IMINOPHOSPHORANE COMPLEXES OF RHODIUM(I) AND X-RAY CRYSTAL-STRUCTURE OF [RH(COD)CL(ET3P=N-PARA-TOLYL)]

New rhodium(I)-iminophosphorane complexes [RhL2Cl(R3P=NR′)], in which the iminophosphorane ligand is coordinating as a two electron donor, have been prepared by bridge splitting reactions in benzene or chloroform between [RhL2Cl]2 (L=CO, L2=COD) and the parent iminophosphoranes R3P=NR′ (1). In solution an equilibrium is established between the product [RhL2Cl(R3P=NR′)] and its constituting compounds. This equilibrium lies completely to the product side for L=CO, whereas for L2=COD it is dependent on the substituents on N and P, the temperature and the molar ratio Rh:R3P=NR′. The molecular structure of [Rh(COD)Cl(Et3P=N-p-tolyl)] (3a) has been determined by means of X-ray crystallography. Complex 3a crystallizes in space group P21/a with a=23.134(4), b=10.946(2), c=8.686(2) Å and β=90.12(2)°, and the structure was refined to R=0.036 by using 6363 independent reflections. The structure of 3a consists of a square planar rhodium complex in which the iminophosphorane is coordinated via the lone pair on nitrogen. Important dimensions are d(RhN)=2.142(3) Å, d(NP)=1.608(3) Å and <(RhNP)=121.0°. © 1990.