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Mixed donor-functionalised phosphinomethanide complexes of the alkali metals; synthesis, structures, and solution dynamics

Lookup NU author(s): Dr Corinne Wills, Dr Keith Izod, Jonathan Young, Emeritus Professor Bill Clegg, Dr Ross Harrington

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Abstract

The mixed donor tertiary phosphine {(Me3Si)(2)CH}P(C6H4-2-CH2NMe2)(C6H4-2-CH2OMe) (11) is accessible via the stepwise addition of [Li(C6H4-2-CH2NMe2)] followed by [Li(C6H4-2-CH2OMe)] to the dichlorophosphine {(Me3Si)(2)CH}PCl2. Phosphine 11 is readily deprotonated by (BuLi)-Li-n to give the lithium phosphinomethanide [[{(Me3Si)(2)C}P(C6H4-2-CH2NMe2)(C6H4-2-CH2OMe)]Li] (15), which undergoes metathesis reactions with the alkoxides MOBut [M = Na, K] to give the heavier alkali metal phosphinomethanides [[{(Me3Si)(2)C}P(C6H4-2-CH2NMe2)(C6H4-2-CH2OMe)] M(L)(n)](x) in good yield [M = Na (12), (L)(n) = Et2O, x = 1; M = K (13), n = 0, x = 2]. Compounds 12 and 13 adopt monomeric and dimeric structures, respectively, in the solid state. Variable-temperature NMR studies indicate that compounds 12 and 13 are highly fluxional in solution; this fluxionality arises from a dynamic equilibrium between two conformers, which differ in the orientation of the aromatic rings of the ligand. The nature of these conformers and their relative energies have been probed by DFT calculations, which show the two principal conformers to differ in energy by just 1.6 kcal mol(-1). Calculation of the H-1 NMR shielding tensors using the GIAO method reveals that the low field chemical shifts of one benzylic and one aromatic proton in the ground state conformer are due to their close proximity to the carbanion centre.


Publication metadata

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

Publication type: Article

Publication status: Published

Journal: Dalton Transactions

Year: 2009

Issue: 31

Pages: 6159-6165

Print publication date: 01/01/2009

ISSN (print): 1477-9226

ISSN (electronic): 1477-9234

Publisher: Royal Society of Chemistry

URL: http://dx.doi.org/10.1039/b903119g

DOI: 10.1039/b903119g


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