PREPARATIONS AND REACTIONS OF SOME HYDRIDODINITROGENTRIALKYLPHOSPHINE COMPLEXES OF RHODIUM(I) - STRUCTURE OF A DINITROGEN-BRIDGED RHODIUM(I) DIMER, [RHH(P(I-PR)3)2]2(MU-N2)

The reduction of RhCl3 - 3 H2O by sodium amalgam in THF solution under an atmosphere of N2 and in the presence of an excess of a phosphine ligand has resulted in the formation of the hydridodinitrogen complexes RhH(N2)-(PPh(t-Bu)2)2 (I), RhH(N2)(P(t-Bu)3)2 (II), and [RhH(P(cyclo-C6H11)3)2] 2(μ-N2)(V), and a hydridotrisphosphine complex RhH(P(i-Pr)3)3 (X). The dinitrogen coordination is stable in I but N2 is readily lost from other dinitrogen complexes, permitting the isolation of three-coordinate hydridobisphosphine rhodium(I) complexes RhH(P(t-Bu)3)2 (VII) and RhH(P(cyclo-C6H11)3)2 (VIII). Trihydrido complexes RhH3L2 (L = PPh(t-Bu)2 (XI), P(t-Bu)3 (XII), P(cyclo-C6H11)2 (XIII), and P(i-Pr)3 (XIV)) have been synthesized by the reaction of the above rhodium (I) compounds with H2. By treatment of the corresponding trihydrido complexes with N2 we have been able to obtain RhH(N2)-(P(cyclo-C6H11)3) 2 (III) and RhH(N2)(P(i-Pr)3) 2 (IV). Loss of N2 from IV results in the formation of [RhH(P(i-Pr)3)2]2(μ-N2) (VI) and RhH(P(i-Pr)3)2 (IX). The crystal and molecular structure of [RhH(P(i-Pr)3)2]2(μ-N2) (VI) has been determined at -85°C. The compound crystallizes in the triclinic space group C{A figure is presented}P1 with two molecules in a cell dimensions a 12.703(16), b 16.455(16), c 11.389(8) Å, α 90.25(9), β 103.87(3), γ 97.58(3)°, V 2289 Å3. The final conventional and weighted agreement indices on Fo for Fo2τ3σ(Fo2) are 0.051 and 0.060, respectively. The dinitrogen ligand of VI linearly bridges two planar RhHP2 fragments with NN separation of 1.134(5) Å and an average RhN bond distance of 1.977(6) Å. The dihedral angle between the two RhHP2 fragments is 55.2°. Overall, the dimeric complex effectively has D2 (222) symmetry. © 1979.