RhI-complexes of ditopic bis(pyrazol-1-yl)borate ligands: Assessment of their catalytic activity towards phenylacetylene polymerization

Two dinuclear RhI-cyclooctadiene complexes [1,4-(cod)Rh(B(R’)pz2)-C6H4-(B(R’)pz2)Rh(cod)], linked by a ditopic scorpionate ligand, have been prepared and fully characterized (R′ = Ph (2), C6F5 (2F); pz = pyrazolide). Both compounds were tested as catalysts for phenylacetylene polymerization but showed no catalytic activity. Attempts at the synthesis of corresponding complexes of the sterically more demanding ligands View the MathML source[1,4-(B(R′)pz2Ph)-C6H4-(B(R′)pz2Ph)]2- (R′ = Ph (4), C6F5 (4F); pzPh = 3-phenylpyrazolide) resulted in B–N bond cleavage and formation of the dinuclear complex [(cod)Rh(μ-pzPh)2Rh(cod)] (5). Complex 5 proved to be an efficient catalyst for the preparation of highly stereoregular head-to-tail cis-transoidal poly(phenylacetylene).