Synthesis, NMR characterisation and X-ray structures of mixed chalcogenido PNP ligands containing tellurium: crystal structures of (SePr2PNP)-Pr-i(H)Pr-i(2) and [NaN((EPPr2)-Pr-i)(2)](infinity) (E = Se, Te)

Reaction of HN((PPr2)-Pr-i)(2) with one equivalent of selenium in hexane at room temperature yields the monoselenide as the P-H tautomer Se=(PPr2)-Pr-i-N=P(H)Pr-i(2) (2b). Deprotonation of 2b with (n)butyllithium in the presence of TMEDA at -78 degrees C followed by addition of tellurium produces the air-sensitive, mixed chalcogenido complex [(TMEDA)Li((SePPr)-Pr-i,)((TePPr)-Pr-i,)N] (8Li) in > 97% purity after recrystallisation. Similarly, deprotonation of Te=(PPr2)-Pr-i-N=P(H)Pr-i(2), (2c), followed by addition of sulfur, gives the sulfur analogue [(TMEDA)Li((SPPr2)-Pr-i)((TePPr2)-Pr-i)N] (Mi) in > 99% purity. The symmetrical complexes [(TMEDA)Li(SePiPr,),N] (4Li) and [(TMEDA)Li((TePPr2)-Pr-i),N] (Ki) are produced by similar methods. Compounds 2b, 4Li, 5Li, 7Li and 8Li were characterised in solution by multinuclear (H-1, P-31, Se-77 and Te-125) NMR spectroscopy and their solid-state structures were determined by X-ray crystallography. The X-ray crystal structures of the polymeric chains [NaN((EPPr2)-Pr-i,)(2)](infinity) (4Na, E = Se and 5Na, E = Te) are also reported.