Metal complexes of new scorpionate ligands: 2,2′-Bis(pyrazolyl)ethylamine and its derivatives

Abstract

The new bis(pyrazolyl)amine ligand NH 2CH 2CH(pz) 2 ( 1) was prepared from the reaction of N-[2,2-bis(pyrazolyl)ethyl]-1,8-naphthalimide with hydrazine monohydrate. A substituted derivative, C 6H 5CH 2NHCH 2CH(pz) 2 ( 2), was prepared by the reaction of 1 with benzaldehyde followed by reduction with NaBH 4. Ligand 1 was also converted by two methods to the new bitopic, para-linked bis(pyrazolyl)amine ligand p-C 6H 4(CH 2NHCH 2CH(pz) 2) 2, ( 3). The reactions of the ligands 1– 3 with [Cu(PPh 3) 2]NO 3 yields {(PPh 3)Cu[(pz) 2CHCH 2NH 2]}NO 3, {(PPh 3)Cu[(pz) 2CHCH 2NHCH 2C 6H 5]}NO 3 and {[(PPh 3)Cu] 2[ p-((pz) 2CHCH 2NHCH 2) 2C 6H 4]}(NO 3) 2·solvate, respectively. Complex {(N 3) 2Cu[(pz) 2CHCH 2NHCH 2C 6H 5]} was obtained from a methanol solution of 2, copper(II) acetate monohydrate and sodium azide. The complex {Cd[(pz) 2CHCH 2NHCH 2C 6H 5] 2}(PF 6) 2·3C 3H 6O was synthesized by reaction of the protonated form of ligand 2, [(pz) 2CHCH 2NH 2CH 2C 6H 5]PF 6, with Cd(acac) 2. In all of the structures the ligands are tridentate, bonding to the metal through the lone pair on the amine group as well as through the pyrazolyl rings – they act as true scorpionates. The solid state structures all have extensive non-covalent interactions, with the N–H functional groups of the amines participating in both N–H⋯π and N–H⋯O or N–H⋯N hydrogen bonding interactions.