The reaction of gaseous HCl with K[B(CF 3 ) 4 ] in diethyl ether gave the oxonium acid [H(OEt 2 ) 2 ][B(CF 3 ) 4 ] as a stable salt at room temperature. Syntheses of [Ph 3 C][B(CF 3 ) 4 ] and [Ph 3 C][(CF 3 ) 3 BCN] were accomplished from the corresponding potassium salts and Ph 3 CCl. The metathesis reaction of Ag[B(CN) 4 ] with trityl bromide resulted in formation of [Ph 3 C]-[B(CN) 4 ]. Treatment of Cp 2 ZrMe 2 with [H(OEt 2 ) 2 ][B(CF 3 ) 4 ], [Ph 3 C][B(CF 3 ) 4 ], [Ph 3 C][(CF 3 ) 3 -BCN], and [Ph 3 C][B(CN) 4 ], monitored by NMR spectroscopy, showed the formation of [Cp 2 ZrMe(OEt 2 )] + , [(Cp 2 ZrMe) 2 -µ-Me] + , [Cp 2 ZrMe] + , Cp 2 ZrMe{NCB(CF 3 ) 3 }, and Cp 2 Zr{NCB-(CN) 3 } 2 , respectively. Attempted polymerizations of propene with catalysts generated in situ from rac-Et(1-Ind) 2 ZrMe 2 and [H(OEt 2 ) 2 ][B(CF 3 ) 4 ], [Ph 3 C][B(CF 3 ) 4 ], or [Ph 3 C][B(CN) 4 ] yielded only little to no polymer, possibly due to the low solubility of the catalysts in the reaction medium.

New unbridged mixed-ligand zirconocenes were synthesized, characterized, and studied in the copolymerizations of ethylene-propylene (EP) and ethylene-1-hexene (EH). The MAO-activated metallocene [1-benzyl-2-(3′,5′-di-tert-butyl)phenylindenyl][2-phenylindenyl]zirconium dichloride (8) catalyzed EP and EH copolymerizations with products of reactivity ratios greater than one (r erp ) 2.4, rerh ) 2.2) to give rubbery, semicrystalline, high-melting polymers. Crystallinity was detected by differential scanning calorimetry (DSC) in both EP and EH copolymers containing only 50 mol % ethylene. Solvent fractionation of high ethylene content EH copolymers revealed that these copolymers were composed of a small ether-soluble fraction and heptane-soluble and heptane-insoluble fractions whose compositions and sequence distributions matched closely with those of the unfractionated polymer. Collectively, the reactivity ratios, DSC, and fractionation results gave evidence that these copolymers contained long crystallizable ethylene sequences. A comparison of the melting point behavior of a series of ethylene-1-hexene copolymers with 80 mol % ethylene revealed a sensitive dependence of the melting transition to the comonomer sequence distribution.

Irradiation (λ >300 nm) of eight two‐component solid solutions of β‐arylacrylamides, prepared by melting and crystallising equimolar quantities of the amides tr‐ArCH:CHCONE where Ar=C6H5, p‐MeOC6H4, p‐ClC6H4, p‐MeC6H4, and 2‐thienyl, which appeared in the α crystal form, gave three photoproducts for each system studied: two α‐truxillic homodimers, derived from the respective monomers, and an α‐truxillic heterodimer. No other isomers were found. Similarly, two‐component solid solutions were prepared by melting and crystallising ring‐substituted cinnamic acids (tr‐ArCH:CHCO2H, where Ar=C6H5 (α‐form), p—ClC6H4(β), p‐MeC6H4(α), p‐MeOC6H4(γ), o‐ClC6H4(β) and o‐CH3C6H4(γ)) and irradiated. A solid solution of two α‐type acids (each photodimerising in the solid to α‐truxillic acid) behaved like the amides, affording two α‐truxillic homodimers and an α‐truxillic heterodimer. A solid solution of an α‐type acid with a β‐type acid (photodimerising to β‐truxinic acids) gave six photoproducts: three α‐truxillic acid dimers and three β‐truxinic acid dimers (i.e., four homodimers and two heterodimers). Irradiation of a solution of a γ‐type acid (non‐photodimerising in the solid state) with an α‐type acid afforded α‐truxillic dimers (two homodimers and one heterodimer). The above results are consistent with mutual miscibility of the two components which gives rise to mixed crystal formation and subsequent photo‐behaviour within each crystal which is characteristic of the particular lattice type. However, irradiation of the mixed crystals from p‐methoxycinnamic acid (γ‐type) and p‐chlorocinnamic acid (β‐type), which afford two α‐truxillic dimers (methoxy‐homodimer and methoxy, chloro‐heterodimer) and two β‐truxinic dimers (chloro‐homodimer and methoxy, chloro‐heterodimer) indicates that new phases, unobserved for the pure compounds, can also be generated. The new dimers were all characterised by the NMR and mass spectra of their dimethyl ester derivatives and, when possible, by conversion to known compounds.

A new disilyl‐bridged complex, [(N‐tert‐butylamido)(3‐indenyl)tetramethyldisilyl]titanium dichloride (3), was synthesized and activated with methylaluminoxane (MAO) for propylene homopolymerization and ethylene/propylene and ethylene/1‐hexene copolymerizations. A polypropylene with a slight isotactic enrichment was obtained. The number of regioerrors present in the polypropylene was somewhat smaller than that found in most polypropylenes made from monosilyl‐bridged [(N‐tert‐butylamido)(3‐indenyl)dimethylsilyl]titanium dichloride. The regioerrors detected in the copolymers obtained from 3/MAO were on the order of the amounts observed in polymers made with the monosilyl‐bridged constrained geometry catalysts. Ethylene copolymers of propylene and 1‐hexene had random sequence distributions and showed significant comonomer incorporation. Because of the presence of regioerrors, a modified method for determining the monomer composition and sequence distribution was developed from the direct measurement of the monomer content from the number of methylene and methine carbons per polymer chain, regardless of propylene inversion. An estimate of the error in the copolymerization reactivity ratio determination for regioirregular ethylene/α‐olefin copolymers was obtained by the calculation of the reactivity ratios from monomer dyad sequences, with consideration given to the contribution of major regioirregular sequences. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3840–3851, 2005