Preparation of bis(aryldiazene) and new aryldiazenido complexes of rhenium

Mixed-ligand hydride ReH₂(NO)L(PPh₃)₂ complexes L=P(OEt)₃ or PPh(OEt)₂] were prepared by allowing the ReH₂(NO)(PPh₃)₃ species to react with an excess of phosphite. Treatment of ReH₂(NO)L(PPh₃)₂ hydrides with an equimolar amount of aryldiazonium cations ArN₂⁺ gives the mono-aryldiazene ReH(ArNNH)(NO)L(PPh₃)₂]BPh₄ complexes (Ar=C₆H₅, 4-CH₃C₆H₄), while treatment with an excess of ArN₂⁺ yields bis(aryldiazene) Re(ArNNH)₂(NO)L(PPh₃)₂](BPh₄)₂ derivatives. Binuclear {ReH(NO)L(PPh₃)₂}₂(μ-HNNArArNNH)](BPh₄)₂ and {Re(4-CH₃C₆H₄NNH)(NO)L(PPh₃)₂}₂(μ-HNNArArNNH)](BPh₄)₄ complexes (ArAr=4,4′-C₆H₄C₆H₄, 4,4′-C₆H₄CH₂C₆H₄) were also prepared. The reaction of the triphenylphosphine ReH₂(NO)(PPh₃)₃ complex with aryldiazonium cations was studied and led exclusively to mono-aryldiazene ReH(ArNNH)(NO)(PPh₃)₃]BPh₄ and {ReH(NO)(PPh₃)₃}₂(μ-HNNArArNNH)](BPh₄)₂ derivatives. The complexes were characterised spectroscopically (IR, NMR) using the ¹⁵N-labelled derivatives. The aryldiazenido ReH(C₆H₅N₂){PPh(OEt)₂}₄]BPh₄ complex was prepared by allowing trihydride ReH₃PPh(OEt)₂]₄ to react with phenyldiazonium tetrafluoroborate. A reaction path involving the aryldiazene ReH₂(C₆H₅NNH){PPh(OEt)₂}₄]⁺ intermediate was also proposed.