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) 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 CHCl 3 solution and at ca. 482-487 and 530-533 nm in the solid state.