Compounds of nickel(II) with 5 RS,7 RS,12 RS,14 RS-5,12-dimethyl-7,14-diphenyl-1,4,8,11-tetraazacyclotetradecane, rrL 2; the structures of [Ni(rrL 2)(acac)]ClO 4 and [Ni(rrL 2)][ZnCl 4]·MeNO 2

Abstract

Nickel(II) complexes of the 14-membered cyclic tetraamine 5 RS,7 RS,12 RS,14 RS-5,12-dimethyl-7,14-diphenyl-1,4,8,11-tetraazacyclotetradecane, rrL 2, are prepared by reduction of 7 RS,14 RS-(5,12-dimethyl-7,14-diphenyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene)nickel(II) perchlorate with NaBH 4 in acetonitrile/methanol and also by reaction of the ligand (formed by the reduction of 5,12-dimethyl-7,14-diphenyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene) with nickel(II) salts. Most nickel(II) compounds of rrL 2 have the macrocycle in folded coordination, with N-configuration V (1 RS,4 RS,8 RS,11 RS), with a chelate (acac −=pentane-2,4-dionato, μ-C 2O 4 2− , CH 3CO 2 − , NO 3 − , NO 2 − , HCO 3 − , BH 4 − ), cis-unidentate additional ligands (H 2O, NCS −) or cis-bridging ligands, for [{Ni(rrL 2)} 2X 2](ClO 4) 2 (X=Cl −, Br −, CN −), completing octahedral coordination. The cation of 1 RS,4 RS,5 RS,7 RS,8 RS,11 RS,12 RS,14 RS-[Ni(rrL 2)(acac)]ClO 4 has twofold symmetry with NiN(1)=2.111(3), NiN(4)=2.141(3), NiO=2.028(3) Å, N(1)NiN(8)=99.8(2), N(4)NiN(11)=173.5(2)°. In the absence of effective additional ligands the S=1 square-planar cation [Ni(rrL 2)] 2+ is stable. The salt 1 RS,4 SR,5 RS,7 RS,8 RS,11 SR,12 RS,14 RS-[Ni(rrL 2)][ZnCl 4]·MeNO 2 has N-configuration I with the four NH groups oriented to one side of the N 4 donor ‘plane’, which has a ±0.011 Å tetrahedral twist, with the nickel ion 0.031 Å from this plane, displaced away from the NH groups, with NiN mean=1.925(4) Å. Molecular modeling studies of the isomeric [Ni(rrL 2)] 2+ cations are described.