Synthesis, characterization and molecular structure of tetrakis(2,6-diethylphenylisocyanide)bis(perchlorato)cobalt(II). An example of dissimilarity between perchlorate and tetrafluoroborate salts

Abstract

Reaction of 2,6-Et 2C 6H 3NC in 5:1 mole ratio with Co(II) produces Co(CNR) 5X 2·H 2O, R=2,6-Et 2C 6H 3; X=ClO 4, BF 4; but the perchlorate salt spontaneously decomposes in solid state to Co(CNR) 4(ClO 4) 2. The species Co(CNR) 4(ClO 4) 2 was determined by X-ray crystallography to contain equivalent, monodentate, trans-coordinated perchlorate ions with average CoO bond length 2.266(7) Å, and inequivalent arylisocyanide ligands with average CoC bond lengths 1.896(13) and 1.887(11) Å in approximately square planar coordination (CCoC bond angles 87.8(4) and 92.2(4)°, i.e. trans-[Co(CNR) 4(ClO 4) 2]. Inequivalency of the arylisocyanides is achieved primarily through different tilt of the phenyl rings relative to the CoC 4 plane and location of the perchlorates directly above or below one pair of CNR. The complex crystallizes in triclinic space group P 1 with a=11.550(3), b=13.464(4), c=15.684(3) Å, α=77.39(2), β=68.43(2), γ=86.17(3)°. 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(ClO 4) 2] and [Co(CNR) 5](BF 4) 2·H 2O. Previously reported [Co(CNC 6H 3Me 2-2,6) 4](ClO 4) 2 should now be formulated as trans-[Co(CNC 6H 3Me 2- 2,6) 4(ClO 4) 2, but the tetrafluoroborate ions in both Co(CNC 6H 3Et 2-2,6) 5(BF 4) 2·H 2O and Co(CNC 6H 3Me 2-2,6) 5(BF 4) 2·0.5H 2O are probably ionic.