Polymerization Isomerism in [MFe(CO)4n]n- (M = Cu, Ag, Au; N = 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.