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An intramolecularly base-stabilized diphosphagermylene and two unusual germanium(II) ate complexes: A structural, NMR, and DFT study

Lookup NU author(s): Dr Keith Izod, Emeritus Professor William McFarlane, Dr Ben Allen, Emeritus Professor Bill Clegg, Dr Ross Harrington

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Abstract

The reaction between GeCl2-dioxane and 1 equiv of {R(C 6H4-2-CH2NMe2)P}K (5) yields the heteroleptic complex {R(C6H4-2-CH2NMe 2)P}GeCl (6) [R = (Me3Si)2CH]. Treatment of GeI2 with 2 equiv of the potassium salt 5 gives the homoleptic, intramolecularly base-stabilized diphosphagermylene {R(C5H 4-2-CH2NMe2)P}2Ge (7) in good yield. In contrast, treatment of GeI2 with 2 equiv of {R(C 6H4-2-CH2NMe2)P}Li (4) in ether reproducibly yields the unusual ate complex {R(C6H 4-2-CH2NMe2)P}2GeLi 2I2(OEt2)3 (8), whereas treatment of GeI2 or GeCl2-dioxane with 3 equiv of 5 yields the cage ate complex {R(C6H4-2-CH2NMe 2)P}3-GeK (9). The solid-state structures of 7-9 have been determined by X-ray crystallography, and the dynamic behavior of 6-9 in solution has been studied by multielement and variable-temperature NMR experiments. DFT calculations on the model complex {(Me)(C6H 4-2-CH2-NMe2)P}GeCl (6a) indicate that inversion at germanium via a planar transition state is disfavored [E inv = 38.5 kcal mol-1] with respect to inversion at phosphorus [Einv = 21.0 kcal mol-1]; inversion at germanium is calculated to proceed via an edge-inversion rather than vertex-inversion process. For the model diphosphagermylene {(Me)(C 6H4-2-CH2NMe2)P}2-Ge (7a) the lowest energy process for epimerization is calculated to be inversion at germanium via a pseudo-trigonal bipyramidal intermediate [Einv = 3.0 kcal mol-1]. Inversion at germanium (via a vertex-inversion process) is calculated to have a barrier of 48.0 kcal mol-1, whereas the barriers to inversion at phosphorus are 24.0 and 18.5 kcal mol-1 for the chelating and terminal phosphorus atoms, respectively. © 2005 American Chemical Society.


Publication metadata

Author(s): Izod K, McFarlane W, Allen B, Clegg W, Harrington RW

Publication type: Article

Publication status: Published

Journal: Organometallics

Year: 2005

Volume: 24

Issue: 9

Pages: 2157-2167

Print publication date: 25/04/2005

ISSN (print): 0276-7333

ISSN (electronic): 1520-6041

Publisher: American Chemical Society

URL: http://dx.doi.org/10.1021/om0501125

DOI: 10.1021/om0501125


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