Alkyl Substituent Effects in Diamagnetic Dithiocarbamate Cobalt(III) and Nickel(II) Complexes

Abstract

Single-crystal X-ray structure determinations have been recorded at 295 K for the tris(dithiocarbamato)cobalt(III) compounds: [Co(S₂CN(CH₂)₄)₃], [Co(S₂CNEt₂)₃] (redeterminations), [Co(S₂CN(CH₂Ph)₂)₃], and [Co(S₂CNPrⁱ₂)₃] at 120 and 295 K. [Co(S₂CN(CH₂)₄)₃] crystallizes in the space group C2/c with a 28.984(15), b 14.416(2), c 16.206(15)Ǻ, β 104.20(5)°, Z 12; [Co(S₂CNEt₂)₃] also crystallizes in space group C2/c with a 14.097(3), b 10.305(2), c 17.070(7)Ǻ, β 110.19(3)°, Z 4; [Co(S₂CN(CH₂Ph)₂)₃] crystallizes in space group P2₁ with a 11.851(6), b 29.920(8), c 12.395(3)Ǻ, β 97.74(4)°; [Co(S₂CNPrⁱ₂)₃] crystallizes in space group R3c with a 13.367(6)Ǻ, α 58.04(2)° (295 K); a 13.155(6)Ǻ, α 58.59(3)° (120 K), Z 2. The structure of [Ni(S₂CNPrⁱ₂)₂] has been redetermined, the complex crystallizing in the space group P2₁/c with a 8.147(2), b 17.820(3), c 15.630(3)Ǻ, β 110.32(2)°, Z 4. The results obtained from this study support the hypothesis, put forward by Ymen and Stahl, that the influence of aliphatic hydrocarbon substituents on the ligand-field strength at the sulfur atoms of the dithiocarbamate ligand is not through the π bonding network of the conjugated S₂CN moiety, but, rather, intraligand S…H-C interactions which increase with increasing bulk of the substituent atoms. Unlike the free anion systems, or the iron(III) complexes, however, the changes in the S-C-S angles with increasing field strength, while observable, are very small.