Late to the Party: Synthesis and Characterization of Tellurium and Selenium Half-Sandwich Complexes

We report the synthesis and characterization of the first series of tellurium and selenium complexes featuring an eta(5)-cydopentadienyl ligand. Reaction of Ph3TeX (X = CI, S-2 CNEt2) with MCpR (M = Li, K; R = H, Me-4, Me-5) results in high yields of [Cp][TePh3] (1), [Cp-me4][TePh3] (2), and [Cp*][TePh3] (3), respectively. Similarly, reaction of Ph 3 SeCI with LiCp and KCp* furnishes [Cp][SePh3] (4) and [Cp*][SePh3] (5). Each was characterized by X-ray crystallography, revealing similar eta(5)-coordination with little distortion from an idealized half-sandwich geometry, presumably from the remaining lone pair on tellurium and selenium. The Te-centroid distances are relatively long (1: 2.770(3), 2: 2.746(1), and 3: 2.733(1) angstrom), suggesting a mostly ionic interaction. Se-centroid distances (4: 2.748(3), 5: 2.707(2), 2.730(2) angstrom) were found to be surprisingly similar despite its smaller atomic radius. Compounds 2, 3, and 5 display rapid decomposition at room temperature, extruding a phenylated cyclopentadiene and the respective diphenylchalcogenide. The nature of bonding within these complexes was investigated through DFT methods and found to be primarily ionic in nature.

Automated summary

The synthesis and characterization of tellurium and selenium complexes with an eta(5)-cydopentadienyl ligand were reported. The complexes showed similar coordination structures with relatively long Te-centroid distances and surprisingly similar Se-centroid distances. Additionally, some compounds exhibited rapid decomposition at room temperature, indicating specific reactivity. Bonding within the complexes was primarily found to be ionic in nature based on DFT methods.