Metal-assisted preparation of the alkenyl ketone and carbonyl complexes from 1-alkyne and H2O: C–C triple bond cleavage of terminal alkyne

Reactions of Cp*RhCl2(PPh3) (1) with 1-alkyne and H2O in the presence of KPF6 generated alkenyl ketone complexes [Cp*Rh(CRdouble bond; length as m-dashCHCOCH2R)(PPh3)](PF6) (2) (R = Ph (a), C6H4−p-Me (b), C6H4-p-COOMe (c), C6H4-p-NO2 (d)). A similar complex [Cp*Rh(CPhdouble bond; length as m-dashCHCOCH2Ph)(PMePh2)](PF6) (2e) was obtained by use of Cp*RhCl2(PMePh2). It was revealed by X-ray analyses of 2b, 2c and 2e that the complexes 2 consist of the five-membered ring structures bound by the carbon and oxygen atoms of the alkenyl ketone group. Similar reactions of Cp*IrCl2(PPh3) (6) or (C6Me6)RuCl2(PPh3) (7) proceeded with a cleavage of C–C triple bond of 1-alkyne without formation of an alkenyl ketone complex, affording the corresponding carbonyl complexes, [Cp*IrCl(PPh3)(CO)](PF6) (8) or [(C6Me6)RuCl(PPh3)(CO)](PF6) (9). The diphosphine complexes [(Cp*MCl2)2{μ-diphos}] (4: M = Rh, diphos = dppm,; 12a: M = Ir, diphos = dppm; 12b: M = Ir, diphos = dppb) gave a Cl-bridged rhodium complex [{Cp*Rh(μ-Cl)}2{μ-dppm}](PF6)2 (5), mono-carbonyl or dicarbonyl iridium complexes,[(Cp*IrCl2){μ-dppm}{Cp*IrCl(CO)}](PF6)(13a) or [{Cp*IrCl(CO)}2{μ-dppb}](PF6)2 (14b), respectively.