Cyanosilylation of Aromatic Aldehydes by Cationic Ruthenium(II) Complexes of Benzimidazole-Derived O-Functionalized N-Heterocyclic Carbenes at Ambient Temperature under Solvent-Free Conditions.

A series of ruthenium complexes, namely, [{1-(N-R(1)-2-acetamido)-3-(R(2))-benzimidazol-2-ylidine}Ru(p-cymene)Cl]Cl, where {R(1) = 2,6-(i-Pr)(2)C(6)H(3), R(2) = i-Pr (1c); R(1) = 2,6-(i-Pr)(2)C(6)H(3), R(2) = Et (2c); R(1) = 2,4,6-(CH(3))(3)C(6)H(2), R(2) = Et (3c)}, of benzimidazole-derived N/O-functionalized N-heterocyclic carbene ligands successfully carried out the cyanosilylation reaction of aromatic aldehydes and heteroaryl aldehydes with trimethylsilyl cyanide, providing good to excellent yields (ca. 60-95%) at room temperature under solvent-free condition. The ruthenium (1-3)c complexes were synthesized from the silver (1-3)b analogues in ca. 67-80% yields. The silver (1-3)b complexes exhibited an argentophilic d (10)···d (10) interaction in its dinuclear macrometallacyclic motif, as observed by a short Ag···Ag contact of 3.1894(3) à in single-crystal X-ray diffraction studies for a representative silver complex 2b and also in photoluminescence studies that showed characteristic emission band(s) at ca. 534-536 nm in the CHCl(3) solution and at ca. 482-487 and 530-533 nm in the solid state.