Substituted 2,2′-Bis(2-oxidobenzylideneamino)-4,4′-dimethyl-1,1′-biphenyl Complexes of Zinc

The condensation reaction of 2,2-diamino-4,4-dimethyl-6,6'-dibromo-1,1-biphenyl with 2-hydroxybenzaldehyde as well as 5-methoxy-, 4-methoxy-, and 3-methoxy-2-hydroxybenzaldehyde yields 2,2-bis(salicylideneamino)-4,4-dimethyl-6,6-dibromo-1,1-biphenyl (1a) as well as the 5-, 4-, and 3-methoxy-substituted derivatives 1b, 1c, and 1d, respectively. Deprotonation of substituted 2,2-bis(salicylideneamino)-4,4-dimethyl-1,1-biphenyls with diethylzinc yields the corresponding substituted zinc 2,2-bis(2-oxidobenzylideneamino)-4,4-dimethyl-1,1-biphenyls (2) or zinc 2,2-bis(2-oxidobenzylideneamino)-4,4-dimethyl-6,6-dibromo-1,1-biphenyls (3). Recrystallization from a mixture of CH2Cl2 and methanol can lead to the formation of methanol adducts. The methanol ligands can either bind as Lewis base to the central zinc atom or as Lewis acid via a weak O-HO hydrogen bridge to a phenoxide moiety. Methanol-free complexes precipitate as dimers with central Zn2O2 rings.