Pentamethyl antimony

With the exception of nitrogen, all of the Group Vb elements are expected to form pentacoordinate compounds in their 5+ oxidation state, and this is, indeed, the case with some of the halides, alkoxides, etc. It was not until the pioneering work of Georg Wittig and his collaborators, however, that the first examples of pentaorganyls of these borderline elements between metals and metalloids were reported (95-99, 102, 104). In this early investigation, a complete set of the pentaphenyls could be obtained and characterized (95-99, 102), but apart from the pentamethyl-antimony case, all attempts for the preparation of pentaalkyl derivatives failed (104). 

In analogy with these reactions Wittig and Torsell500 prepared pentamethyl-antimony by interaction of methyllithium and trimethylstibine dibromide or tetramethylstibonium iodide. 

Antimonate, tris(ethyl dithiocarbonate)-electron pair, 37 Antimony, biphenyltriphenyl-stereochemistry, 46 Antimony, pentaflnoro-lone electron pair structure, 50 Antimony, pentamethyl- H NMR, 41 Antimony, pentaphenyl-stereochemistry, 40 structure, 39 Antimony, pentatolyl-stereochemistry, 40... 

Pentamethylphospforane, P(CH3)5, is unknown, but both arsenic and antimony form stable pentamethyl derivatives. Bi(CH3)5 explodes on warming to room temperature. P, As, Sb and Bi all from solid pentaphenyl derivatives, the least stable of these compounds is BiPhj. 

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. ... 

---