Homoleptic, heteroleptic and mixed-valent thallium and indium complexes of multidentate chalcogen-centred PCP-bridged ligands

Abstract

The metathetical reaction of [Li(TMEDA)][HC(PPh₂Se)₂] ([Li(TMEDA)]1) with TlOEt in a 1 : 1 molar ratio afforded a homoleptic Tl(I) complex as an adduct with LiOEt, Tl[HC(PPh₂Se)₂]·LiOEt (7), which undergoes selenium–proton exchange upon mild heating (60 °C) to give the mixed-valent Tl(I)/Tl(III) complex {[Tl][Tl{(Se)C(PPh₂Se)₂}₂]}_∞ (8). Treatment of TlOEt with [Li(TMEDA)]₂[(SPh₂P)₂CE′E′C(PPh₂S)₂] (3b, E′ = S; 3c, E′ = Se) in a 2 : 1 molar ratio produced the binuclear Tl(I)/Tl(I) complexes Tl₂[(SPh₂P)₂CE′E′C(PPh₂S)₂] (9b, E′ = S; 9c, E′ = Se), respectively. Selenium–proton exchange also occurred upon addition of [Li(TMEDA)]1 to InCl₃ to yield the heteroleptic complex (TMEDA)InCl[(Se)C(PPh₂Se)₂] (10a). Other examples of this class of In(III) complex, (TMEDA)InCl[(E′)C(PPh₂E)₂] (10b, E = E′ = S; 10c, E = S, E′ = Se) were obtained viametathesis of InCl₃ with [Li(TMEDA)]₂[(E′)C(PPh₂E)₂] (2b, E = E′ = S; 2c, E = S, E′ = Se, respectively). All new compounds have been characterized in solution by ¹H and ³¹P NMR spectroscopy and the solid-state structures have been determined for 8, 9c and 10a–c by single-crystal X-ray crystallography. Complex 8 is comprised of Tl⁺ ions that are weakly coordinated to octahedral [Tl{(Se)C(PPh₂Se)₂}₂]⁻ anions to give a one-dimensional polymer. The complex 9c is comprised of two four-coordinate Tl⁺ ions that are each S,S′,S′′,Se bonded to the hexadentate [(SPh₂P)₂CSeSeC(PPh₂S)₂]²⁻ ligand in which d(Se–Se) = 2.531(2) Å. The six-coordinate In(III) centres in the distorted octahedral complexes 10a–c are connected to a tridentate [(E′)C(PPh₂E)₂]²⁻ dianion, a chloride ion and a neutral bidentate TMEDA ligand.