Synthesis and Redox Behaviour of the Chalcogenocarbonyl Dianions [(E)C(PPh₂S)₂]²⁻: Formation and Structures of Chalcogen–Chalcogen Bonded Dimers and a Novel Selone

Bond Stretching and Redox Behavior in Coinage Metal Complexes of the Dichalcogenide Dianions [(SPh2P)2CEEC(PPh2S)2]2− (E=S, Se): Diradical Character of the Dinuclear Copper(I) Complex (E=S)

“…0.18 Å, and these values are in the same range as the (C)Se−Se(C) distances of 2.610(2)-2.688(2) Å in 5a and 5b, indicative of a much weaker chalcogen-chalcogen interaction in 5c. The (C)S−S(C) contacts in 5c are elongated by 0.32 and 0.50 Å, respectively, compared to the corresponding distance in the dilithium reagent 4c, [10] and they are up to 32% longer than a typical S−S single bond (ca. 2.06 Å).…”

“…[10,11] Most notably, however, the (C)S−S(C) bond lengths of 2.540(4) Å (molecule A) and 2.720(3) Å (molecule B) exhibit a significant disparity of ca. 0.18 Å, and these values are in the same range as the (C)Se−Se(C) distances of 2.610(2)-2.688(2) Å in 5a and 5b, indicative of a much weaker chalcogen-chalcogen interaction in 5c.…”

“…[9] These fascinating and structurally diverse complexes prompted us to design a direct synthesis of the novel trichalcogeno dianions, [(E)C(PPh2S)2] 2− (3b, E = Se; 3c, E = S), by using Le Floch's dianion 1 in a reaction with elemental sulfur or selenium. [10] The all-selenium derivative 3a cannot be obtained via this route because of the unavailability of Li2[C(PPh2Se)2] owing to cleavage of P-Se bonds by RLi reagents. [7] Our investigations of the one-electron oxidation of 3b,c generated the novel dichalcogenides, [(SPh2P)2CEEC(PPh2S)2] 2− (4b, E = Se; 4c, E = S), which are formally dimers of the corresponding radical anions [(E)C(PPh2S)2] •− with moderately elongated (by ca.…”

“…8 %) central chalcogen-chalcogen bonds. [10] In a preliminary communication, we described the generation of dinuclear Cu(I)/Cu(I) complexes of the type 5 by three different routes: (a) treatment of monoanion 2 with CuCl2 via proton-selenium exchange and a redox process (5a), (b) the redox reaction of the monomeric dianion 3b with CuCl2 (5b), and (c) metathesis of dimeric dianion 4b with CuCl (5b). [11] The η 2 ,η 2 -Se2 bonding motif established for complexes 5a and 5b represents a new coordination mode for generic RSe-SeR ligands.…”

“…[12] Coordination of 4a and 4b to the two copper centers resulted in a (further) elongation of the central selenium-selenium bond compared to the corresponding distance in the terminally E,E'-chelated Li + derivatives. [10,11] Metal complexes of the generic bis(organochalcogenides), RE−ER (E = S, Se), have attracted attention as biological models that can simulate, for example, redox processes and catalytic functions displayed by natural enzymes. [13] In part, this is due to the propensity of these systems to undergo oxidative addition with transition metals resulting in chalcogen-chalcogen bond cleavage, [14] therefore simulating, for example, biologically significant compounds with copperdisulfide interactions.…”