Structural, Spectroscopic, and Photochemical Investigation of an Octahedral NO-Releasing {RuNO}7 Species

Abstract

Ru(Me3[9]aneN3)(bpy)(NO)](BF4)2 ([1](BF4)2) was explored by single-crystal X-ray diffractometry, leading to the first crystal structure of an octahedral {RuNO}7 complex. The metal resides on the center of a distorted octahedron, with dN-O and Ru-N-O at 1.177(3) Å and 141.6(2)°, respectively. [1](BF4)2 can be stored indefinitely under argon. Solutions of [1]2+ show no signs of decomposition when protected from air and light. The electron paramagnetic resonance X-band spectrum at 85 K in vitrified acetonitrile (MeCN) shows signals consistent with an S = 1/2 spin state, better described as RuIINO• (g = [2.030, 1.993, 1.880] and A = [11.0, 30.4, 3.9]/10-4 cm-1). In water, the {RuNO}7 species reacts with O2 in a 1:4 stoichiometry. The reaction is first-order in both reactants with k = (1.9 ± 0.2) M-1 s-1 at 25 °C (ΔH‡ = 11.5 ± 0.3 kJ mol-1 ΔS‡ = -189 ± 1 J K-1 mol-1). Solutions of [1]2+ evolve NO when irradiated a 365 nm with øNO = 0.024 and 0.090 mol einstein-1 in H2O and MeCN, respectively.