Research Guides

Main-Group and Organometallic Chemistry

Research in the Goicoechea group is primarily focused on the chemistry of negatively charged metal and semi-metal clusters, but also encompasses research on main-group elements in unusually low oxidation states, p-block species exhibiting multiple bonds, and transition-metal organometallic complexes. 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 main-group cluster chemistry as the solution-phase reactivity of the "naked" polyanions of groups 14 and 15 has been explored. The use of transition-metal reagents (particularly open-shell species) has resulted in the isolation of a series of novel species in which the metal atoms play an essential role in the stabilization of large, otherwise unattainable geometries (see Figure 1 for selected examples).

Figure 1. [Fe@Ge₁₀]^3– (left) and [Ru@Ge₁₂]^3– (right): Two classes of unprecedented endohedral three-connect clusters.

The ability of Zintl ions to undergo nucleophilic and electrophilic substitution allows for their integration into cluster-assembled materials. The clusters isolated to date represent the first steps in a nascent area of chemistry where many interesting 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 species. For example, we have carried out extensive work on the synthesis of 1,2,3-triphospholides (and their heavier arsenic congeners) which are related to the ubiquitous cyclopentadienyl ligand. More recently, we have shown that reactions between the phosphaethynolate anion (PCO^–) and ammonium salts afford phosphinecarboxamide (a phosphorus-containing relative of urea; Figure 2). Studies on the reactivity of this fundamental small molecule are currently on-going.

Figure 2. Synthesis of phosphinecarboxamide (or carbomylphosphine) a phosphorus-containing analogue of urea.

(3) 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.

"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.