The Ruthenium Nitrosyl Moiety in Clusters: Trinuclear Linear μ-Hydroxido Magnesium(II)-Diruthenium(II), μ 3 -Oxido Trinuclear Diiron(III)-Ruthenium(II), and Tetranuclear μ 4 -Oxido Trigallium(III)-Ruthenium(II) Complexes.

The ruthenium nitrosyl moiety, {RuNO} 6 , is important as a potential releasing agent of nitric oxide and is of inherent interest in coordination chemistry. Typically, {RuNO} 6 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 3 -oxido clusters [Fe 2 RuCl 4 (μ 3 -O)(μ-OMe)(μ-pz) 2 (NO)(Hpz) 2 ] ( 6 ) and [Fe 2 RuCl 3 (μ 3 -O)(μ-OMe)(μ-pz) 3 (MeOH)(NO)(Hpz)][Fe 2 RuCl 3 (μ 3 -O)(μ-OMe)(μ-pz) 3 (DMF)(NO)(Hpz)] ( 7 ·MeOH·2H 2 O) and the heterotetranuclear μ 4 -oxido complex [Ga 3 RuCl 3 (μ 4 -O)(μ-OMe) 3 (μ-pz) 4 (NO)] ( 8 ) were prepared from trans -[Ru(OH)(NO)(Hpz) 4 ]Cl 2 ( 5 ), which itself was prepared via acidic hydrolysis of the linear heterotrinuclear complex {[Ru(μ-OH)(μ-pz) 2 (pz)(NO)(Hpz)] 2 Mg} ( 4 ). Complex 4 was synthesized from the mononuclear Ru complexes (H 2 pz)[ trans -RuCl 4 (Hpz) 2 ] ( 1 ), trans -[RuCl 2 (Hpz) 4 ]Cl ( 2 ), and trans -[RuCl 2 (Hpz) 4 ] ( 3 ). The new compounds 4 - 8 were all characterized by elemental analysis, ESI mass spectrometry, IR, UV-vis, and 1 H NMR spectroscopy, and single-crystal X-ray diffraction, with complexes 6 and 7 being characterized also by temperature-dependent magnetic susceptibility measurements and Mössbauer spectroscopy. Magnetometry indicated a strong antiferromagnetic interaction between paramagnetic centers in 6 and 7 . The ability of 4 and 6 - 8 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 6 by DFT and ab initio CASSCF/NEVPT2 calculations indicated a redox-noninnocent behavior of the NO ancillary ligand in 6 , which was also manifested in TD-DFT calculations of its electronic absorption spectrum. The electronic structure of 6 was also studied by an X-ray charge density analysis.