Reactivity of 2-chalcogenopyridines with palladium-phosphine complexes: isolation of different complexes depending on the nature of chalcogen atom and phosphine ligand

Reactions of either Pd(0) phosphine complexes with dipyridyldichalcogenides or [PdCl2((PP)-P-boolean AND)] ((PP)-P-boolean AND = dppe, dppp) with pyridylchalcogenolate ions have been examined and a variety of Pd(II) complexes have been isolated and characterized. Oxidative addition of {SeC5H3(3-R)N}(2) (R = H or Me) to [Pd((PP)-P-boolean AND)(2)] ((PP)-P-boolean AND = dppe, dppp) gave either a mononuclear complex, [Pd{2-Se-C5H3(3-R)N}(2)((PP)-P-boolean AND)] (for (PP)-P-boolean AND/R: dppe/H or Me; dppp/H) or a cationic binuclear complex, [Pd-2{mu-SeC5H3(3-Me)N}(2)(dppp)(2)](2+) (4b) (R = Me) whereas reactions involving the tellurium analogue exclusively afforded trinuclear complexes, [Pd-3(mu-Te)(2)(PnP)(3)]Cl-2 ((PP)-P-boolean AND = dppe (2) or dppp (6)). The latter was also obtained in the substitution reaction between [PdCl2((PP)-P-boolean AND)] and NaTeC5H3(3-R) N. The substitution reactions between [PdCl2(dppe)] and Pb{EC5H3(3-R)-N}(2) yielded mononuclear complexes, [Pd{2-E-C5H3(3-R)N}(2)(dppe)] (1a-1e) (E = S, Se or Te) while in the case of [PdCl2(dppp)], the reactions resulted in the formation of mono-, bi- and tri- nuclear complexes depending on the nature of the chalcogen atom (E = S, Se or Te) and the substituent on the pyridyl ring (R = H or Me). Treatment of dipyridyl ditellurides, {TeC5H3(3-R)N}(2) (R = H or Me), with [Pd(PPh3)(4)] gave expected tellurolate complexes, [Pd{2-TeC5H3(3-R)N}(2)(PPh3)(2)] (7a, 7b) which on prolonged standing in CDCl3 solution gave green crystals of [PdCl{2-Te(Cl)(2)C5H3(3-Me)N}(PPh3)] (9). The molecular structures of {TeC5H3(3-Me)N}(2), [Pd-2{mu-TeC5H3(3-Me)N}(2)(dppp)(2)]Cl-2 center dot 3H(2)O (5 center dot 3H(2)O), [Pd-3(mu-Te)(2)(dppp)(3)]Cl-2 center dot 3CHCl(3) (6 center dot 3CHCl(3)) and [PdCl{2-Te(Cl)(2)C5H3(3-Me)N}(PPh3)] (9) were established by single crystal X-ray diffraction analyses.