Titanocene dichloride

Last updated
Titanocene dichloride
IUPAC name
Other names
titanocene dichloride, dichlorobis(cyclopentadienyl)titanium(IV)
3D model (JSmol)
ECHA InfoCard 100.013.669 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 215-035-9
PubChem CID
RTECS number
  • XR2050000
UN number 3261
  • InChI=1S/2C5H5.2ClH.Ti/c2*1-2-4-5-3-1;;;/h2*1-5H;2*1H;/q2*-1;;;+4/p-2 X mark.svgN
  • InChI=1/2C5H5.2ClH.Ti/c2*1-2-4-5-3-1;;;/h2*1-5H;2*1H;/q2*-1;;;+4/p-2/r2C5H5.Cl2Ti/c2*1-2-4-5-3-1;1-3-2/h2*1-5H;/q2*-1;+2
  • [cH-]1cccc1.[cH-]1cccc1.Cl[Ti+2]Cl
Molar mass 248.96 g/mol
Appearancebright red solid
Density 1.60 g/cm3, solid
Melting point 289 °C (552 °F; 562 K)
sl. sol. with hydrolysis
Dist. tetrahedral
Hazards [1]
GHS labelling:
H315, H335
P201, P202, P261, P264, P270, P271, P280, P281, P301+P310, P301+P312, P302+P352, P304+P340, P305+P351+P338, P308+P313, P312, P330, P332+P313, P337+P313, P362, P403+P233, P405, P501
NFPA 704 (fire diamond)
NFPA 704.svgHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability (red): no hazard codeInstability 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g. calciumSpecial hazards (white): no code
Related compounds
Related compounds
Zirconocene dichloride
Hafnocene dichloride
Vanadocene dichloride
Niobocene dichloride
Tantalocene dichloride
Molybdocene dichloride
Tungstenocene dichloride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

Titanocene dichloride is the organotitanium compound with the formula (η5-C5H5)2TiCl2, commonly abbreviated as Cp2TiCl2. This metallocene is a common reagent in organometallic and organic synthesis. It exists as a bright red solid that slowly hydrolyzes in air. [2] It shows antitumour activity and was the first non-platinum complex to undergo clinical trials as a chemotherapy drug. [3]


Preparation and structure

The standard preparations of Cp2TiCl2 start with titanium tetrachloride. The original synthesis by Wilkinson and Birmingham, using sodium cyclopentadienide, [4] is still commonly used: [5]

2 NaC5H5 + TiCl4 → (C5H5)2TiCl2 + 2 NaCl

It can also be prepared by using freshly distilled cyclopentadiene rather than its sodium derivative: [6]

2 C5H6 + TiCl4 → (C5H5)2TiCl2 + 2 HCl

Focusing on the geometry of the Ti center, Cp2TiCl2 adopts a distorted tetrahedral geometry (counting Cp as a monodentate ligand). The Ti-Cl distance is 2.37 Å and the Cl-Ti-Cl angle is 95°. [7]


Halide replacement reactions

Cp2TiCl2 serves as a source of Cp2Ti2+. A large range of nucleophiles will displace chloride. With NaSH and with polysulfide salts, one obtains the sulfido derivatives Cp2Ti(SH)2 and Cp2TiS5. [8]

The Petasis reagent, Cp2Ti(CH3)2, is prepared from the action of methylmagnesium chloride [9] or methyllithium [10] on Cp2TiCl2. This reagent is useful for the conversion of esters into vinyl ethers.

The Tebbe reagent Cp2TiCl(CH2)Al(CH3)2, arises by the action of 2 equivalents Al(CH3)3 on Cp2TiCl2. [11] [12]

Reactions affecting Cp ligands

One Cp ligand can be removed from Cp2TiCl2 to give tetrahedral CpTiCl3. This conversion can be effected with TiCl4 or by reaction with SOCl2. [13]

The sandwich complex (Cycloheptatrienyl)(cyclopentadienyl)titanium is prepared by treatment of titanocene dichloride with lithium cycloheptatrienyl. [14]

Titanocene itself, TiCp2, is so highly reactive that it rearranges into a TiIII hydride dimer and has been the subject of much investigation. [15] [16] This dimer can be trapped by conducting the reduction of titanocene dichloride in the presence of ligands; in the presence of benzene, a fulvalene complex, μ(η55-fulvalene)-di-(μ-hydrido)-bis(η5-cyclopentadienyltitanium), can be prepared and the resulting solvate structurally characterised by X-ray crystallography. [17] The same compound had been reported earlier by a lithium aluminium hydride reduction [18] and sodium amalgam reduction [19] of titanocene dichloride, and studied by 1H NMR [20] prior to its definitive characterisation. [15] [16]

"Titanocene" is not Ti(C5H5)2, but rather this isomer with a fulvalene dihydride structure. GreenTitanoceneWeakM-M.png
"Titanocene" is not Ti(C5H5)2, but rather this isomer with a fulvalene dihydride structure.


Reduction with zinc gives the dimer of bis(cyclopentadienyl)titanium(III) chloride in a solvent-mediated chemical equilibrium: [21] [22]

N-RB equilibrium.jpg

Cp2TiCl2 is a precursor to TiII derivatives. Reductions have been investigated using Grignard reagent and alkyl lithium compounds. More conveniently handled reductants include Mg, Al, or Zn. The following syntheses demonstrate some of the compounds that can be generated by reduction of titanocene dichloride in the presence of π acceptor ligands: [23]

Cp2TiCl2 + 2 CO + Mg → Cp2Ti(CO)2 + MgCl2
Cp2TiCl2 + 2 PR3 + Mg → Cp2Ti(PR3)2 + MgCl2

Alkyne derivatives of titanocene have the formula (C5H5)2Ti(C2R2) and the corresponding benzyne complexes are known. [24] One family of derivatives are the titanocyclopentadienes. [25] Rosenthal's reagent, Cp2Ti(η2-Me3SiC≡CSiMe3), can be prepared by this method. Two structures are shown, A and B, which are both resonance contributors to the actual structure of Rosenthal's reagent. [26]

Synthesis of rosenthal reagent with titanocene.svg

Titanocene equivalents react with alkenyl alkynes followed by carbonylation and hydrolysis to form bicyclic cyclopentadienones, related to the Pauson–Khand reaction. [27] A similar reaction is the reductive cyclization of enones to form the corresponding alcohol in a stereoselective manner. [28]

Reduction of titanocene dichloride in the presence of conjugated dienes such as 1,3-butadiene gives η3-allyltitanium complexes. [29] Related reactions occur with diynes. Furthermore, titanocene can catalyze CC bond metathesis to form asymmetric diynes. [25]

Derivatives of (C5Me5)2TiCl2

Many analogues of Cp2TiCl2 are known. Prominent examples are the ring-methylated derivatives (C5H4Me)2TiCl2 and (C5Me5)2TiCl2.


Titanium catalysts are an attractive from the perspective of green chemistry, i.e. the low toxicity and high abundance of titanium. [30]

Medicinal research

Titanocene dichloride was investigated as an anticancer drug. In fact, it was both the first non-platinum coordination complex and the first metallocene to undergo a clinical trial. [3] [31]

Related Research Articles

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

A metallocene is a compound typically consisting of two cyclopentadienyl anions (C
, abbreviated Cp) bound to a metal center (M) in the oxidation state II, with the resulting general formula (C5H5)2M. Closely related to the metallocenes are the metallocene derivatives, e.g. titanocene dichloride or vanadocene dichloride. Certain metallocenes and their derivatives exhibit catalytic properties, although metallocenes are rarely used industrially. Cationic group 4 metallocene derivatives related to [Cp2ZrCH3]+ catalyze olefin polymerization.

<span class="mw-page-title-main">Titanium tetrachloride</span> Inorganic chemical compound

Titanium tetrachloride is the inorganic compound with the formula TiCl4. It is an important intermediate in the production of titanium metal and the pigment titanium dioxide. TiCl4 is a volatile liquid. Upon contact with humid air, it forms thick clouds of titanium dioxide and hydrochloric acid, a reaction that was formerly exploited for use in smoke machines. It is sometimes referred to as "tickle" or "tickle 4" due to the phonetic resemblance of its molecular formula to the word.

<span class="mw-page-title-main">Tebbe's reagent</span> Chemical compound

Tebbe's reagent is the organometallic compound with the formula (C5H5)2TiCH2ClAl(CH3)2. It is used in the methylidenation of carbonyl compounds, that is it converts organic compounds containing the R2C=O group into the related R2C=CH2 derivative. It is a red solid that is pyrophoric in the air, and thus is typically handled with air-free techniques. It was originally synthesized by Fred Tebbe at DuPont Central Research.

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

The Petasis reagent, named after Nicos A. Petasis, is an organotitanium compound with the formula Cp2Ti(CH3)2. It is an orange-colored solid.

Vanadocene dichloride is an organometallic complex with formula (η5-C5H5)2VCl2 (commonly abbreviated as Cp2VCl2). It is a structural analogue of titanocene dichloride but with vanadium(IV) instead of titanium(IV). This compound has one unpaired electron, hence Cp2VCl2 is paramagnetic. Vanadocene dichloride is a suitable precursor for variety of bis(cyclopentadienyl)vanadium(IV) compounds.

<span class="mw-page-title-main">Hapticity</span> Number of contiguous atoms in a ligand that bond to the central atom in a coordination complex

In coordination chemistry, hapticity is the coordination of a ligand to a metal center via an uninterrupted and contiguous series of atoms. The hapticity of a ligand is described with the Greek letter η ('eta'). For example, η2 describes a ligand that coordinates through 2 contiguous atoms. In general the η-notation only applies when multiple atoms are coordinated. In addition, if the ligand coordinates through multiple atoms that are not contiguous then this is considered denticity, and the κ-notation is used once again. When naming complexes care should be taken not to confuse η with μ ('mu'), which relates to bridging ligands.

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

Organotitanium chemistry is the science of organotitanium compounds describing their physical properties, synthesis, and reactions. Organotitanium compounds in organometallic chemistry contain carbon-titanium chemical bonds. They are reagents in organic chemistry and are involved in major industrial processes.

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

Dicarbonylbis(cyclopentadienyl)titanium is the chemical compound with the formula (η5-C5H5)2Ti(CO)2, abbreviated Cp2Ti(CO)2. This maroon-coloured, air-sensitive species is soluble in aliphatic and aromatic solvents. It has been used for the deoxygenation of sulfoxides, reductive coupling of aromatic aldehydes and reduction of aldehydes.

Niobocene dichloride is the organometallic compound with the formula (C5H5)2NbCl2, abbreviated Cp2NbCl2. This paramagnetic brown solid is a starting reagent for the synthesis of other organoniobium compounds. The compound adopts a pseudotetrahedral structure with two cyclopentadienyl and two chloride substituents attached to the metal. A variety of similar compounds are known, including Cp2TiCl2.

<span class="mw-page-title-main">Organozirconium and organohafnium chemistry</span>

Organozirconium chemistry is the science of exploring the properties, structure, and reactivity of organozirconium compounds, which are organometallic compounds containing chemical bonds between carbon and zirconium. Organozirconium compounds have been widely studied, in part because they are useful catalysts in Ziegler-Natta polymerization.

Zirconocene dichloride is an organozirconium compound composed of a zirconium central atom, with two cyclopentadienyl and two chloro ligands. It is a colourless diamagnetic solid that is somewhat stable in air.

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

Sodium cyclopentadienide is an organosodium compound with the formula C5H5Na. The compound is often abbreviated as NaCp, where Cp is the cyclopentadienide anion. Sodium cyclopentadienide is a colorless solid, although samples often are pink owing to traces of oxidized impurities.

In organometallic chemistry, bent metallocenes are a subset of metallocenes. In bent metallocenes, the ring systems coordinated to the metal are not parallel, but are tilted at an angle. A common example of a bent metallocene is Cp2TiCl2. Several reagents and much research is based on bent metallocenes.

Molybdocene dichloride is the organomolybdenum compound with the formula (η5-C5H5)2MoCl2 and IUPAC name dichlorobis(η5-cyclopentadienyl)molybdenum(IV), and is commonly abbreviated as Cp2MoCl2. It is a brownish-green air- and moisture-sensitive powder. In the research laboratory, it is used to prepare many derivatives.

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

Titanocene pentasulfide is the organotitanium compound with the formula (C5H5)2TiS5, commonly abbreviated as Cp2TiS5. This metallocene exists as a bright red solid that is soluble in organic solvents. It is of academic interest as a precursor to unusual allotropes of elemental sulfur as well as some related inorganic rings.

<span class="mw-page-title-main">Pentamethylcyclopentadienyl ruthenium dichloride dimer</span> Chemical compound

Pentamethylcyclopentadienyl ruthenium dichloride is an organoruthenium chemistry with the formula [(C5(CH3)5)RuCl2]2, commonly abbreviated [Cp*RuCl2]2. This brown paramagnetic solid is a reagent in organometallic chemistry. It is an unusual example of a compound that exists as isomers that differ in the intermetallic separation, a difference that is manifested in a number of physical properties.

<span class="mw-page-title-main">Bis(cyclopentadienyl)titanium(III) chloride</span> Chemical compound

Bis(cyclopentadienyl)titanium(III) chloride, also known as the Nugent–RajanBabu reagent, is the organotitanium compound which exists as a dimer with the formula [(C5H5)2TiCl]2. It is an air sensitive green solid. The complex finds specialized use in synthetic organic chemistry as a single electron reductant.

<span class="mw-page-title-main">(Cyclopentadienyl)titanium trichloride</span> Chemical compound

(Cyclopentadienyl)titanium trichloride is an organotitanium compound with the formula (C5H5)TiCl3. It is a moisture sensitive orange solid. The compound adopts a piano stool geometry.

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

Decamethyltitanocene dichloride is an organotitanium compound with the formula Cp*2TiCl2 (where Cp* is C5(CH3)5, derived from pentamethylcyclopentadiene). It is a red solid that is soluble in nonpolar organic solvents. The complex has been the subject of extensive research. It is a precursor to many organotitanium complexes. The complex is related to titanocene dichloride, which lacks the methyl groups.

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

Hafnocene dichloride is the organohafnium compound with the formula (C5H5)2HfCl2. It is a white solid that is sparingly soluble in some organic solvents. The lighter homologues zirconacene dichloride and titanocene dichloride have received much more attention. While hafnocene is only of academic interest, some more soluble derivatives are precatalysts for olefin polymerization. Moreso than the Zr analogue, this compound is highly resistant to reduction.


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Further reading