Conformation versus Coordination: Synthesis and Structural Investigations of Tellurium(II) Dithiolates Derived from β-Donor-Substituted Thiols

New methods of preparing tellurium(II) dithiolates, Te(SR)2, are presented. Te(SCH2CH2OAc)2, 1, was made from
Te(SCH2CH2OH)2 by acetylation of the hydroxyl groups. Te(SCH2CH2SAc)2, 2, [Te(SCH2CH2NH3)2]Cl2, 3, and Te(SC6H4(o-NH2))2, 4, were synthesized by ligand exchange reactions of Te(StBu)2 with 2 equiv of HSCH2CH2SAc,
[HSCH2CH2NH3]Cl, and HSC6H4(o-NH2), respectively. Of all compounds, 4 exhibits the strongest thermal sensitivity
toward decomposition and the largest low-field shift of the 125Te NMR signal, two features that are attributed to
weak Te···N interactions. The structural parameters of the CSTeSC unit exhibit very similar values for all four
compounds, while the torsion angles of the side chains differ between the molecules, a feature rationalized by ab
initio studies. In the solid state, different kinds of intermolecular aggregation and contacts to the Te atoms are
present. 1 and 2 crystallize in the same space group (orthorhombic, Pbcn) and exhibit C2 symmetric molecules,
with two intermolecular Te···S contacts, leading to a trapezoidal coordination mode of the Te atoms. SCCE and
CSCEC (with E = O, S) torsion angles represent the major differences between 1 and 2, which are attributed to
their unlike intermolecular hydrogen bridges. In the solid state structure of 3, [Te(SCH2CH2NH3)2]2+ cations and Cl-
anions form a three-dimensional network via N−H···Cl and C−H···Cl hydrogen bonds (triclinic, P1̄). Two neighboring
[Te(SCH2CH2NH3)2]2+ cations are linked via two Te···S contacts, and each Te atom forms one additional Te···Cl
contact, resulting in a slightly distorted trapezoidal coordination mode. In the solid state structure of 4, adjacent
molecules form Te···Te and Te···N contacts as well as hydrogen bridges. Two chemically different Te atoms are
present, both of which are tetracoordinate with distorted sawhorse configurations. The absence of intramolecular
Te···O, Te···S, or Te···N contacts in 1, 2, and 4, respectively, is attributed to the conformational rigidity of the
CSTeS unit, where conformation ruling coordination is the case.