Compounds of nickel(II) with 5 RS,7 RS,12 SR,14 SR-5,12-dimethyl-7,14-diphenyl-1,4,8,11-tetraazacyclotetradecane, mmL 2; the structures of δ-[Ni(mmL 2)](ClO 4) 2, trans-β-[Ni(mmL 2)(NO 2- N) 2] and cis-α-[Ni(mmL 2)(acac)]ClO 4

Abstract

Reduction of the imine functions of 7 RS,14 SR-(5,12-dimethyl-7,14-diphenyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene)nickel(II) gives the meso–meso (5 RS,7 RS,12 SR,14 SR) and rac-meso (5 RS,7 RS,12 RS,14 SR) isomers of (5,12-dimethyl-7,14-diphenyl-1,4,8,11-tetraazacyclotetradecane)nickel(II), [Ni(mmL 2)] 2+ and [Ni(rmL 2)] 2+, in approximately 6:1 proportions. Most compounds of [Ni(mmL 2)] 2+ have the amine in planar coordination with the 1 RS,4 RS,8 SR,11 SR N-configuration III (labelled β) of the nitrogen centres as square-planar singlet ground state salts β-[Ni(mmL 2)]X 2 (X −=ClO 4 − , 1/2[ZnCl 4] 2−) or as octahedral triplet ground state compounds trans-β-[Ni(mmL 2)X 2] (X −=Cl −, Br −, I −, N 3 − NO 3 − , HCO 3 − , MeCO 3 − , NCS −, NO 2 − , CN −), trans-β-Ni(mmL 2)(CN)(ClO 4), bis-adducts trans-β-[Ni(mmL 2)Y 2](ClO 4) 2 (Y=MeCN, DMSO, DMF, pyridine, MeNO 2, NH 3) and trans-μ-anion polymeric compounds β-[Ni(mmL 2)Z] (Z 2−=C 2O 4 2− , SO 4 2− , CO 3 2− , [Ni(CN) 4] 2−). Centrosymmetrical trans-β-[Ni(mmL 2)(NO 2- N) 2] has N-configuration III, with all chelate rings in optimum chair or gauche conformations, with all substituents equatorially oriented and with mean distances NiN amine=2.083(2), NiN nitro=2.183(2) Å. Reaction of trans-β-[Ni(mmL 2)(HCO 3) 2]·H 2O with alcohols form compounds of mono-alkyl carbonate esters, trans-β-[Ni(mmL 2)(CO 2OR) 2]. Compounds cis-α-[Ni(mmL 2)(A)]ClO 4 (A=pentane-2,4-dionato −, 1/2C 2O 4 2− ) have the macrocycle folded. The acac − compound has the 1 RS,4 RS,8 RS,11 RS N-configuration V with mean distances NiN=2.121(3), NiO=2.042(3) Å and angles N(4)NiN(11)=173.2(1), N(1)NiN(8)=95.1(1)°, with one six-membered chelate ring in a chair conformation with the substituents equatorially oriented and the other in a boat conformation that orients the substituents pseudo-equatorially. The folded macrocycle compounds react with acid to form a metastable [Ni(mmL 2)] 2+ cation, isolated as the perchlorate salt δ-[Ni(mmL 2)](ClO 4) 2 with the 1 RS,4 RS,5 SR,7 SR,8 SR,11 RS,12 RS,14 RS configuration, N-configuration II. The square-planar cation is tetrahedrally twisted with N-atoms ±0.103 Å and Ni atom 0.043 Å from the best N 4 plane, with mean NiN=1.933(6) Å. One six-membered chelate ring is in a chair conformation with the substituents equatorially oriented, and the other in a twist conformation with the methyl substituent axially and the phenyl substituent equatorially oriented. Relative strain energies for the isomeric cations were calculated by molecular mechanics.