Synthesis, NMR characterisation and X-ray structures of mixed chalcogenido PNP ligands containing tellurium: crystal structures of SeiPr2PNP(H)iPr2 and [NaN(EPiPr2)2]∞ (E = Se, Te)

Abstract

Reaction of HN(PⁱPr₂)₂ with one equivalent of selenium in hexane at room temperature yields the monoselenide as the P–H tautomer SePⁱPr₂–NP(H)ⁱPr₂ (2b). Deprotonation of 2b with ⁿbutyllithium in the presence of TMEDA at −78 °C followed by addition of tellurium produces the air-sensitive, mixed chalcogenido complex [(TMEDA)Li(SePⁱPr₂)(TePⁱPr₂)N] (8Li) in >97% purity after recrystallisation. Similarly, deprotonation of TePⁱPr₂–NP(H)ⁱPr₂ (2c), followed by addition of sulfur, gives the sulfur analogue [(TMEDA)Li(SPⁱPr₂)(TePⁱPr₂)N] (7Li) in >99% purity. The symmetrical complexes [(TMEDA)Li(SePⁱPr₂)₂N] (4Li) and [(TMEDA)Li(TePⁱPr₂)₂N] (5Li) are produced by similar methods. Compounds 2b, 4Li, 5Li, 7Li and 8Li were characterised in solution by multinuclear (¹H, ³¹P, ⁷⁷Se and ¹²⁵Te) NMR spectroscopy and their solid-state structures were determined by X-ray crystallography. The X-ray crystal structures of the polymeric chains [NaN(EPⁱPr₂)₂]_∞ (4Na, E = Se and 5Na, E = Te) are also reported.