Synthesis, Reactivity, and Solid State Structures of Four-Coordinate Iron(II) and Manganese(II) Alkyl Complexes

Abstract

Synthesis and characterization of new, four-coordinate, high-spin iron(II) and manganese(II) complexes of the general form L2MR2 (L2 = neutral chelating ligand, R = alkyl) are described. Alkylation of the α-diimine complex, [ArNC(Me)−C(Me)NAr]FeCl2 (Ar = 2,6-diisopropylphenyl), as well as the enantiopure iron dichloride compounds, (−)-(sparteine)FeCl2 and (S)-(tBuBox)FeCl2 ((S)-(tBuBox) = 2,2-bis[2-[4(S)-(R‘)-1,3-oxazolinyl]propane), with LiCH2SiMe3 afforded the corresponding dialkyl derivatives. Solution magnetic susceptibility measurements and X-ray diffraction studies reveal each of the new iron(II) bis-trimethylsilylmethyl complexes to be high-spin, S = 2, tetrahedral molecules. In addition (−)-(sparteine)Fe(CH2CMe3)2, (−)-(sparteine)Fe(CH2C6H5)2, and (S)-(tBuBox)Fe(CH2C6H5)2 were also prepared and characterized by NMR spectroscopy and elemental analysis. An enantiopure, high-spin, tetrahedral manganese(II) dialkyl complex, (−)-(sparteine)Mn(CH2SiMe3)2, has also been synthesized. The catalytic activity of the new iron complexes in carbon−carbon bond forming processes has been evaluated, and stoichiometric reactions of the dialkyls with olefins, carbon monoxide, and the Lewis acid B(C6F5)3 have been examined.

Bispidine Coordination Chemistry

“…The coordination chemistry of sparteine is not extensively explored, but recent reports have described the synthesis, spectroscopic properties and structures of a row of its transition metal complexes (9)(10)(11)(12)(13)(14)(15). One possible reason for the poorly studied coordination chemistry of sparteine is the fact that differently substituted and enantiomerically pure derivatives of sparteine require some effort and are expensive to synthesize (16,17), which limits their application to a few small-scale experiments.…”

Olefin Polymerization with Non-metallocene Catalysts (Late Transition Metals)

“…Fe and Co complexes with bidentate N-ligands such as a-and b-diimine [190], bisoxazoline, and sparteine [191] are much less active for ethylene polymerization, and afford low molecular weight oligomer. Combination of bis(imino)pyridine CoMe complex and Li[B(C 6 F 5 ) 4 ] promotes ethylene polymerization with low activity [192].…”

Manganese(II) halogeno complexes with neutral tris(3,5-diisopropyl-1-pyrazolyl)methane ligand: Synthesis and ethylene polymerization

“…These manganese(II) complexes with the neutral tridentate methane ligand have a six-coordinated structure, as determined by X-ray structural analysis. Moreover, manganese complex can be converted to alkyl manganese species [15,27,28]. Thus, it is assumed that the polymerization on this manganese catalyst follows a mechanism similar to that of the polymerization on group 4 metallocene catalysts.…”