fac-[Re(CO)3(dmso-O)3](CF3SO3): a new versatile and efficient Re(i) precursor for the preparation of mono and polynuclear compounds containing fac-[Re(CO)3]+ fragments

Abstract

We show here that the new complex fac-[Re(CO)₃(dmso-O)₃](CF₃SO₃) (1), efficiently prepared in one step from [ReBr(CO)₅] and featuring a broad range of solubility, is, in general, a better precursor for the one-step synthesis of mono- and polynuclear inorganic compounds containing fac-[Re(CO)₃]⁺ fragments compared to the commonly used (NEt₄)₂fac-[ReBr₃(CO)₃] and fac-[Re(CO)₃(CH₃CN)₃](Y) (Y = PF₆, BF₄, ClO₄) species. Compound 1 is the first example of a Re(I)–dmso complex structurally characterized and confirms the rule that dmso is always O-bonded when trans to CO. The reactivity of 1 was tested in the one-step preparation of several new and known complexes. The O-bonded sulfoxides of 1 are replaced under mild conditions by tri- (L₃) and bidentate ligands (L₂) to produce fac-[Re(CO)₃(L₃)]⁺ and fac-[Re(CO)₃(L₂)(dmso-O)]⁺ compounds, respectively. An excess of monodentate ligands (L) and more forcing conditions are needed to prepare fac-[Re(CO)₃(L)₃]⁺ compounds. The new compounds include fac-[Re(CO)₃(bipy)(dmso-O)](CF₃SO₃) (4), that turned out to be an excellent precursor for binding the luminescent fac-[Re(CO)₃(bipy)]⁺ fragment to polytopic ligands for the construction of more elaborate assemblies. One example reported here is the two-step preparation of fac-[{Re(CO)₃(bipy)}(µ-4,4′-bipy){Ru(TPP)(CO)}](CF₃SO₃) (8) (TPP = tetraphenylporphyrin). The X-ray structures of the new compounds 1, 4, of the bis-porphyrin complex fac-[Re(CO)₃Cl(4′MPyP)₂] (13) (4′MPyP = 5-(4′pyridyl)-10,15,20-triphenylporphyrin), and of the rhenium–cyclophane [{(CO)₃Re(µ-OH)₂Re(CO)₃}₂(µ-4,4′-bipy)₂] (15), among others, are described. Compound 1 might find useful applications in supramolecular chemistry (metal-mediated assembly of large architectures), in the in situ preparation of stable Re compounds to be used in nuclear medicine, and for the labeling of biomolecules.