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

The reaction of 1-(2-bromophenyl)-4-phenyl-1-1,2,3-triazole (1) with PhPCl yielded bisphosphine, 5-(diphenylphosphanyl)-1-(2-(diphenylphosphanyl)phenyl)-4-phenyl-1-1,2,3-triazole (2). Bisphosphine 2 exhibits ambidentate character in either the κ-P,N or κ-P,P coordination mode. Treatment of 2 with [M(CO)(piperidine)] (M = Mo and W) yielded κ-P,N and κ-P,P coordinated Mo and W complexes [M(CO)(2)] [M = W-κ-P,N (4); Mo-κ-P,P (5); W-κ-P,P (6)] depending on the reaction conditions. Formation and stability of κ-P,P coordinated Mo and W complexes were assessed by time dependent P{H} NMR experiments and DFT studies. The complex 4 on treatment with [AuCl(SMe)] afforded the hetero-bimetallic complex [μ-PN,P-{-PhP(CH){1,2,3-NC(Ph)C(PPhAuCl)}-κ-P,N}W(CO)] (7). The 1 : 1 reaction between 2 and [CpRu(PPh)Cl] yielded [(η-CH)RuCl{-PhP(CH){1,2,3-NC(Ph)C(PPh)}}-κ-P,P] (8), whereas the similar reaction with [Ru(η--cymene)Cl] in a 2 : 1 molar ratio produced a cationic complex [(η--cymene)RuCl{-PhP(CH){1,2,3-NC(Ph)C(PPh)}}-κ-P,N]Cl (9). Similarly, treatment of 2 with [M(COD)(Cl)] (M = Pd and Pt) in a 1 : 1 molar ratio yielded Pd and Pt complexes [{-PhP(CH){1,2,3-NC(Ph)C(PPh)}-κ-P,P}PdCl] (10) and [{-PhP(CH){1,2,3-NC(Ph)C(PPh)}-κ-P,P}PtCl] (11). The reaction of 2 with 2 equiv. of [AuCl(SMe)] afforded [AuCl{-PhP(CH){1,2,3-NC(Ph)C(PPh)}}-μ-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.