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

Alkynyl Pd(II) azido complexes of the type [Pd(N3)(Ctriple bond; length of mdashCsingle bondR)L2] (1–3) were obtained by reactions of aqueous NaN3 with [Pd(Cl)(Ctriple bond; length of mdashCsingle bondR)L2] (R = Ph or C(O)OMe). Treating compounds 1–3 with organic isocyanides (R–NC) afforded novel complexes, trans-[Pd(Ctriple bond; length of mdashCsingle bondPh)(Ndouble bond; length as m-dashCdouble bond; length as m-dashNsingle bondR)(PMe3)2] (R = 2,6-Me2C6H3 (4) or 2,6-Et2C6H3 (5)) and trans-[Pd(Ctriple bond; length of mdashCsingle bondR)(CN4-t-Bu)L2] (6: L = PMe3, R = Ph; 7: L = PEt3, R = C(O)OMe; 8: L = PMe3, R = C(O)OMe), which contain either a carbodiimido or a C-coordinated tetrazolato group. Reactions of compounds 1 and 2 with R–Ndouble bond; length as m-dashCdouble bond; length as m-dashS (R = 2,6-Me2C6H3 or CH2CH3) and 1,4-phenylene diisothiocyanate (C6H4(Ndouble bond; length as m-dashCdouble bond; length as m-dashS)2) smoothly proceeded to give tetrazole–thiolato complexes, trans-[Pd(Ctriple bond; length of mdashCPh)(SCN4–R)L2] (L = PMe3, R = Et (9) or 2,6-Me2C6H3 (10); L = PEt3, R = 2,6-Me2C6H3 (11)), and a phenylene-bridged dinuclear Pd(II) tetrazole–thiolato complex, [(PEt3)2(Ctriple bond; length of mdashCPh)Pd(SCN4-(μ-C6H4)–SCN4)Pd(Ctriple bond; length of mdashCPh)(PEt3)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 C6F5CN and Me3SiCN (organic nitriles, R–CN) gave an N-coordinated Pd(II)-tetrazolato compound {trans-[Pd(Ctriple bond; length of mdashCsingle bondPh)(N4C–C6F5)(PMe3)2] (13)} and a mixture of Pd(II)-cyano complexes {trans-[Pd(Ctriple bond; length of mdashCsingle bondPh)(CN)(PEt3)2] (14) and [Pd(CN)2(PEt3)2] (15)}, respectively. Bis(phosphine) bis(cyano) complexes of Pd and Ni, [M(CN)2L2] (L = PEt3, PMe3; L2 = DEPE), could be obtained independently by the reactions of [M(N3)2L2] with excess Me3SiCN in organic solvents.