Synthesis of novel symmetrical and unsymmetrical dirhenium complexes with a [re₂o₂] core: {cpre[oc(x)n(ph)]} ₂(μ-o)₂ and {cpreo}{cpre[oc(x)n(ar)]}(μ-o)₂ (x=o, s)

In the presence of triphenylphosphine Cp*ReCO₃reacts with aryl isothiocyanates in an equal equivalence via an intermediate (Cp*ReO)₂(μ-O)₂ to give novel unsymmetrical dirhenium oxo complexes with a [Re₂O₂] core, {Cp*ReO}{Cp*Re[OC(S)N(Ar)]}(μ-O)₂ (la: Ar=C₆H₅; lb: Ar=m-F₃CC₆H₄), while under the same conditions a monorhenium oxo complex Cp*Re(O)[OC(O)N(Ph)] (2) as the main product and an unsymmetrical dirhenium oxo complex {Cp*ReO} {Cp*Re[OC(O)N(Ph)]}(μ-O)₂ (3) are afforded from the reaction of Cp*ReO₃ with aryl isocyanates. By contrast, only (Cp*ReO)₂(μ-O)₂ is formed from the reaction of Cp*ReCO₃with alkyl isothiocyanates in the presence of triphenylphosphine. Both unsymmetrical dirhenium oxo complexes 1 and 3 can further react with a large excess of aryl isothiocyanates and -isocyanates to form symmetrical dirhenium complexes {Cp*Re[OC(X)N(Ph)]}2(μ-O)2 (4: X=S; 5: X=0).