CYCLO-TRIPHOSPHORUS AND CYCLO-TRIARSENIC AS LIGANDS IN DOUBLE SANDWICH COMPLEXES OF COBALT AND NICKEL

The reaction of white phosphorus or yellow arsenic with cobalt and nickel tetrafluoroborate in the presence of the tri-(tertiary phosphine) 1, 1, 1-tris(diphenylphosphinomethyl)ethane, CH3C(CH2PPh2)3, triphos, gives a series of metal complexes each containing the novel cyclic P3 or As3 group. These compounds have the general formula [M2(D3)(triphos)2] Yn; (M = Co, Ni; D = P, As; Y- = BF4 -, BPh4 -; n = 1, 2). The X-ray structure determinations performed on the complexes [Ni(P3)- (triphos)2](BPh4)r2.2·5(CH3)2CO, [Co, Ni(P3)(triphos)2](BPh4)2-2(CH3)2CO, and [Co2(As3)(triphos)2](BPh4)2 have shown that the compounds are of double-sandwich structure with two molecules of triphos as external “slices”. The internal layer in each complex is formed by an unprecedented cyclo-triphosphorus or cyclo-triarsenic unit acting as a 3π system which connects the two metal atoms. These double-decker [(triphos)M-μ-η3-D3M(triphos)] Yn complexes are air stable. The number of valence electrons ranges from 31 to 34 along the series of complexes. The number of unpaired electrons, calculated on the basis of the magnetic moments, varies from zero to two electrons for the dinuclear complex cation. This is rationalized by a qualitative MO approach. © 1979, American Chemical Society. All rights reserved.