Polymerization Isomerism in [{MFe(CO)₄}_<i>n</i>]^<i>n</i>− (M = Cu, Ag, Au; <i>n</i> = 3, 4) Molecular Clusters Supported by Metallophilic Interactions

Triangular clusters [{MFe­(CO)4}3]3– (M = Cu, 4; Ag, 5; Au, 6) were selectively obtained by heating Fe­(CO)4(MIMes)2 (M = Cu, 1; Ag, 2; Au, 3; IMes = C3N2H2(C6H2Me3)2). 1–3 were synthesized by reacting Na2[Fe­(CO)4]·2thf with 2 equiv of M­(IMes)­Cl. As previously described, the direct reactions of Na2[Fe­(CO)4]·2thf with one equivalent of M­(I) salts resulted in the triangular cluster [{CuFe­(CO)4}3]3– for Cu, whereas the square clusters [{MFe­(CO)4}4]4– were formed for Ag and Au. Thus, depending on the synthetic protocol adopted, both the triangular [{MFe­(CO)4}3]3– and square [{MFe­(CO)4}4]4– polymerization isomers can be selectively obtained, at least for Ag and Au. Polymerization isomerism, that is two compounds having the same elemental compositions but different molecular weights, was investigated in [{MFe­(CO)4}n]n− (n = 3, 4; M = Cu, Ag, Au) by means of structural and theoretical methods and the role of metallophilic interactions was computationally studied by means of the atoms-in-molecules (AIM) approach