Issue 16, 2009

The effect of redox-active cyanomanganese(I) ligands on intramolecular electron transfer to, and alkyne alignment in, M(CO)(RC[triple bond, length as m-dash]CR)Tp′ (M = Mo or W) units

Abstract

The complexes [(η-C5Me5)(ON)LMn(μ-CN)M(CO)(RC[triple bond, length as m-dash]CR)Tp′]+ (L = CNXyl, M = Mo; L = CNBut, M = Mo or W, R = Ph or Me) and trans- or cis-[(dppm){(EtO)3P}(OC)2Mn(μ-CN)M(CO)(PhC[triple bond, length as m-dash]CPh)Tp′]+, and their linkage isomers [(η-C5Me5)(ON)LMn(μ-NC)M(CO)(PhC[triple bond, length as m-dash]CPh)Tp′]+ and trans- or cis-[(dppm){(EtO)3P}(OC)2Mn(μ-NC)M(CO)(PhC[triple bond, length as m-dash]CPh)Tp′]+, undergo two one-electron oxidations. The complexes [(η-C5Me5)(ON)LMn(μ-XY)M(CO)(RC[triple bond, length as m-dash]CR)Tp′]+ (XY = CN or NC) are oxidised first at the N-bound metal centre and then at the C-bound centre. For [(dppm){(EtO)3P}(OC)2Mn(μ-XY)M(CO)(PhC[triple bond, length as m-dash]CPh)Tp′]+, the trans isomers are first oxidised at manganese whereas the cis isomers are first oxidised at M. Thus, the order of one-electron oxidation of the two series of binuclear monocations is influenced by linkage isomerisation of the cyanide bridge and cis-trans isomerisation of the Mn(CO)2 group. IR spectroscopic changes on reaction of Ag+ with [(η-C5Me5)(ON)(ButNC)Mn(μ-CN)W(CO)(MeC[triple bond, length as m-dash]CMe)Tp′]+ are consistent with one-electron at the N-bound tungsten centre. Likewise, trans-[(dppm){(EtO)3P}(OC)2Mn(μ-NC)M(CO)(PhC[triple bond, length as m-dash]CPh)Tp′]+ (M = Mo or W) give the stable dications [(dppm){(EtO)3P}(OC)2Mn(μ-NC)M(CO)(PhC[triple bond, length as m-dash]CPh)Tp′]2+. Significantly longer Mn-P bond distances in trans-[(dppm){(EtO)3P}(OC)2Mn(μ-NC)Mo(CO)(PhC[triple bond, length as m-dash]CPh)Tp′]2+ than in trans-[(dppm){(EtO)3P}(OC)2Mn(μ-NC)Mo(CO)(PhC[triple bond, length as m-dash]CPh)Tp′]+ are consistent with one-electron oxidation first at Mn(I); the alignment of the (CN)Mn(CO)2{P(OEt)3}(dppm) fragment relative to the alkyne in trans-[(dppm){(EtO)3P}(OC)2Mn(μ-NC)Mo(CO)(PhC[triple bond, length as m-dash]CPh)Tp′]+ suggests it acts as a π-acceptor, in contrast to related species such as trans-(NC)Mn(CO)2{P(OEt)3}(dppm) and (NC)Mn(NO){P(OPh)3}(π-C5H4Me) which behave as simple N-donors.

Graphical abstract: The effect of redox-active cyanomanganese(I) ligands on intramolecular electron transfer to, and alkyne alignment in, M(CO)(RC [[triple bond, length as m-dash]] CR)Tp′ (M = Mo or W) units

Supplementary files

Article information

Article type
Paper
Submitted
19 Sep 2008
Accepted
20 Nov 2008
First published
27 Jan 2009

Dalton Trans., 2009, 3062-3073

The effect of redox-active cyanomanganese(I) ligands on intramolecular electron transfer to, and alkyne alignment in, M(CO)(RC[triple bond, length as m-dash]CR)Tp′ (M = Mo or W) units

C. J. Adams, N. G. Connelly and S. Onganusorn, Dalton Trans., 2009, 3062 DOI: 10.1039/B816420G

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