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

Alkynyl Pd(II) azido complexes of the type [Pd(N-3)(CdropC-R)L-2] (1-3) were obtained by reactions of aqueous NaN3 with [Pd(Cl)(CdropC-R)L-2] (R = Ph or C(O)OMe). Treating compounds 1-3 with organic isocyanides (R-NC) afforded novel complexes, trans-[Pd(CdropC-Ph)(N=C=N-R)(PMe3)(2)] (R = 2,6-Me2C6H3 (4) or 2,6-Et2C6H3 (5)) and trans-[Pd(CdropC-R)(CN4-t-Bu)L-2] (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-N=C=S (R = 2,6-Me2C6H3 or CH2CH3) and 1,4-phenylene diisothiocyanate (C6H4(N=C=S)(2)) smoothly proceeded to give tetrazole-thiolato complexes, trans-[Pd(CdropCPh)(SCN4-R)L-2] (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)(CdropCPh)Pd(SCN4-(mu-C6H4)-SCN4)Pd(CdropCPh)(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 vcorresponding reactions of compounds land 2 with C6F5CN and Me3SiCN (organic nitriles, R-CN) gave an N-coordinated Pd(II)-tetrazolato compound {trans-[Pd(CdropC-Ph)(N4C-C6F5)(PMe3)(2)] (13)} and a mixture of Pd(II)-cyano complexes {trans[Pd(CdropC-Ph)(CN)(PEt3)(2)] (14) and [Pd(CN)2(PEt3)21 (15), respectively. Bis(phosphine) bis(cyano) complexes of Pd and Ni, [M(CN)(2)L-2] (L = PEt3, PMe3; L-2 = DEPE), could be obtained independently by the reactions of [M(N-3)(2)L-2] with excess Me3SiCN in organic solvents. (C) 2004 Elsevier B.V. All rights reserved.