Research Guides

Main-group and Organometallic Chemistry

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-atomic 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 paradigms.

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) Phospha-organic chemistry

The isolobal relationship between a methine moiety (C-H) and a phosphorus atom allows for the synthesis of interesting variants of organic molecules. This has led to phosphorus being referred to as the “carbon-copy”. Our research group is interested in the synthesis and chemical properties of group 15 analogues of more traditional organometallic molecules. Recent research in this area has focused on the synthesis of 1,2,3-triphospholide ligands (and their heavier arsenic congeners) which are related to the ubiquitous cyclopentadienyl  ligand (Figure 2). We are interested in the coordination chemistry of such ligands on account of their increased π-acceptor properties (relative to Cp) and their ability to pre-organize substrates via interactions with the Lewis basic phosphorus atoms of the ring. Other studies on group 15 analogues of unsaturated organic molecules are also currently on-going.

Figure 2. Ligand displacement reaction involving 1,2,3-tripnictolide anions.

(3) The chemistry of redox active "non-innocent" ligand systems

Studies carried out by our research group have yielded a route for the synthesis of bulk quantities of 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 3). 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 3. Synthesis of [Fe(2,2'-bipyridine)(mes)₂]^–.

"Phosphinecarboxamide: A Phosphorus-Containing Analogue of Urea and Stable Primary Phosphine". Jupp, A. R.; Goicoechea, J. M. J. Am. Chem. Soc. 2013, 135, 19131-19134.

"The 2-Phosphaethynolate Anion: A Convenient Synthesis and [2+2] Cycloaddition Chemistry". Jupp, A. R.; Goicoechea, J. M. Angew. Chem., Int. Ed. 2013, 52, 10064-10067.

"Transition Metal Complexes of Anionic N-Heterocyclic Dicarbene Ligands". Musgrave, R. A.; Turbervill, R. S. P; Irwin, M.; Goicoechea, J. M. Angew. Chem., Int. Ed. 2012, 51, 10832-10835.

"[Co(η⁵-P₅){η²-P₂H(mes)}]²⁻: A phospha-organometallic complex obtained by the transition-metal-mediated activation of the heptaphosphide trianion". Knapp, C, M.; Westcott, B. H.; Raybould, M. A. C.; McGrady, J. E.; Goicoechea, J. M. Angew. Chem., Int. Ed. 2012, 51, 9097-9100.

"Synthesis of 1,2,3-tripnictolide anions by reaction of group 15 Zintl ions with acetylene. Isolation of [E₃C₂H₂]^– (E = P, As) and preliminary reactivity studies". Turbervill, R. S. P.; Goicoechea, J. M. Chem. Commun. 2012, 48, 6100-6102.

"The bis(hydrogenheptaphosphide)iron(II) dianion: a Zintl ion analogue of ferrocene?". Knapp, C. M.; Large, J. S.; Rees, N. H.; Goicoechea, J. M. Chem. Commun. 2011, 47, 4111-4113.

"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.

"[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 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.