After postdoctoral fellowships with P. J. Bailey at the
University of Edinburgh, Keith Izod at
Newcastle University as the Wilfred Hall Research Fellow, and
Polly Arnold at the
University of Nottingham, Liddle began his independent academic career at the University of Nottingham with a Royal Society University Research Fellowship (2007–2015) held with a proleptic Lectureship. He was promoted to Associate Professor and Reader in 2010 and Professor of Inorganic Chemistry in 2013. He moved to the University of Manchester in 2015 as Head of Inorganic Chemistry and Co-Director of the Centre for Radiochemistry Research. He is Director of the National Nuclear User Facility at the Centre for Radiochemistry Research since 2019, and he held an Engineering and Physical Sciences Research Council Established Career Fellowship (2015–2021). He was Chairman of COST Action CM1006, a 22 country, research network of over 120 research groups in f-block chemistry (2011–2015), is an advisor to the Commonwealth Scholarship Commission (2013–), and was an elected category 3 member of Senate, the University of Manchester (2016–2019). Liddle's research is focused on synthetic inorganic chemistry, particularly making early transition metal, lanthanide, and actinide complexes to explore their structure, bonding, reactivity, and magnetism. In 2011 he reported a
single-molecule magnet based on
depleted uranium. In 2013 he reported the isolation of a terminal uranium(VI) nitride akin to examples previously restricted to cryogenic matrix isolation experiments , and that formed the basis from which to report the electronic structure of uranium nitrides including quantifying the covalence of the uranium-nitrogen triple bond by using 15N NMR spectroscopy. In 2013, his research group disclosed the first f-element cyclobutadienyl complexes. Between 2014-2025 he reported a range of M=EH bonds (M = Th, U; E = N, P, As, and Sb) along with phosphide, arsenido, and stibido derivatives. In 2019 his research group isolated a uranium(V)-dinitrogen complex. In 2021, Liddle reported a tri-thorium cluster featuring two-electron σ-aromatic actinide metal-metal bonding, and in follow-up work reported one-electron analogues that exhibit exalted diamagnetism and were found to be open-shell aromatic superatoms. Before the synthesis of those metal-metal complexes, examples of actinide-actinide bonding had been restricted to matrix isolation experiments and fullerene-encapsulated species. In 2022, he reported a terminal neptunium(V)-mono(oxo) complex. Before the synthesis of this complex all transuranium-ligand multiple bond complexes required two or more metal-ligand multiple bonds to be stable. Following on from his reports of U=C double bonds over uranium oxidation states +3 to +6 , in 2022 and 2024 he reported neptunium- and plutonium- diphosphonioalkylidenes and -
N -heterocyclic carbenes. In 2018 he introduced titanium as a catalytically active metal in molecular dinitrogen to ammonia catalysis chemistry, and in 2025, in collaboration with the Mazzanti group at École Polytechnique Fédérale de Lausanne, he reported catalytic conversion of side-on bound dinitrogen to ammonia at uranium. He has also reported investigations on the basic properties of actinides, including homologation of carbon monoxide, showing that the inverse-trans-influence is general, reversible oxidative addition/reductive elimination at uranium, demonstrating the structure-directing role of f-orbital overlap-driven covalency, establishing pushing-from-below for thorium, introducing Frustrated Lewis Pair chemistry to the actinides , explaining anomalous magnetism of uranium(IV), inverting the fundamental disproportionation chemistry of uranium, and using actinides to stabilise unusual main group species. == Honours and awards ==