Penta-alkyls and aryls

Penta-alkyls and aryls. The penta-alkyls and -aryls R5M are of interest both structurally and in connection with the relative stabilities of the H-S oxidation state. Only antimony appears to form a pentamethyl derivative, MesSb (a liquid bp 126-127°, from MeLi + Me3Sb or Me4SbBr), which is surprisingly thermally stable, and unlike trimethylstibine it does not inflame in the air, though it oxidizes quickly and is decomposed by water. Its vibrational spectra are consistent with a trigonal bipyramidal structure. With an excess of methyl-lithium it forms the salt Li SbMe4.  

All three Group VB metals, like phosphorus, form crystalline penta-phenyl derivatives PhjM. An X-ray diffraction study of the antimony compound has shown a square pyramidal arrangement of phenyl groups 

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Antimony forms nnmerons stable pentavalent organo-metallic componnds among these are penta alkyls and aryls, mixed organohalides, and varions chalcogen and nitrogen derivatives. 

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