Abstract :
The structural chemistry of the binary zinc-triad (group 12) dithiocarbamates (−S2CNRR′)2 (R/R′ = alkyl/aryl), along with related 1,1-dithiolate ligands, i.e. dithiophosphates [−S2P(OR)2] and dithiocarbonates (xanthates; −S2COR), have long attracted the attention of structural chemists owing to their diversity of structures/supramolecular association patterns in the solid state (Cox & Tiekink, 1997[Cox, M. J. & Tiekink, E. R. T. (1997). Rev. Inorg. Chem. 17, 1-23.]; Tiekink, 2003[Tiekink, E. R. T. (2003). CrystEngComm, 5, 101-113.]). The common structural motif adopted by all elements is one that features two chelating ligands and two tridentate ligands (chelating one metal atom and simultaneously bridging to a second), leading, usually, to a centrosymmetric binuclear molecule. Indeed, most zinc dithiocarbamate structures adopt this motif, but when the R/R′ are bulky, a mononuclear species with tetrahedrally coordinated zinc atoms is found; significantly greater structural variety has been noted for the binary zinc dithiophosphates and xanthates (Lai et al., 2002[Lai, C. S., Lim, Y. X., Yap, T. C. & Tiekink, E. R. T. (2002). CrystEngComm, 4, 596-600.]; Tan et al., 2015[Tan, Y. S., Ooi, K. K., Ang, K. P., Akim, A. M., Cheah, Y.-K., Halim, S. N. A., Seng, H.-L. & Tiekink, E. R. T. (2015). J. Inorg. Biochem. 150, 48-62.]). More diversity in structural motifs is noted in the binary cadmium dithiocarbamates with the recent observation of linear polymeric forms with hexacoordinated cadmium atoms (Tan et al., 2013[Tan, Y. S., Sudlow, A. L., Molloy, K. C., Morishima, Y., Fujisawa, K., Jackson, W. J., Henderson, W., Halim, S. N., Bt, A., Ng, S. W. & Tiekink, E. R. T. (2013). Cryst. Growth Des. 13, 3046-3056.], 2016[Tan, Y. S., Halim, S. N. A. & Tiekink, E. R. T. (2016). Z. Kristallogr. 231, 113-126.]; Ferreira et al., 2016[Ferreira, I. P., de Lima, G. M., Paniago, E. B., Pinheiro, C. B., Wardell, J. L. & Wardell, S. M. S. V. (2016). Inorg. Chim. Acta, 441, 137-145.]). Systematic studies indicated solvent-mediated transformations between polymeric and binuclear structural motifs, with the latter being the thermodynamically more stable (Tan et al., 2013[Tan, Y. S., Sudlow, A. L., Molloy, K. C., Morishima, Y., Fujisawa, K., Jackson, W. J., Henderson, W., Halim, S. N., Bt, A., Ng, S. W. & Tiekink, E. R. T. (2013). Cryst. Growth Des. 13, 3046-3056.], 2016[Tan, Y. S., Halim, S. N. A. & Tiekink, E. R. T. (2016). Z. Kristallogr. 231, 113-126.]). The greatest structural diversity among the zinc-triad dithiocarbamates is found for the binary mercury compounds, where mononuclear, binuclear and polymeric structures have been observed, as summarized very recently (Jotani et al., 2016[Jotani, M. M., Poplaukhin, P., Arman, H. D. & Tiekink, E. R. T. (2016). Acta Cryst. E72, 1085-1092.]). Complementing the structural motifs already mentioned for zinc and cadmium is a trinuclear species, {Hg[S2CN(tetrahydroquinoline)]2}3 (Rajput et al., 2014[Rajput, G., Yadav, M. K., Thakur, T. S., Drew, M. G. B. & Singh, N. (2014). Polyhedron, 69, 225-233.]), with the central HgII atom being hexacoordinated, as in the polymeric form, and the peripheral HgII atoms being coordinated as in the binuclear form, indicating the possibility that this is an intermediate metastable form in the crystallization of this compound. In light of the above, when crystals of the title compound became available, namely {Cd[S2CN(Me)Ph]2}2, (I)[link], its crystal and molecular structures were studied, along with an evaluation of the supramolecular association in the crystal through an analysis of the Hirshfeld surface.
