The experimental electron density study of Ti(C(5)H(4)Me)(2)[(CH(2))(2)CMe(2)] provides direct evidence for the presence of (C-C)-->Ti agostic interactions. In accord with the model of Scherer and McGrady, the C(alpha)-C(beta) bond densities no longer show cylindrical symmetry in the vicinity of the Ti atom and differ markedly from those of the other C-C bonds. At the points along the C(alpha)-C(beta) bond where the deviation is maximal the electron density is elongated toward the metal center.
View Article and Find Full Text PDFThis paper presents novel measurements and calculations of the olefinic (13)C chemical shift tensor principal values in several metal diene complexes. The experimental values and the calculations show shifts as large as 70 ppm with respect to the values in the parent olefinic compounds. These shifts are highly anisotropic, with the largest ones observed in the less shielded principal components and the smallest ones in the most shielded principal components of the tensor.
View Article and Find Full Text PDFThe reaction of the half-open titanocene, Ti(C5H5)(c-C8H11)(PMe3) (c-C8H11 = cyclooctadienyl), with two equivalents of PhC2SiMe3 leads to their incorporation and coupling to the dienyl fragment. One alkyne inserts into a C-H bond of the central CH2 group of the c-C8H11 ligand's edge-bridge, while the second undergoes a 5+2 coupling with the dienyl fragment, yielding coordinated sigma-allyl and olefin fragments, as demonstrated by X-ray diffraction. Together with the C5H5 and PMe3 coordinations, this leads to a 14-electron count.
View Article and Find Full Text PDFThe normally remarkably inert SF6 has been found to be quite reactive toward low valent organometallic compounds, under conditions in which usually powerful fluorinating agents may be less reactive. Reaction of SF6 with Ti[1,3-C5H3(t-Bu)2](6,6-dmch)(PMe3), for example, leads to {Ti[1,3-C5H3(t-Bu)2]F2}4 (dmch = dimethylcyclohexadienyl), whose structure is based on a cube of fluoride ions with the ligated titanium centers situated above four coplanar face centers.
View Article and Find Full Text PDFThe silylation of SBA-15 enhances the reducibility of cobalt oxides on a SBA-15 supported cobalt catalyst, and consequently increases the catalytic activity for Fischer-Tropsch synthesis of hydrocarbons from syngas and selectivity for longer chain products.
View Article and Find Full Text PDFMolecules of the form Cp(6,6-dmch)ZrX(2) (Cp = eta(5)-cyclopentadienyl, X = Cl, Br, I; 6,6-dmch = eta(5)-6,6-dimethylcyclohexadienyl) have been synthesized, and the molecular and electronic structures have been investigated. These molecules allow direct comparison of the bonding and properties of pentadienyl and cyclopentadienyl ligands in the same high-oxidation-state metal complexes. Unlike the well-known Cp(2)ZrX(2) analogues, these Cp(6,6-dmch)ZrX(2) molecules are intensely colored, indicating significantly different relative energies of the frontier orbitals.
View Article and Find Full Text PDFThe synthesis and characterization of the open hafnocene, Hf(2,4-C7H11)2(PMe3)(C7H11 = dimethylpentadienyl), is reported. Additionally, a much improved synthetic procedure has been developed for Hf(2,4-C7H11)2(PEt3). Structural data have been obtained for these complexes, and for Ti(2,4-C7H11)2(PEt3) and Zr(2,4-C7H11)2(PMe3), thereby allowing for detailed comparisons between all M(2,4-C7H11)2(PX3) species (M = Ti, Zr, Hf; X = Me, Et).
View Article and Find Full Text PDFThe crystal structure and electron density (ED) distribution of an imine coupling product with an open zirconocene, Zr(2,4-C(7)H(11))[(i-Pr)NCHPhCH(2)CMe=CHCMe=CH(2)] (C(7)H(11) = dimethylpentadienyl), have been derived from accurate synchrotron X-ray diffraction measurements. The molecular structure reveals asymmetric coordination of Zr by the pentadienyl (2,4-C(7)H(11)) ligand (