An investigation into the dynamic solution-state speciation of a ruthenium dinitrogen complex and its application as an activated precursor

Synthesis of a novel ruthenium bridging dinitrogen complex [{CpRu(dppe)}2(μ-η1:η1-N2)][OTf]2 (1A-N2-b) is reported from the reaction between [CpRu(dppe)Cl] and trimethylsilyl trifluoromethylsulfonate. It is reported that dinitrogen complex 1A-N2-b displays well-defined homogeneous solid-state speciation, with the N-N triple bond characterised being characteristic of weak dinitrogen activation. Analysis of 1A-N2-b by solution-state NMR spectroscopy shows a complex equilibrium between a range of weakly coordinating ruthenium complexes. A detailed investigation into the solution-state equilibrium observed for 1A-N2-b is reported. The combination of analysis by solution-state variable temperature NMR spectroscopy and vibrational spectroscopy in conjunction with isotopic labelling using 15N2 has allowed for both terminal and bridging dinitrogen modes to be characterised as components of this equilibrium. Evidence has been presented that claims these two dinitrogen complexes are in an equilibrium with proposed [CpRu(dppe)OTf] and [CpRu(κ4-dppe)][OTf] complexes.
1A-N2-b is reported to react with a wide range of donor ligands such as terminal alkenes, alkynes, nitriles and isocyanides. This has resulted the synthesis of a library of organometallic complexes where a mixture of novel complex synthesis, optimisation of the synthesis of previously reported complexes and updating characterisation of literature compounds has been found. A novel deactivation pathway is reported when reacting 1A-N2-b with internal alkyne 1-phenylpropyne, where via an intermediate η2- alkyne metal complex, a C-H activation of dppe ortho C-H aryl bond occurs, forming a novel κ2:η2-dppe-alkene complex.