Reactivity of 6-(2-tolyl)- and 6-(2,6-xylyl)-2,2 '-bipyridines with palladium(II) derivatives. Selective C(sp(3))-H vs. C(sp(2))-H activation RID D-3096-2011

Two new 6-substituted 2,2'-bipyridines, L, 6-(2-tolyl)bipy, L-1, and 6-(2,6-xylyl)bipy, L-2, have been synthesized. Their reactions with Na-2[PdCl4] or {Pd(OAc)(2)} afford either 1:1 adducts [Pd(L)X-2] (X = Cl, OAc) or five-membered cyclometallated derivatives [Pd(L-1-H)X] arising from C(sp(2))-H activation. From the chloro-alkyl intermediates [Pd(L)(Me)Cl], in the presence of Na[BAr4'] (Ar'=3,5-(CF3)(2)C6H3 cationic species [Pd(L)(Me)(S)](+) (L=L-1, L-2; S=CH3CN) can be obtained. At variance, in less coordinating solvents, e.g. dichloromethane, unexpected activation of a C(sp(3))-H bond occurs with loss of methane, to afford 6-membered cyclometallated derivatives. The latter species were isolated as [Pd(L-H)(PPh3)][BAr4']. (C) 2003 Elsevier Science B.V. All rights reserved.