Cationic Rh and Ir complexes containing bidentate imidazolylidene-1,2,3-triazole donor ligands: synthesis and preliminary catalytic studies.

A series of new cationic Rh(I), Rh(III) and Ir(III) complexes containing hybrid bidentate N-heterocyclic carbene­1,2,3-triazolyl donor of general formulae [Rh(CaT)(COD)]BPh4 (2a­d), [Rh(CaT)(CO)2]BPh4 (3a­d) and [M(CaT)(Cp*)Cl]BPh4 (M = Rh, 4a­d; M = Ir, 5a­c), where CaT = bidentate N-heterocyclic carbene­triazolyl ligands, COD = 1,5-cyclooctadiene and Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl, were synthesised. The imidazolium­1,2,3-triazolyl pre-ligands (1a­c and 1e­i) were readily prepared using the Cu(I) catalysed 'click reaction' between phenyl azide or benzyl azides with propargyl functionalised imidazolium salts. The single crystal solid state structures of complexes 2a­d; 3a­b; 4a­d and 5a­b confirm the bidentate coordination of the NHC­1,2,3-triazolyl ligand with the NHC coordinating via the 'normal' C2-carbon and the 1,2,3-triazolyl donor coordinating via the N3' atom to form six membered metallocycles. These complexes are the first examples of Rh and Ir complexes containing the hybrid NHC­1,2,3-triazolyl ligands which exhibit a bidentate coordination mode. A number of these complexes showed limited efficiency as catalysts for the intramolecular hydroamination of 4-pentyn-1-amine to 2-methylpyrroline.