Amidine functionalized phosphines: tuneable ligands for transition metals

Wilkins, Lewis C., Melen, Rebecca L. ORCID: https://orcid.org/0000-0003-3142-2831, Platts, James A. ORCID: https://orcid.org/0000-0002-1008-6595 and Newman, Paul D. ORCID: https://orcid.org/0000-0002-1808-1211 2017. Amidine functionalized phosphines: tuneable ligands for transition metals. Dalton Transactions 46 (41) , pp. 14234-14243. 10.1039/C7DT03343E

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Abstract

Attachment of racemic 1,3,5,7-tetramethyl-2,4,6-trioxa-8-phosphatricyclo[3.3.1.13,7]decane (α,β-CgP) to (1R,5S)-1,8,8-trimethyl-2,4-diazabicyclo[3.2.1]oct-2-ene gave a diastereomeric mixture of a novel amidine–phosphine ligand, α,β-CgPAm. The phosphination was completely selective for the 4-position of the bicyclic amidine and there was no subsequent 1,2-migration of the α,β-CgP group. Methylation of the non-phosphinated nitrogen gave the amidinium salt [α,β-CgPAmMe]BF4 as a diastereomeric mixture. The donating ability of α,β-CgPAm and [α,β-CgPAmMe]+ has been assessed through the synthesis and characterization of appropriate Rh(I), Au(I) and Pt(II) complexes. As expected α,β-CgPAm is a better net donor than the cationic derivative as shown by the magnitude of the νCO stretches in the IR spectra of the [Rh(L)(CO)(acac)]0/+ complexes and through determination of the relative energies of the HOMO and LUMO orbitals for both ligands by DFT. Attempts to resolve [Au(α,β-CgPAmMe)Cl]BF4, [Pt(α,β-CgPAmMe)Cl3], [Rh(α,β-CgPAmMe)(acac)(CO)]BF4 and [Rh(α,β-CgPAmH)(acac)(CO)]BF4 by fractional crystallization were unsuccessful as diastereomeric mixtures were obtained in every case; the structures of the last three complexes have been determined by single-crystal X-ray techniques and compared with related literature complexes.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Chemistry
Publisher:	Royal Society of Chemistry
ISSN:	1477-9226
Date of First Compliant Deposit:	5 October 2017
Date of Acceptance:	29 September 2017
Last Modified:	07 Nov 2023 06:17
URI:	https://orca.cardiff.ac.uk/id/eprint/105190

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