Alkyne and CO Coupling Reactions with the Vinylidene Ligand in the Complex Mn2(CO)7[.mu.-.eta.2-C:CMe(CO2Et)

Abstract

Reaction of the vinylidene complex Mn[sub 2](CO)[sub 8][mu]-[eta][sup 2]-C=CMe(CO[sub 2]Et) (1a) with CO (at 1000 psi) at 87[degree]C yielded the new compound (OC)[sub 4]Mn[(EtO[sub 2]C)MeC=CC=OC=OC=CMe(CO[sub 2]-Et)] Mn (CO)[sub 4] (2) in 59% yield and Mn[sub 2](CO)[sub 10]. Compound 2 is believed to have been formed by the carbonylation of the vinylidene ligand, cleavage of a Mn(CO)[sub 5] fragment, and a coupling of two metal groupings containing carbonylated vinylidene ligands. The reaction of 1a with a combination of MeC=VCOEt and CO yielded only the compound (OC)[sub 4]Mn[EtO[sub 2]C)-MeC=CC=CMe(CO[sub 2]Et)]Mn(CO)[sub 4] (3) in 72% yield. Compound 3 contains a 3,4-dimetallo-2,5-bis(ethoxycarbonyl)-2,4-hexadiene group formed by the coupling of two vinylidene ligands at the vinylidene carbon atoms. When the reaction of 1a with MeC=COEt was performed in the absence of CO, the three isomeric products Mn[sub 2](CO)[sub 7](CO)[sub 7](C(Me)C(OEt)C[=CMe(CO[sub 2]Et)]C -(Me)C(OEt)RTBC (4a), Mn[sub 2](CO)[sub 7](C(Me)C(OEt)C[=CMe(CO[sub 2]Et)]C (OEt)C (Me))d Mn[sub 2](CO)[sub 7]-(C(OEt)C(Me)C)CMe(CO[sub 2]Et) C(Me)C(OEt) (4c) were formed in low yields. 12 refs., 5 figs., 16 tabs.