13C and 31P NMR studies on geometrical non-rigidity in heterobinuclear complexes [WM(CO)3(PPh3)25-C5H5)] (M Rh, Cu)

W. Edward Lindsell, Peter J. Tomb

Research output: Contribution to journalArticle

Abstract

13C NMR studies on [W2(CO)6Cp2] (Cp = ?5-C5H5), including a 2D EXSY study, confirm that simple rotation about the WW bond is responsible for the isomerisation in solution. Variable temperature 31P{1H} and 13C{1H} NMR spectra of [WRh(µ-CO)2(CO)(PPh3)2Cp] establish that a pseudo-rotational process, with ?G 27.9 ± 0.8 kJ mol-1 at -108 ± 8°C, results in interchange of the inequivalent PPh3 groups and all the CO ligands. The mechanism of this facile fluxional process is discussed in relation to that of [W2(CO)6Cp2], and an intermediate (or transition state) of the type [WRh(µ-CO)3(PPh3)2Cp] is proposed. Variable temperature 31P{1H} and 13C{1H} NMR spectra of [WCu(CO)3(PPh3)2Cp] in solvents of various polarities establish a related geometrical non-rigidity for this complex, but with ?G ca. 39-41 kJ mol-1, in the range -57 to -69°C; this result, considered along with the very low electrical conductivity in acetone, suggests that an intramolecular mechanism also operates for this interchange. © 1989.

Original languageEnglish
Pages (from-to)245-253
Number of pages9
JournalJournal of Organometallic Chemistry
Volume378
Issue number2
Publication statusPublished - 5 Dec 1989

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