Solid and solution state flexibility of sterically congested bis(imino)bipyridine complexes of zinc(ii) and nickel(ii)†
Abstract
Two new sterically demanding CR}2C10H6N2 (R = H (L1), Me (L2)), have been prepared in high yield by the condensation reaction of
CR)2C10H6N2 (R = H, Me). Palladium(0)-mediated cross coupling of 2-(Bu3Sn)-6-{C(Me)OCH2CH2O}C5H3N with 2-Br-6-{C(Me)OCH2CH2O}C5H3N, followed by an acid-mediated deprotection, has been employed as an efficient route to the precursor 6,6′-bis(acetyl)-2,2′-bipyridine. Reaction of aldimino L1 with two equivalents of MX2 [MX2 = ZnCl2, NiCl2 or (DME)NiBr2] in n-BuOH at elevated temperature gives the five-coordinate mononuclear complexes [(L1)MX2] (M = Zn, X = Cl 1; M = Ni, X = Cl 2a; M = Ni, X = Br 2b) as the sole products, in which one imine group is bound and the other uncoordinated (endo-exo). In the case of diamagnetic 1, VT
CMe)-6′-(CH
O)C10H6N2)ZnCl2] (3) (endo-imine, exo-formyl). Single crystal X-ray structures are reported for L1, 1, 2a, 3, 4 and 5.