The Ruthenium Nitrosyl Moiety in Clusters: Trinuclear Linear μ-Hydroxido Magnesium(II)-Diruthenium(II), μ-Oxido Trinuclear Diiron(III)-Ruthenium(II), and Tetranuclear μ-Oxido Trigallium(III)-Ruthenium(II) Complexes.

The ruthenium nitrosyl moiety, {RuNO}, is important as a potential releasing agent of nitric oxide and is of inherent interest in coordination chemistry. Typically, {RuNO} is found in mononuclear complexes. Herein we describe the synthesis and characterization of several multimetal cluster complexes that contain this unit. Specifically, the heterotrinuclear μ-oxido clusters [FeRuCl(μ-O)(μ-OMe)(μ-pz)(NO)(Hpz)] () and [FeRuCl(μ-O)(μ-OMe)(μ-pz)(MeOH)(NO)(Hpz)][FeRuCl(μ-O)(μ-OMe)(μ-pz)(DMF)(NO)(Hpz)] (·MeOH·2HO) and the heterotetranuclear μ-oxido complex [GaRuCl(μ-O)(μ-OMe)(μ-pz)(NO)] () were prepared from -[Ru(OH)(NO)(Hpz)]Cl (), which itself was prepared via acidic hydrolysis of the linear heterotrinuclear complex {[Ru(μ-OH)(μ-pz)(pz)(NO)(Hpz)]Mg} (). Complex was synthesized from the mononuclear Ru complexes (Hpz)[-RuCl(Hpz)] (), -[RuCl(Hpz)]Cl (), and -[RuCl(Hpz)] (). The new compounds - were all characterized by elemental analysis, ESI mass spectrometry, IR, UV-vis, and H NMR spectroscopy, and single-crystal X-ray diffraction, with complexes and being characterized also by temperature-dependent magnetic susceptibility measurements and Mössbauer spectroscopy. Magnetometry indicated a strong antiferromagnetic interaction between paramagnetic centers in and . The ability of and - to form linkage isomers and release NO upon irradiation in the solid state was investigated by IR spectroscopy. A theoretical investigation of the electronic structure of by DFT and CASSCF/NEVPT2 calculations indicated a redox-noninnocent behavior of the NO ancillary ligand in , which was also manifested in TD-DFT calculations of its electronic absorption spectrum. The electronic structure of was also studied by an X-ray charge density analysis.