Synthesis, characterization and x-ray structure of hetero-polynuclear thiocyanates of iron(II) and mercury(II) with 5,7-dimethyl[1,2,4]triazolo[1,5,- a]pyrimidine-N 3 and water as ligands

Abstract

The synthesis and characterization of heteronuclear compounds of formula FeHg(NCS) 4(dmtp) 2(H 2O 1.5 ( I), FeHg(NCS) 4(dmtp) 2(H 2O) ( II) and FeHg(NCS) 4(dmtp)(H 2O) 2·(Me 2CO) ( III) with dmtp = 5,7-dimethyl[1,2,4]triazolo[1,5- a] pyrimidine (C 7H 8N 4) are described. Infrared spectra of these compounds have shown the presence of both S-coordinating and N,S-bridging thiocyanate ligands; moreover, ligand field spectra have indicated an octahedral coordination geometry for the iron ions. The structures of these compounds were elucidated by X-ray diffraction methods. Crystals of I are triclinic, space group P 1 , with a = 16.318(10), b = 18.389(14), c = 10.089(4) Å, α = 105.15(4), β = 101.24(6), γ = 83.31(9)°, Z = 2; crystals of II are monoclinic, space group P2 1/ n, with a = 11.599(7), b = 16.54(5), c = 14.766(10) Å, β = 98.47(5)°, Z = 4; crystals of III are monoclinic, space group P2/ n, with a = 12.285(7), b = 13.689(6), c = 7.562(5) Å, β = 96.28(3)°, Z = 2. The structures were solved from diffractometer data by Patterson and Fourier methods and refined by full-matrix least-squares to R = 0.044 for I, 0.038 for II and 0.058 for III. The structure of I consists of two different octahedral complexes, [Fe(NCS) 3(dmtp) 2(H 2O)] ( a) and [Fe(NCS) 2(dmtp) 2(H 2O) 2] ( b) (in which nitrogen atoms from both thiocyanate groups and dmtp ligands besides water molecules are involved in coordination), and tetrahedral [Hg(SCN) 4] complexes bridging either two or three iron atoms. In II [Hg(SCN) 4] and [Fe(NCS) 3(dmtp) 2(H 2O)] complexes are present, the octahedral iron complex differing from the complex ( a) only in the mutual orientations of the dmtp molecules. The structure of III consists of [Hg(SCN) 4] and [Fe(NCS) 3(dmtp)(H 2O) 2] complexes together with acetone molecules of crystallization; the octahedral iron complex, involving only one dmtp molecule, can be derived from the complex ( b) replacing a dmtp molecule by a thiocyanate ligand. The thiocyanate groups which bridge heterometals determine one-, two- and three-dimensional systems in I, III and II respectively.