Synthesis and substitution reactions of a heterodimetallic molybdenum–manganese complex, [MoMn(µ-H)(µ-PPh2)(η5-C5H5)(CO)6]; X-ray crystal structure of [MoMn(µ-H)(µ-PPh2)(η5-C5H5)(CO)4(dppm-PP′)]

Abstract

The photolytic reaction of [MoMn(η⁵-C₅H₅)(CO)₈] with PPh₂H gives [MoMn(µ-H)(µ-PPh₂)-(η⁵-C₅H₅)(CO)₆](1) and [Mo₂(µ-H)(µ-PPh₂)(η⁵-C₅H₅)(CO)₄] as the major products. Complex (1) reacts photolytically with two-electron donor ligands, L, to give the substituted complexes [MoMn(µ-H)(µ-PPh₂)(η⁵-C₅H₅)(CO)₅L][L = P(OMe)₃(2a), PPh₃(2b), or CNCH₂Ph (2c)], [MoMn(µ-H)(µ-PPh₂)(η⁵-C₅H₅)(CO)₄L₂][L = P(OMe)₃(3a), L₂= dppm-PP′(3b)(dppm = Ph₂PCH₂PPh₂), or L = CNCH₂Ph (3c)], and [MoMn(µ-H)(µ-PPh₂)(µ-L)(η⁵-C₅H₅)(CO)₄][L = dppm-PP′(4)]. An n.m.r. study reveals that the ligands L in complexes (2) and (3) have replaced respectively one or two carbonyl groups on the manganese atom. This has been confirmed for (3b) by X-ray analysis. Complex (4), an isomer of (3b) in which the dppm ligand adopts a bridging rather than a chelating bonding mode, is formed irreversibly from (3b) on photolysis.