Six-coordinated dibenzyl Zr complex bearing an [OSSO]-type tetradentate ligand was synthesized, and the structure was fully characterized by NMR spectroscopy and X-ray crystallography. The zirconium complex has C(2) symmetry in solution. Owing to an effect of the cyclooctane ring structure, the combination of the zirconium complex and B(C(6)F(5))(3) or (Ph(3)C)[B(C(6)F(5))(4)] as the activator exhibited high activity toward polymerization of 1-hexene to yield highly isotactic poly(1-hexene).

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2-(1,3-Dimethylimidazolidinio)diselenocarboxylate ( 16) was obtained in 48% yield as thermally stable, dark green crystals by reaction of 2-methylene-1,3-dimethylimidazolidine (7) with Se 2 Cl 2 in the presence of Et 3 N. The reaction of 16 with elemental sulfur gave 2-(1,3-dimethylimidazolidinio)dithiocarboxylate (20) in 95% yield by exhaustive selenium-sulfur exchange, whereas the use of a limited amount of sulfur allowed the preparation of 2-(1,3-dimethylimidazolidinio)selenothiocarboxylate ( 19) as dark red crystals. X-ray crystallographic analyses revealed that the planes of the carbenium ion and CX 2 -(X ) S, Se) parts of 16 and 20 are nearly perpendicular to each other. The observed geometries (including bond angles and lengths) of 16 and 20 were reproduced satisfactorily by ab initio calculations (B3LYP/6-31G* level). Discussion is also made on the structures of 16, 19, and 20 on the basis of spectroscopic data (NMR, IR, and UV/vis). Methylation of 16 with MeI furnished the carbenium iodide (26a), which possesses a diselenoester moiety, as thermally labile, green crystals. The reaction of 16 with two molar amounts of DMAD provided the 1:2 adduct (30a) in 67% yield. The reaction of 16 with N- [(p-tolylsulfonyl)imino]phenyliodinane gave the inner salt (35) in 68% yield with loss of selenium atom from the initial adduct (33).

The first examples of palladium(II) hydrido complexes having a dihydrosilyl or dihydrogermyl ligand, [PdH(EH2Trip)(dcpe)] (E = Si (2), Ge (4); dcpe = 1,2-bis(dicyclohexylphosphino)ethane), were synthesized by oxidative addition of an overcrowded primary silane and germane, TripEH3 (E = Si (1), Ge (3); Trip = 9-triptycyl) with [(μ-dcpe)Pd]2 in toluene. The molecular structures of complexes 2 and 4 were established by single-crystal X-ray analysis, which showed a distorted-square-planar geometry around the palladium centers, probably due to the steric requirements of the chelating dcpe ligand and the bulky 9-triptycyl group on the silicon or germanium atom. A variable-temperature NMR experiment on the palladium silyl complex 2 indicated that the intramolecular interchange of coordination environments between the silyl and hydrido ligands through an Si–H σ-complex intermediate occurs on the NMR time scale.

Oxidation of 3,4-di-t-butyl- and 3,4-di-1-adamantyl-, and 2,4-di-t-butylthiophenes with an equimolar amount of m-chloroperbenzoic acid in the presence of BF3•Et2O gave the corresponding thiophene 1-oxides in good yields, which are stable enough to be isolated in pure crystalline form. An X-ray single crystal structure analysis led to the conclusion that thiophene 1-oxides would not be aromatic.