1609173-26-3Relevant academic research and scientific papers
Combined experimental and theoretical study of bis(diphenylphosphino)(N -thioether)amine-type ligands in nickel(II) complexes for catalytic ethylene oligomerization
Ghisolfi, Alessio,Fliedel, Christophe,Rosa, Vitor,Monakhov, Kirill Yu.,Braunstein, Pierre
, p. 2523 - 2534 (2014)
Starting from the new ligands bis(diphenylphosphino)(N-4-(methylthio) phenyl)amine (4, N(PPh2)2(p-C6H 4)SMe) and its monosulfide derivative (Ph2P)N{P(S)Ph 2}(p-C6H4)SMe (4·S), we have prepared and characterized, including by X-ray crystallographic studies, their Ni(II) complexes [NiCl2{(Ph2P)2N(p-C6H 4)SMe-P,P}] (5) and [NiCl2{(Ph2P)N{P(S)Ph 2}(p-C6H4)SMe-P,S}] (6), respectively. The bis-sulfide compound N{P(S)Ph2}2(p-C6H 4)SMe (4·S2) was also prepared and structurally characterized. Computational studies showed that the combined influence of stronger P donors and a four-membered-ring P,P chelate leads to complex 5 being thermodynamically more stable than 6, which contains one weaker P-S donor group but a five-membered P,P-S chelate ring. For comparison, the bis-chelate complex [Ni{(Ph2P)N{P(S)Ph2}(p-C6H4)SMe-P,S} 2](BF4)2 (7), the monochelate complexes [NiBr2{(Ph2P)N{P(S)Ph2}(p-C6H 4)SMe-P,S}] (8) and the Pd(II) analogue of 6, [PdCl 2{(Ph2P)N{P(S)Ph2}(p-C6H 4)SMe-P,S}] (9), were synthesized and structurally characterized and their solution behavior was investigated. The catalytic activity and selectivity in ethylene oligomerization of the Ni(II) complexes 5 and 6 and their known N-(methylthio)propyl analogues [NiCl2{(Ph2P) 2N(CH2)3SMe-P,P}] (2) and [NiCl 2{(Ph2P)N{P(S)Ph2}(CH2) 3SMe-P,S}] (3), which were obtained from the bis(diphenylphosphino) (N-(methylthio)propyl)amine ligand N(PPh2)2(CH 2)3SMe (1) and its monosulfide derivative (Ph 2P)N{P(S)Ph2}(CH2)3SMe (1·S), respectively, revealed a significant influence of the nature of the N-substituent (aryl vs alkyl thioether) and of the chelate ring size (P,P vs P,P-S). DFT calculations showed that the trend in ΔErel, [NiCl2(P,P)] > [NiCl2(P,P-S)] > [NiCl 2(P-S,P-S)], results from the stronger covalent character of the Ni-P vs Ni-S bond. Using AlEtCl2 as cocatalyst, mostly ethylene dimers were produced, with significant amounts of trimers (selectivity in the range 11-36%). Productivities up to 40400 and 48200 g of C2H 4/((g of Ni) h), with corresponding TOF values of 84800 and 101100 mol of C2H4/ ((mol of Ni) h), were obtained with precatalysts 2 and 3, respectively.
