Tellurium complexes with new, large-bite dithio ligands. The crystal structures of cis- and trans- [Te{Ph2P(S)NP(S)(OPh)2}2] and [(4-MeOC6H4TeCl3)2{μ-iPr2P(S)FcP(S)iPr2}]

Reaction of the protonated large-bite bidentate ligand Ph2P(S)NHP(S)(OPh)2 with [Te{NH2)2CS}4]Cl2 resulted in the complex [Te(LL)2], (1a), where (LL)−=Ph2P(S)NP(S)(OPh)2. When (LL)− reacted with 4-MeOC6H4TeCl3, an isomeric complex, 1b, resulted. Reaction between the less basic ligand iPr2P(S)FcP(S)iPr2 (Fc=ferrocene) and 4-MeOC6H4TeCl3 yielded the complex [(4-MeOC6H4TeCl3)2 {μ-iPr2P(S)FcP(S)iPr2}], (2). X-ray crystallographic studies show that 1a and 1b both are square planar complexes of Te(II), 1a being asymmetric and ‘cis’ with two short TeS bonds trans to two long TeS bonds (average bond lengths being 2.5415 and 2.9050 Å). Isomer 1b is centrosymmetric, ‘trans’, with nearly equal TeS bond lengths averaging 2.6805 Å. Complex 2 is an addition compound where the large dithio ligand bridges two 4-MeOC6H4TeCl3 units through weak TeS bonds. The resulting coordination around each Te(IV) atom is ψ-octahedral with the lone pair of electrons and aryl in axial positions relative to the TeCl3S equatorial plane. Here the TeS bond lengths are 2.7560(16) and 2.6910(12) Å. The trans influence of the dithio ligand in 2 is smaller than that of Cl−, resulting in an average TeCl bond length trans to sulfur of only 2.4196 Å, while the other TeCl bond lengths average 2.4959 Å. The reason for the lower basic nature of the ligand with a PFcP backbone compared to those with PNP backbones, is that it lacks a central charge donating group like N̈−.