Ethylene copolymers with propene and/or 1,3-butadiene were obtained using bis(q5-cyclopen-tadieny1)zirconium dichloride (1) or ethylenebis[l-3a,7a-q-(4,5,6,7-tetrahydro)-l -indenyl]zirconium dichloride (2) and methylalumoxane as catalytic systems. A detailed 13C NMR analysis of the copolymers was performed. The resonances in the olefinic region of the terpolymers were assigned to ethylene/butadiene/ethylene and propene/butadiene/ethylene sequences while the butadiene/propene sequence was ruled out. Analogously, no polymers were obtained from the polymerization of propene in the presence of 1,3-butadiene. It is thus shown that the conjugated diene is an inhibitor for the polymerization of a-olefins. The presence of tmns-l,2-cycIopentane rings was detected both in the ethylene/butadiene copolymers and in the ethylene/propene/butdiene terpolymers. A different behaviour of the two catalysts was observed. 0 1991, Huthig & Wepf Verlag, Basel CCC 0025-1 16)3/91/$05.00

We report synthesis, X-ray crystal structure, conformational behaviour, and complexation properties of cavitand (1).Cavitands are synthetic organic compounds with enforced concave sur€aces of molecular dimensions .1 Such compounds are of interest as receptor sites in enzyme-mimicking Among the cavitands synthesized so far (1) is particularly Macrocyclic octol (2)t is obtained as single pure isomer+ in 1-All new compounds and cavitates gave satisfactory analytical and spectral data.attractive Owing to the presence Of a solvation-temperature-$ Tetramer (2), depicted in its crown conformation in Scheme 1, is the

SUMMARY: A new class of highly effective homogeneous palladium bis(methoxycarbonyl) complexes Pd(L1L)(COOMe) 2 , where (L1L) are substituted phenanthroline ligands, has been developed for the production of syndiotactic alternating styrene-carbon monoxide copolymers. The essential feature of this novel catalytic system is that it is formed by palladium complex, Pd(L1L)(COOMe) 2 , an acid cocatalyst, (L1L)HPF 6 , bearing a weakly coordinating counter anion, and an oxidant, such as 1,4-naphthoquinone (1,4-NQ). The palladium/acid cocatalyst molar ratio has been explored. A maximum of copolymerization activity was obtained at 1/1 molar ratio. For a series of palladium catalysts, Pd(phen)(COOMe) 2 appeared to be the most active one. The effect of substituents at the ligand in Pd(L1L)(COOMe) 2 on the copolymerization activity was studied. The tacticity of alternating copolymers obtained with different Pd(L1L)(COOMe) 2 catalysts was determined by NMR spectroscopy. The copolymers were thermally characterised by TGA and DSC.

A detailed microstructural characterization of ethylene-propene copolymers, obtained with a high yield Ti-catalyst and showing elastomeric properties, was carried out by 13C NMR spectroscopy. These copolymers show no inversions in propene insertion, a tendency to form blocks of ethylene and propylene, and the presence of both isotactic and atactic blocks of propylene.Furthermore, in these polymers the reactivity ratio product (rl . rz) and the experimental versus calculated triad distribution point to the presence of components which are heterogeneous with respect to the monomer distribution and composition. 13C NMR analysis of fractions, separated by hexane and ether, supports the above hypothesis.

Several [Ti,(OR),MtX,], complexes were prepared from MtX, (Mt = Mg, Zn; X = C1, Br, I) and Ti(OR), (R = ethyl, propyl, butyl). 'H and 13C NMR in toluene-d, solution and crosspolarization/magic-angle spinning (CP/MAS) 13C NMR spectra were taken of some complexes. The obtained spectra allowed to deduce their molecular structure in solution and to compare them with that of [Ti,(OC,H5),C1],Mg,CI, obtained by single-crystal X-ray diffraction analysis.