Insertion of alkynes into molybdenum–phosphine and –carbon bonds. Crystal structures of the alkyne–ylide complex [MoO(SC6H2Pri3-2,4,6)2{η2-CHC(tol)}{C(tol)CHPMePh2}] (tol = C6H4Me-4) and the phosphonium–alkylidene complex [MoO(SC6H2Pri3-2,4,6)3{C(Ph)CHC(Ph)CH2PMe2Ph}]

Abstract

Treatment of [MoH(SC₆H₂R₃-2,4,6)₃(PMePh₂)] 1a (R = Me or Prⁱ) with HCCR′ (R′Ph or C₆H₄Me-4) in tetrahydrofuran (thf)–MeOH gave the diamagnetic ylide complexes [MoO(SC₆H₂R₃-2,4,6)₂{η²-CHC(R′)}{C(R′)CHPMePh₂}] 2, the source of the oxide ligand most probably being adventitious water. The crystal structure of one example, 2a (R′ = C₆H₄Me-4, R = Prⁱ), confirms their structure [Mo–O 1.69(2), Mo–C_ylide 2.12(3), Mo–C_alkyne 2.07(3) and 2.21(3) Mo–S 2.410(9) and 2.475(9), Ph₂MeP–C 1.77(3)Å]. Treatment of [MoH(SC₆H₂Prⁱ₃-2,4,6)₃(PMe₂Ph)₂] 1b with HCCPh under similar conditions gave the phosphonium–alkylidene complex [MoO(SC₆H₂Prⁱ₃-2,4,6)₃{C(Ph)CHC(Ph)CH₂PMe₂Ph}] 3, whose crystal structure has been determined [Mo–O 1.691(3), Mo–C 1.990(5), Mo–S 2.424(1), 2.434(1) and 2.432(1), PhMe₂P–C 1.808(6) Å]. Spectroscopic data for these complexes are discussed. Neither PhCCPh nor PhCCMe reacted with 1b.