Hydrosilylation of RN=CH Imino-Substituted Pyridines without a Catalyst

Abstract

Treatment of the neutral pyridine-based ligands L¹ -L³ , bearing either one or two RN=CH imine moieties {where L¹ and L² are N,N-chelating ligands 2-(RN=CH)C₅ H₄ N (R=Ph (L¹ ) or R=2,4,6-Ph₃ C₆ H₂ (L² )) and L³ is the N,N,N-chelating ligand 2,6-(RN=CH)₂ C₅ H₃ N (R=2,6-iPr₂ C₆ H₃ )}, with HSiCl₃ yielded N→Si-coordinated silicon(IV) amides 2-{Cl₃ SiN(R)CH₂ }C₅ H₄ N (1, R=Ph; 2, R=2,4,6-Ph₃ C₆ H₂ ) and 2-{Cl₃ SiN(R)CH₂ }-6-(RN=CH)C₅ H₄ N (3, R=2,6-iPr₂ C₆ H₃ ). The organosilicon amides 1-3 are the products of spontaneous hydrosilylation of the RN=CH imine moiety induced by N→Si coordination of the proposed N,N-chelated chlorosilanes L¹ →SiHCl₃ (1 a), L² →SiHCl₃ (2 a), and L³ →SiHCl₃ (3 a). Furthermore, the reaction of L³ with an excess of HSiCl₃ provided the intramolecularly coordinated chlorosilicon diamide cyclo-{(C₅ H₃ N)-1,3-(CH₂ NR)₂ }SiCl₂ (4) (R=2,6-iPr₂ C₆ H₃ ) as the product of spontaneous reduction of both RN=CH imine moieties. The compounds have been characterized by NMR spectroscopy (1-4) and single-crystal X-ray diffraction analysis (1, 3, and 4). The mechanism of the hydrosilylation of the second RN=CH imine moiety in 3 by an excess of SiHCl₃ has also been studied. The experimental work is supplemented by DFT calculations.

Keywords: NMR spectroscopy; density functional calculations; hydrosilylation; intramolecular coordination; silicon.