Reactions of Ru(C(ident to)CPh)(PPh_3)_2Cp with tetracyanoethene: cycloaddition, formation of unusual #eta#~2-CNR complexes and oligomerisation via bridging cyanocarbon ligands

摘要

Thermolysis of Ru{#eta#~3-C(CN)_2CPhC=C(CN)_2}(PPh_3)Cp (2), obtained from Ru(C(ident to)CPh)(PPh_3)_2Cp and tetracyanoethene, has given the three complexes Ru{#eta#~1,#eta#~2(C,N)-C(CN)=C(CN)CPh=C(CN)(C=N)}(PPh_3)Cp (3), {Ru(PPh_3)Cp}{#mu#-N:#eta#~3-NCC(CN)=CPhC(CN)_2}{#mu#-#eta#~1:N-C(CN)=C(CN)CPh=C(CN)_2}{RuCp} (4) and {Ru[#eta#~3-C(CN)_2=CPhC=C(CN)_2]Cp}_3 (5). All four complexes have been characterized by single-crystal X-ray structure determinations and contain isomeric forms of the C_4(CN)_4Ph ligand. Unusual features of the molecular structures are (i) the presence of a side-on (#eta#~2) CN group in 3; (ii) formation of a second isomer of the polycyano-carbon ligand by CN migration to an adjacent carbon, in 3 and 4; (iii) the use of one or more CN groups to bridge ruthenium centers in 4 and 5; and (iv) the complete loss of PPh_3 ligands during the formation of the trimer 5. Although there are three crystallographically distinct RuCp groups in 5, only one Cp resonance is found in solution NMR spectra, suggesting that oligomer formation by facile CN-Ru bond breaking and making is occurring.