STUDY OF THE MUTUAL INFLUENCE OF LIGANDS IN COBALT(II) COMPLEXES CONTAINING THIOCYANATE AND IMIDAZOLE DERIVATIVES

The cobalt(II) complexes of formula [Co(NCS)(2)L-2] and [Co(NCS)(2)L-4 '] (L=imidazole (iz) derivatives, 1-Meiz (1), 2-Meiz (2), 2-Etiz (3),2 -Isopropiz (4), 2-Pheniz (5), 1,2-Me(2)iz (6), Biz (7), 2-Mebiz (8),2- Etbiz (9); L'=iz (10), 1-Meiz (11)) have been synthesized and characte rized by spectroscopic methods and magnetic measurements. The crystal and molecular structures of complexes 6 and 11 have been determined by X-ray diffraction methods. Complex 6 crystallizes in the orthorhombic space group Pnma with cell constants a=9.209(3), b=12.462(5), c=14.85 1(3) Angstrom; V=1704.3(9) Angstrom(3), D (calc., Z=4)=1.43 g cm(-3), M-r=367.35, F(000)=640, lambda(Mo K alpha)=0.71079 Angstrom, mu=11.2 c m(-1) and T=293 K. Complex 11 crystallizes in the monoclinic space gro up P2(1)/n with cell constants a=7.689(2), b=11.095(1), c=14.156(2) An gstrom, beta=93.46(2)degrees; V=1205.4(3) Angstrom(3), D (calc., Z=2)= 1.39 g cm(-3), M-r=503.51, F(000)=534, lambda(Mo K alpha)=0.71079 Angs trom, mu=8.56 cm(-1) and T=293 K. 2553 (6) and 2485 (11) reflections w ere collected over the range 1 less than or equal to theta less than o r equal to 25; from these, 1571 (6) and 1977 (11) (independent and wit h I greater than or equal to 3 sigma(I)) were used in the structural a nalysis. The final value of the R-w residual was 0.077 and 0.042 for 6 and 11, respectively. The structure of 6 is built up by [Co(NCS)(2)(1 ,2-Me(2)iz)(4)] mononuclear units where the metal atom exhibits an app roximately tetrahedral configuration: the Co-N bond distances and N-Co -N bond angles vary in the range 1.958(8)-1.922(8) Angstrom and 114.7( 3)-108.3(3)degrees, respectively, The structure of 11 consists of [Co( NCS)(2)(1-Meiz)(4)] monomeric units where two N-coordinated thiocyanat e groups in trans position and four 1-methylimidazole ligands build a slightly distorted CoN6 octahedral environment. The Co-N bond lengths lie in the range 2.158(2)-2.135(3) Angstrom being significantly longer than the related ones observed in 6.