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 Ph(2)PCl yielded bisphosphine, 5-(diphenylphosphanyl)-1-(2-(diphenylphosphanyl)phenyl)-4-phenyl-1H-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.