Carbodiphosphoranes cyclic

Transition Metal Complexes with Cyclic Carbodiphosphoranes. 82... 

Transition metal complexes of coordination mode I with the cyclic carbodiphosphorane shown in Fig. 13 were obtained upon reacting the ligand with CuCl (46), [AuCl(SMe)2] (Cl exchange by Ot-Bu gives (47) and (48)) [138], [ClRh(CO)2]2 (49), [ClRh(nbd)]2 (50), or [ClPd(aUyl)]2 (51) [39 2]. A collection of the metal complexes is presented in Fig. 29. 

Cyclic double ylids with aliphatic ring members occur solely as carbodiphosphoranes (24, 25). The related benzo-heterocycle exists as a 1,3-bis-ylid IQ, however, and is easily transformed into a cyclic diphosphonium-triple-ylid 1A (26). 

From carbodiphosphoranes R3P=C=PR3 and dialkyl-gold(III) halides, cyclic ylide complexes containing four Au-C <7-bonds are obtained in a multiple transylidation reaction (equation 24). Related thiophosphorus ylides and sulfonium and sulfoxonium ylides are equally effective in the formation of Au-C <7-bonds, and a series of analogous gold thiophosphonium and sulfoxonium-methyhde complexes is available (equations 25-27). ... 

Carbodiphosphoranes (bistriorgano)phosphoranylideneniethanes, hexaorganocarbodiphosphoranes) may be generated from suitable phosphonium salt precursors by dehydrohalogenation or dehalogena-tion. Since the first synthesis of hexaphenylcarbodiphosphorane, a series of symmetrical, unsymmetri-cal, mixed alkyl/phenyl, cyclic and difunctional carbodiphosphoranes have been prepared. Compounds synthesized until 1984 have been listed. 

The formation of the phosphine (79) on base-treatment of methyltrimesityl-phosphonium bromide is the only reported example of an uncatalysed Stevens rearrangement of a phosphonium ylide. However, Schmidbaur has now shown that this is incorrect and the product is in fact the phosphine (81), probably formed via the tautomeric ylide (80). Attempts to prepare the carbodiphos-phorane (82) led to a related reaction to give the cyclic carbodiphosphorane (83). 

Cyclic carbodiphosphoranes with localised multiple bonds can be prepared in scheme... 

Bertrand and coworkers have reviewed the topic of stable carbenes based on scaffolds other than diaminocarbenes [47]. Diphosphinocarbenes, aminophosphi-nocarbenes, cyclic (alkyl)amino carbenes, cyclic (amino)ylidic carbenes, cycloprope-nylidenes, cyclic bent allenes, carbodiphosphoranes, and vinylidenephosphoranes have all been reported (examples 37-44, respectively, in Figure 1.24a). Use of the [RhCl(CO)2(L)j system for measuring TEPs allows the electron-donating ability of these systems to be ranked and compared to those of NHCs and abnormally bound NHCs (Figure 1.24b). 

Gold(I) complexes bearing bulky cyclic carbodiphosphorane ligands (Fig. 3) showed for the first time to be active in the hydroalkoxylation of acrylonitrile yielding the anti-Markovnikov product [174]. 

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