"Unsymmetrical" diruthenium amidinates in which the μ₂-amidinate bridge Is perpendicular to the Ru-Ru axis: Synthesis and reactions of derivatives of [(η⁵-C₅Me ₅)Ru(μ-amidinate)Ru(η⁵-C₅H ₅)]⁺

New diruthenium complexes, of which two organoruthenium species, (η⁵-C₅Me₅)Ru and (η⁵-C ₅H₅)Ru, are linked by a bridging amidinate ligand, were synthesized and characterized. Treatment of (η⁵-C ₅Me₅)Ru(η-amidinate) [amidinate: _iPrN=C(Me) N_iPr] with [(η⁵-C₅H₅)Ru-(η- NCMe)₃]⁺PF₆^- resulted in formation of a cationic diruthenium amidinate, [(η⁵-C₅Me ₅)-Ru(μ₂-amidinate)Ru(η⁵-C ₅H₅)(η-NCMe)]⁺PF₆^- (4), which was converted to (η⁵-C₅Me ₅)Ru-(μ₂-amidinate)Ru(η⁵-C ₅H₅)X [X = Cl (5a), Br (5b)] by treatment with the halide anion. The molecular structures and spectroscopic data of 4 and 5a including their solution dynamics are compared with their bis-pentamethylcyclopentadienyl homologues, [(η⁵-C₅Me₅)Ru- (μ₂-aimdinate)Ru(η⁵-C₅Me ₅)(η-NCMe)]⁺PF₆^- and (η⁵-C₅Me₅)Ru(μ₂-amidinate) Ru(η⁵-C₅H₅)Cl. Treatment of 5a with TlBF₄ produced a diruthenium complex, [(η⁵-C ₅Me₅)Ru(μ₂-amidinate)-Ru(η⁵- C₅H₅)]⁺BF₄^- (6), bearing 34 valence electrons, which was isolated and characterized by spectroscopy. The coordinatively unsaturated nature of 6 was evidenced by facile reactions with two-electron-donor ligands, NCMe, PMe₃, ^tBuNC, and CO. The coordinatively unsaturated complex 6 and its precursors, 4 and 5, exhibited catalytic activity toward cyclization of N-tosyl-N-allyltrichloroacetamide, which was compared with the corresponding bis-pentamethylcyclopentadienyl homologues.