Structures of the Radical P[N(SiMe3)2](NPri2), its Dimer, Cation and Chloro-derivative

Bezombes, Jean-Philippe, Borisenko, Konstantin B, Hitchcock, Peter B, Lappert, Michael F, Nycz, Jacek E, Rankin, David W H and Robertson, Heather E (2004) Structures of the Radical P[N(SiMe3)2](NPri2), its Dimer, Cation and Chloro-derivative. Dalton Transactions (13). pp. 1980-1988. ISSN 1477-9226

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Treatment of PCl[N(SiMe3)2](NPri2) (1) with potassium–graphite in thf afforded the colourless, crystalline diphosphine {P[N(SiMe3)2](NPri2)}2 (2) in good yield. Sublimation of 2in vacuo yielded the yellow phosphinyl radical P[N(SiMe3)2](NPri2) (3), which upon cooling reverted to 2; the latter in C6D6 at 298 K was a mixture of rac and meso diastereoisomers. The yellow, crystalline phosphenium salt {P[N(SiMe3)2](NPri2)}[AlCl4] (4) was obtained from 1 and ½Al2Cl6 in CH2Cl2. By single-crystal X-ray diffraction (XRD) the structures of the known compound 1 and of 2 and 4 were determined. The structure of the radical 3, formed by the thermal homolytic dissociation of the diphosphine 2, was determined in the gas phase by electron diffraction (GED), utilising data from UMP2/6-31+G* ab initio calculations. The model of the molecule in the GED structure analysis was described by a set of internal coordinates and an initial set of Cartesian coordinates from ab initio calculations, facilitating the structure analysis. The experimental data were found to be consistent with the presence of a single conformer of the radical in the gas phase. The computed standard homolytic dissociation enthalpy of the P–P bond in the corresponding diphosphine 2, corrected for BSSE, 54 kJ mol−1, is substantially reduced compared to the dissociation enthalpy of tetramethyldiphosphine by the reorganisation energies of the fragments that form upon dissociation. The intrinsic energy content of the P–P bond in the diphosphine 2 was estimated to be 286 kJ mol−1, in agreement with the results of previous work on a series of crowded diphosphines.

Item Type: Article
Additional Information: First report of the structures and DFT on PII radical and rac-and meso-diastereoisomers of (PII)2. MFL directed the work and is principle author and one of two corresponding authors.
Schools and Departments: School of Life Sciences > Chemistry
Depositing User: EPrints Services
Date Deposited: 06 Feb 2012 21:22
Last Modified: 13 Jun 2012 14:12
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