| Abstrakt: |
The halide ligands of [Fe4C(CO)12(CuCl)2]2−(1) and [Fe5C(CO)14CuCl]2−(2) can be displaced by N-, P- or S-donors. Beside substitution, the clusters easily undergo structural rearrangements, with loss/gain of metal atoms, and formation of Fe4Cu/Fe4Cu3metallic frameworks. Thus, the reaction of 1with excess dppe yielded [{Fe4C(CO)12Cu}2(μ-dppe)]2−(3). [{Fe4C(CO)12Cu}2(μ-pyz)]2−(4) was obtained by reaction of 2with Ag+and pyrazine. [Fe4C(CO)12Cu-py]−(5) was formed more directly from [Fe4C(CO)12]2−, [Cu(NCMe)4]+and pyridine. [Fe4Cu3C(CO)12(μ-S2CNEt2)2]−(6) and [{Fe4Cu3C(CO)12(μ-pz)2}2]2−(7) were prepared by substitution of the halides of 1with diethyldithiocarbamate and pyrazolate, in the presence of Cu(i) ions. All of these products were characterized by X-ray analysis. 3and 4and 5are square based pyramids, with iron in the apical sites, the bridging ligands connect the two copper atoms in 3and 4. 6and 7are octahedral clusters with an additional copper ion held in place by the two bridging anionic ligands, forming a Cu3triangle with Cu–Cu distances ranging 2.63–3.13 Å. In 7, an additional unbridged cuprophilic interaction (2.75 Å) is formed between two such cluster units. DFT calculations were able to reproduce the structural deformations of 3–5, and related their differences to the back-donation from the ligand to Cu. Additionally, DFT found that, in solution, the tight ion pair [NEt4]27is almost isoenergetic with the monomeric form. Thus, 3, 4and 7are entities of nanometric size, assembled either through conventional metal–ligand bonds or weaker electrostatic interactions. None of them allows electronic communication between the two monomeric units, as shown by electrochemistry and spectroelectrochemical studies. (dppe = PPh2CH2CH2PPh2, pyz = pyrazine C4N2H4, py = pyridine C5H5N, pz = pyrazolate C3N2H3−). [ABSTRACT FROM AUTHOR] |
