Modification of Iron(II) tridentate bis(imino)pyridine complexes by a boryl group for the production of alpha-olefins at high temperature

作者：Ionkin Alex S^*; Marshall William J; Adelman Douglas J; Fones Barbara Bobik; Fish Brian M; Schiffhauer Matthew F

来源：Organometallics, 2008, 27(8): 1902-1911.

DOI：10.1021/om800036b

A new series of boryl-substituted bis(imino)pyridine ligands [o-PinacoIB-Ph-N=C(Me)-Py-C(Me)=N- Ph-o-BPinaeoll, Pinacol = (-O-(Me)(2)C-C(Me)(2)-O-) (6), [2,4,6-tri-Me-Ph-N=C(Me)-Py-C(Me)=N-Ph-o-BPinacol] (11), [4-bromo-2,6-di-Me-Ph-N=C(Me)-Py-C(Me)=N-Ph-o-BPinacol] (12), [2,4,6-tri-Me-Ph-N=C(Me)-Py-C(Me)=N-Ph-m-BPinacol] (14), [2,4,6-tri-Me-Ph-N=C(Me)-Py-C(Me)=N-Ph-p-BPinacol] (17), and [4-Bromo-2,6-di-Me-Ph-N=C(Me)-Py-C(Me)=N-Ph-p-BPinacol] (18), and their corresponding Fe(II) complexes [o-PinacolB-Ph-N=C(Me)-Py-C(Me) N-Ph-o-BPinacol)FeCl(2)] (3), [{2,4,6-tri-Me-Ph-N=C(Me)-Py-C(Me)=N-Ph-o-BPinaco}FeCl(2)] (19), [{4-bromo-2,6-di-Me-Ph-N=C(Me)-Py-C(Me)=N-Ph-o-BPinacol} FeCl(2)] (20), [2,4,6-tri-Me-Ph-N=C (Me)-Py-C(Me)=N-Ph-m-BPinacol}- FeCl(2)] (21), [2,4,6-tri-Me-Ph-N=C(Me)-Py-C(Me)=N-Ph-p-BPinacol) FeCl(2)] (22), and [(4-bromo-2,6-di-Me-Ph-N=C(Me)-Py-C(Me)=N-Ph-p-BPinacol)FeCl(2)] (23) were synthesized. According to X-ray analysis, the introduction of boryl groups in the ortho-positions of the complex as in 3 caused the shortening of the axial Fe-N bond lengths (up to 0.02 angstrom) vs the analogous Fe(II) complex with ortho-methyl groups [{o-Me-Ph-N=C(Me)-Py-C(Me)=N-Ph-o-Me)FeCl(2)], 1. The comparisons of the axial bond lengths in ortho-boryl-substituted isomer 19 with para-boryl -substituted 22 revealed that these bonds are shorter in the ortho-isomer (2.201(11) angstrom) than in the para-isomer (2.232(2) angstrom). An interesting structural feature of 3 is that it exists in the unexpected "up-up" conformer in the solid state, despite reasonable bulkiness of dioxaboranyl substituents in ortho-positions. Complexes 21-23 afforded very productive catalysts for the production of alpha-olefins with a more linear Schultz-Flory distribution and with the least amounts of the heavier insoluble fractions of a-olefins than the parent methyl-substituted Fe(II) complex 1.

• 出版日期2008-4-28