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Issue 5, 2011
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An evaluation of monovalent osmium supported by the PNP ligand environment

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Abstract

Nitrogen is essential to reaction of (PNP)OsI (PNP is N(SiMe2CH2PtBu2)2) and Mg powder in THF, to give equimolar (PNP)OsH(N2) and hydrido carbene [(tBu2PCH2SiMe2)N(SiMe2CH2PtBu(CMe2CH)]OsH. This reaction is attributed to H2 evolution from solid magnesium, rather than high energy H atom transfer between molecules, but relies also on the strong π-basicity of Os in favoring α-H migration from the metallated tBu group on Os to form the second product, the hydrido carbene species. The path to two different products begins because the simple N2 adduct of (PNP)OsI undergoes spontaneous heterolytic H–C splitting of the tBu methyl group, to produce a secondary amine intermediate [(tBu2PCH2SiMe2)N(H)(SiMe2CH2PtBu(CMe2CH2)]OsI(N2) which can then be dehydrohalogenated by Mg. The analogous reaction for (PNP)RuCl shows production of only (PNP)RuH(N2), with none of the hydride carbene dehydrogenation product. Comparative (Ruvs. Os) DFT calculations reveal the reaction steps where the Os analog is much more exothermic, accounting for certain reaction selectivities.

Graphical abstract: An evaluation of monovalent osmium supported by the PNP ligand environment

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Supplementary files

Article information


Submitted
09 Aug 2010
Accepted
26 Nov 2010
First published
16 Dec 2010

Dalton Trans., 2011,40, 1105-1110
Article type
Paper

An evaluation of monovalent osmium supported by the PNP ligand environment

N. Tsvetkov, H. Fan and K. G. Caulton, Dalton Trans., 2011, 40, 1105
DOI: 10.1039/C0DT00989J

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