Substitution reactions of a heterodimetallic molybdenum–manganese complex

Abstract

The reactions of [MoMn(µ-C₅H₄PPh₂)(CO)₇]1 with phosphines and with isonitriles have been studied. Less bulky phosphines give derivatives of 1 of the type [MoMn(µ-C₅H₄PPh₂)(CO)₆L], which are monosubstituted at the manganese atom [L = PPh₂H 2a, PPh₂Me 2b, PPhMe₂2c or P(OMe)₃2f] whereas more bulky phosphines substitute only at the molybdenum atom (L = PPh₃3a). Phosphines of intermediate bulk give both types of derivative depending on the reaction conditions (L = PPh₂Et 2e or 3b, PPh₂CHCH₂2d or 3c). Disubstituted derivatives, [MoMn(µ-C₅H₄PPh₂)(CO)₅L₂][L = PPh₂Me 4a, PPh₂CHCH₂4b or P(OMe)₃4c], obtained by reaction of 1 with excess of the appropriate ligand, have one substituent on the manganese and one on the molybdenum atom. Isonitriles give derivatives [MoMn(µ-C₅H₄PPh₂)(CO)₆L](L = CNCH₂Ph 2g or CNBu^t2h) which are monosubstituted at the manganese atom but in a different position to the phosphine derivatives 2a–2f. Thermolysis of the diphenylphosphine derivative 2a gives [MoMn(µ-C₅H₄PPh₂)(µ-H)(µ-PPh₂)(CO)₅]5a and thermolysis of either one of the vinylphosphine derivatives 2d or 3c gives a complex [MoMn(µ-C₅H₄PPh₂)(µ-PPh₂CHCH₂)(CO)₅]6 in which the vinylphosphine ligand is bonded through phosphorus to manganese and through the vinyl group to the molybdenum atom. Hydrogenation of 6 gives 3b in a reaction which involves a transfer of the co-ordination of the vinylphosphine phosphorus atom from manganese to molybdenum. Addition reactions of 6 with CO and P(OMe)₃ involve a similar transfer to give [MoMn(µ-C₅H₄PPh₂)(CO)₆(PPh₂CHCH₂)]3c and [MoMn(µ-C₅H₄PPh₂)(CO)₅(PPh₂CHCH₂){P(OMe)₃}]7 respectively. The structures of [MoMn(µ-C₅H₄PPh₂)(CO)₆(PPh₂Et)]3b and [MoMn(µ-C₅H₄PPh₂)(µ-H)(µ-PPh₂)(CO)₅]5a have been determined by X-ray analysis.