Pas de Deux of an NO Couple: Synchronous Photoswitching from a Double‐Linear to a Double‐Bent Ru(NO)(2) Core under Nitrosyl Charge Conservation

The {Ru(NO)(2)}(10) dinitrosylruthenium complex [Ru(NO)(2)(PPh(3))(2)] (1) shows photo‐induced linkage isomerism (PLI) of a special kind: the two NO ligands switch, on photo‐excitation, synchronously from the ground state (GS) with two almost linear RuNO functions to a metastable state (MS) which persists up to 230 K and can be populated to ≈50 %. The MS was experimentally characterised by photo‐crystallography, IR spectroscopy and DS‐calorimetry as a double‐bent variant of the double‐linear GS. The experimental results are confirmed by computation which unravels the GS/MS transition as a disrotatory synchronous 50° turn of the two nitrosyl ligands. Although 1 shows the usual redshift of the N−O stretch on bending the MNO unit, there is no increased charge transfer from Ru to NO along the GS‐to‐MS path. In terms of the effective‐oxidation‐state (EOS) method, both isomers of 1 and the transition state are Ru(−II)(NO(+))(2) species.