Facile Synthesis of Bis(dichalcogenophosphinate)s and a Remarkable [Li₈(OH)₆]²⁺ Polyhedron

The synthesis and characterization of three lithium complexes of novel bis(dichalcogenophosphinate) ligands are reported: (PhP(S)2CH2CH2P(S)2Ph)Li2(THF)4 (2), (PhP(Se)2CH2CH2P(Se)2Ph)Li2(THF)4·(PhP(Se)2CH2CH2P(Se)2Ph)Li2(THF)6 (3), and [PhP(Te)2CH2CH2P(Te)2Ph][Li8(OH)6(THF)8] (4). The synthetic route to these complexes proceeds via the insertion reaction of elemental chalcogens into the phosphorus−lithium bonds of 1,2-dilithio-1,2-di(phenylphosphine)ethylene (1). X-ray analysis of 2 revealed isobidentate coordination of the lithiums by the dithiophosphinate groups. In contrast, the diselenophosphinate groups in 3 coordinate the lithium centers in both isobidentate and monodentate modes, and the ditellurophosphinate groups in 4 form non-coordinate separate ion pairs. The countercation in 4 is shown to be a unique [Li8(OH)6]2+ rhombic dodecahedral polyhedron, putatively formed from the capping of a hexameric [Li(OH)]6 aggregate with lithium cations on its open faces.