Chalcogenide/Chalcogenolate Structural Isomers of Organo Group 13 Element Derivatives: Reactions of the Dimetallenes Ar′MMAr′ (Ar′ = C₆H₃-2,6-(C₆H₃-2,6-Prⁱ₂)₂; M = Ga or In) with N₂O or S₈ To Give (Ar′M^IIIE)₂ (E = O or S) and the Synthesis and Characterization of [Ar′EM^I]₂ (M = In or Tl; E = O, S)

Dimeric arylgallium/indium chalcogenides 7−10 of formula [Ar′ME]₂ (Ar′ = C₆H₃-2,6-(C₆H₃-2,6-Prⁱ₂)₂; M = Ga or In, E = O or S) were synthesized by the treatment of Ar′MMAr′ with N₂O or elemental sulfur and characterized by NMR spectroscopy and X-ray crystallography. Their structures feature three-coordinate, +3 oxidation state metal centers with planar M₂E₂ cores. The cores were almost perfectly square for E = O, but for E = S, they were distorted parallelograms in 7−10. The M–E bond lengths were shorter than those in the higher aggregated species [RME]_n (n ≥ 4) but comparable to those in M³⁺ aryloxides or thiolates featuring three-coordinate metals. Short M···M separations [2.553(1) Å in 7, 2.8882(4) Å in 8, 2.8276 Å (avg.) in 9, and 3.1577(8) Å in 10] are observed. Low oxidation heavier group 13/group 16 chalcogenolate isomers 16−19 of formula [Ar′EM]₂ (M = In or Tl, E = O or S) were also synthesized and characterized. In the +1 compounds [Ar′EIn]₂ (O, 16; S, 19) together, with the In +3 species [Ar′InE]₂ (O, 8; S, 10), represent the first structurally characterized isomeric pairs of organo group 13 metal/chalcogen derivatives. The E−M bonds in 16−19 were 2.3329 (avg.), 2.560 (avg.), 2.8189 (avg.), and 2.897 Å (avg.), respectively, which are 0.3−0.4 Å longer than the corresponding In−chalcogen distances in 8 and 10 as a result of the lower oxidation state, the large In⁺ ionic size, and the reduced ionic contribution to the bond strength in 16 and 19. The compounds 16−19 also displayed M−arene interactions to the flanking aryl rings of the Ar′ ligands. The Tl−arene contacts in the crystal structure of 17 are preserved in solution, as evidenced by ¹³C−Tl coupling. Attempts to thermally interconvert the isomeric pairs 8, 10 and 16, 18 led to decomposition of the complexes.