Dicationic ruthenium(II) complexes containing bridged η¹:η⁶-phosphinoarene ligands for the ring-opening metathesis polymerization

Tertiary phosphines with pendant genes R₂PR' (R = Cy, Ph; R' = CH₂CH₂Ph or CH₂CHPh₂) (1-4) were synthesized and converted to the corresponding chelating ruthenium(II) complexes [RuCl₂(η¹:η⁶-R₂PR')] (1a-4a). Halide exchange yielded [RuI₂(η¹:η⁶-R₂PR')] (1b,3b), which were structurally characterized by single crystal X-ray diffraction. The systems (1a,2a,4a) were activated for ROMP of norbomene by addition of a diazo compound (trimethylsilyldiazomethane) and AgBF₄ (A), by a diazo compound alone (B) or by a combination of the sodium salt NaB(Ar(f))₄(Ar(f) = 3,5-(CF₃)₂C₆H₃) and methanol (C). The influence of the thereby created differing number of accessible coordination sites on the polymerization activity and the polymer microstructure (cis/trans ratio) was investigated. The nucleophilicity of the counter ion was found to play a crucial role in terms of catalytic activity. (C) 2000 Elsevier Science B.V.