Binuclear platinum-iridium complexes: synthesis, reactivity and luminescence.

The chemistry of the heterobinuclear platinum–iridium complex [PtIr(CO)3(μ-dppm)2][PF6], 1, dppm = Ph2PCH2PPh2, is described. The reaction of a hydride with 1 gave [HPtIr(CO)2(μ-dppm)2], by displacement of the carbonyl ligand from platinum, while reaction of 1 with dihydrogen, hydrogen chloride or Ph2MeSiH gave the fluxional complex [PtIrH4(CO)(μ-dppm)2][PF6], [PtIrH2Cl2(CO)(μ-dppm)2][PF6], or [PtIrH(SiMePh2)(CO)2(μ-dppm)2][PF6], respectively, by oxidative addition at iridium. Complex 1 reacted, often regioselectively, with several alkynes to give the μ–η1,η1 bridging alkyne complexes [PtIr(μ-RCCR′)(CO)2(μ-dppm)2][PF6], R = H, R′ = Ph, 4-C6H4Me, CO2Me; R = Ph, R′ = CO2Me; R = R′ = CO2Me. The complex [PtIr(μ-HCC-4-C6H4Me)(CO)2(μ-dppm)2][PF6] reacted reversibly with CO to give [PtIr(μ-HCC-4-C6H4Me)(CO)3(μ-dppm)2][PF6] and [PtIr(CO)3(μ-dppm)2][PF6], 1. With HCl, [PtIr(μ-HCC-4-C6H4Me)(CO)2(μ-dppm)2][PF6] reacted to give [PtIrHCl(μ-HCC-4-C6H4Me)(CO)2(μ-dppm)2][PF6], by oxidative addition at iridium, and then the alkenylplatinum derivative [PtIrCl{HCCH(4-C6H4Me)}(CO)2(μ-dppm)2][PF6]. [PtIr(μ-HCC-4-C6H4Me)(CO)2(μ-dppm)2][PF6] reacted slowly with dihydrogen to give 4-MeC6H4CHCH2 and [PtIrH4(CO)(μ-dppm)2][PF6]. The complex [PtIr(μ-HCCPh)(CO)2(μ-dppm)2][PF6] is intensely luminescent in solution at room temperature, with features characteristic of a d8–d8 face-to-face complex.