Phosphine methylenes

The Wittig reaction consists in the replacement of carbonyl oxygen of aldehydes and ketones by a methylene group with the aid of phosphine-methylenes resulting in the formation of cis or trans olefines. The reaction proceeds through the nucleophilic addition of Wittig reagent (phosphine methylene) across the > C = O bond and formation of an intermediate cyclic. 

A somewhat different problem occurs in the question of the structure of, say, the phosphine oxides, the phosphine methylenes or the sul-phoxides. Again in a 3s3p framework the structure of triphenyl phosphine oxide must be written with the oxygen attached by a conventional coordinate link. On the other hand the use of d-orbitals allows the removal of the excess negative charge on the oxygen atom by the formation of a t-bond (Fig. 3). 

Phosphine methylenes, R3p=CH2, are strong Lewis bases and bring about cleavage of Si-M bonds with intermediate formation of an adduct (entries 61 and 65). This is a useful way of synthesizing C-silyl derivatives. 

Not only hydrido derivatives can enter into this reaction entries 68 and 69 show that siloxy compounds and C-silyl-substituted phosphine methylenes also undergo exchange (303, 306, 310). In the latter case, the silyl group with the most electronegative substituents moves to carbon. Respective examples are... 

Eijectron spin resonance spectra alkyls and aryls, 7, 173 anion radicals from acylsilanes, 7, 138 metal nitrosyls, 7, 234 phosphine methylenes, 9, 298 Elimination reactions, 7, 166-167 Exchange reactions ferrocenes, 10, 80, 91 organo-Group II compounds, 8, 170-176... 

Tandem ene reactions of phosphaalkynes with terminal alkenes have been followed by P NMR spectroscopy, and as part of a multinuclear NMR spectroscopy study, P NMR was used to follow the reaction of phosphaalkynes with decaborane to form new phosphaborane compounds (phosphine-methylene ylides), nido-RC(H)PBioHi3. 

P2CjH, Phosphine, 1,2-ethanediyl-bis(dimethyl-iridium complex, 21 100 P2C25H22, Phosphine, methylene-... 

At least three names are available for the compound H3P=CH2. These are phosphine methylene, methylene phosphonium ylid and phosphonium methylide moreover, the compound can be classed as a phosphorane The compound PhjP Rj may be called triphenylphosphonium methylide, tri-phenylphosphonium methanide or triphenyl-methylenephosphorane. The pyridine analogue, C5H5P, has been known variously as phosphobenzene, phosphabenzene, phosphorin, and most recently, phosphinine. The term phosphane for (1) in Table 1.4 and its derivatives is the most recent and the most systematic, but it is difficult to see how the more widespread and firmly rooted term phosphine will ever be replaced. In addition, adoption of the term phosphane would put it in line with such little-used terms as carborane for CH4, nitrane for NH3 and oxane for HjO. 

Methyl phosphine Methylene phosphine Methylidyne phosphine... 

Wittig G, Schollkopf U (1954) Uber Triphenyl-phosphin-methylene als olefinbUdende Reagenzien I. Chem Ber 87(9) 1318-1330... 

On new organic phosphorus bonding III Phosphine methylene derivatives and... 

---