Ruthenated Acetonitrile: Unusual Brønsted Acidity of a Polar “Aprotic” Solvent
Addition of acetonitrile to the complex [Ru(η5-indenyl)(PR2)(PPh3)] (1) gives the unusual metalation product [Ru(η5-indenyl)(CH2CN)(HPR2)(PPh3)] (2), which has been structurally characterized. This reaction clearly demonstrates high Brønsted basicity at the terminal phosphido ligand in 1. 31P{1H} NM...
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Published in | Organometallics Vol. 27; no. 19; pp. 5025 - 5032 |
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Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
American Chemical Society
13.10.2008
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Online Access | Get full text |
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Summary: | Addition of acetonitrile to the complex [Ru(η5-indenyl)(PR2)(PPh3)] (1) gives the unusual metalation product [Ru(η5-indenyl)(CH2CN)(HPR2)(PPh3)] (2), which has been structurally characterized. This reaction clearly demonstrates high Brønsted basicity at the terminal phosphido ligand in 1. 31P{1H} NMR studies show that less acidic N-donor solvents simply disrupt the Ru−P π-bond in 1 to give adducts [Ru(η5-indenyl)(L)(HPR2)(PPh3)] (L = benzonitrile (6) or pyridine (7)), which are in equilibrium with 1 and free L. The analogous acetonitrile adduct (4) was observed by NMR at 240 K during the formation of 2, but is quickly replaced by 2 at higher temperatures. NMR studies of an alternate route to the metalated complex 2, starting from the cationic N-bound acetonitrile adduct [Ru(η5-indenyl)(NCCH3)(HPCy2)(PPh3)][PF6] (3a), along with the demonstrated lability of the benzonitrile and pyridine adducts, suggest that the metalation of acetonitrile by 1 proceeds via an intermolecular C−H addition across the RuP double bond, rather than the intramolecular C−H activation of N-bound acetonitrile. This is confirmed by the observation, by 31P{1H} NMR, of multiple product isotopomers in the reaction of 1 with a 1:1 mixture of d 3- and d 0-acetonitrile. O-Donor solvents also deprotonated by 1 include water, alcohols, and acetone, which give the complexes [Ru(η5-indenyl)(X)(HPCy2)(PPh3)], where X = OR (8), CH2(O)CH3 (10). |
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Bibliography: | istex:E17F42820790F42B3628B1143139EB1DDBBC7F61 1H and 13C NMR data for 2a,b and 3a,b; spectra illustrating sample purity, structure diagnosis and isotope labeling; details of line shape analyses and van’t Hoff calculations, and a crystallographic information file (CIF). This material is available free of charge via the Internet at http://pubs.acs.org. ark:/67375/TPS-0CZS9030-B |
ISSN: | 0276-7333 1520-6041 |
DOI: | 10.1021/om800343x |