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Issue 40, 2011
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Indenyl ring slippage in crown thioether complexes [IndMo(CO)2L]+ and C–S activation of trithiacyclononane: Experimental and theoretical studies

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Abstract

The macrocycle 1,4,7-trithiacyclononane (ttcn) reacts with [(η5-Ind)Mo(CO)2(NCMe)2]+ (or [(η5-Ind)Mo(CO)22-dme)]+) to give [(η3-Ind)Mo(CO)23-ttcn)]+ as the BF4 salt (1), but its reaction with [(η5-Ind)Mo(CO)2(C3H6)(FBF3)] affords the C–S bond cleavage product [(η5-Ind)Mo(CO)(κ3-1,4,7-trithiaheptanate)]BF4 (6), which has been characterised by X-ray crystallography (Ind = C9H7, indenyl). In contrast to ttcn, the macrocycles 1,3,5-trithiane (tt) and 1,4,7,10-tetrathiacyclododecane (ttcd) fail to induce changes in the coordination mode of indenyl: tt and ttcd react with [(η5-Ind)Mo(CO)2(NCMe)2]+ (or [(η5-Ind)Mo(CO)22-dme)]+) to give [(η5-Ind)Mo(CO)22-tt)]+ (2), characterised by X-ray crystallography, and [(η5-Ind)Mo(CO)22-ttcd)]+ (3), respectively. The cyclopentadienyl (Cp = C5H5) analogues [(η5-CpMo(CO)22-tt)]+ (4) and [(η5-CpMo(CO)22-ttcn)]+ (5) have also been synthesised and 5 characterised by X-ray crystallography. DFT calculations showed that the η5-Ind/Cp coordination mode is always the most stable. However, a molecular dynamics study of the macrocycles conformations revealed that the major conformer of ttcn was a chair, which favoured κ3 coordination. As indenyl complexes undergo slippage with a small barrier (<10 kcal mol−1), the kinetically preferred species [(η3-Ind)Mo(CO)23-ttcn)]+ (1) is the observed one. The conversion to 6 proceeds stepwise, with loss of ethylene followed by loss of CO, as calculated by DFT, with a barrier of 38.7 kcal mol−1, consistent with the slow uncatalysed reaction.

Graphical abstract: Indenyl ring slippage in crown thioether complexes [IndMo(CO)2L]+ and C–S activation of trithiacyclononane: Experimental and theoretical studies

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Publication details

The article was received on 08 Apr 2011, accepted on 21 Jun 2011 and first published on 16 Aug 2011


Article type: Paper
DOI: 10.1039/C1DT10607D
Citation: Dalton Trans., 2011,40, 10513-10525
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    Indenyl ring slippage in crown thioether complexes [IndMo(CO)2L]+ and C–S activation of trithiacyclononane: Experimental and theoretical studies

    C. A. Gamelas, N. A. G. Bandeira, C. C. L. Pereira, M. J. Calhorda, E. Herdtweck, M. Machuqueiro, C. C. Romão and L. F. Veiros, Dalton Trans., 2011, 40, 10513
    DOI: 10.1039/C1DT10607D

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