MOLECULAR SOLID-STATE ORGANOMETALLIC CHEMISTRY OF TRIPODAL (POLYPHOSPHINE)METAL COMPLEXES - CATALYTIC-HYDROGENATION OF ETHYLENE AT IRIDIUM

The solid-gas reactions of [(triphos)Ir(H)2(C2H4)]BPh4 (1) with CO, C2H4, and H-2 are described [triphos = MeC(CH2PPh2)3]. The gaseous reactants promote the elimination of ethane from 1 and the formation of [(triphos)Ir(CO)2]BPh4, [(triphos)Ir(C2H4)2]BPh4, and [(triphos)Ir(H)2]BPh4, respectively. The latter 16-electron species is isolable in the solid state at temperatures <70-degrees-C. At higher temperatures, [(triphos)Ir(H)2]+ dimerizes in the solid state to give the tetrahydride [(triphos)HIr(mu-H)2HIr(triphos)]2+. Dimerization is avoided when the unsaturated fragment is incorporated into the lattice of a polyoxometalate cluster such as PW12O403-. The complex [(triphos)Ir(H)2(C2H4)]BPh4 is an effective catalyst for the hydrogenation of ethylene in the solid state at 60-degrees-C. Comparisons are made with analogous fluid solution-phase systems.