No abstract

Lithium cyclopentadienide adds to a variety of isocyanates [R−NCO, R = tert-butyl (a), n-butyl (b), cyclohexyl (c), phenyl (d), 3-pyridyl (e), 2-tetrahydropyranyl (f), adamantyl (g)] to yield the monocarbamoyl-substituted cyclopentadienides C5H4CONHR- 3 admixed with varying amounts of the respective 1,2-dicarbamoyl-substituted C5H3(CONHR)2 - systems 4 and a corresponding quantity of the C5H5 - starting material. Subsequent treatment of these reaction mixtures with anhydrous FeCl2 gave the 1,1‘-dicarbamoylferrocenes 6 and the corresponding monocarbamoylferrocenes 5, which were easily separated by chromatography. The carbamoylferrocenes 5b, 5c, and 6d were characterized by X-ray crystal structure analyses. The (N-phenyl- and (N-adamantylcarbamoyl)cyclopentadienides were treated with CpTiCl3 to give the carboxamide-substituted titanocene dichloride complexes [Cp(C5H4CONHR)TiCl2] 8a (R = Ph) and 8b (R = adamantyl), respectively. Complex 8b was also characterized by X-ray diffraction. The valine ester-derived isocyanate reacts with lithium cyclopentadienide to give the N-valinyl-substituted carbamoylcyclopentadienide 3h. Subsequent treatment with FeCl2 or FeCl2/CpLi, respectively, produces the 1,1‘-difunctionalized ferrocene 6h or the monofunctionalized ferrocene 5h. Both complexes were characterized by X-ray crystal structure analyses.

6‐Amino‐6‐methylfulvene (4) is cleanly N‐acylated by treatment with pivaloylchloride/triethylamine to give the fulvene (C5H4)=C(CH3)NHCOCMe3 (5c). Treatment of 4 with trimethylchlorosilane similarly yields the mono‐N‐silylated fulvene (C5H4)=C(CH3)NHSiMe3 (7). Both 5c and 7 are cleanly doubly deprotonated e.g. by treatment with LDA to give ligand systems [(C5H4)C(=CH2)NR]Li2 [8a (R = COCMe3) and 8b (R = SiMe3), respectively]. Their treatment with MCl4 · 2 THF (M = Ti, Zr) yield the spiro‐metallocenes [(C5H4)C(=CH2)NR]2M (9, 10). Complex 10a (M = Zr, R = COCMe3) was characterized by X‐ray diffraction. The reaction of 8a with (Et2N)2ZrCl2 in THF gives rise to the formation of [(C5H4)C(=CH2)NCOCMe3]Zr(NEt2)2 (11) (70 % isolated), and the reaction of 8b with (Et2N)2ZrCl2 yields [(C5H4)C(=CH2)NSiMe3]Zr(NEt2)2 (12) (76 % isolated). Treatment of complex 12 with an excess of methylalumoxane (MAO) in toluene solution results in the generation of an active homogeneous Ziegler catalyst for the polymerization of ethene. A comparison with the usually employed [(Me5C4)SiMe2NCMe3]ZrCl2/MAO “constrained‐geometry” Ziegler catalyst system reveals a similar catalyst activity and performance of this novel type of a C1‐bridged “constrained‐geometry” catalyst as it is exemplified by the [(C5H4)C(=CH2)NSiMe3]ZrX2 (12)/MAO combination.

The combination of time‐of‐flight secondary mass spectrometry (ToF‐SIMS) and monochromatized x‐ray photoelectron spectroscopy (XPS) has proved to be a valuable tool for the analysis of chemically modified polymer surfaces. By applying these techniques in situ, together with a plasma modification chamber and a Knudsen cell, we have investigated the plasma modification of polyimide in an oxygen plasma and the first steps of copper deposition on the untreated and the plasma‐modified polyimide substrate. Characterization of the initial stages of copper deposition by XPS and comparison with the untreated and the plasma‐modified substrate indicate that, in the case of the untreated substrate, copper binds to the carbonyl group of the repeat unit, whereas after plasma modification a great number of C–O and C–N functionalities are available as binding sites for the metal overlayer. The molecular ion species identified by ToF‐SIMS allow the identification of specific plasma‐induced fragmentation mechanisms and confirm the interface reaction mechanisms deduced from the XPS results. The nature and amount of copper–substrate bonds are directly correlated to the adhesion strength of the copper/polyimide interface as measured by the force applied in a standard industrial peel test. Copyright © 1999 John Wiley & Sons, Ltd.

Treatment of sodium cyclopentadienide with two molar equivalents of tert‐butyl isocyanate yields sodium 1,2‐bis(N‐tert‐butylcarbamoyl)cyclopentadienide (6). The [C5H3(1,2‐CONHCMe3)2]Na reagent 6 adds to Cp2Zr(CH3)Cl (8) to yield Cp2Zr(CH3)[C5H3(CONHCMe3)2] (9). In 9 the C5H3(CONHCMe3)2 ligand is bonded to zirconium through one of its carboxamido‐oxygen atoms (ĸO‐coordination). Treatment of 6 with CpZrCl3(THF)2 yields CpZrCl2[C5H3(CONHCMe3)2](THF) 11. In 11 the 1,2‐bis(N‐tert‐butylcarbamoyl)cyclopentadienide moiety serves as a Cs‐symmetric chelate ligand, binding to zirconium through both carbamoyl oxygens (ĸ2O,O′‐coordination). The same seven‐membered metallacyclic structural type is found in the reaction products of 6 with ZrCl4(THF)2 in 1:1 and 2:1 molar ratios. The former yields the distorted octahedral complex ZrCl3[C5H3(CONHCMe3)2](THF) (12), the latter gives the chiral octahedral system ZrCl2[C5H3(CONHCMe3)2]2 (13). In solution, complex 13 undergoes a thermally induced enantiomerization process (Λ → Δ interconversion), for which a Gibbs activation energy of ΔG‡enant = 14.0 ± 0.3 kcal mol−1 was determined by dynamic 1H‐NMR spectroscopy. The ĸ2O,O′‐coordination of the [C5H3(1,2‐CONHCMe3]− ligand in the complexes 11, 12, and 13 was secured by X‐ray crystal structure analyses.