Pentaalkylstiboranes

It is, therefore, to be expected that a compound such as trimethyl-methylene stiborane, (CHs SbCtE, should be relatively unstable and attempts to synthesize this species would have to be carried out at low temperature. Another difficulty arises from the experimental fact (104) that all conventional methods of synthesis for stibonium ylides lead to pentaalkylstiboranes instead of ylides (see Introduction). Thus mcthyl-ation of (CH3)4SbX or (CHY) sHbX2 halides by organometallic reagents of lithium, magnesium, aluminum, or zinc invariably yield (CHY) 5Sb as the sole product. 

Pentaalkylstiboranes are pale yellow liquids that can be distilled under reduced pressure (Table IV). Although distillation at atmospheric pressure is also possible, it is to be avoided. A violent explosion was reported in one case when a larger quantity of (CH3)6Sb was rectified (still temperature 160°C) (33). When small amounts of IRSb compounds are heated, slow thermal decomposition is observed, which leads to trialkylantimony compounds, alkane and alkene (86a) ... 

The chemical reactions of pentaalkylstiboranes have only recently been studied by a number of groups. The bulk of the reactions, some of which... 

Only toward the strongest nucleophiles do the pentaalkylstiboranes act as Lewis acids. This reaction principle is involved in the interaction of pentamethylantimony with methyllithium, which is believed to yield a hexamethylantimonate complex ... 

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