Some reactions of an η3-tetracyanobutadienyl-ruthenium complex

Abstract

In the η³-butadienyl complex Ru{η³-C(CN)₂CPhCC(CN)₂}(PPh₃)Cp 1, which is formed from Ru(CCPh)(PPh₃)₂Cp and tcne, a CN group reacts with MeO⁻ to give the methoxy-amide Ru{NHC(OMe)C(CN)CCPhC(CN)₂}(PPh₃)Cp 2, in which the NH has displaced the CC 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)CCPhC(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)]NCC(CN)CCPhC(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.