Random copolymers with 2,2'-dioxy-1,1'-biphenyl-phosphazene and chiral 2,2'-dioxy-1,1'-binaphthylphosphazene units functionalized in the 6,6'-positions with PPh2 groups as precursors for Ru(arene) catalysts

The chiral phosphazene copolymers {[NP(O2C12H8)](0.9)[NP(O2C20H12)](0.1)} (1) and {[NP(O2C12H8)](0.9)[NP(O2C20H10Br2)](0.1)} (n) (2) [(O2C12H8) = 2,2'-dioxy-1,1'-biphenyl; (O2C20H12) = R-2,2'-dioxy-1,1'-binaphthyl and (O2C20H10Br2) = R-6,6'-dibromo-2,2'-dioxy-1,1'-binaphthyl] were prepared by sequential substitution from [NPCl2] (n) and the corresponding dihydroxy-biphenyl or binaphthyl reagents in the presence of Cs2CO3 and K2CO3. The reaction of (2) with (BuLi)-Bu-t in THF, followed by addition of PPh2Cl and a treatment with SiHCl3/PPh3 to eliminate any oxidized OC6H4P(O)Ph-2 groups, gave the phosphine containing copolymer {[NP(O2C12H8)](0.9)[NP(O2C20H10[PPh2](2))](0.1)} (n) (3), that was used as a chiral ligand to support [Ru(p-cymene)Cl] complexes. The resulting catalyst was active for hydrogen transfer from isopropyl alcohol to acetophenone but the placement of the Ru centers in the 6,6'-positions of the binaphthoxyphosphazene units induced no enantioselectivity.