A new disilyl-bridged complex, [(N-tert-butylamido)(3-indenyl)tetra-methyldisilyl]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/alpha-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. (c) 2005 Wiley Periodicals, Inc.