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

Abstract

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 κ2-P,N or κ2-P,P coordination mode. Treatment of 2 with [M(CO)4(piperidine)2] (M = Mo and W) yielded κ2-P,N and κ2-P,P coordinated Mo0 and W0 complexes [M(CO)4(2)] [M = W-κ2-P,N (4); Mo-κ2-P,P (5); W-κ2-P,P (6)] depending on the reaction conditions. Formation and stability of κ2-P,P coordinated Mo0 and W0 complexes were assessed by time dependent 31P{1H} NMR experiments and DFT studies. The complex 4 on treatment with [AuCl(SMe2)] afforded the hetero-bimetallic complex [μ-PN,P-{o-Ph2P(C6H4){1,2,3-N3C(Ph)C(PPh2AuCl)}-κ2-P,N}W(CO)4] (7). The 1:1 reaction between 2 and [CpRu(PPh3)2Cl] yielded [(η5-C5H5)RuCl{o-Ph2P(C6H4){1,2,3-N3C(Ph)C(PPh2)}}-κ2-P,P] (8), whereas the similar reaction with [Ru(η6-p-cymene)Cl2]2 in a 2:1 molar ratio produced a cationic complex [(η6-p-cymene)RuCl{o-Ph2P(C6H4){1,2,3-N3C(Ph)C(PPh2)}}-κ2-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)}-κ2-P,P}PdCl2] (10) and [{o-Ph2P(C6H4){1,2,3-N3C(Ph)C(PPh2)}-κ2-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)}}-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.