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Dynamic behavior of intramolecularly base-stabilized phosphatetrylenes: insights into the inversion processes of trigonal pyramidal geramanium(II) and tin(II) centers

Izod, Keith, Stewart, John, Clark, Ewan R., McFarlane, William, Allen, Ben, Clegg, William, Harrington, Ross W. (2009) Dynamic behavior of intramolecularly base-stabilized phosphatetrylenes: insights into the inversion processes of trigonal pyramidal geramanium(II) and tin(II) centers. Organometallics, 28 (12). pp. 3327-3337. ISSN 0276-7333. (doi:10.1021/om8011757) (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided)

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Official URL
http://www.dx.doi.org/10.1021/om8011757

Abstract

The reaction between SnCl2 and either 1 or 2 equiv of the lithium salt [{(Me3Si)2CH}(C6H 4-2-CH2NMe2)P]Li gives the heteroleptic compound [{(Me3Si)2CH}(C6H4-2- CH2NMe2)P]SnCl (7) and the homoleptic, intramolecularly base-stabilized diphosphastannylene [{(Me3Si)2CH}(C 6H4-2-CH2NMe2)P]2Sn (8), respectively, in good yields. The solid state structure of 8 shows that the tin(II) center is three-coordinate, bound by the N and P atoms of a chelating phosphide ligand and the P atom of a second phosphide ligand. Both 7 and 8 are highly dynamic in solution. Variable-temperature NMR spectra suggest that compound 7 and its germanium analogue 5 are subject to two distinct dynamic processes in polar solvents, which are attributed to the formation of adducts between either 5 or 7 and the free phosphine {(Me3Si) 2CH}(C6H4-2-CH2NMe2)PH (9) and interconversion between diastereomers of these adducts. Adduct formation is observed only in polar solvents and may be associated with the formation of weakly bound [[{(Me3Si)2CH}(C6H 4-2-CH2NMe2)P]E(L)]+ ··· Cl- ion pairs in solution. The dynamic behavior of 8 has been studied by multielement and variable-temperature NMR experiments; at high temperatures there is rapid equilibrium between diastereomers, but at low temperatures a single diastereomer predominates and exchange between the chelating and terminal phosphide ligands is frozen out. DFT calculations on the model compound {(Me)(C6H4-2-CH 2NMe2)P}SnCl (7a) suggest that epimerization occurs either through a vertex-inversion process at phosphorus [Einv) 65.3 kJ mol-1] or an edge-inversion process at tin [Einv) 141.0 kJ mol-1], of which the former is clearly favored. DFT calculations on the model complex {(Me)(C6H4-2-CH2NMe 2)P}2Sn (8a) indicate that the lowest energy dynamic process involves exchange between the chelating and terminal phosphide ligands via a pseudotrigonal bipyramidal intermediate [E)-12.6 kJ mol-1]. Inversion at tin in 8a (via an unusual hybrid edge/vertex-inversion process) is calculated to have a barrier of 206.3 kJ mol-1, whereas the barriers to vertex-inversion at phosphorus are 59.4 and 51.0 kJ mol-1 for the chelating and terminal phosphorus atoms, respectively.

Item Type: Article
DOI/Identification number: 10.1021/om8011757
Uncontrolled keywords: Adduct formation, DFT calculation, Diastereomer, Diastereomers, Dynamic behaviors, Dynamic process, Energy dynamics, Epimerization, Good yield, Heteroleptic, High temperature, Homoleptic, Interconversion, Inversion process, Ion pairs, Lithium salts, Low temperatures, Model complexes, Model compound, Multi-element, Phosphide ligands, Phosphorus atom, Polar solvents, Rapid equilibrium, Solid-state structures, Variable-temperature NMR, Atoms, Chelation, Germanium, Ligands, Lithium, Nuclear magnetic resonance, Nuclear magnetic resonance spectroscopy, Phosphorus, Phosphorus compounds, Probability density function, Silicon, Sulfur compounds, Tin, Crystal atomic structure
Subjects: Q Science > QD Chemistry
Divisions: Faculties > Sciences > School of Physical Sciences > Functional Materials Group
Depositing User: Giles Tarver
Date Deposited: 29 Jul 2015 15:19 UTC
Last Modified: 29 May 2019 14:57 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/49883 (The current URI for this page, for reference purposes)
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