Di- and Trinuclear Polyhydride Complexes Containing Ruthenium and Rhenium. Synthesis, Site Exchange, and H/D Exchange of Hydride Ligands

Abstract

Novel di- and trinuclear heterometallic polyhydride complexes containing both ruthenium and rhenium atoms have been synthesized. Treatment of (Cp‘RuH2)2 (1) with Cp‘ReH6 affords the heterobimetallic polyhydride complex Cp‘Ru(μ-H)3ReH2Cp‘ (6) together with the corresponding two heterotrimetallic polyhydride complexes (Cp‘Ru)2(Cp‘Re)(μ-H)4 (7) and (Cp‘Ru)(Cp‘Re)2(H)5 (8). These new polyhydride complexes have notably only C5Me5 groups as auxiliary ligands. A new class of a dinuclear polyhydride complex, Cp‘Ru(μ-H)3ReH(triphos) (9), which has a different kind of auxiliary ligand on each of the metal centers, has been prepared by the reaction of (triphos)ReH5 (4; triphos = CH3C(CH2PPh2)3) with (Cp‘RuOMe)2 (5). The trinuclear polyhydride 7 is alternatively synthesized by way of an intermediary cationic complex, [(Cp‘Ru)2(Cp‘Re)(μ-H)5][BF4] (10a), obtained by treatment of 6 with HBF4. Treatment of (Cp‘ReH3)2 (3) with 5 results in the formation of the trimetallic complex 8 with a triangular Re2Ru framework. The X-ray diffraction studies have proved the bimetallic structures of 6 and 9, which have both terminal and bridging hydrides. The hydride ligands coordinated in both 6 and 9 exchange coordination sites, and the exchange process has been analyzed by means of NMR spectroscopy. The molecular structures of trinuclear clusters 7‘ and 10b‘ have been determined by X-ray diffraction studies. The trinuclear complexes 7, 8, and 10 undergo an H/D exchange reaction between the hydride ligands and atmospheric D2. The H/D exchange reaction of hydride in complexes 7 and 8 with C6D6 is a slow process, because of the bulkiness of the C6D6 molecule relative to the size of the reaction field surrounded by the three Cp‘ groups.