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 [(η 6 -C 6 Me 6 )RuH(P⌒O)][BF 4 ] ( 5a − c; P⌒O = η 2 -( O, P )-chelated ether−phosphine; a, Ph 2 PCH 2 CH 2 OCH 3; b, Ph 2 PCH 2 C 4 H 7 O 2 (C 4 H 7 O 2 = 1,3-dioxanyl); c, Ph 2 PCH 2 C 3 H 5 O 2 (C 3 H 5 O 2 = 1,3-dioxolanyl)), each having a Ru−O and Ru−H functionality, were obtained by hydride abstraction from (η 6 -C 6 Me 6 )RuH 2 (P∼O) ( 4a − c, P∼O = η 1 -( P )-coordinated ligand) with Ph 3 CBF 4 . 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 [(η 6 -C 6 Me 6 )RuH(P∼O)L][BF 4 ] ( 6a − c, 7a − c, 8a − c, 10a − c; L = CO, CH 3 CN, t -BuNC, C 2 H 4 ). 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-CS 2 -coordinated intermediate followed by an insertion of CS 2 into the Ru−H bond to give the dithioformato complexes [(η 6 -C 6 Me 6 )RuH(P∼O)(S 2 CH)][BF 4 ] ( 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.