Co(II), Ni(II), and Zn(II) compounds of the new tridentate ligand N,N-bis(2-ethyl-5-methyl-imidazol-4-ylmethyl)aminopropane (biap). X-ray structures of biap center dot H2O, [Co(biap)(NCS)(OAc)], [Ni(biap)(NCS)(OAc)], [Ni(biap)(NCS)(2)(MeCN)](MeCN), and [Ni(biap)(2)](BF4)(2)(EtOH)

The syntheses and characterizations are described of 18 transition metal co ordination compounds with the novel tridentate ligand N,N-bis(2-ethyl-5-met hyl-imidazol-4-ylmethyl)-aminopropane (biap). Compounds with formulae [M(bi ap)-(X)(Y)(H2O)(n)].(solvent) with X-, Y- = Cl-, Br-, NO3-, CH3COO- and NCS -, and n = 0 or 1, and [M(biap)(2)](BF4)(2).(solvent), with M = Co2+, Ni2+, and Zn2+, as well as the dinuclear complexes [Ni(biap)X-2](2) (X- = Cl-, N CS-) have been isolated. The ligand biap acts as a tridentate ligand in all compounds, either meridionally or facially, except for the cobalt compound [Co(biap)(NCS)(OAc)], where the X-ray structure indicates that the amine n itrogen is weakly bonded, almost only semi-coordinated (Co-N = 2.387(4) Ang strom). The ligand biap, synthesized in a very simple one-pot and one-step condensation reaction, crystallizes with one molecule of water, viz. biap . H2O. Its single-crystal X-ray structure reveals a three-dimensional networ k based on hydrogen bonds, whereby the water oxygen is tetrahedrally connec ted to four imidazole-nitrogens of three biap molecules. Eighteen coordinat ion compounds have been obtained with salts of divalent cobalt, nickel, and zinc. Single-crystal X-ray structures have been obtained for four of the c ompounds. The nickel(II) ion is (distorted) octahedrally surrounded by biap nitrogens and/or anion or solvent nitrogens or oxygens, resulting in the c hromophores NiN6, NiN3N2N, and NiN3NO2 for [Ni(biap)(2)](BF4)(2).(EtOH) (14 ), [Ni(biap)(NCS)(2)(MeCN)].(MeCN) (13), and [Ni(biap)(NCS)(OAc)] (12), res pectively. The ligand is coordinated meridionally in 13, but facially in 14 and 12, illustrating its flexibility. The cobalt(II) ion in [Co(biap)(NCS) (OAc)] (4) is in a very distorted pseudo-octahedral environment, which can be regarded as distorted tetrahedral when considering didentate coordinatio n of the biap and monodentate coordination of the acetate ion. This severel y distorted geometry is reflected in the unusual ligand field spectrum of t his cobalt complex. Spectroscopic characterization (IR, LF and NMR) of the compounds shows a remarkable variety in composition and geometry, partly de termined by the solvent used for the synthesis of the complexes. The flexib ility of the tridentate ligand, which can bind mer or fac, with one or two ligands coordinated to the metal ion is quite unexpected in view of the ass umed steric crowding from the ethyl- and propyl-chains. (C) 2000 Elsevier S cience S.A. All rights reserved.