Issue 20, 2011

Structural variations, electrochemical properties and computational studies on monomeric and dimeric Fe–Cu carbide clusters, forming copper-based staple arrays

Abstract

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/Fe4Cu3 metallic frameworks. Thus, the reaction of 1 with excess dppe yielded [{Fe4C(CO)12Cu}2(μ-dppe)]2 (3). [{Fe4C(CO)12Cu}2(μ-pyz)]2 (4) was obtained by reaction of 2 with 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 1 with diethyldithiocarbamate and pyrazolate, in the presence of Cu(I) ions. All of these products were characterized by X-ray analysis. 3 and 4 and 5 are square based pyramids, with iron in the apical sites, the bridging ligands connect the two copper atoms in 3 and 4. 6 and 7 are octahedral clusters with an additional copper ion held in place by the two bridging anionic ligands, forming a Cu3 triangle 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]27 is almost isoenergetic with the monomeric form. Thus, 3, 4 and 7 are 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).

Graphical abstract: Structural variations, electrochemical properties and computational studies on monomeric and dimeric Fe–Cu carbide clusters, forming copper-based staple arrays

Supplementary files

Article information

Article type
Paper
Submitted
14 Dec 2010
Accepted
08 Feb 2011
First published
04 Apr 2011

Dalton Trans., 2011,40, 5464-5475

Structural variations, electrochemical properties and computational studies on monomeric and dimeric Fe–Cu carbide clusters, forming copper-based staple arrays

R. D. Pergola, M. Bruschi, A. Sironi, M. Manassero, C. Manassero, D. Strumolo, S. Fedi and P. Zanello, Dalton Trans., 2011, 40, 5464 DOI: 10.1039/C0DT01766C

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