Reactivity of alkynyl Pd(II) azido complexes toward organic isocyanides, isothiocyanates, and nitriles

Abstract

Alkynyl Pd(II) azido complexes of the type [Pd(N 3)(C C R)L 2] ( 1– 3) were obtained by reactions of aqueous NaN 3 with [Pd(Cl)(C C R)L 2] (R = Ph or C(O)OMe). Treating compounds 1– 3 with organic isocyanides (R–NC) afforded novel complexes, trans-[Pd(C C Ph)(N C N R)(PMe 3) 2] (R = 2,6-Me 2C 6H 3 ( 4) or 2,6-Et 2C 6H 3 ( 5)) and trans-[Pd(C C R)(CN 4- t-Bu)L 2] ( 6: L = PMe 3, R = Ph; 7: L = PEt 3, R = C(O)OMe; 8: L = PMe 3, R = C(O)OMe), which contain either a carbodiimido or a C-coordinated tetrazolato group. Reactions of compounds 1 and 2 with R–N C S (R = 2,6-Me 2C 6H 3 or CH 2CH 3) and 1,4-phenylene diisothiocyanate (C 6H 4(N C S) 2) smoothly proceeded to give tetrazole–thiolato complexes, trans-[Pd(C CPh)(SCN 4–R)L 2] (L = PMe 3, R = Et ( 9) or 2,6-Me 2C 6H 3 ( 10); L = PEt 3, R = 2,6-Me 2C 6H 3 ( 11)), and a phenylene-bridged dinuclear Pd(II) tetrazole–thiolato complex, [(PEt 3) 2(C CPh)Pd(SCN 4-(μ-C 6H 4)–SCN 4)Pd(C CPh)(PEt 3) 2] ( 12), respectively. Complexes 9– 12 contain the Pd–S bond that is formed by the dipolar cycloaddition of the organic isothiocyanate to the Pd–azido bond. In contrast, the corresponding reactions of compounds 1and 2 with C 6F 5CN and Me 3SiCN (organic nitriles, R–CN) gave an N-coordinated Pd(II)-tetrazolato compound { trans-[Pd(C C Ph)(N 4C–C 6F 5)(PMe 3) 2] ( 13)} and a mixture of Pd(II)-cyano complexes { trans-[Pd(C C Ph)(CN)(PEt 3) 2] ( 14) and [Pd(CN) 2(PEt 3) 2] ( 15)}, respectively. Bis(phosphine) bis(cyano) complexes of Pd and Ni, [M(CN) 2L 2] (L = PEt 3, PMe 3; L 2 = DEPE), could be obtained independently by the reactions of [M(N 3) 2L 2] with excess Me 3SiCN in organic solvents.