21 Å [8] | |
[VCl6]2- | red | (t2g)1 | octahedral | V1−Cl = 2.29 Å [9] | |
[CrCl6]3− | pink [3] | (t2g)3 | octahedral [10] [3] | ||
[Cr2Cl9]3− | red | (d3)2 | face-sharing bioctahedron | Cr-Cl(terminal) = 2.31 Å, 2.42 (terminal) (Et2NH2+ salt) [11] | |
[MnCl4]2− [12] | pale pink to while | (eg)2(t2g)3 | tetrahedral | Mn-Cl bond length = 2.3731-2.3830 Å [13] | |
[MnCl6]2− | dark red | (t2g)3(eg)1 | octahedral | Mn-Cl distance = 2.28 Å K+ salt [14] ) salt is isostructural with K2PtCl6 | |
[MnCl6]3− | brown [3] | (t2g)3(eg)1 | octahedral [10] [3] | ||
[Mn2Cl6]2− | yellow-green | (eg)2(t2g)3 | bitetrahedral | Mn-Cl(terminal) bond length = 2.24 Å Mn-Cl(terminal) bond length = 2.39 Å [15] (PPN+)2 salt | |
[Mn3Cl12]6− | pink | (t2g)3(eg)2 | cofacial trioctahedron | Mn-Cl distance = --- Å [(C(NH2)3]+ 6 salt [16] | |
[FeCl4]2− [12] | cream | (eg)3(t2g)3 | tetrahedral((Et4N+)2 salt) [12] | ||
[FeCl4]− | (eg)2(t2g)3 | tetrahedral | Fe-Cl bond length = 2.19 Å [17] | ||
[FeCl6]3− | orange | (t2g)3(eg)2 | octahedral [3] | ||
[Fe2Cl6]2− | pale yellow | (eg)2(t2g)3 | bitetrahedral | Fe-Cl(terminal) bond length = 2.24 Å Fe-Cl(terminal) bond length = 2.39 Å [15] (PPN+)2 salt | |
[CoCl4]2− [12] | blue [12] | (eg)4(t2g)3 | tetrahedral | ||
[Co2Cl6]2− | blue [15] | (eg)4(t2g)3 | bitetrahedral | Mn-Cl(terminal) bond length = 2.24 Å Co-Cl(terminal) bond length = 2.35 Å [15] (PPN+)2 salt | |
[NiCl4]2− [12] | blue [12] | (eg)4(t2g)4 | tetrahedral | Ni-Cl bond length = 2.28 Å (Et4N+)2 salt [18] | |
[Ni3Cl12]6− | orange [19] | (t2g)6(eg)2 | confacial trioctahedral | ((Me2NH2+)2)8 salt double salt with two Cl− Ni-Cl bond length = 2.36-2.38 Å [19] | |
[CuCl4]2− [12] | orange [20] yellow (flattened tetrahedral) [21] green (square planar) [22] | (t2g)6(eg)3 | flattened tetrahedral or square planar [23] [24] | Cu-Cl bond length = 2.24 Å | |
[Cu2Cl6]2− | red | [(t2g)6(eg)3]2 | edge-shared bis(square planar) [25] | Cu-Cl(terminal) = 2.24 Å Cu-Cl(bridging) = 2.31 Å | |
[ZnCl4]2− | white/colorless | d10 | tetrahedral | ||
Some homoleptic complexes of the second row transition metals feature metal-metal bonds.
Complex | colour | electron config. | structure | geometry | comments |
---|---|---|---|---|---|
[ZrCl6]2− | yellow | d0 | octahedral | Zr-Cl distance = 2.460 Å (Me4N+)2 salt [27] | |
[Zr2Cl10]2− | colorless | (d0)2 | edge-shared bioctahedral | Zr-Cl = 2.36 Å (terminal), 2.43 Å (bridging) N(PCl3)2)+ salt [4] | |
Nb2Cl10 | yellow | (d0)2 | edge-shared bioctahedral [Nb2Cl10] | 3.99 Å [28] | |
[NbCl6]− | yellow | d0 | octahedral | Nb-Cl = 2.34 Å N(PCl3)2)+ salt [4] | |
[Nb6Cl18]2− | black | (d2)4(d3)2 (14 cluster electrons) | cluster Nb---Nb bonding | Nb-Cl = 2.92 Å (K+)2 salt [29] | |
MoCl6 | black | d0 | octahedron | Mo−Cl = 2.28 -2.31 Å [8] | |
[MoCl6]2− | yellow | (t2g)2 | octahedron | Mo−Cl = 2.37, 2.38, 2.27 Å [30] | |
[MoCl6]3− | pink | (t2g)3 | octahedral | ||
[Mo2Cl8]4− | purple [31] | 2(d4) | Mo-Mo quadruple bond | ||
[Mo2Cl9]3− | 2(d3) | face-shared bioctahedral | Mo-Mo (triple) bond length = 2.65 Å Mo-Cl (terminal) bond length = 2.38 Å Mo-Cl (bridging) bond length = 2.49 Å [32] [33] | ||
Mo2Cl10 | green | (d1)2 | edge-sharing bioctahedra [34] | ||
[Mo2Cl10]2− | (d2)2 | edge-sharing bioctahedra [35] | |||
[Mo5Cl13]2− | brown [31] | d2d2d2d2d3 | incomplete octahedron [36] | ||
[Mo6Cl14]2− | yellow | d4 | octahedral cluster | (4-HOPyH+)2 salt [37] | |
[TcCl6]2− | yellow | (t2g)3 | octahedron | Tc-Cl = 2.35 Å for As(C6H5)4+ salt [38] | |
[Tc2Cl8]2− | green | (t2g)4 | Tc-Tc quadruple bond | Tc-Tc = 2.16, Tc-Cl = 2.34 Å for NBu4+ salt [39] | |
[RuCl6]2− | brown | (t2g)4 | octahedral | (EtPPh3+)2 salt [40] | |
[Ru2Cl9]3− | red | [(t2g)5]2 | cofacial bioctahedral | Ru-Ru bond length = 2.71 Å; Ru-Cl(terminal) = 2.35 Å, Ru-Cl(bridging) = 2.36 Å ((Et4N)+)3 salt [41] | |
[Ru3Cl12]4− | green | (d5)2(d6) | cofacial trioctahedral | Ru-Ru bond lengths = 2.86 Å Ru-Cl bond lengths = 2.37-2.39 Å (Et4N+)2(H7O3+)2 salt [42] | |
[RhCl6]3− | red | (t2g)6 | octahedral | H2N+(CH2CH2NH3+)2 salt) [43] | |
[Rh2Cl9]3− | red-brown | (t2g)6 | octahedral | Rh-Cl(terminal) = 2.30 Å, Rh-Cl(terminal) = 2.40 Å ((Me3CH2Ph)+)3 salt) [32] | |
[PdCl4]2− | brown | d8 | square planar | ||
[Pd2Cl6]2− [44] | red ((Et4N+)2 salt) | d8 | square planar | ||
[Pd3Cl8]2− [45] | orange brown ((Bu4N+)2 salt) | d8 | square planar | ||
[PdCl6]2− | brown | d6 | octahedral | Pd(IV) | |
[Pd6Cl12] | yellow-brown | d8 | square planar [46] | ||
[AgCl2]− | white/colorless | d10 | linear | salt of [K(2.2.2-crypt)]+ [47] | |
[CdCl4]2− | white/colorless | d10 | tetrahedral | Et4N+ salt, Cd-Cl distance is 2.43 Å [26] | |
[Cd2Cl6]2− | white/colorless | d10 | edge-shared bitetrahedron | (C6N3(4-C5H4N)33+ salt [48] | |
[Cd3Cl12]6− | white/colorless | d10 | octahedral (central Cd) pentacoordinate (terminal Cd's) cofactial trioctahedral | (C6N3(4-C5H4N)33+ salt [48] (3,8-Diammonium-6-phenylphenanthridine3+)2 [49] | |
[Cd6Cl19]7− | white/colorless | d10 | octahedron of octahedra | 4,4'-(C6H3(2-Et)NH3+)2 salt [50] |
Complex | colour | electron config. | structure | geometry | comments |
---|---|---|---|---|---|
[HfCl6]2− | white | d0 | octahedral | Hf-Cl distance = 2.448 A ((Me4N+)2 salt) [27] | |
[Hf2Cl10]2− | colorless/white | d0 | edge-shared bioctahedral [51] | ||
[Hf2Cl9]− | colorless/white | (d0)2 | face-shared bioctahedral [52] | ||
[TaCl5] | white | d0 | edge-shared bioctahedral | ||
[TaCl6]− | white/colourless | d0 | octahedral | Ta-Cl = 2.34 Å (N(PCl3)2)+ salt) [4] | |
[Ta6Cl18]2- | green | d0 | octahedral | Ta-Ta = 2.34 Å (H+2 salt hexahydrate [53] | |
WCl6 | blue | d0 | octahedral | 2.24–2.26 Å [54] | |
[WCl6]2− | (t2g)2 | octahedral | W-Cl distances range from 2.34 to 2.37 Å (PPh4+ salt) [55] | ||
[WCl6]− | (t2g)1 | octahedral | W-Cl distance = 2.32 Å (Et4N+ salt) [56] | ||
W2Cl10 | black [57] | (t2g1)2 | bioctahedral | W-W distance = 3.814 Å [58] | |
[W2Cl8]4− | blue | 2(d4) | W-W quadruple bond | dW-W = 2.259 Å [Na(tmeda)+]4 salt [59] | |
[W2Cl9]2− | d3d2 | face-sharing bioctahedral | W-W distance = 2.54 Å W-Cl(terminal) = 2.36 Å, W-Cl(bridge) = 2.45 Å ((PPN+)2 salt) [60] | ||
[W2Cl9]3− | d3d3 | octahedral | W-Cl distance = 2.32 Å (Et4N+ salt) [60] | ||
[W3Cl13]3− | d3,d3,d4 | [W3(μ3-Cl)(μ-Cl)3Cl9]3- | W-W distances = 2.84 Å [61] | ||
[W3Cl13]2− | d3,d4,d4 | [W3(μ3-Cl)(μ-Cl)3Cl9]2- [61] | W-W distances = 2.78 Å [61] | ||
[W6Cl14]2- | yellow [62] | (d4)6 | see Mo6Cl12 | ||
[ReCl6]− | red-brown | (t2g)2 | octahedral | Re-Cl distance = 2.24-2.31 Å (PPh4+ salt) [63] | |
[ReCl6] | (t2g)1 | octahedral | Re-Cl distance = 226.3(6) Å [8] | ||
[ReCl6]2− | green | (t2g)3 | octahedral | Re-Cl distance = 2.35-2.38 Å ((PPN+)2 salt) [64] | |
[Re2Cl9]2− | (t2g)3(t2g)4 | face-sharing bioctahedral | Re-Re distance = 2.48 Å Re-Cl distances = 2.42 Å (bridge), 2.33 Å (terminal) ((Et4N+)2 salt) [65] | ||
[Re2Cl9]− | ((t2g)3)2 | face-sharing bioctahedral | Re-Re distance = 2.70 Å Re-Cl distances = 2.41 (bridge), 2.28 Å (terminal) (Bu4N+ salt) [65] | ||
[OsCl6]− | dark green | (t2g)3 | octahedral | dOs-Cl = 2.30 Å for Et4N+ [66] and Ph4P+ [67] salts | |
[OsCl6]2− | yellow-orange | (t2g)4 | octahedral [67] | Os-Cl distance 2.33 Å | |
[Os2Cl8]2− | green | (d5)2 | square antiprism | dOs-Os = 2.182 Å, dOs-Cl = 2.32 Å (Bu4N+)2 salt [68] | |
[Os2Cl10]2− | green | (d4)2 | octahedral | dOs-Cl(terminal) = 2.30 Å dOs-Cl(bridging) = 2.42 Å (Et4N+)2 salt [66] | |
[IrCl6]3− | red | (t2g)6 | octahedral | Ir-Cl = 2.36 Å [69] | |
[IrCl6]2− | brown | (t2g)5 | octahedral | Ir-Cl = 2.33 Å [70] | |
[Ir2Cl9]3− | - | ((t2g)6)2 | bi-octahedral [71] | ||
[PtCl4]2− | pink | d8 | square planar | ||
[PtCl6]2− | yellow | d6 | octahedral | Pt-Cl distance = 2.32 Å Et4N+ salt, ((Me4N+)2 salt) [27] | |
[Pt2Cl9]− | red (Bu4N+ salt) | ((t2g)6)2 | octahedral | Pt-Clt and Pt-Clbridge = 2.25, 2.38 Å [72] | |
[Pt2Cl10]2− | yellow-brown (PPN+ salt) | ((t2g)6)2 | edge-shared bioctahedral | Pt-Clt and Pt-Clbridge = 2.27, 2.37 Å [72] | |
[Pt6Cl12] | yellow-brown | (d8)6 | square planar | Pt-Cl = 2.31 [73] | |
[AuCl2]− | white/colorless | d10 | linear | Au-Cl distances of 2.28 Å NEt4+ salt [74] | |
Au4Cl8 | black | (d10)2(d8)2 | linear and square planar | rare example of mixed valence, molecular chloride [75] | |
[AuCl4]− | yellow | d8 | square planar | Au-Cl distances of 2.26 Å NBu4+ salt [76] | |
[HgCl4]2− | white/colorless | d10 | tetrahedral | Hg-Cl distance is 2.46 Å [26] Et4N+ salt | |
[Hg2Cl6]2− | white/colorless | d10 | edge-shared bitetrahedral | Hg-Cl distance is 2.46 Å [77] Bu4N+ salt |
Heteroleptic complexes containing chloride are numerous. Most hydrated metal halides are members of this class. Hexamminecobalt(III) chloride and Cisplatin (cis-Pt(NH3)2Cl2) are prominent examples of metal-ammine-chlorides.
As indicated in the table below, many hydrates of metal chlorides are molecular complexes. [78] [79] These compounds are often important commercial sources of transition metal chlorides. Several hydrated metal chlorides are not molecular and thus are not included in this tabulation. For example the dihydrates of manganese(II) chloride, nickel(II) chloride, copper(II) chloride, iron(II) chloride, and cobalt(II) chloride are coordination polymers.
Formula of hydrated metal halides | Coordination sphere of the metal |
---|---|
TiCl3(H2O)6 | trans-[TiCl2(H2O)4]+ [80] |
VCl3(H2O)6 | trans-[VCl2(H2O)4]+ [80] |
CrCl3(H2O)6 | trans-[CrCl2(H2O)4]+ |
CrCl3(H2O)6 | [CrCl(H2O)5]2+ |
CrCl2(H2O)4 | trans-[CrCl2(H2O)4] |
CrCl3(H2O)6 | [Cr(H2O)6]3+ [81] |
MnCl2(H2O)6 | trans-[MnCl2(H2O)4] |
MnCl2(H2O)4 | cis-[MnCl2(H2O)4] [82] |
FeCl2(H2O)6 | trans-[FeCl2(H2O)4] |
FeCl2(H2O)4 | trans-[FeCl2(H2O)4] |
FeCl3(H2O)6 | one of four hydrates of ferric chloride, [83] |
FeCl3(H2O)2.5 | cis-[FeCl2(H2O)4]+ [84] |
CoCl2(H2O)6 | trans-[CoCl2(H2O)4] |
CoCl2(H2O)4 | cis-[CoCl2(H2O)4] |
NiCl2(H2O)6 | trans-[NiCl2(H2O)4] |
NiCl2(H2O)4 | cis-[NiCl2(H2O)4] |
Metal chlorides form adducts with ethers to give transition metal ether complexes.
Cuprates are a class of compounds that contain copper (Cu) atom(s) in an anion. They can be broadly categorized into two main types:
In chemistry, water(s) of crystallization or water(s) of hydration are water molecules that are present inside crystals. Water is often incorporated in the formation of crystals from aqueous solutions. In some contexts, water of crystallization is the total mass of water in a substance at a given temperature and is mostly present in a definite (stoichiometric) ratio. Classically, "water of crystallization" refers to water that is found in the crystalline framework of a metal complex or a salt, which is not directly bonded to the metal cation.
In chemistry, tellurate is a compound containing an oxyanion of tellurium where tellurium has an oxidation number of +6. In the naming of inorganic compounds it is a suffix that indicates a polyatomic anion with a central tellurium atom.
Scandium(III) chloride is the inorganic compound with the formula ScCl3. It is a white, high-melting ionic compound, which is deliquescent and highly water-soluble. This salt is mainly of interest in the research laboratory. Both the anhydrous form and hexahydrate (ScCl3•6H2O) are commercially available.
Titanium(III) chloride is the inorganic compound with the formula TiCl3. At least four distinct species have this formula; additionally hydrated derivatives are known. TiCl3 is one of the most common halides of titanium and is an important catalyst for the manufacture of polyolefins.
Titanium(II) chloride is the chemical compound with the formula TiCl2. The black solid has been studied only moderately, probably because of its high reactivity. Ti(II) is a strong reducing agent: it has a high affinity for oxygen and reacts irreversibly with water to produce H2. The usual preparation is the thermal disproportionation of TiCl3 at 500 °C. The reaction is driven by the loss of volatile TiCl4:
There are three sets of Indium halides, the trihalides, the monohalides, and several intermediate halides. In the monohalides the oxidation state of indium is +1 and their proper names are indium(I) fluoride, indium(I) chloride, indium(I) bromide and indium(I) iodide.
Rhenium pentachloride is an inorganic compound with the formula Re2Cl10. This red-brown solid is paramagnetic.
Monofluorophosphate is an anion with the formula PO3F2−, which is a phosphate group with one oxygen atom substituted with a fluoride atom. The charge of the ion is −2. The ion resembles sulfate in size, shape and charge, and can thus form compounds with the same structure as sulfates. These include Tutton's salts and langbeinites. The most well-known compound of monofluorophosphate is sodium monofluorophosphate, commonly used in toothpaste.
Difluorophosphate or difluorodioxophosphate or phosphorodifluoridate is an anion with formula PO2F−2. It has a single negative charge and resembles perchlorate and monofluorosulfonate in shape and compounds. These ions are isoelectronic, along with tetrafluoroaluminate, phosphate, orthosilicate, and sulfate. It forms a series of compounds. The ion is toxic to mammals as it causes blockage to iodine uptake in the thyroid. However it is degraded in the body over several hours.
The telluride iodides are chemical compounds that contain both telluride ions (Te2−) and iodide ions (I−). They are in the class of mixed anion compounds or chalcogenide halides.
Sulfidostannates, or thiostannates are chemical compounds containing anions composed of tin linked with sulfur. They can be considered as stannates with sulfur substituting for oxygen. Related compounds include the thiosilicates, and thiogermanates, and by varying the chalcogen: selenostannates, and tellurostannates. Oxothiostannates have oxygen in addition to sulfur. Thiostannates can be classed as chalcogenidometalates, thiometallates, chalcogenidotetrelates, thiotetrelates, and chalcogenidostannates. Tin is almost always in the +4 oxidation state in thiostannates, although a couple of mixed sulfides in the +2 state are known,
A chloride nitride is a mixed anion compound containing both chloride (Cl−) and nitride ions (N3−). Another name is metallochloronitrides. They are a subclass of halide nitrides or pnictide halides.
A Phosphide chloride is a mixed anion compound containing both phosphide (P3−) and chloride (Cl−) ions.
Arsenide bromides or bromide arsenides are compounds containing anions composed of bromide (Br−) and arsenide (As3−). They can be considered as mixed anion compounds. They are in the category of pnictidehalides. Related compounds include the arsenide chlorides, arsenide iodides, phosphide bromides, and antimonide bromides.
Arsenide chlorides or chloride arsenides are compounds containing anions composed of chloride (Cl−) and arsenide (As3−). They can be considered as mixed anion compounds. They are in the category of pnictidehalides. Related compounds include the arsenide bromides, arsenide iodides, phosphide chlorides, and antimonide chlorides.
An iodide nitride is a mixed anion compound containing both iodide (I−) and nitride ions (N3−). Another name is metalloiodonitrides. They are a subclass of halide nitrides or pnictide halides. Some different kinds include ionic alkali or alkaline earth salts, small clusters where metal atoms surround a nitrogen atom, layered group 4 element 2-dimensional structures, and transition metal nitrido complexes counter-balanced with iodide ions. There is also a family with rare earth elements and nitrogen and sulfur in a cluster.
Carbide chlorides are mixed anion compounds containing chloride anions and anions consisting entirely of carbon. In these compounds there is no bond between chlorine and carbon. But there is a bond between a metal and carbon. Many of these compounds are cluster compounds, in which metal atoms encase a carbon core, with chlorine atoms surrounding the cluster. The chlorine may be shared between clusters to form polymers or layers. Most carbide chloride compounds contain rare earth elements. Some are known from group 4 elements. The hexatungsten carbon cluster can be oxidised and reduced, and so have different numbers of chlorine atoms included.
In chemistry, a transition metal ether complex is a coordination complex consisting of a transition metal bonded to one or more ether ligand. The inventory of complexes is extensive. Common ether ligands are diethyl ether and tetrahydrofuran. Common chelating ether ligands include the glymes, dimethoxyethane (dme) and diglyme, and the crown ethers. Being lipophilic, metal-ether complexes often exhibit solubility in organic solvents, a property of interest in synthetic chemistry. In contrast, the di-ether 1,4-dioxane is generally a bridging ligand.
Indium(I) chloride is the chemical compound with the formula InCl. Indium monochloride occurs as a yellow cubic form below 120 °C and above this temperature as a red orthorhombic form. InCl is one of three known indium chlorides.
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