SYNTHESIS, CHARACTERIZATION AND MOLECULAR-STRUCTURE OF TETRAKIS(2,6-DIETHYLPHENYLISOCYANIDE)BIS(PERCHLORATO)COBALT(II) - AN EXAMPLE OF DISSIMILARITY BETWEEN PERCHLORATE AND TETRAFLUOROBORATE SALTS

Reaction of 2,6-Et2C6H3NC in 5:1 mole ratio with Co(II) produces Co(CNR)5X2.H2O, R = 2,6-Et2C6H3; X = ClO4, BF4; but the perchlorate salt spontaneously decomposes in solid state to Co(CNR)4(ClO4)2. The species Co(CNR)4(ClO4)2 was determined by X-ray crystallography to contain equivalent, monodentate, trans-coordinated perchlorate ions with average Co-O bond length 2.266(7) angstrom, and inequivalent arylisocyanide ligands with average Co-C bond lengths 1.896(13) and 1.887(11) angstrom in approximately square planar coordination (C-Co-C bond angles 87.8(4) and 92.2(4)-degrees, i.e. trans-[Co(CNR)4(ClO4)2]. Inequivalency of the arylisocyanides is achieved primarily through different tilt of the phenyl rings relative to the CoC4 plane and location of the perchlorates directly above or below one pair of CNR. The complex crystallizes in triclinic space group P1BAR with a = 11.550(3), b = 13.464(4), c = 15.684(3) angstrom, alpha = 77.39(2), beta = 68.43(2), gamma = 86.17(3)-degrees. Final discrepancy values of R = 0.0726 (R(w) = 0.0573) were obtained from 3723 unique, observed reflections. Solid state physical properties (IR, diffuse reflectance and magnetic susceptibility) are compared for [Co(CNR)4(ClO4)2] and [Co(CNR)5](BF4)2.H2O. Previously reported [Co(CNC6H3Me2-2,6)4](ClO4)2 should now be formulated as trans-[Co(CNC6H3Me2-2,6)4(ClO4)2], but the tetrafluoroborate ions in both Co(CNC6H3Et2-2,6)5(BF4)2.H2O and Co(CNC6H3Me2-2,6)5(BF4)2.0.5H2O are probably ionic.