Novel 1,2,3-triazolyl phosphine with a pyridyl functionality: synthesis, coinage metal complexes, photophysical studies and Cu(I) catalyzed C-O coupling of phenols with aryl bromides.

This manuscript describes the synthesis and coinage metal complexes of pyridine appended 1,2,3-triazolyl-phosphine [2-{(C 6 H 4 N)(C 2 (PPh 2 )N 3 C 6 H 5 )}] (1), photophysical studies and their catalytic application. The reactions of 1 with copper salts afforded dimeric complexes [{Cu(μ 2 -X)} 2 {2-(C 6 H 4 N)(C 2 (PPh 2 )N 3 C 6 H 5 )} 2 ] (2, X = Cl; 3, X = Br; and 4, X = I). The crystal structure indicates that the Cu⋯Cu distance in 4 (2.694 Å) is significantly shorter than that in complexes 3 (3.0387 Å) and 2 (3.104 Å), indicating strong cuprophilic interactions which is also supported by NBO calculations, signifying the involvement of 3d z 2 orbitals from each Cu atom contributing to the bonding interaction. The fluorescence studies on complexes 2-4 carried out in the solid state showed broad emission bands around 560 nm on excitation at λ ex = 420 nm. Complex 4 on treatment with two equivalents of 1,10-phenanthroline yielded a mononuclear complex 5 which showed almost complete quenching of fluorescence in the solid state, clearly indicating that the emissive properties of 4 are mainly due to the Cu⋯Cu interaction, along with (M + X)LCT. The reactions of 1 with silver salts led to the isolation of dimeric complexes [{Ag(μ 2 -X)} 2 {2-(C 6 H 4 N)(C 2 (PPh 2 )N 3 C 6 H 5 )} 2 ] (6, X = Cl; 7, X = Br; and 8, X = I) in good yield. The reaction between 1 and [AuCl(SMe 2 )] yielded [{AuCl}{2-(C 6 H 4 N)(C 2 (PPh 2 )N 3 C 6 H 5 )}] (9). The molecular structures of 2-5 and 7-9 were confirmed by single crystal X-ray analysis. The complex 4 is found to be an excellent catalyst for C-O coupling under mild conditions.