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)