Tungsten complexes phosphinidene

Cowley and coworkers have reported two other reactions. One is the reaction of the silylphosphide 11a with dichloroborane, which afforded the diphosphadiboratane, resulting in the formation of the phosphaborene by flash-vacuum pyrolysis (equation 101)135. The other is the reaction of the silylphosphide 11a with ( j5-C5H4Me)2WCl2, which gave compounds 14 and 15 (equation 102)136. A phosphinidene tungsten complex was assumed to be a reactive intermediate. 

As we discovered that bulky electrophilic terminal phosphinidene tungsten complexes with CsMes or CH(SiMe3)2 at the phosphoms do not dimerize in the absence of trapping reagents [16, 17], we became interested in their fate. 

Although the chemistry of short-lived electrophilic terminal phosphinidene tungsten complexes [11, 12] has received increased attention during the recent years, partially because of the versatility of 2//-azaphosphirene complexes [13, 14], only a single example of a rearrangement yielding a P-Cl-substituted ri -phosphaalkene complex - via a 1,2-chlorine shift - has been reported so far [15]. 

Phosphinidenes (R-P), short-lived, reactive intermediates that are isoelec-tronic with nitrenes and carbenes, are accessible by fragmentation of phos-phiranes, phosphol-3-enes, triazaphospholenes, and oxazaphospholenes and can be characterized by trapping reactions. The metal-complexed species [R-P-M, e.g., M = W(CO)5] are more stable (but also not isolable) and react more selectively. As a model example we describe the transformation of (3,4-dimethyl-l-phenylphosphole)(pentacarbonyl)tungsten 4 with dimethyl acetylenedicarboxylate to the 7-phosphanorbomadiene derivative 5.11 The (phosphinidene)(pentacarbonyl)tungsten complex 6 is generated from the latter by a [4+ 1]-cycloreversion and trapped with diphenylacetylene via a [2+1]-cycloaddition to furnish the triphenyl-2-phosphirene complex 7 (Scheme l).12... 

Summary Thermal rearrangement of the short-lived phosphinidene complex [(OC)5W PCH(SiMe3)2 ] yielded stereoselectively an ri -f-phosphaalkene tungsten complex via 1,2-silyl shift this product was isolated and unambiguously characterized by multinuclear NMR spectroscopy. We also report preliminary studies on the reactivity of this T] - -phosphaalkene complex toward (Me2N)3P, cyclopentadiene and DMAD. 

Fig. 2. Phosphinidene (la, lb) and phosphaalkene tungsten complexes (2a, 2b) and transition states (TS a, TS b).

The phosphinidene-bridged system 140 was obtained by reaction of W(CPh)( / -CjH5)(CO)2 with the tungsten phosphine complex shown in [Eq. (127) (150). CuCl-induced elimination of the substituted benzene... 

Further progress has been reported in the area of terminal phosphinidene complexes. A range of tungsten phosphinidene... 

As we have just learned, the attempt to synthesize a bridging phosphinidene complex without zr-donor contribution from the phosphorus atom lone pair failed for the W/Fe couple due to the ligand lability of the tungsten fragment. The... 

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