Synthesis, reactions and characterization of homo- and heterobimetallic Mo/W μ-alkyne complexes containing functionally substituted cyclopentadienyl ligands: The crystal structure of [ ν5-MeO 2CC 5H 4(CO) 2MoW(CO) 2C 5H 4Et- ν5]( μ-C 2H 2)

Abstract

Through in situ reaction of acetylene with a mixture of three triply bonded complexes [ ν 5-R 1C 5H 4(CO 2Mo] 2, [ ν 5-R 2C 5H 4(CO) 2W] 2, ν 5-R 1C 5H 4(CO) 2MoW(CO) 2C 5H 4R 2- ν 5, prepared by refluxing a diglyme solution of two dimers [ ν 5-R 1C 5H 4 (CO) 3Mo] 2 and [ ν 5-R 2C 5H 4(CO) 3W] 2, five new μ-alkyne compounds [ ν 5-MeO 2CC 5H 4(O) 2W] 2( μ-C 2H 2) ( 2a), [ ν 5-MeO 2CC 5H 4(CO) 2MoW(CO) 2C 5H 4Et- ν 5] ( μ-C 2H 2) ( 3a, R 1 = H, R 2 = CO 2Me; 3b, R 1 = C(O)Me, R 2 = H; 3c, R 1 = C(O)Me, R 2 = CO 2Me; 3d, R 1 = CO 2Me, R 2 = Et) were obtained. Further reaction of 1b with PhCHO in aqueous NaOH solution gave an aldol condensation product, [ ν 5-PhCHCHC(O)C 5H 4(CO) 2Mo] 2 (μ-C 2H 2) ( 4), whereas 3b and 3c reacted with NaBH 4 in MeOH to afford corresponding reductive products [ ν 5-MeCH(OH)C 5H 4(CO) 2MoW(CO) 2C 5H 4R- ν 5] ( 5, R = H; 6, R = CO 2Me). All these new complexes were fully characterized by combustion analysis, IR, 1H NMR and mass spectroscopy, and by X-ray crystallography.