Thallium cyclopentadienyl complexes

Cyclopentadienylthallium is a light yellow solid that decomposes at 230°. It is stable for several months if stored under N2 in a Schlenk flask kept in the dark. Slow decomposition takes place in the air and light, whereupon the solid turns brown, but pure product may be sublimed away from this material. The IR spectrum shows absorption bands at 3022, 1584, 995, and 725 cm" Cycloi>entadienylthallium is insoluble in most organic solvents. It may be handled in air, and it is normally heated at reflux in THF solution with the substrate for about 2h under an inert gas atmosphere. When allowed to react with metal halides, the insoluble thallium halide produced may be filtered from the reaction solution. Most cyclopentadienyl complexes are air- and moisture-sensitive and should be handled with appropriate techniques. ... 

The preparation of two cyclo-octatetraene-gold complexes, (ct)AuCl and (cot)-AU2CI4, has been reported. The structures of biscyclo-octatetraenyl complexes of titanium, vanadium, thallium, and uranium, were deduced from their i.r. spectra. Protonation of (p-cyclo-octatetraene) (p-cyclopentadienyl) complexes has been studied. For the ruthenium and osmium complexes protonation occurs on the eight-membered ring to give CgH moiety co-ordinated to the metal atom via both an T -alkyl and an olefin-metal bond. For the cobalt and rhodium complexes a bicyclic cation (287) is produced which undergoes isomerization to the monocyclic (288). ... 

Section II. A regioselective introduction of disilanyl bridges is necessary in the process to synthesize complexes with ligands of types 36 or 37109, and this has been made possible by methylation of the cyclopentadienyl fragments. Due to prototropic rearrangements, the protonated derivatives of 36 and 37 exist as a complicated mixture of isomers. The synthesis of the thallium derivative of 37109 is shown in equation 51. 

Two arene cyclopentadienyl osmium complexes of type 191 have been prepared in moderate yields (17-43%) by reacting precursor 144 with thallium cylopentadienide in acetonitrile (73). 

In a first approximation supra-Cp metal complexes can be prepared the same way as normal or other Cp-metal and organo-metal bonds in general. The methods used most often (see Appendix) are the metathesis reaction [Eq. (1)] followed in number by oxidative additions (Eq. (2)] and metallation/deprotonation reactions [Eq. (3)]. The latter is especially important for the cyclpentadienyl alkali metal compounds. A useful variation of reaction (3) is the formation of CpTl in an acid/base reaction from cyclopentadiene and thallium ethoxide [Eq. (3b)]. This represents a convenient route to cyclopentadienylthallium compounds, which are also valued (in place of Cp alkalis) as mild Cp-transfer reagents for the synthesis of difficultly isolable cyclopentadienyl derivatives (77). 

Two other exchange reactions have been reported cyclopentadienyl-thallium and pentafluorophenylsilver react with a copper(I) halide to give cyclopentadienylcopper complexes (86) and pentafluorophenylcopper (203), respectively. 

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