A theoretical study nickel-catalyzed cyclopropanation reactions. Nickel(0) versus nickel(II)

Abstract

A theoretical investigation at DFT (B3LYP) level on the cyclopropanation reactions catalyzed by nickel(0) and nickel(II) have been extensively investigated. The computation results show that the active catalytic species formed by a CH 2 fragment and the Cl 2Ni(PH 3) 2 is carbenoids (PH 3) 2Ni(CH 2Cl)Cl (IMA) and (PH 3)Ni(CH 2PH 3)Cl 2 (IMB), but both the carbenes (Cl 2NiCH 2 (IMC), (PH 3) 3NiCH 2 (IME) and (PH 3) 2NiCH 2 (IMG)) and carbenoids (ClNiCH 2Cl (IMD), Ni(CH 2PH 3)(PH 3) 2 (IMF) and Ni(CH 2PH 3)PH 3 (IMH)) are active catalytic species obtained from NiCl 2, Ni(PH 3) 3, Ni(PH 3) 2 and a CH 2 fragment. The cyclopropanation reaction proceeds through either concerted or multistep reaction pathway. The most favor cyclopropanation reactions catalyzed by nickel(II) is multistep pathway for IMD with a barrier of 21.65 kcal mol −1 but is endothermic 6.74 kcal mol −1, and the most favor nickel(0) catalyzed cyclopropanation reactions is also multistep pathway for IME, IMH and IMG species all with barriers of 21.93 kcal mol −1 but the downhill potential energy surface discloses that each step of the cyclopropanation reaction are all irreversible. Thus, nickel(0) catalyzed cyclopropanation reaction proceed easer than nickel(II).