Phosphinidene ligands

An aminophosphinidene complex Cp Os(CO)2 PCl(N-Tr2) was prepared by reaction of [Cp Os(CO)2] with Tr2NPCl2. As with Fischer carbenes (see Fischer-type Carbene Complexes), the nitrogen group stabilizes the electron-deficient phosphorus atom of the phosphinidene ligand. Based on a crystal structure of the ruthenium analog, there is likely... 

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

As a first step towards understanding this phenomenon, it helps to realize that the structure of the chloro-complex in Fig. 7.31 comes from a x-ray crystal structure determination, and is thus the structure of the complex in the solid state and not in solution. It also helps to note that the zirconium moiety is an anion (LF is the counter cation), making the phosphinidene-ligand effectively a two electron donor. 

Square RU4 unit capped on one side by 18 a /Z4-phosphinidene ligand and, on the other, by the benzyne (ortbo-dimetallated benzene). d(Ru-Ru) = 2.791-2.943 A. 

Carbonyl and phosphinidene ligands capping 3 or 4 metals - A CO ligand contributes 2/n electrons to the NVE of a metal atom, n being the number of metal atoms in the cluster that are capped by the carbonyl. 

Complex 114 has a f/oto-trigonal-bipyramidal structure with the phosphinidene ligand capping one face of the OS4 tetrahedron. No X-ray crystallography data are available for 114, but its structure is based on the similarity of the synthetic route and of its IR spectrum to that of the ruthenium analog, 27. Unlike the Ru analog, there is partial rigidity of the carbonyls in 114 as shown by C NMR spectroscopy. 

Hadi GAA, Fromm K, Blaurock S, Jelonek S, Hey-Hawkins E (1997) Organometallic tantalum complexes with phosphine, phosphanido and phosphinidene ligands. Syntheses... 

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