Pentaphenyl antimony

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... 

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). 

For the pentaarylphosphorane and pentaarylarsorane type the combination of each two phenyl groups to form a 2,2 -biphenylylene ligand had led to spirocyclic species which generally were of much higher stability then the simple pentaphenyl derivatives. In the antimony series, however, such a distinct stabilizing effect was no longer observable. 

Mass spectra of pentaphenyl-, methyl bis-2,2 -biphenylene and phenylbis-2,2 -biphenylene antimonys have been investigated by Hellwinkel et al.51. Mossbauer spectra of Ph5Sb and Ph5Sb 1/2 C6H12 have been determined by Long et al.52 and IS values of 4.6 and 4.2 0.1 mm/s respectively have been reported. 

Beta-decay of 125antimony in pentaphenyl antimony formed tetraphenyl 125tellurium in 60% yield7,8. 

Beta-decay of antimony in pentaphenyl antimony formed tetraphenyl tellurium in 60% yield . 

The organic moiety most suitable to establish a stable sigma carbon-metal bond in difficult cases seems to be an electronegative radical such as the phenyl or acetylenic group. Examples of new and interesting phenyl organometallic compounds are triphenylchromium (64), pentaphenyl-antimony, tetraphenyltellurium, and triphenyliodine (134)- Nickel and other metals can be transformed into acetylides (89). 

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. 

In contrast, the less-strained four-rr-electron cyclopentadienyl cation is very unstable. The p R+ has been estimated as -40, using an electrochemical cycle. Solvolysis of cyclopentadienyl halides assisted by silver ion is extremely slow, even though the halide is in an allylic position. " When the bromide and antimony pentafluoride react at -78°C, the product has an EPR spectrum indicating that the cyclopentadienyl cation is a triplet, in agreement with HMO and more sophisticated MO calculations. The pentachloro derivative is also a triplet, but the pentaphenyl ion is a singlet. ... 

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