Tellurium complexes with new, large-bite dithio ligands. The crystal structures of cis- and trans- [Te{Ph 2P(S)NP(S)(OPh) 2} 2] and [(4-MeOC 6H 4TeCl 3) 2{μ- iPr 2P(S)FcP(S) iPr 2}

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Reaction of the protonated large-bite bidentate ligand Ph 2P(S)NHP(S)(OPh) 2 with [Te{NH 2) 2CS} 4]Cl 2 resulted in the complex [Te(LL) 2], ( 1a), where (LL) −=Ph 2P(S)NP(S)(OPh) 2. When (LL) − reacted with 4-MeOC 6H 4TeCl 3, an isomeric complex, 1b, resulted. Reaction between the less basic ligand i Pr 2P(S)FcP(S) i Pr 2 (Fc=ferrocene) and 4-MeOC 6H 4TeCl 3 yielded the complex [(4-MeOC 6H 4TeCl 3) 2 {μ- i Pr 2P(S)FcP(S) i Pr 2}], ( 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-MeOC 6H 4TeCl 3 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 TeCl 3S 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 N ̈ − .