The mutual influence of ligands in transition metal coordination compounds with multiple metal-ligand bonds

The Coordination and Bioinorganic Chemistry of Molybdenum

Mechanisms for the reactions of molybdenum in enzymes

Oxo-species of molybdenum(IV), (V), and (VI) are discussed with particular reference to (a) their structures (stereochemistry, bond lengths and bond angles), (b) vibrational spectra, and (c) molybdenum—oxygen bonding. The possible significance for molybdenum-containing enzymes of the trans -effect of molybdenum-oxygen multiple bonds is considered.

Structure and bonding in molecular oxo-molybdenum compounds☆

The electrochemistry of molybdenum(V) and of a 2:2 dimeric molybdenum(V)-riboflavin anion radical complex has been investigated by cyclic voltammetry, controlled potential electrolysis, u.v.-visible spectrophotometry and e.s.r. spectroscopy. On the basis of the electrochemical results and associated spectroscopic and e.s.r. studies, mechanisms for the electron transfer sequence of the molybdenum—riboflavin combination are proposed. The dimeric complex appears to be a useful model for xanthine oxidase and related molybdo—flavoprotein enzymes. The structures of the molybdenum(V, VI) complexes with 8-quinolinol (Q) and 2-methyl-8-quinolinol (2-MeQ) in dimethyl sulphoxide solution have been investigated by proton n.m.r. and infrared spectroscopy. The metal oxo oxygens of the Mo(VI) O 2 Q 2 complex are cis to each other, as are the oxygens of the oxo-bridged dimeric Mo(V) 2 O 3 Q 4 complex. The n.m.r. results indicate the existence of strong, covalent metal-to-ligand oxygen bonding but, by virtue of the trans effect exhibited by the oxo oxygens, only weak, labile metal—nitrogen interactions. The implications of the weak Mo-N bonding for the molybdenum-flavin interaction in metalloflavoenzymes are discussed.

Electrochemical and NMR studies of molybdenum-flavin model compounds in aprotic solvents

X-Ray crystal studies of MoO2(C9H6NO)2 reveal that the O–Mo–O group has the cis-configuration.

Yu. A. Sokolova

Papers

The crystal structure of dioxobis-8-hydroxyquinolinatomolybdenum(VI)