Complex formation by molybdenum(II) chloride

Abstract

Molybdenum(II) chloride reacts with various unidentate ligands to form complexes [(Mo₆Cl₈)Cl₄L₂] whose ultraviolet spectra are closely similar to those of the parent chloride and the acid H₂[(Mo₆Cl₈)Cl₆],8H₂O. The electrolytic conductivities of the freshly-dissolved complexes are low. The importance of six-co-ordination to the Mo₆Cl₈ cluster is shown by the existence of complexes [(Mo₆Cl₈)Cl₃(PPh₃)₃]Cl and [(Mo₆Cl₈)Cl₂(PPh₃)₂(EtOH)₂]Cl₂ which are, respectively, 1 : 1 and 2 : 1 electrolytes. Bipyridyl, o-phenanthroline, and o-phenylenebis(dimethylarsine) give complexes of the type [(Mo₆Cl₈)X₂L₂]X₂(X = Cl or I) which are also 2 : 1 electrolytes. Terpyridyl yields derivatives [(Mo₆Cl₈)X₃terpy]X. Evidence on the mode of co-ordination of these ligands is discussed.