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

Abstract Tertiary phosphines with pendant arenes R 2 PR′ (R=Cy, Ph; R′=CH 2 CH 2 Ph or CH 2 CHPh 2 ) ( 1 – 4 ) were synthesized and converted to the corresponding chelating ruthenium(II) complexes [RuCl 2 (η 1 :η 6 -R 2 PR′)] ( 1a – 4a ). Halide exchange yielded [RuI 2 (η 1 :η 6 -R 2 PR′)] ( 1b , 3b ), which were structurally characterized by single crystal X-ray diffraction. The systems ( 1a , 2a , 4a ) were activated for ROMP of norbornene by addition of a diazo compound (trimethylsilyldiazomethane) and AgBF 4 (A), by a diazo compound alone (B) or by a combination of the sodium salt NaB(Ar f ) 4 (Ar f =3,5-(CF 3 ) 2 C 6 H 3 ) 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.