The preparation and structure of bis(tri-p-tolylphosphine)(azobenzene)nickel(0), Ni[P(C₆H₄CH₃)₃]₂[(C₆H₅NNC₆H₅]

The compound, bis(tri-p-tolylphosphine)(azobenzene)nickel(0), Ni[P(C₆H₄CH₃)₃]₂[C₆H₅NNC₆H₅], has been prepared by the reaction of tri-p-tolylphosphine and azobenzene with bis(1,5-cyclooctadiene)nickel(0) in hexane. The structure of the complex has been determined at room temperature from three-dimensional X-ray data collected by counter methods. The structure has been refined by least-squares techniques to a final R factor on F of 6.6% based on 3516 observations above background. The material crystallizes in the triclinic space group C¹_i-P1, with two molecules in a cell of dimensions a = 12.448(11), b = 17.671(20), c = 12.226(13) Å, α 95.79(5). β 118.34(3), 97.14(4)°. The Ni atom has trigonal coordinationif the azoben- zene is regarded as a monodentate ligand. The inner coordination sphere is essentially planar, with the two nitrogen atoms equidistant from the metal atom. The structure is compared with that of Ni[(CH₃)₃CNC]₂[C₆H₅NNC₆H₅], a similar complex studied earlier in this laboratory. Observed differences in the coordinated azobenzenes have been related to observed spectral differences.