Ruthenium carbonyl cluster complexes with oxygen ligands. Reactions between Ru 3(CO) 12 and 4-methoxyphenol or 2-naphthol. Crystal structure of Ru 4(μ 3-OC 6H 4OMe-4) 2(μ-Cl)(μ-OC 6H 4OMe-4)(CO) 10, an unusual mixed-valence cluster complex

Abstract

The reaction between 4-methoxyphenol and Ru 3(CO) 12 in cyclohexane has been investigated and found to afford a hexaruthenium ‘raft’ cluster Ru 6(μ-H) 2(μ 5-η 7-OC 6H 3OMe-4)(CO) 16 ( 3a), together with tetraruthenium clusters incorporating three (Ru 4(μ 3-OC 6H 4OMe-4) 2(μ-Cl)(μ-OC 6H 4OMe-4)(CO) 10 ( 3b)) or four (Ru 4(μ 3-OC 6H 4OMe-4) 2(μ-OC 6H 4OMe-4) 2(CO) 10 ( 3c)) aryloxo ligands; similarly, reaction of Ru 3(CO) 12 with 2-naphthol afforded the analogous Ru 6(μ-H) 2(μ 5-η 7-OC 10H 6)(CO) 16 ( 4a), Ru 4(μ 3-OC 10H 7) 2(μ-Cl)(μ-OC 10H 7)(CO) 10 ( 4b) and Ru 4(μ 3-OC 10H 7) 2(μ-OC 10H 7) 2(CO) 10 ( 4c). The source of chloride in 3b and 4b is believed to be carbon tetrachloride contaminant in the cyclohexane. An X-ray diffraction study reveals that 3b contains an Ru 3(CO) 8 unit linked to an Ru(CO) 2 moiety by two asymmetric triply-bridging and one asymmetric doubly-bridging 4-methoxyphenoxo ligands, and an asymmetric doubly-bridging chloro ligand; this interaction is strongly suggestive of a higher oxidation state ruthenium linked to a trinuclear cluster of formally zero oxidation state. The dynamic 13C NMR spectra of 4c have been recorded, and are consistent with restricted rotation about the ArO linkage of the μ 2-coordinated naphthoxo ligands at low temperature.