Structural diversity in the mercury(II) bis(N,N-dialkyldithiocarbamate) compounds: an example of the importance of considering crystal structure whenrationalising molecular structure

The crystal and molecular structures of four compounds of the general formu la Hg(S2CNR2)(2) are reported. The pale-yellow crystals of [Hg(S2CNiBu2)(2) ] are monoclinic, space group C2/c with unit cell dimensions a = 26.27(2) A ngstrom, b = 13.654(8) Angstrom, c = 13.863(5) Angstrom, beta = 96.64(4)deg rees, Z = 8 and D-x = 1.639 Mgm(-3). The yellow crystals of [Hg(S2CN(iPr)Cy )(2)] are triclinic, space group PT with unit cell dimensions a = 12.291(9) Angstrom, b = 11.534(6) Angstrom, c = 9.559(4) Angstrom, alpha = 69.82(4)de grees, beta = 88.94(4)degrees, gamma = 72.00(5)degrees, Z = 2 and D-x = 1.7 47 Mg m(-3) Crystals of yellow [Hg(S2CN(Et)Cy)(2)] are monoclinic, space gr oup P (1) over bar with unit cell dimensions a = 8.459(6) Angstrom, c = 19. 506(9) Angstrom, c = 13.955(6) Angstrom, beta= 92.89(4)degrees, Z = 4 and D -x = 1.748 Mg m(-3). The yellow crystals of [Hg(S2CN(Et)Cy)(2)] are monocli nic, space group C2/c with unit cell dimensions a = 23.210(6) Angstrom, b = 16.48(1) Angstrom, c=16.285(6) Angstrom, beta=126.81(2)degrees, Z = 8 and D-x = 1.623 Mg m(-3). The structures were solved by direct methods and each refined by a full-matrix least squares procedure to final R = 0.037 using 2994 reflections for [Hg(S2CN(Bu-2)(2)] t o R = 0.043 using 3861 reflection s for [Hg(S2CN(iPr)Cy)(2)]; to R = 0.041 for 2895 reflections for [Hg(S2CN( Et)Cy)(2)]; and to R = 0.065 for 2640 reflections for [Hg(S(2)CNnBu(2))(2)] . A monomeric featuring distorted tetrahedral geometries, is2640 motif, fea turing found for the structures or [Hg(S2CNiBu2)(2)] [Hg(S2CN(iPr)Cy)(2)]. By contrast, dimeric structures, arising from the presence of bridging dith iocarbamate ligands, are found in the structures of [Hg(S2CN(Et)Cy)(2)] and [Hg(S(2)CNnBu(2))(2)]. A critical examination of crystal structure for thes e and related systems enables a qualitative explanation for the structural diversity observed in the Hg(S2CNR2)(2) compounds. The primary coordination about the mercury centers in Hg(S2CNR2)(2) is linear and other association s, be they intra- or intermolecular, give rise to distortions from linearit y and result in varied coordination geometries. The nature of the additiona l interactions is dictated by the need to maximise intermolecular associati ons. Thus, when there are no steric restrictions precluding association in the lattice,Hg-S interactions are present that give rise to dimeric structu res or 2-dimensional layer structures in the case when R = H.