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-R1-2-acetamido)-3-(R2)-benzimidazol-2-ylidine}­Ru­(p-cymene)­Cl]­Cl, where {R1 = 2,6-(i-Pr)2C6H3, R2 = i-Pr (1c); R1 = 2,6-(i-Pr)2C6H3, R2 = Et (2c); R1 = 2,4,6-(CH3)3C6H2, R2 = 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 d10···d10 interaction in its dinuclear macrometallacyclic motif, as observed by a short Ag···Ag contact of 3.1894(3) Å 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 CHCl3 solution and at ca. 482–487 and 530–533 nm in the solid state.