Complex bridging phosphinidene

Fig. 7.21 P chemical shift values of a series of complexes with a bridging phosphinidene ligand...

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... 

The difference in the phosphorus resonance for a terminal and a bridging phosphinidene complex can be seen in a series of zirconium complexes shown in Figs. 7.29 and 7.30. 

Phosphine sulfides, with trinuclear Ru clusters, 6, 748 Phosphinidene-bridged ditantalum(IV) complexes, preparation, 5, 183 Phosphinidenes... 

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... 

Transition metal phosphinidene complexes were originally prepared in order to access what was expected to be a rich chemistry of phosphorus(I)T However, terminal phosphinidenes have been found to be difficult to prepare, partly because they tend to either catenate or bridge. This is a manifestation of the double-bond rule for the main group elements. However, breakthroughs in syntheses of these complexes came about through the use of devious synthetic techniques in combination with sterically encumbered ligands. 

Heating toluene solutions of 25-27 to 70°C in the presence of Pd/C resulted in dehydrogenation and formed neutral dinuclear phosphinidene-bridged zirconocene(iv) complexes (Scheme 12). In the case of 27, dehydrogenation proceeded in refluxing toluene without a catalyst. 

The bridging zirconium phosphinidene complexes in Fig. 7.30 are expected to resonate upheld from the terminal ones in Fig. 7.29, since terminal phosphinidene complexes are far better suited for. -donor interactions of the phosphorus atom towards the metal than are the bridging ligands. 

Rather fewer bridged phosphide complexes of type (8.54b) have been prepared, and known phos-phinidene complexes of type (8.54c) are even fewer in number. Phosphide groups function as p-type ligands, whereas in phosphinidene complexes the P atom may be linked to various numbers of metal atoms although it is usually 3 or 4. 

The complexes with a double bond M=0 and M=NR, i.e. metal-oxo and metal-imido are isoelectronic to metal-carbene complexes and show, as the latter, a rich chemistry, all the more so as the binary complexes M(=0)n and M(=NR)n are well known. - - The phosphinidenes M=PR and the nitrido complexes M=N, isoelectronic to metal carbynes, are also known. All these ligands can bridge two or three metals, in which case there is no multiple bond. 

Phosphido- and phosphinidene-bridged complexes have been prepared from the non-metal-metal bonded [Gp2Fe2(GO)4(/i-PPhR)] (R = H, Me, Ph, GH2SiMe3), photolysis resulting in GO loss and formation of [Gp2Fe2(GO)2(/i-GO)(/i-PPhR)], while reaction with KOBu at —78°G (R = H) affords the unstable phosphinidene complex [Cp2Fe2(CO)4(Ai-PPh)]+. ... 

Typical metal frameworks for bridging /X3-phosphinidene (//3-PR) clusters (cf. Scheme 1) involve Fe3 triangles 48-50, and an acyclic, folded Fe3 linkage 51, and tetrairon //4-PR complexes of 12- and 13-types (Scheme 1) are also known (COMC (1995)). 

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