Crystal structures of chromium and tungsten pentacarbonyl complexes of N,N′-dimethylimidazolidine-2-thione

Abstract

Crystals of chromium and tungsten pentacarbonyl complexes of N,N′-dimethylimidazolidine-2-thione (T) are isotypic with similar cell dimensions. They are triclinic, space group P 1 ( C i , No. 2), Z = 2. For Cr(CO) 5T, a = 8.263(3), b = 9.786(4), c = 9.474(3) Å, α = 84.26(2), β = 102.26(2), γ = 113.76(2)°, V = 685.1(4) Å 3, D c = 1.562 g/cm 3; for W(CO) 5T, a = 8.426(1), b = 9.895(1), c = 9.552(1) Å, α = 84.42(1), β = 102.46(1), γ = 114.56(1)°, V = 707.3(1) Å 3 D c = 2.132 g/cm 3. The structures, solved with 1453 and 3414, observed Mo-Kα diffractometer data to R factors of 0.082 and 0.032 respectively for the Cr and W compounds, consist of discrete neutral molecules, the metal being six coordinated in a slightly distorted octahedral geometry. The CrS and WS bonds are 2.510(3) and 2.617(2) Å respectively, whereas the MC(carbonyl) bonds trans to the S atoms are shorter at 1.827(10) (M = Cr) and 1.956(6) Å (M = W) compared to the average of CrC = 1.89(2) Å and WC = 2.03(1) Å. The SMC angles involving the carbonyl groups that point in the direction of the thione are widened (SCrC = 95.0(3)°; SWC = 94.8(2)°), indicating a slight steric effect. The differences between corresponding CrX and WX (X are the donating atoms) of these two complexes indicate a stronger WS bond than CrS. This is also reflected in a longer CS bond (1.716(7) vs. 1.697(12) Å) in the W complex.