Parahydrogen derived illumination of pyridine based coordination products obtained from reactions involving rhodium phosphine complexes

Rongrong Zhou, Juan A. Aguilar, Adrian Charlton, Simon B. Duckett, Paul I P Elliott, Rathika Kandiah

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

The reactions of RhCl(PBz3)3 with H2 and pyridine or 4-methylpyridine yield RhCl(H)2(PBz3) 2(py) and RhCl(H)2(PBz3)2(4-Me-py), respectively. These species undergo hydride site exchange via the loss of the pyridyl donor and formation of RhCl(H)2(PBz3)2 which contains equivalent hydride ligands; for the py system the activation free energy, ΔG300, is 57.4 ± 0.1 kJ mol-1 while for 4-Me-py the value is 59.6 ± 0.3 kJ mol -1. These products only showed parahydrogen enhancement in the corresponding hydride resonances when a sacrificial substrate was added to promote hydrogen cycling. When RhCl(PPh3)3 was used as the precursor similar observations were made, while when RhCl(PCy 3)2(C2H4) was examined, H 2 addition led to the formation of the binuclear complex (H) 2Rh(PCy3)2(μ-Cl)2Rh(H) 2(PCy3)2 which was differentiated from RhCl(H)2(PCy3)2 on the basis of the similarity in diffusion coefficient (5.5 × 10-9 m2 s -1) to that of (H)2Rh(PPh3) 2(μ-Cl)2Rh(PPh3)2 (5.3 × 10-9 m2 s-1). The detection of RhCl(H) 2(PCy3)2(py) was facilitated when pyridine was added to a solution of RhCl(PCy3)2(C2H 4) before the introduction of H2. During these reactions trace amounts of the double substitution products, RhCl(H) 2(phosphine)(py)2, were also detected.

Original languageEnglish
Pages (from-to)3773-3779
Number of pages7
JournalDalton Transactions
Issue number23
Early online date8 Sep 2005
DOIs
Publication statusPublished - 7 Dec 2005
Externally publishedYes

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