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 CH2 fragment and the Cl2Ni(PH3)2 is carbenoids (PH3)2Ni(CH2Cl)Cl (IMA) and (PH3)Ni(CH2PH3)Cl2 (IMB), but both the carbenes (Cl2NiCH2 (IMC), (PH3)3NiCH2 (IME) and (PH3)2NiCH2 (IMG)) and carbenoids (ClNiCH2Cl (IMD), Ni(CH2PH3)(PH3)2 (IMF) and Ni(CH2PH3)PH3 (IMH)) are active catalytic species obtained from NiCl2, Ni(PH3)3, Ni(PH3)2 and a CH2 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 21.65kcalmol−1 but is endothermic 6.74kcalmol−1, and the most favor nickel(0) catalyzed cyclopropanation reactions is also multistep pathway for IME, IMH and IMG species all with barriers of 21.93kcalmol−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). [Copyright &y& Elsevier]