Synthesis and Catalytic Activity of (η6‐p‐Cymene)(phosphane)ruthenium(II) Complexes Supported on Poly(biphenoxyphosphazene) or Chiral Poly(binaphthoxyphosphazene) Copolymers

The polyphosphazene random copolymer containing diphenylphosphane ligands {[NP(OC6H4PPh2)2]0.4[NP(O2C12H8)]0.6}n (1a) (O2C12H8 = 2,2′-dioxy-1,1′-biphenyl), and the chiral binaphthoxy analogues {[NP(OC6H4PPh2)2]0.1[NP(O2C20H12)]0.9}n [O2C20H12 = (R)-2,2′-dioxy-1,1′-binaphthyl] (1b) and {[NP(OC6H4PPh2)2]0.2[NP(O2C20H10Br2)]0.8}n [O2C20H10Br2 = (R)-2,2′-dioxy-6,6′-dibromo-1,1′-binaphthyl] (1c), reacted in dichloromethane at room temperature with appropriate amounts of the dimeric complex [Ru(η6-p-cymene)Cl(μ-Cl)]2 to give the corresponding polymeric (phosphane)RuII complexes {[NP(OC6H4PPh2[RuCl2(η6-p-cymene)]x)2]0.4[NP(O2C12H8)]0.6}n [x = 0.5 (2a), 1 (2b)], {[NP(OC6H4PPh2[RuCl2(η6-p-cymene)])2]0.1[NP(O2C20H12)]0.9}n (3) and {[NP(OC6H4PPh2[RuCl2(η6-p-cymene)])2]0.2[NP(O2C20H10Br2)]0.8}n (4). The isolated products are soluble reddish solids, and are thermally very stable with very high glass transition temperatures. The reaction of 1b or 1c with the cationic precursor [RuCl(PPh3)2(η6-p-cymene)][PF6] in refluxing THF gave the crosslinked insoluble cationic polymeric complexes {[NP(OC6H4PPh2)2]0.1[NP(O2C20H12)]0.9[RuCl(η6-p-cymene)(PF6)]0.05}n (5) and {[NP(OC6H4PPh2)2]0.2[NP(O2C20H10Br2)]0.8[RuCl(η6-p-cymene)(PF6)]0.08}n (6). All the complexes were active catalysts in transfer hydrogenation of acetophenone by propan-2-ol, but the C2-pockets containing the catalytic centers gave no enantioselectivity because of the conformational behavior of the chiral derivatives. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)