Stepwise and Selective Carborane Substitution in the B(3,6) Positions of a 16<i>e</i> CpCo Half-Sandwich Complex Containing a Chelating <i>ortho</i>-Carborane-1,2-dithiolate Ligand

The reactions of the 16e half-sandwich complex, CpCo(S2C2B10H10) (1), with alkynones at ambient temperature lead to complexes CpCo(S2C2B10H9)(CHCH−C(O)R) (R = Ph (2), 2-naphthyl (3)). Both 2 and 3 are still 16e half-sandwich complexes containing a B(3)-substituted ortho-carborane-1,2-dithiolate ligand. Treatment of 2 with excess alkynes R1CCR2 (R1 = H, R2 = Ph, C(O)Ph, CO2Me; R1 = R2 = CO2Me) affords five complexes, CpCo(S2C2B10H8)(CH2CPh)(CHCH−C(O)Ph) (4), CpCo(S2C2B10H8)(CHCH−C(O)Ph)2 (5), CpCo(S2C2B10H8)(CHCH−CO2Me)(CHCH−C(O)Ph) (6), CpCo(S2C2B10H9)(MeO2C−CC−CO2Me)(CHCH−C(O)Ph) (7), and CpCo(S2C2B10H9)(MeO2C−CC−CO2Me)2(CHCH−C(O)Ph) (8). Complex 4 is an 18e complex bearing a B−CH2 unit. Both 5 and 6 retain a 16e half-sandwich structure but contain a B(3,6)-disubstituted ortho-carborane-1,2-dithiolate ligand. However, in 7 and 8 one or two alkynes are inserted into one of the Co−S bonds to generate 18e species, respectively. Heating 7 leads to the 16e complex, CpCo(S2C2B10H8)(MeO2C−CCH−CO2Me)(CHCH−C(O)Ph) (9), having a B(3,6)-disubstituted ortho-carborane-1,2-dithiolate ligand as in 5 and 6. All complexes were fully characterized by spectroscopic techniques and elemental analysis. The solid-state structures of 2 and 3 and 5−9 were further characterized by X-ray structural analysis.