Solution studies of Ru{sub 2}(O{sub 2}Cr){sub 4}{sup n+} complexes (n = 0, 1; O{sub 2}CR = octanoate, crotonate, dimethylacrylate, benzoate, p-toluate) and solid-state structures of Ru{sub 2}(O{sub 2}C-p-tolyl){sub 4}(THF){sub 2}, [Ru{sub 2}(O{sub 2}c-p-tolyl){sub 4}(THF){sub 2}]{sup +}[BF{sub 4}]{sup {minus}}, and Ru{sub 2}(O{sub 2}C-p-tolyl){sub 4}(CH{sub 3}CN){sub 2}: Investigations of the axial ligation of the Ru{sub 2} core
- Indiana Univ., Bloomington, IN (United States); and others
Ru{sub 2}(O{sub 2}C(CH{sub 2}){sub 6}CH{sub 3}){sub 4} (1a) is soluble in both coordinating (THF, CH{sub 3}OH, CH{sub 3}CN) and noncoordinating solvents (benzene, toluene, cyclohexane, CH{sub 2}Cl{sub 2}), allowing its solution properties to be investigated by {sup 1}H and {sup 13}C NMR spectroscopy, UV/visible spectroscopy, resonance Raman spectroscopy, and cyclic voltammetry. In noncoordinating solvents, 1a exists as an oligomer, presumably by way of axial intermolecular -(--[Ru{sub 2}]--O--){sub n}-interactions. {sup 1}H NMR studies of 1a and [Ru{sub 2}(O{sub 2}C(CH{sub 2}){sub 6}CH{sub 3}){sub 4}]{sup +}[X]{sup {minus}}([1a]{sup +}[X]{sup {minus}}), where X = Cl, BF{sub 4}, or O{sub 2}C(CH{sub 2}){sub 6}CH{sub 3}, indicate that both dipolar and contact mechanisms contribute to the paramagnetic shifts of the protons. Resonances for axial and equatorial ligands are shifted upfield and downfield, respectively, by a dipolar mechanism. Aromatic ligands in the axial sites, e.g. pyridine and pyrazine, experience an enhanced upfield shift by direct {pi}-delocalization. Comparison of the {sup 1}H NMR signals for M{sub 2}(O{sub 2}CR){sub 4} compounds where M = Ru and O{sub 2}CR = benzoate, toluate, butyrate, crotonate, and dimethylacrylate with those where M = Mo indicates that the equatorial carboxylate ligands in the diruthenium species also experience {pi}-contact shifts. Variable-temperature studies and calculated estimates of dipolar shifts indicate a significant zero-field splitting contribution to the dipolar shift. The arrangements of the toluate rings in Ru{sub 2}(O{sub 2}C -p-tolyl){sub 4}-(THF){sub 2}, Ru{sub 2}(O{sub 2}C-p-tolyl){sub 4}(CH{sub 3}CN){sub 2}, and [Ru{sub 2}(O{sub 2}C-p-tolyl){sub 4}(THF){sub 2}]{sup +}[BF{sub 4}]{sup {minus}} deviate by 15(1), 2.3(2), and 7.3{degrees}, respectively, form alignment with the Ru-Ru axis.
- OSTI ID:
- 476871
- Journal Information:
- Inorganic Chemistry, Vol. 35, Issue 12; Other Information: PBD: 5 Jun 1996
- Country of Publication:
- United States
- Language:
- English
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