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Agostic-type B - H⋯Pb interactions stabilize a dialkylplumbylene. Structure of and bonding in [{nPr2P(BH3)}(Me 3Si)C(CH2)]2Pb

Lookup NU author(s): Dr Keith Izod, Emeritus Professor William McFarlane, Dr Corinne Wills, Professor William Clegg, Dr Ross Harrington

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Abstract

The reaction between Cp2Pb and 1 equiv of [[{nPr 2P(BH3)] (Me3Si)C(CH2)]Li(THF) 2]2 in toluene affords the dialkylplumbylene [{nPr 2P(BH3)}(Me3Si)C(CH2)] 2Pb (10) in excellent yield; compound 10 may readily be separated into its two diastereomeric forms by a simple crystallization procedure. X-ray crystallography shows that rac- and meso-10 crystallize as discrete dialkylplumbylenes in which there are either two (rac-10) or one (meso-10) short agostic-type B - H⋯Pb contacts; for meso-10 there is a secondary, weak B - H⋯Pb contact, which affords this diastereomer a further, weak stabilization. Multielement and variable-temperature NMR studies indicate that, while rac-10 is essentially static in solution, meso10 undergoes dynamic exchange between the free and bound BH3 groups. Unusually, the methylene backbone protons in both diastereomers (at low temperature for meso-10) lic within the range 2.5-6.5 ppm, possibly due to the close proximity of the 6s lone pair on the lead center. DFT studies indicate that there is significant delocalization of B - H σ-bonding electron density into the vacant lead 6p orbital, furnishing an overall stabilization of 40.6 and 30.3 kcal mol-1 for rac- and meso-10, respectively. © 2008 American Chemical Society.


Publication metadata

Author(s): Izod K, McFarlane W, Wills C, Clegg W, Harrington RW

Publication type: Article

Publication status: Published

Journal: Organometallics

Year: 2008

Volume: 27

Issue: 17

Pages: 4386-4394

ISSN (print): 0276-7333

ISSN (electronic): 1520-6041

Publisher: American Chemical Society

URL: http://dx.doi.org/10.1021/om800598b

DOI: 10.1021/om800598b


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