Here we present the first synthetic route to bis(η 5 :η 1 -pentafulvene)zirconium complexes as well as investigations of several consecutive reactions. Sodium amalgam reduction of ZrCl 4 in the presence of a bulky substituted pentafulvene in THF leads to the formation of [η 5 :η 1 -C 5 H 4  CR 2 ] 2 Zr(THF) (2a, R = p-tol; 2b, R = Ph). The molecular structure of 2a has been determined by single-crystal X-ray diffraction and exhibits an unusually large Zr−C exo distance (2.708(2) Å) caused by the bulky substituents at the exocyclic carbon, which allows THF coordination. The reaction of 2a with H-acidic compounds such as hydrogen chloride, amines, and water were examined: addition of HCl leads to the dichloride complex [η 5 -C 5 H 4 -CH(p-tol) 2 ] 2 ZrCl 2 (3) and treatment of 2a with p-methylaniline forms the bis-amide complex [η 5 -C 5 H 4 -CH(p-tol) 2 ] 2 Zr(NH-p-tol) 2 (4), whereas addition of the sterically more demanding dicyclohexylamine furnishes the monoamide complex [η 5 :η 1 -C 5 H 4 C(p-tol) 2 ][η 5 -C 5 H 4 -CH(p-tol) 2 ]Zr(NCy 2 ) (5). The cyclotrimeric compound {[η 5 -C 5 H 4 -CH(p-tol) 2 ] 2 Zr(μ-O)} 3 (6) is obtained by reaction of 2a with water. Moreover, insertion reactions of CX multiple bonds (X = N, O) into the Zr−C exo (Fv) bond of 2a result in the formation of the zirconacycles [η 5 :η 1 -C 5 H 4 -C(p-tol) 2 -C(C 6 H 4 Cl)N−] 2 Zr (7), [η 5 :η 1 -C 5 H 4 -C(p-tol) 2 -MeC 4 H 6 N−] 2 Zr (8), and [η 5 :η 1 -C 5 H 4 -C(p-tol) 2 -C(Ph) 2 O−] 2 Zr (9). Finally, 2a is a valuable agent for the activation of molecular hydrogen under ambient conditions. In this regard, only one pentafulvene ligand per zirconium atom is protonated and the dinuclear zirconium hydride complex {[η 5 :η 1 -C 5 H 4 C(p-tol) 2 ][η 5 -C 5 H 4 -CH(p-tol) 2 ]Zr(μ-H)} 2 (10) is isolated. All compounds were confirmed by single-crystal X-ray diffraction and NMR spectroscopic measurements.

The reaction of Cp*MCl3 (M = Zr, Zr1; M = Hf, Hf1) with the reducing agent Na/Hg (20% Na) and with sterically encumbered pentafulvenes adamantylidenepentafulvene AdFv, 6,6′-di-p-tolylpentafulvene pTol 2 Fv, and benzofulvenes adamantylidenebenzofulvene AdBzFv, 10,10′-di-p-tolylbenzofulvene pTol 2 BzFv, and 10,10′-diphenylbenzofulvene Ph 2 BzFv yielded the corresponding pentafulvene complexes (η5-pentamethylcyclopentadienyl)­metal­(η5:η1-pentafulvene)­chloride (Zr2a,b, Hf2a,b) and benzofulvene complexes (η5-pentamethylcyclopentadienyl)­metal­(η5:η1-benzofulvene)­chloride (Zr3a–c, Hf3a). This reductive complexation approach can be used in a multigram scale and mostly very good yields (up to 92%). In addition to NMR spectroscopic analyses, the pentafulvene complex Zr2b and benzofulvene complex Zr3b were characterized by X-ray crystallography, showing mainly the π–η5:σ–η1 dianionic bonding mode together with slight influence of the π–η2:π–η3:σ–η1 bonding mode. By use of the prochiral benzofulvenes the corresponding complexes Zr3a–c and Hf3a are furthermore obtained in a diastereoselective manner.

The reaction of bis(η :η -pentafulvene)titanium complexes with an allylidenephosphorylide Ph P=C(H)- C(H)=CH leads to binuclear zigzag hexapentaene titanium complexes (Ti2a, Ti2b). The formation of the central C H unit can be described as a spontaneous double C-H bond activation process, leading to an R P=C=C=CH intermediate, as a synthon for a titanabutatriene fragment [(Cp ) Ti=C=C=CH ] (R: 2-adamantyl, CH(p-tol) ). In a subsequent dimerization Ti2a and Ti2b are formed, proofed by single-crystal X-ray diffraction and NMR measurements. The reaction sequence is confirmed by DFT calculations.

The effect of molecular weight and long‐chain branching on the crystallization analysis fractionation (CRYSTAF) of ethylene homopolymers was investigated. Several ethylene homopolymers were prepared with different molecular weights and levels of long‐chain branching to isolate these effects from the dominant effect of comonomer content on crystallizability measured by CRYSTAF. Molecular weight effects might be significant for samples with number‐average molecular weights below 5000, but this effect can be corrected if terminal methyl groups are taken into account. Long‐chain branching has only a very small effect on the CRYSTAF profile of the samples investigated in this study. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1616–1628, 2001

C14H 23 Cl 2 OTi, monoclinic, P21/c (no. 14), a = 12.3163 (7)