Thallium complexes hydrides

Alkali metal 1-methyl- and 1-phenyl-borinates are also available from bis(borinato)cobalt complexes (see below) on treatment with sodium or potassium cyanide in an aprotic solvent like acetonitrile. Cobalt cyanide precipitates and the alkali borinate remains in solution. After addition of thallium(I) chloride to some complexes, thallium 1-methyl- or 1-phenyl-borinate could be isolated as pale yellow solids, the only main group borinates isolated hitherto. They are insoluble in most organic solvents but readily soluble in pyridine and DMSO. The solids are stable on treatment with water and aqueous potassium hydride, but are decomposed by acids <78JOM(153)265). 

Allyl hydride complexes of osmium are isolated from treatment of phosphine-substituted osmacyclobutane complex 114 with a thallium salt (Scheme 21). The reaction initially provides a mixture of an unstable -benzyl hydride complex 115 and the rf -allyl hydride complex 116 the -benzyl intermediate ultimately isomerizes to the latter complex, a very rare instance of isolable allylic hydride products generated from a starting metallacyclobutane <2004OM4858>. 

Reactions.—Cleavage of prenyl and allyl ethers has been discussed earlier in this Report. Some aliphatic ethers can be cleaved by thallium(iii) nitrate in acetic anhydride.New reagents for the demethylation of aryl methyl ethers include the stable, crystalline, and easily handled complexes of boron halides BBr3 and BCI3 with dimethyl sulphide,and the salt obtained from treatment of N-methylaniline with sodium hydride in HMPA. The latter system cleaves methyl aryl ethers more readily than benzyl aryl ethers. 

No monomeric alkali metal alkyls or aryls are known, as those crystal structures which have been determined indicate electron-deficient, e.g. (MeLi), or ionic (K Me ) constitutions. The dialkyls of the lighter second group metals are mostly electron-deficient dimers or polymers, but those of zinc, cadmium and mercury are monomers with a linear structure as expected from participation of one (metal) s and one p orbital (with or without dji participation). In the third group the pattern is more complex. Whereas the trialkylboranes are monomeric, boron hydrides (and alkyl hydrides) and polyboron compounds form electron-deficient structures. Aluminium alkyls and alkyl hydrides are normally electron-deficient dimers or trimers gallium trialkyls are monomeric though the trivinyl is a dimer trimethylindium is a weakly associated tetramer in the solid state, otherwise all indium and thallium trialkyls appear to be monomers. 

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