1,151,005. Condensation catalysts. E. I. DU PONT DE NEMOURS & CO. 8 Sept., 1967 [12 Sept., 1966], No. 41184/67. Heading B1E [Also in Division C5] Condensation catalysts comprise (a) an organoaluminum halide and (b) a biphosphine complex consisting of one mole of cobalt hydride or of cobalt (o) complexed with 2 moles of a bisphosphine of formula (I) in which, when the Co compound is a hydride, each Q group is alkyl, cycloalkyl, aryl or aralkyl, not more than two Q groups being methyl, and when the Co compound is Co(O) all the Q groups are aryl, (a) and (b) being mixed in such proportions that there are at least two aluminum atoms per cobalt atom in the catalyst. Typical catalyst starting materials are bis[ethylenebis(diphenylphosphine)] Co(O) and monoisobutylaluminum dichloride.