Synthesis and reactivities of a bis(cyanamido)-capped triruthenium complex

Abstract

The tetraruthenium complex [Cp*RuCl]₄ (Cp* = η⁵-C₅Me₅) reacts with Na₂NCN to afford the anionic bis(cyanamido)-capped triruthenium complex [(Cp*Ru)₃(µ₃-NCN)₂]⁻ (2⁻), which undergoes single electron oxidation to form [(Cp*Ru)₃(µ₃-NCN)₂] upon workup with 1 equiv. of [Cp₂Fe](PF₆) (Cp = η⁵-C₅H₅). Treatment of 2⁻ with 1 equiv. of HCl at room temperature leads to the protonation of one of the Ru–Ru edges to give the hydrido-bridged complex [(Cp*Ru)₃(µ-H)(µ-NCN)₂], while the cationic side-on NCNH₂ complex [(Cp*Ru)₃(µ-Cl)(µ₃-NCN)(µ₃-NCNH₂-1κC,N:2κC:3κN)]Cl (5) is obtained by the reaction of 2⁻ with an excess amount of HCl at −78 °C. On the other hand, the reaction of 2⁻ with BR₃ (R = Et, Ph) results in the ligation of two BR₃ molecules to the terminal nitrogen atoms of the cyanamido ligands to yield the bis(borane) adduct (PPN)[(Cp*Ru)₃{(µ₄-NCN)(BR₃)}₂] (6, PPN = Ph₃PNPPPh₃). 6b (R = Et) slowly liberates one BEt₃ molecule in acetone to give the mono(borane) adduct (PPN)[(Cp*Ru)₃(µ₃-NCN){(µ₄-NCN)(BEt₃)}] (7). 2⁻ is also shown to react with [AuCl(PPh₃)] or PhCOCl to afford the tetranuclear heterometallic complex [(Cp*Ru)₃(µ₃-NCN){(µ₄-NCN)(AuPPh₃)}] (8) or the benzoylcyanamido complex [(Cp*Ru)₃(µ₃-NCN)(µ₃-NCNCOPh)] in which the Au(PPh₃)⁺ or benzoyl fragment is bound to the terminal nitrogen atom of a cyanamido ligand. The molecular structures of PPN⁺2⁻, 5·C₆H₆, 7 and 8·C₆H₆ have been determined by single-crystal X-ray analyses.