Spacially confined M-2 centers (M = Fe, Co, Ni, Zn) on a sterically bulky binucleating support: Synthesis, structures and ethylene oligomerization studies

作者：Champouret Yohan D M; Fawcett John; Nodes William J; Singh Kuldip; Solan Gregory A^*

来源：Inorganic Chemistry, 2006, 45(24): 9890-9900.

DOI：10.1021/ic061286x

Two new bulky aryl-bridged pyridyl-imine compartmental ( pro) ligands, 2,6- {( 2,6- i- Pr2C6H3) NdC( Me) C5H3N}(2)C6H3Y ( Y = H L-1, OH L-2- H), have been prepared in moderate to good overall yields via a Stille-type cross-coupling approach. The molecular structure of L-2- H reveals a transoid configuration within the pyridyl-imine units with a hydrogen- bonding interaction maintaining the phenol coplanar with one of the adjacent pyridine rings. The interaction of 2 equiv of MX2 with L-1 in n- BuOH at 110 degrees C gives the binuclear complexes, [( L-1) M2X4] ( M) Fe, X) Cl ( 1a); M) Co, X) Cl ( 1b); M) Ni, X) Br ( 1c); M) Zn, X) Cl ( 1d)), in which the metal centers adopt distorted tetrahedral geometries and occupy the two pyridyl-imine cavities in L1. In contrast, deprotonation of L-2-H occurs upon reaction with 2 equiv of MX2 to afford the phenolate- bridged species [( L-2) M-2( A-X)X-2] ( M) Fe, X) Cl (2a); M) Co, X) Cl (2b); M) Ni, X) Br (2c); M) Zn, X) Cl ( 2d)). H-1 NMR studies of diamagnetic 1d and 2d reveal that the limited rotation of the N- aryl groups in 1d is further impeded in 2d by steric interactions imparted by the two closely located N- aryl groups. Partial displacement of the bridging bromide in 2c results upon its treatment with acetonitrile to afford [( L2) Ni2Br3( NCMe)] [ 2c( MeCN)]; no such reaction occurs for 2a, 2b, or 2d. Upon activation with excess methylalumoxane ( MAO), 1b, 1c, 2b, and 2c show some activity for alkene oligomerization forming low molecular- weight materials with methyl- branched products predominating for the nickel systems. Single- crystal X- ray diffraction studies have been performed on L2- H, 1c, 2b, 2c, 2c( NCMe), and 2d.

• 出版日期2006-11-27