A SIMPLE ROUTE FOR SYNTHESES OF TRIHALIDE-BRIDGED CARBONYL DIRUTHENIUM(II,III) COMPLEXES: CRYSTAL AND MOLECULAR STRUCTURE OF ttt-[RuIICl2(CO)2(PPh3)2],[(CO)(AsPh3)2RuII(μ-Cl3)RuIIICl2(AsPh3)] AND ([CO)(PPh3)2RuII(μ-Br3)RuIIIBr2(PPh3)], SPECTROSCOPIES, ELECTROCHEMISTRY AND PROPERTIES

The triply halide-bridged binuclear complexes [Ru2Cl5(CO)(AsPh3)3] (AsPh3 = triphenylarsine), [Ru2Cl5(CO)(PPh3)2(AsPh3)] (PPh3 = triphenylphosphine), [Ru2Cl5(CO)(AsPh3)2(PPh3)], [Ru2 Br5(CO)(PPh3)3], [Ru2Cl5(CO)(P{p-tol}3)2(PPh3)] (P{p-tol}3 = tri-p-tolylphosphine) and [Ru2 Br2Cl3(PPh3)2(AsPh3)] were prepared from the precursor compounds ttt-[RuX2(CO)2(P)2] (X = Cl or Br) and [RuY3(P')2S]·S (Y = Cl or Br; P=PPh3, AsPh3 or P{p- tol}3 and P' = AsPh3 or PPh3; S=DMA or MeOH, where DMA = N,N'-dimethylacetamide). The molecular structures of the binuclear complexes [Ru2Cl5(CO)(AsPh3)3] (P21/c), [Ru2Br5(CO)(PPh3)3] (P21/c) and ttt-[RuCl2(CO)2(PPh3)2] (P1) were determined by X-ray diffraction methods. The complexes are always formed by two Ru atoms bridged through three halide anions, two of which are × type (from the RuII precursor) and the other is Y type (from the rutheniumIII precursor) confirming our previously suggested mechanism for obtaining this class of complexes. The RuII atom is also coordinated to a carbon monoxide molecule and two P ligands from the ttt-starting isomer whereas the RuIII atom is bonded to two non-bridging Y halides and one P' molecule. The presence of RuIII was confirmed by EPR data, a technique that was also useful to suggest the symmetry of the complexes. The absence of intervalence charge-transfer transitions (IT) in the near infrared spectrum confirms that the binuclear complexes have localized valence. The IR spectra of the complexes show; (CO) bands close to 1970 cm-1 and ν(Ru-Cl) or(Ru-Br) bands at about 230-380 cm-1 corresponding to halides at terminal or bridged positions. Two widely separated redox processes, RuII/RuII←RuII/RuIII→RuIII/RuIII, were observed by cyclic voltammetry and differential pulse voltammetry.