The effect of µ-CN linkage isomerism and ancillary ligand set on directional metal–metal charge-transfer in cyanide-bridged dimanganese complexes†‡
Abstract
The reaction of [Mn(CN)L′(NO)(η5-C5R4Me)] with cis- or trans-[MnBrL(CO)2(dppm)], in the presence of Tl[PF6], gives homobinuclear cyanomanganese(I) complexes cis- or trans-[(dppm)(CO)2LMn(µ-NC)MnL′(NO)(η5-C5R4Me)]+, linkage isomers of which, cis- or trans-[(dppm)(CO)2LMn(µ-CN)MnL′(NO)(η5-C5R4Me)]+, are synthesised by reacting cis- or trans-[Mn(CN)L(CO)2(dppm)] with [MnIL′(NO)(η5-C5R4Me)] in the presence of Tl[PF6]. X-Ray structural studies on the isomers trans-[(dppm)(CO)2{(EtO)3P}Mn(µ-NC)Mn(CNBut)(NO)(η5-C5H4Me)]+ and trans-[(dppm)(CO)2{(EtO)3P}Mn(µ-CN)Mn(CNBut)(NO)(η5-C5H4Me)]+ show nearly identical molecular structures whereas cis-[(dppm)(CO)2{(PhO)3P}Mn(µ-NC)Mn{P(OPh)3}(NO)(η5-C5H4Me)]+ and cis-[(dppm)(CO)2{(PhO)3P}Mn(µ-CN)Mn{P(OPh)3}(NO)(η5-C5H4Me)]+ differ, effectively in the N- and C-coordination respectively of two different optical isomers of the pseudo-tetrahedral units (NC)Mn{P(OPh)3}(NO)(η5-C5H4Me) and (CN)Mn{P(OPh)3}(NO)(η5-C5H4Me) to the octahedral manganese centre. Electrochemical and spectroscopic studies on [(dppm)(CO)2LMn(µ-XY)MnL′(NO)(η5-C5R4Me)]+ show that systematic variation of the