Synthesis, characterization and reactivity of arene ruthenium compounds based on 2,2′-dipyridylamine and di-2-pyridylbenzylamine and their applications in catalytic hydrogen transfer of ketones

Abstract

The synthesis and characterization of cationic arene ruthenium compounds [(η⁶-p-ⁱPrC₆H₄Me)RuCl(κ²-dpa)]BF₄ (1), [(η⁶-C₆H₆)RuCl(κ²-dpa)]BF₄ (2), [(η⁶-p-ⁱPrC₆H₄Me)-RuCl(κ²-dpb)]BF₄ (3), [(η⁶-p-ⁱPrC₆H₄Me)RuCl(κ²-dpb)]PF₆CH₃OH (4) and [(η⁶-C₆H₆)-RuCl(κ²dpb)]PF₆ (5) (arene = C₆H₆ or p-ⁱPrC₆H₄Me; dpa = 2,2′-dipyridylamine and dpb = di-2-pyridylbenzylamine) have been described. Reactions of the representative compounds 1 and 3 with NaN₃, NaCN, and NH₄SCN afforded substitution products [(η⁶-p-ⁱPrC₆H₄Me)-Ru(κ²-dpa)(N₃)]BF₄ (6), [(η⁶-p-ⁱPrC₆H₄Me)Ru(κ²-dpa)(CN)]BF₄ (7), [(η⁶-p-ⁱPrC₆H₄Me)-Ru(κ²-dpa)(NCS)]BF₄ (8), [(η⁶-p-ⁱPrC₆H₄Me)Ru(κ²-dpb)(N₃)]BF₄ (9), [(η⁶-p-ⁱPrC₆H₄Me)-Ru(κ²-dpb)(CN)]BF₄ (10) and [(η⁶-p-ⁱPrC₆H₄Me)Ru(κ²-dpb)(NCS)]BF₄ (11). The compounds under investigation have been characterized by elemental analyses, spectroscopic and electrochemical studies. Molecular structures of 1, 3, 4 and 5 have been determined crystallographically. The compounds 1–3 and 5 exhibited moderate catalytic activity in the reduction of ketones into corresponding alcohol in absence of a base.