Cyanosilylation of carbonyl compounds catalyzed by half-sandwich (η6-p-cymene) Ruthenium(II) complexes bearing heterocyclic hydrazone derivatives

A new half-sandwich ruthenium(II) complexes with heterocyclic hydrazone ligands and its behaviour as catalyst for the cyanosilylation of a wide range of carbonyl compounds, at room temperature, with excellent yields. [Display omitted] •Synthesis of half-sandwich (η6-p-cymene) ruthenium(II) complexes bearing heterocyclic hydrazone ligands.•All complexes display a typical three-legged piano‐stool geometry.•Complexes show excellent catalytic activity against the synthesis of Cyanosilylation of Carbonyl compounds.•Catalytic studies optimized parameters as solvent, temperature and catalyst.•Complex with more widespread aromatic aldehydes shows better catalytic activity. A new class of half-sandwich (ƞ6-p-cymene) ruthenium(II) complexes supported by heterocyclic hydrazone derivatives of general formula [Ru(ƞ6-p-cymene)(Cl)(L)] where L represents N’-((1H-pyrrol-2-yl)methylene)furan-2-carbohydrazide (L1), N’-((1H-pyrrol-2-yl)methylene)thiophene-2-carbohydrazide (L2) or N’-((1H-pyrrol-2-yl)methylene)isonicotinohydrazide (L3) were synthesized. Both ligand precursors and complexes were characterized by elemental and spectral analysis (IR, UV–Vis, NMR and mass spectrometry). The molecular structures of all Ru complexes [Ru(ƞ6-p-cymene)(Cl)(L)] were determined by single-crystal X-ray diffraction as three-legged piano-stool. The Ru(II) complexes were used as catalysts for the cyanosilylation of aldehydes (aliphatic, aromatic, α,β-unsaturated and heterocyclic aldehydes) with trimethylsilyl cyanide (TMSCN). All reactions were performed at room temperature and catalytic conditions as solvents, catalyst and catalyst loading were experimentally optimized. Using 0.5 mol% of Ru catalyst 3 in Et2O it was possible to prepare cyanosilylethers in good-to-excellent isolated yields.