Dr. Chris Adams' research
My research follows two main strands:
1: Organometallic molybdenum chemistry
Working in collaboration with Professor Connelly
and his group, I've been looking at the ESR spectra of some 19- and 17- electron alkyne compounds of (mainly) molybdenum. Ions such as 1
(right) have a relativey low-lying LUMO, and can be chemically reduced by decamethylcobaltocene. The resulting radicals are not stable enough to be isolated, but are readily detected by ESR, and show some interesting properties. At high temperatures the alkyne moves back and forth in a windscreen-wiper fashion, meaning that the two phosphorus atoms are in the same environment, and the resulting ESR pattern is a triplet. As the temperature is lowered though, the motion of the alkyne is slowed until it becomes essentially stationary. At this point it lines up nearer to one phosphorus atom than the other, rendering them inequivalent, and the pattern changes to a doublet. The resonance of an electron is so fast (GHz, compared to MHz for protons in NMR) that for a compound to be fluxional on the ESR timescale is unusual; for this to be temperature dependant is exceedingly rare. See J. Chem. Soc., Chem. Commun.
, 2001, 2458, for further information.
We're currently doing some experiments with 13C labelled alkynes, in order to better see coupling to the central carbon atoms of the alkyne, which will (hopefully!) allow us to determine the unpaired electron density on these atoms, and thus their likely chemical behaviour.
Some of the other molybdenum-alkyne chemistry stuff we've done can be seen in Organometallics, 2002, 21, 3454 and J. Chem. Soc., Dalton Trans., 2001, 1284
2: Oxalate and dithiooxalate chemistry
In collaboration with Professor Orpen
and his group, I've been synthesising some oxalate and dithiooxalate compounds of ruthenium and iron. His group have done work on the hydrogen-bonding properties of this kind of molecule, but I've become interested in the electrochemical and magnetic properties as well. For example, the iron(III) complex ion [FeCl2
(below) unexpectedly forms a cyclic tetramer in the solid state. We're currently working on this and similar species such as [Fe2
Some of my work on ruthenium dithiooxalate compounds has appeared in J. Chem. Soc., Dalton Trans., 2002, 1545.
3: Ruthenium acetylide chemistry
There have been a lot of papers in the past three years concerning the chemistry of platinum acetylide compounds such as 2
(below), which have long lived excited states and luminesce nicely - see J. Chem. Soc., Dalton Trans.
, 2000, 63 for the start of these. One problem with these compounds is that they're fairly insoluble, and one way to overcome this would be to occupy the axial positions on the metal with solubilising ligands. You can't do this if the metal is platinum, which likes to be square planar, but if you change the metal to ruthenium it should be possible. Thus, I'm currently investigating compounds like 3
, which turn out to have interesting properties in their own right. So, for example, the complexes are redox active (unlike the platinum analogues), and the way the electrons move around within the molecule depends upon the oxidation state.