Chian Sing Lai

Supramolecular association in organomercury(II) 1,1-dithiolates. Complementarity between Hg⋯S and hydrogen bonding interactions in organomercury(II) 2-amino-cyclopent-1-ene-1-carbodithioates

A survey of the supramolecular associations operating in the crystal structures of organomercury 1,1-dithiolates shows that owing to the presence of Hg⋯S interactions, dimeric, 1-, 2- and 3-dimensional architectures are generated. Introducing hydrogen-bonding functionality into the 1,1-dithiolate ligand allows for the formation of both intra- and intermolecular hydrogen bonds as well as Hg⋯S interactions, so that 2- and 3-dimensional architectures are formed that are distinct for each of the two polymorphic forms of MeHg(S2CC5H6NH2-2) and for PhHg(S2CC5H6NH2-2).

Supramolecular aggregation in diimine adducts of zinc(II) dithiophosphates: controlling the formation of monomeric, dimeric, polymeric (zig-zag and helical), and 2-D motifs

The interplay between steric demands of dithiophosphate-bound R groups in Zn(S2P(OR)2)2 on the one hand and the coordination requirements of a variety of di-pyridyl-type bases on the other, is shown to be pivotal in determining supramolecular aggregation patterns in a series of their adducts. Thus, the combination of sterically demanding cyclohexyl groups and the congested trans-1,2-bis(2-pyridyl)ethylene ligand leads to a mononuclear species, but replacing the cyclohexyl by the less bulky isopropyl group allows for dimer formation in the structure of [Zn(S2P(OiPr)2)2(2-NC5H4C(H)C(H)C5H4N-2)0.5]2; a similar motif is found when pyrazine is the bridging ligand. These molecules aggregate in the solid-state to form chains via C–H⋯O interactions. Zig-zag polymers are found when the somewhat less congested 2,2′-dithiopyridine and bis(4-pyridyl)amine ligands are used as the bridges; the hydrogen-bonding functionality in the latter leads to a 2-D motif. Finally, exploiting the curved nature of the 1,3-bis(4-pyridyl)propane ligand leads to the formation of helical chains.

Steric control over polymer formation and topology in adducts of zinc dithiophosphates formed with bridging bipyridine ligands

A series of Zn(S2P(OR)2)2, R = iPr and Cy, adducts with bridging bipyridine ligands, i.e. 4,4′-bipyridine, trans-1,2-bis(4-pyridyl)ethylene and 1,2-bis(4-pyridyl)ethane have been investigated. The topology of the polymeric structures, i.e. zig-zag versus straight chain, can be controlled by the nature of the bridging bipyridine ligand in the case of adducts formed by Zn(S2P(OCy)2)2, an effect that can be traced to the steric bulk of the cyclohexyl groups. Polymer formation is precluded in the case of the adduct formed between Zn(S2P(OCy)2)2 and 4,4′bipyridine, again a result that is directly ascribed to the steric bulk of the thiolate residue.

Formation of antimony sulfide powders and thin films from single-source antimony precursors

Solvothermal and hydrothermal methods have been employed to generate nano-sized Sb2S3 (stibnites) from a variety of xanthate, dithiocarbamate and dithiophosphate precursors. The solvothermal method allows control of morphology by regulating precursor and size by reaction time; this process also produces near-uniform and larger particles. The xanthate precursors are far superior to the dithiocarbamates in their ability to produce oxide-free Sb2S3. Aerosol-assisted chemical vapour deposition (AACVD) provided a means to produce good quality films of Sb2S3. The advantages of xanthate precursors is rationalised in terms of a facile, low-temperature Chugaev rearrangement.

Crystal structures of 2,2'-bipyridine adducts of two cadmium O-alkyl dithiocarbonates: rationalisation of disparate coordination geometries based on different crystal packing environments

Abstract Two distinct coordination geometries are found in the structures of Cd(S2COR)2(2,2′-bipyridine). For R = CH2CH2OCH3 (1) a N2S2 donor set defines a distorted tetrahedral geometry for cadmium as the xanthate ligands adopt a monodentate coordination mode. By contrast, a N2S3 donor set is found in the structure where R is butyl (2) as one of the xanthate ligands is chelating. An analysis of the crystal structures shows that both lattices feature extensive C–H...π interactions and that in (1) there are C–H...O interactions that are not present in (2). In (2) there are π...π interactions that are absent in (1). A qualitative argument based on crystal packing considerations is proposed to explain the differences in molecular structures.

The importance of C–H⋯N, C–H⋯π and π⋯π interactions in the crystal packing of the isomeric N1,N4-bis((pyridine-n-yl)methylene)-cyclohexane-1,4-diamines, n = 2, 3 and 4

The molecular structures of the isomeric N1,N4-bis((pyridine-n-yl)methylene)-cyclohexane-1,4-diamines, where n = 2 (1), 3 (2) and 4 (3), show the same effective conformation, in particular between the n-pyridine rings and the bridging cyclohexane rings. Theoretical structures of 1–3 are more symmetric and confirm that the pyridine residues are orthogonal to the plane through the four methylene groups of the bridging cyclohexyl groups. Crystal packing in 1–3 is dominated by C–H⋯Npyridine interactions. In 1, these interactions lead to linear chains and, along with π⋯π contacts, give rise to a layer structure. In 2, the C–H⋯Npyridine interactions extend in three dimensions and are complemented by C–H⋯N imine and C–H⋯π contacts. Finally, in 3, the C–H⋯Npyridine interactions lead to layers that are connected by C–H⋯π interactions to give a 3D network. It appears that in the structures of 1–3, the relative disposition of the pyridine and imine groups allows for the participation of the former in intermolecular interactions owing to their accessibility compared with the latter.

Molecular paving with zinc thiolates

The structure of Zn(S2COnPr)2 features [–Zn–S–C–S–]4 16-membered rings that share two corners with adjacent rings leading to the formation of a chain. This contrasts the situation in closely related Zn(S2COiPr)2, which displays isolated 16-membered rings, and in Zn(S2COEt)2, which adopts a layer structure owing to all corners of the 16-membered rings being shared. If the isolated 16-membered ring is considered as a paving stone, a description of the Zn(S2COR)2 structures ensues where the pavers in R = iPr are connected into a chain for R = nPr and finally into a 2-D architecture (e.g. path) for R = Et, demonstrating steric control over molecular aggregation.

Polymeric topologies in cadmium(II) dithiophosphate adducts of the isomeric n-pyridinealdazines, n = 2, 3 and 4

Abstract A series of crystal structures of adducts formed between cadmium dithiophosphate, Cd(S2P(OiPr)2)2, and the isomeric n-pyridinealdazine ligands, n = 2, 3, and 4, are described. A centrosymmetric dimer is found in the 2 : 1 adduct with the 2-isomer, i.e. [Cd(S2P(OiPr)2)2(2-NC5H4C(H) = C(H)C5H4N-2)0.5]2, in which the cadmium atom exists within a cis-N2S4 donor set and the di-pyridyl-type ligand is tetradentate. By contrast, trans-N2S4 donor sets for cadmium and regular bridging modes of coordination lead to polymers with a step-ladder topology are found in the 1:1 adducts with the 3- and 4-isomeric ligands, i.e. [Cd(S2P(OiPr)2)2(n-NC5H4C(H) = C(H)C5H4N-n)]∞, for n = 3 and 4. Differences in aggregation behaviour are related to the binding requirements of the n-pyridinealdazine ligands.

Prevalance of intermolecular Bi … S interactions in bismuth dithiocarbamate compounds: Bi(S2CNR2)3

A series of crystal structures of tris(N,N-di-isobutyldithiocarbamato)bismuth(III), Bi{S2CN(iBu2)}3 (1), tris(N,N-tetramethylenedithiocarbamato)bismuth(III), Bi{S2CN(CH2)4}3 (2), tris(N,N-hexamethylenedithiocarbamato)bismuth(III) chloroform solvate, Bi(S2CN(CH2)6)3 · CHCl3 (3), and tris(N-methyl, N-phenyldithiocarbamato)-bismuth(III) hemi acetonitrile solvate, Bi(S2CN · (Me)Ph)3 · 0.5 CH3CN (4) has been determined and each structure shows the presence of three chelating dithiocarbamate ligands as well as two (in (1) and (2)) or one (in (3) and (4)) intermolecular Bi … S interactions leading to the formation spherical dimeric aggregates. The conclusion of this structural study is that regardless of the size of the dithiocarbamate-bound R groups, intermolecular Bi … S interactions dominate the crystal packing in Bi(S2CNR2)3.

Phenyl­(pyrrolinedi­thio­carbamato)­mercury(II)

An approximately linear geometry around Hg is found in the title compound, PhHg[S2CN(CH2)4] or [Hg(C6H5)(C5H8NS2)]. Distortions in the geometry arise from intra- and intermolecular Hg⋯S interactions, with the latter resulting in the formation of loosely associated dimeric units.