Research

Research within the Crossley lab is directed toward the synthesis and study of reactive and electronically distinctive molecules from the interface of traditional transition metal and main group chemistry. Current work is focused in three general areas:

Conjugated Phosphacarbon Complexes

The chemistry of low-coordinate phosphorus(III) compounds is well established, having been studied for four decades.  During this time innumerable phosphaalkenes (RP=CR'R''), phosphalkynes (RC≡P) and derivatives thereof have been described and studied, many by collaborators here at Sussex.

molecular structure of a cyaphide-alkynyl complexWe are now extending these concepts toward the realm of molecular electronic materials, seeking to incorporate phosphaalkene and/or phosphaalkyne functions into conjugated organometallic architectures, akin to to those already widely investigated with carbon-rich molecular fragments.

To this end we have recently reported the first complexes to incorporate a cyaphide ligand conjugated, via the metal, to an acetylenic chain, along with a preliminary study of their electronic structure.  We are now working to expand our library of these compounds and develop a fuller understanding of their chemical and electronic nature.

  A ruthenium eta-2 phosphaalkene complexEn route to these materials we also recently demonstrated unprecedented ambiphilic reactivity of novel metalla-phosphaalkenyl compounds toward nucleophilic and electrophilic reagents.  This has provided facile access to rare η2-phosphaalkene complexes, which also include a tethering pyrazole unit and hold potential for catalytic/synthetic development.  

Reactive Phosphanes and Polyphosphanes

Phosphane ligands fulfill a diverse role in modern coordination and organometallic chemistry, whether in stabilising unusual coordination geometries, serving as labile ligands in pro-catalysts or affording asymmetric induction for catalytic processes.  Moreover, organophosphanes serve as precursors to a wide-range of industrially (pharmaceutical, agrochemical, materials) important phosphorus-containing molecules.

In each of these roles, variation of functional substituents around the phosphorus centre facilitates 'fine-tuningThe first diphosphametacyclophane' of the intrinsic electronic character, and hence reactivity, thus tailoring the molecule to suit its desired purpose.  To this end, we are particularly interested in phosphane ligands that represent extremes of electronic and chemical behaviour. For instance, we have recently been studying highly reactive and pyrophoric phosphanes based on the P(SiMe3)2 sub-unit and seeking to moderate and control their reactivity through substituent modification.  We have thus established their viability as ligands, and begun to explore their utility as substrates for the chemical synthesis of more complex, heterocyclic, molecules.

More recently, we have reported the very first example of a diphosphametacyclophane, synthesised under mild conditions, and demonstrated their utility as bridging ligands.  We are now engaged in developing this ligand motif and exploiting it in catalytic systems and for metal sequestraton.

Coordinated Ambiphilic Ligands in Small Molecule Activation

We have been heavily inmetallaboratranevolved (in collaboration with Prof. A.F. Hill, ANU) in the development of the nascent field of 'metallaboratrane' chemistry, concerning transition metal complexes bearing a discrete retrodative metal→boron bond as part of an ambiphilic chelate.  In an extension of this chemistry, in particular the capacity of the M→B bond to effect ligand activation, we are now developing and exploring related systems in the context of activating small-molecular species.