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

The new bis(pyrazolyl)amine ligand NH2CH2CH(pz)2 (1) was prepared from the reaction of N-[2,2-bis(pyrazolyl)ethyl]-1,8-naphthalimide with hydrazine monohydrate. A substituted derivative, C6H5CH2NHCH2CH(pz)2 (2), was prepared by the reaction of 1 with benzaldehyde followed by reduction with NaBH4. Ligand 1 was also converted by two methods to the new bitopic, para-linked bis(pyrazolyl)amine ligand p-C6H4(CH2NHCH2CH(pz)2)2, (3). The reactions of the ligands 1–3 with [Cu(PPh3)2]NO3 yields {(PPh3)Cu[(pz)2CHCH2NH2]}NO3, {(PPh3)Cu[(pz)2CHCH2NHCH2C6H5]}NO3 and {[(PPh3)Cu]2[p-((pz)2CHCH2NHCH2)2C6H4]}(NO3)2·solvate, respectively. Complex {(N3)2Cu[(pz)2CHCH2NHCH2C6H5]} was obtained from a methanol solution of 2, copper(II) acetate monohydrate and sodium azide. The complex {Cd[(pz)2CHCH2NHCH2C6H5]2}(PF6)2·3C3H6O was synthesized by reaction of the protonated form of ligand 2, [(pz)2CHCH2NH2CH2C6H5]PF6, 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.