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Sequential C-H and C-Ru bond formation and cleavage during the thermally induced rearrangement of aryl ruthenium(II) complexes with [CH(CHNMe)-2,6] as a bidentate η-C,N coordinated ligand. the crystal structures of the isomeric pairs [RuCl{η-CH}

Organometallics, ISSN: 0276-7333, Vol: 17, Issue: 21, Page: 4680-4693
1998
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Article Description

New air-stable ruthenium(II) complexes that contain the aryldiamine [CH(CH-NMe) -2,6] (NCN) are described. These complexes are [RuCl{η-C,N-CH(CHMe )-2,6}(η-CH)] (2; CH = p-cymene = CHMe-Pr-4), [Ru{η-C,N-CH(CHNMe )-2,6}(η-CH )(PPh)] (5), and their isomeric forms [RuCl{η-C,N-CH(CHNMe )-2,4}(η-CH)] (3) and [Ru{η-C,N-CH(CHNMe )-2,4}(η-CH )(PPh)] (6), respectively Complex 2 has been prepared from the reaction of [Li(NCN)] with [RuCl(η-CH)], whereas complex 5 has been prepared by the treatment of [RuCl{η-N,C,N-CH(CHNMe )-2,6}(PPh)] (4) with [Na(CH)]. Both 2 and 5 are formally 18-electron ruthenium(II) complexes in which the monoanionic potentially tridentate coordinating ligand NCN is η-C,N-bonded. In solution (halocarbon solvent at room temperature or in aromatic solvents at elevated temperature), the intramolecular rearrangements of 2 and 5 afford complexes 3 and 6, respectively. This is a result of a shift of the metal-C bond from position-1 to position-3 on the aromatic ring of the NCN ligand. The mechanism of the isomerization is proposed to involve a sequence of intramolecular oxidative addition and reductive elimination reactions of both aromatic and aliphatic C-H bonds. This is based on results from deuterium labeling, spectroscopic studies, and some kinetic experiments. The mechanism is proposed to contain fully reversible steps in the case of 5, but a nonreversible step involving oxidative addition of a methyl NCH-H bond in the case of 2. The solid-state structures of complexes 2, 3, 5, and 6 have been determined by single-crystal X-ray diffraction. A new dinuclear 1,4-phenylene-bridged bisruthenium(II) complex, [1,4-{RuCl(η-CH)}{C (CHNMe) -2,3,5,6-C,N,C′,N′}] (9) has also been prepared from the dianionic ligand [C(CHNMe)-2,3,5,6] (CN). The CN ligand is in an η-C,N-η-C′,N′-bis(bidentate) bonding mode. Compound 9 does not isomerize in solution (halocarbon solvent), presumably because of the absence of an accessible C-H bond. Complex 9 could not be isolated in an analytically pure form, probably because of its high sensitivity to air and very low solubility, which precludes recrystallization.

Bibliographic Details

Pablo Steenwinkel; Stuart L. James; Robert A. Gossage; David M. Grove; Huub Kooijman; Wilberth J. J. Smeets; Anthony L. Spek; Gerard van Koten

American Chemical Society (ACS)

Chemistry

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