A NEW TRIDENTATE N,N,S LIGAND AND ITS ZINC-COMPLEXES

The tridentate thiol ligand N-(2-mercaptoethyl)picolylamine (MEPAH) which is obtained from picolylamine and ethylene sulfide shows a very variable zinc complex chemistry. With zinc salts of noncoordinating anions it forms the trinuclear complexes [(MEPA)(4)Zn-3]X(2) (1a-c: X = BF4, ClO4, NO3). With zinc halides it produces the polymeric 1:1 complexes (MEPA)ZnHal (2a,b: Hal = Cl, Br), and with zinc acetate the dimeric 1:1 complex (MEPA)ZnOAc (3) results. The 2:1 complex (MEPA)(2)Zn (4) is obtained by the reaction with Zn[N(SiMe(3))(2)](2). The mixed-ligand complex (MEPA)Zn(2-(hydroxymethyl)benzenethiolate (5) results from Zn[N(SiMe(3))(2)](2). MEPAH, and the thiol, and the mixed-ligand complex (MEPA)Zn(quinoline-2-carboxylate) (6) is formed from Zn(ClO4)(2), MEPAH, and the acid. Crystal structure determinations have revealed one tetrahedral ZnS4 and two octahedral ZnN4S2 units in 1a, trigonal-bipyramidal ZnN2S2Cl coordination in 2a, square-pyramidal ZnN2S2O coordination in 3, tetrahedral ZnN2S2 coordination in 4, and a trigonal-bipyramidal arrangement of the two chelate ligands in 6 yielding a ZnN3SO coordination. The unusual bonding situation (only bidentate) of the MEPA ligand in the 2:1 complex 4 results in the facile conversion of 4 to the trinuclear complexes 1a-c upon reaction with the zinc salts and to the polymeric complex 2a upon reaction with CH2Cl2 or HCl.