Electronic effects in some ruthenium(II)–carbonyl and –tertiary phosphine or –tertiary arsine complexes

Abstract

New complexes of the types [RuX₂(CO)L₃], [RuXY(CO)L₃], [RuX₂(CO)₂L₂], and [Ru₂X₃L₆][anion](X = Cl, Br, or I; Y = H, Cl, Br, I, NO₃, acetate, propionate, or benzoate; L = PR₃ or AsR₃) are described. The hydrido-complexes [RuHX(CO)(PR₃)₃], configuration (III), react with nitric acid or carboxylic acids to give complexes of the type [RuXY(CO)(PR₃)₃](Y = NO₃ or carboxylate) but with halogen acids (HY) mixtures are formed. An arsine hydrido-complex [RuHCl(CO)(AsMe₂Ph)₃] is described. The ruthenium–chlorine stretching frequencies for these complexes are recorded and discussed. Tertiary phosphines cause much weakening of a ruthenium–chlorine bond in trans-position, and carbon monoxide is a poorly trans-bond weakening ligand but causes more weakening than chlorine as trans-ligand. These bond-weakening effects are discussed. There is good correlation between a low ruthenium–chlorine stretching frequency and a high lability of the chlorine towards nucleophilic displacement; inert chlorines show high ruthenium–chlorine stretching frequencies. The stepwise formation of [RulCl(CO)(PMe₂Ph)₃] and [Rul₂(CO)(PMe₂Ph)₃] from [RuCl₂(CO)(PMe₂Ph)₃], configuration (II) by nucleophilic displacement of chloride by iodide, has been followed by an n.m.r. method. N.m.r. data and values for ν_CO are given.