The crystal structure and electron density (ED) distribution of an imine coupling product with an open zirconocene, Zr(2,4-C7H11)[(i-Pr)NCHPhCH2CMeCHCMeCH2] (C7H11 = dimethylpentadienyl), have been derived from accurate synchrotron X-ray diffraction measurements. The molecular structure reveals asymmetric coordination of Zr by the pentadienyl (2,4-C7H11) ligand (〈Zr−C〉 = 2.56(6) Å), the butadiene fragment (〈Zr−C〉 = 2.43(5) Å), and the amide nitrogen atom (Zr−N = 2.0312(5) Å) of the second ligand. The study of the ED and its topological analysis affords new insight into the bonding and electronic structure of the title zirconium complex. The interactions between the metal center and the ligands are represented by a Zr−N bond path and one Zr−C bond path with each of the pentadienyl and butadiene moieties, contrary to the usually depicted global metal−ligand bonding. The butadiene and pentadienyl groups exhibit a polarization of the corresponding π-like ED in the C−Zr directions, indicating that the whole conjugated systems are nonetheless involved. The 4d atomic orbitals of Zr exhibit unusual populations according to ligand field considerations, which reveal a high degree of σ-donation from the conjugated π systems of both ligands. As deduced from numerical integration over the topologically defined atomic basins, the Zr to ligand charge transfer is 1.48 e to the C17NH24 ligand and 0.68 e to dimethylpentadienyl. Topological analysis of a short intramolecular Zr···(C,H) contact provides no indication of the presence of agostic interactions, despite a small Zr−N−C angle of 102.87(4)°. Thus, no bond path and BCP (bond critical point) of the ED are found in the Zr···(C,H) region, which would have provided evidence for such direct interactions, nor is there any evidence for charge accumulation between the Zr and H atoms, or for lengthening of the C−H bond involved in the putative interaction. These characteristics, similar to those in other distorted situations, may be common for other electron-deficient d0 complexes.

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5 ). The reaction of the tetramer with a mixture of 2-methyl-4-phenylpenta(-1,3-or -2,4-)dienes led to the Pdl = 2-Me-4-PhC 5 H 5 complex. In contrast, the reaction of the tetramer with 3-phenylpenta-1,3-diene led to simple incorporation of the η 4 -diene ligand. Structural confirmation of the formulations of the four η 5 -pentadienyl complexes has been achieved, allowing for a number of comparisons to be made regarding the structural effects of phenyl substitution on the (1,5), (2,4) and 3 positions of the open dienyl ligand.

The reactions of two equivalents of the cyclooctadienyl anion with various divalent transition metal salts (M = Ti, V, Cr or Fe) led to the formation of the appropriate bis(cyclooctadienyl)metal complexes, isolable as crystalline compounds. Their constitutions have been established through NMR and mass spectroscopies, elemental analyses, and single crystal X-ray diffraction studies. As with the M(2,4-C 7 H 11 ) 2 and M(6,6-dmch) 2 (C 7 H 11 = dimethylpentadienyl; dmch = dimethylcyclohexadienyl) complexes, the titanium and vanadium compounds adopt low spin configurations, thereby differing from their metallocene analogs. The structures observed for these complexes in the solid state are similar to those of the M(2,4-C 7 H 11 ) 2 complexes. The low spin titanium complex also forms a mono(ligand) adduct with CO, although the binding appears noticeably weak due to the steric influence of the edge bridge.