Titanium bisphenolate complexes [Ti(edbp)Cl-2,] (1), [Ti-2(mu-OEt)(2)(edbp)(2)(OEt)(2)] (2) and [Ti-2(mu-OMe)(2)(edbP)(2)(Me)(2)] (3) (edbpH(2) = 2,2'-ethyl lidenebis (4.6-di-tert-buzylphenol) combined with trialkyl aluminium AlR3 (R = Me, Et, Bu-i) activators induce phenylacetylene (PA) oligo and/or polymerization. It was found that the catalytic activity and products formation depend strongly on the used cocatalyst. The 1/AlEt3 catalyst has the highest activity and selectivity (96% conversion; 98% trans-PPA). The PPA has low M-n values (2200) and PDI exceeding 1.04. Instead, 1/(AlBu3)-Bu-i produces only cyclotrimers. Polymer formed by 2/AlEt3 possesses lower polydispersion index (PDI values 2.5) but high molecular weight (M-n ca. 13 x 10(2)) and was the mixture of cis and trans stereoisomers of PPA. The compound 3 containing terminal methyl groups was unable to promote PA polymerization in absence of activators, only cyclotrimerization products (10% conversion) were formed. (C) 2004 Elsevier B.V. All rights reserved.