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

The reaction of 1-(2-bromophenyl)-4-phenyl-1 H -1,2,3-triazole (1) with Ph 2 PCl yielded bisphosphine, 5-(diphenylphosphanyl)-1-(2-(diphenylphosphanyl)phenyl)-4-phenyl-1 H -1,2,3-triazole (2). Bisphosphine 2 exhibits ambidentate character in either the κ 2 -P,N or κ 2 -P,P coordination mode. Treatment of 2 with [M(CO) 4 (piperidine) 2 ] (M = Mo and W) yielded κ 2 -P,N and κ 2 -P,P coordinated Mo 0 and W 0 complexes [M(CO) 4 (2)] [M = W-κ 2 -P,N (4); Mo-κ 2 -P,P (5); W-κ 2 -P,P (6)] depending on the reaction conditions. Formation and stability of κ 2 -P,P coordinated Mo 0 and W 0 complexes were assessed by time dependent 31 P{ 1 H} NMR experiments and DFT studies. The complex 4 on treatment with [AuCl(SMe 2 )] afforded the hetero-bimetallic complex [μ-PN,P-{ o -Ph 2 P(C 6 H 4 ){1,2,3-N 3 C(Ph)C(PPh 2 AuCl)}-κ 2 -P,N}W(CO) 4 ] (7). The 1 : 1 reaction between 2 and [CpRu(PPh 3 ) 2 Cl] yielded [(η 5 -C 5 H 5 )RuCl{ o -Ph 2 P(C 6 H 4 ){1,2,3-N 3 C(Ph)C(PPh 2 )}}-κ 2 -P,P] (8), whereas the similar reaction with [Ru(η 6 - p -cymene)Cl 2 ] 2 in a 2 : 1 molar ratio produced a cationic complex [(η 6 - p -cymene)RuCl{ o -Ph 2 P(C 6 H 4 ){1,2,3-N 3 C(Ph)C(PPh 2 )}}-κ 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 Pd II and Pt II complexes [{ o -Ph 2 P(C 6 H 4 ){1,2,3-N 3 C(Ph)C(PPh 2 )}-κ 2 -P,P}PdCl 2 ] (10) and [{ o -Ph 2 P(C 6 H 4 ){1,2,3-N 3 C(Ph)C(PPh 2 )}-κ 2 -P,P}PtCl 2 ] (11). The reaction of 2 with 2 equiv. of [AuCl(SMe 2 )] afforded [Au 2 Cl 2 { o -Ph 2 P(C 6 H 4 ){1,2,3-N 3 C(Ph)C(PPh 2 )}}-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.