1,2,3-Triazole based bisphosphine, 5-(diphenylphosphanyl)-1-(2-(diphenylphosphanyl)phenyl)-4-phenyl-1H-1,2,3-triazole: an ambidentate ligand with switchable coordination modes

The reaction of 1-(2-bromophenyl)-4-phenyl-1H-1,2,3-triazole (1) with Ph2PCl yielded bisphosphine, 5-(diphenylphosphanyl)-1-(2-(diphenylphosphanyl)phenyl)-4-phenyl-1H-1,2,3-triazole (2). Bisphosphine 2 exhibits ambidentate character in either the kappa(2)-P, N or kappa(2)-P, P coordination mode. Treatment of 2 with [M(CO)(4)(piperidine)(2)] (M = Mo and W) yielded kappa(2)-P, N and kappa(2)-P, P coordinated Mo-0 and W-0 complexes [M(CO)(4)(2)] [M = W-kappa(2)-P, N (4); Mo-kappa(2)-P, P (5); W-kappa(2)-P, P (6)] depending on the reaction conditions. Formation and stability of kappa(2)-P, P coordinated Mo-0 and W-0 complexes were assessed by time dependent P-31{H-1} NMR experiments and DFT studies. The complex 4 on treatment with [AuCl(SMe2)] afforded the hetero-bimetallic complex [m-PN, P-{o-Ph2P(C6H4){1,2,3-N3C(Ph) C(PPh2AuCl)}-kappa(2)-P, N}W(CO) 4] (7). The 1 : 1 reaction between 2 and [CpRu(PPh3) 2Cl] yielded [(h 5-C5H5) RuCl{o-Ph2P(C6H4){1,2,3-N3C(Ph) C(PPh2)}}-kappa(2)-P, P] (8), whereas the similar reaction with [Ru(h 6-p-cymene) Cl-2] 2 in a 2 : 1 molar ratio produced a cationic complex [(h 6-p-cymene) RuCl{o-Ph2P(C6H4){1,2,3-N3C(Ph) C(PPh2)}}-kappa(2)-P, N] Cl (9). Similarly, treatment of 2 with [M(COD)(Cl)(2)] (M = Pd and Pt) in a 1 : 1 molar ratio yielded PdII and PtII complexes [{o-Ph2P(C6H4){1,2,3-N3C(Ph) C(PPh2)}-kappa(2)-P, P} PdCl2] (10) and [{o-Ph2P(C6H4){1,2,3-N3C(Ph) C(PPh2)}-kappa(2)-P, P} PtCl2] (11). The reaction of 2 with 2 equiv. of [AuCl(SMe2)] afforded [Au2Cl2{o-Ph2P(C6H4) {1,2,3-N3C(Ph) C(PPh2)}}-m-P, P] (12). Most of the complexes have been structurally characterized. Palladium complex 10 shows excellent catalytic activity towards Cu-free Sonogashira alkynylation/ cyclization reactions.