Behavior of (Ether−phosphine)ruthenium(II) Complexes [(η6-C6Me6)RuH(P⌒O)][BF4] Containing Reactive Ru−O and Ru−H Bonds toward Various Small Molecules and Their Application in Ring-Opening Metathesis Polymerization

The ruthenium(II) complexes [(η6-C6Me6)RuH(P⌒O)][BF4] (5a − c; P⌒O = η2-(O,P)-chelated ether−phosphine; a, Ph2PCH2CH2OCH3; b, Ph2PCH2C4H7O2 (C4H7O2 = 1,3-dioxanyl); c, Ph2PCH2C3H5O2 (C3H5O2 = 1,3-dioxolanyl)), each having a Ru−O and Ru−H functionality, were obtained by hydride abstraction from (η6-C6Me6)RuH2(P∼O) (4a − c, P∼O = η1-(P)-coordinated ligand) with Ph3CBF4. A facile Ru−O bond cleavage occurs when 5a − c are reacted with a variety of small molecules. Carbon monoxide, acetonitrile, tert-butyl isocyanide, and ethene were readily added to 5a − c, leading to the corresponding adducts [(η6-C6Me6)RuH(P∼O)L][BF4] (6a − c, 7a − c, 8a − c, 10a − c; L = CO, CH3CN, t-BuNC, C2H4). π/σ rearrangements with incorporation of the Ru−H bonds in 10a − c were not observed. If 5a − c were treated with carbon disulfide, both functionalities were required. Rupture of the Ru−O contact resulted in a π-CS2-coordinated intermediate followed by an insertion of CS2 into the Ru−H bond to give the dithioformato complexes [(η6-C6Me6)RuH(P∼O)(S2CH)][BF4] (9a − c). All compounds were obtained in excellent yields under mild conditions. The structures of 5a, 7c, 8c, and 9a were determined by single-crystal X-ray diffraction methods. Ring-opening metathesis polymerization of norbornene was achieved using complexes 5a − c as the catalyst precursors.