Research Guides

Research Interests and Highlights

Research in the Goicoechea group is primarily focused on the chemistry of highly-reductive compounds, particularly main-group cluster cages and low-valent transition metal complexes of ‘non-innocent’ ligands. Current studies revolve around the chemistry of negatively charged metal and semi-metal cluster species, but also encompass research on main-group elements in unusually low oxidation states and the chemistry of reduced hetero-aromatic ligand systems. Our interests range from traditional coordination chemistry to the chemistry of nanometric molecular systems, and we are particularly fascinated by compounds which fail to obey conventional bonding models.

Our current research can be divided into three main categories: 

(1) Main-group and transition metal cluster chemistry.

Recent years have witnessed a renaissance of Zintl cluster chemistry as the reactivity of the ‘naked’ polyanions of groups 14 and 15 has been explored. The use of transition metal reagents has resulted in the isolation of a series of novel species in which transition metal atoms play an essential role in the stabilization of large, otherwise unattainable geometries (as pictured in Figure 1). Also of interest are recent findings which show that nine-atom group 14 Zintl ions can act a 6 electron donors to electrophilic fragments such as Ni(CO) or Zn(C₆H₅). From a coordination chemist’s viewpoint that makes such clusters analogous to other more traditional organometallic complexes containing ligand systems such as the cyclopentadienyl anion.

Figure 1. [Fe@Ge₁₀]^3–: an unprecedented pentagonal prismatic germanium cage encapsulating an isolated iron atom core.

The ability of Zintl ions to undergo nucleophilic and electrophilic substitution may also allow for their integration as backbones within ligand and spacer group moieties, with the aim of employing them for the construction of cluster-assembled materials. The unique physical properties of these Zintl clusters allows for the development of interesting new species with potential applications in sensors, molecular wires and photochemical systems. The clusters isolated to date represent the first steps in a nascent area of chemistry where many interesting new breakthroughs await. 

(2) The chemistry of reduced hetero-aromatic ligand systems.

Studies carried out by our research group have yielded a route towards the synthesis of bulk quantities of the bipyridyl radical anions and dianions in high yields. Further studies have focused on the coordination chemistry of such species with transition metal complexes and have resulted in the first fully characterized transition metal complex of the 2,2'-bipyridyl radical anion, [Fe(2,2'-bipyridine)(Mes)₂]^– (Figure 2). Bipyridyl radicals and dianions represent a unique postern towards the synthesis of novel complexes and polymers of metal cations interconnected by bridging anionic linkers. We are particularly interested in employing these ligand systems to stabilise metal centres in unusually low oxidation states.

Figure 2. Synthesis of [Fe(2,2'-bipyridine)(Mes)₂]^–. 

(3) Nanoparticle synthesis.

The clusters species mentioned above represent intermediates in the oxidative transformation of negatively charged metal and semi-metal species to the bulk element. As such they are molecular ‘snap-shots’ of a synthetic procedure which may ultimately be used to obtain homo- and hetero-metallic colloids and nanoparticles. A similar approach involving the reduction of cationic metal complexes in the presence of strongly coordinating ligands has already been employed as a synthetic technique towards precious metal nanoparticles. However, this approach often suffers from poor polydispersities due to the kinetic nature of the reaction products. An inverse approach involving the mild oxidation of negatively charged species may be used as a synthetic alternative offering greater molecular control over the species synthesized as well as a wider gamut of available nanoparticle compositions.

"Studies on the reactivity of [Ge₉]^4– towards Fe(COT)(CO)₃: Synthesis and characterization of [Ge₈Fe(CO)₃]^3– and of the anionic organometallic species [Fe(COT)(CO)₃]^–”. Zhou, B.; Goicoechea, J. M. Chem. - Eur. J. 2010,16, 11145-11150.

“Experimental and Computational Study of the Structural and Electronic Properties of Fe^II(2,2'-bipyridine)(mes)₂ and [Fe^II(2,2'-bipyridine)(mes)₂]^–, a Complex Containing a 2,2 '-Bipyridyl Radical Anion”. Irwin, M.; Jenkins, R. K.; Denning, M. S.; Krämer, T; Grandjean, F; Long, G. J.; Herchel, R; McGrady, J. E.; Goicoechea, J. M. Inorg. Chem. 2010, 49, 6160-6171.

“Reactivity Studies of group 15 Zintl ions towards homoleptic post-transition metal organometallics: a 'bottom-up' approach to bimetallic molecular clusters”. Knapp, C.; Zhou, B.; Denning, M. S.; Rees, N. H.; Goicoechea, J. M. Dalton Trans. 2010, 39, 426-436.

“[Pb₉CdCdPb₉]^6–: A Zintl cluster anion with an unsupported cadmium-cadmium bond”. Zhou, B.; Denning, M. S.; Chapman, T. A. D.; McGrady, J. E.; Goicoechea, J. M. Chem. Commun. 2009, 7221-7223.

“Synthesis and Characterization of Alkali-Metal Salts of 2,2′- and 2,4′-Bipyridyl Radicals and Dianions”. Gore-Randall, E.; Irwin, M.; Denning, M. S.; Goicoechea, J. M. Inorg. Chem. 2009, 48, 8304-8316.

“Synthesis and Isolation of [Fe@Ge₁₀]^3–: A Pentagonal Prismatic Zintl Ion Cage Encapsulating an Interstitial Iron Atom”. Zhou, B.; Denning, M. S.; Kays, D. L.; Goicoechea, J. M. J. Am. Chem. Soc. 2009, 131, 2802-2803.

“Coupling Reactions of Functionalized Zintl Ions [E₉Cd(C₆H₅)]^3– (E = Sn, Pb) with Tributyltinhydride: Synthesis and Isolation of {Sn₉CdSn[(CH₂)₃CH₃]₃}^3–”. Zhou, B.; Denning, M. S.; Chapman, T. A. D.; Goicoechea, J. M. Inorg. Chem. 2009, 48, 2899-2907.

“Reductive cleavage of Zn-C bonds by group 14 Zintl anions: Synthesis and characterisation of [E₉ZnR]³⁻ (E = Ge, Sn, Pb; R = Mes, ⁱPr)”. Zhou, B.; Denning, M. S.; Jones, C.; Goicoechea, J. M. Dalton Trans. 2009, 1571-1578.