Some reactions of an ŋ³-tetracyanobutadienyl-ruthenium complex

In the η3-butadienyl complex Ru{η3-C(CN)2CPhC=C(CN)2}(PPh3)Cp 1, which is formed from Ru(C≡CPh)(PPh3)2Cp and tcne, a CN group reacts with MeO− to give the methoxy-amide Ru{NH=C(OMe)C(CN)=CCPh=C(CN)2}(PPh3)Cp 2, in which the NH has displaced the C=C from the Ru centre with formation of a RuC3N ring. “Click addition” of azide to a CN group in 1 gives the oligomeric tetrazolato complex Ru{N3N[Na(OEt2)]=CC(CN)=CCPh=C(CN)2}(PPh3)Cp 3, also containing a RuC3N ring. Salt-elimination reactions of 3 with MeOTf, FeCl(dppe)Cp, RuCl(dppe)Cp* and trans-PtCl2{P(tol)3}2 result in selective substitution at one nitrogen atom of the RuC3N ring. Geometries of 1 and the anion in 3 were computed by DFT methods. Preferences for CN groups attacked in the nucleophilic and cycloaddition reactions of 1 are supported by NBO calculations. Alkylation of 1 in reactions with 1,2-dimethoxyethane gave two isomers of Ru{N3[CH(CH2OMe)(OMe)]N=CC(CN)=CCPh=C(CN)2}(PPh3)Cp 8 and 9, differing in the sites of attachment of the alkyl group, likely by radical processes. The molecular structures of eight complexes are reported, including a re-determination of 1. Computed NMR chemical shifts are used to reassign the butadienyl carbon resonances in the 13C NMR spectrum of 1.