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 ReH3[PPh(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.