High Pressure Coordination Chemistry: The Search for New
Phenomena
Alexander J. BlakeSchool of ChemistryThe University of Nottingham
PACCON2014
Introduction
Experimental
Initial results for [PdCl2([9]aneS3)]
High pressure facilities
HP studies
[MX2([9]aneS3)] complexes
[Pd([9]aneS3)(PPh3)2][PF6]2
[Pt([9]aneS3)(PPh3)2][PF6]2
Multi-phase [PdCl2([9]aneS2O)]
Current and future work
Acknowledgements
Outline of Talk
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Pressure in the solar system
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Location Pressure/bar
Interplanetary space 10-9
Surface of Mars 10-2
Surface of the Earth 1
Surface of Venus 90
Marianas Trench 1,100
Centre of Jupiter 40,000,000
Centre of the sun 150,000,000,000
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Under our feet:pressure increases with depth
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Depth /km Pressure/bar
3 (crust) 1,000
400 (upper mantle ends) 133,000
2900 (mantle/core boundary) 1,300,000
6371 (centre of the earth) 3,500,000
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Pressure around us
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System Pressure/bar
Car tyre 2
Bicycle tyre 8
Pressure washer 100
Stiletto heel 50-110
Rifle chamber 4,000
Synthesis of diamonds 55,000
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Pressure in chemistry
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Application Pressure/bar
A hydrogenation reaction 3
Ethene polymerisation 10-40
Critical pressure for CO2 73
Haber process 200
KBr press for IR disks 10,000
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Very high pressures
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Pressure/kbar
Possible processes
up to 100 van der Waals space compressed
30-200 coordination, packing changes
100 melting point of ice = 400ºC
300-600 deformation of covalent bonds
400 organic solid-state reactions
1,000 nearly all elements become metallic
“very high” electrons move off atoms
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High pressure crystallography
from 1950’s onward
• initial interest from geophysics and astrophysics
• rocks, minerals, seismology, phase transitions
• planetary interiors
from early 1990’s
• work on molecular compounds
• compressed liquids: acetone, phenol, alcohols
• solvates, pharmaceuticals, energetic materials
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High pressure crystallography
Very few metal-organic compounds reported, e.g.
• bis(dimethylglyoximato)platinum(II) O…O proton transfer
• spin-crossover in Fe(II) complexes
• resistivity in BEDT-TTF salts as a function of pressure
• pressure-dependence of structure in LiCp and KCp
• pressure-induced metal-to-insulator transitions in Pt(dmg)2
• metal-organic networks: (4-chloropyridinium)2[CoX4])
• some recent studies of copper complexes, MOFs, etc
• typically a few structures a year, but growing steadily J. P. Tidey, H. L. S. Wong, M. Schröder and A. J. Blake, Coord. Chem. Rev. 2014, submitted
Experimental – the Technology
• pressure = force/area• 1 Nm-2 = 1 Pa = 10-5 bar• diamond anvil cell (~100 kbar)• small sample compartment• pressure-transmitting medium• measure pressure by ruby
fluorescence
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Diamond Anvil Cell
5 cm
fully assembled
metal cell body
Allen screws
aperture (200 μm)
support
(goniometer head)
Fits easily into the palm of a handFits a ‘standard’ X-ray diffractometer
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Experimental issues
limited extent of data
limited quality of data
diamond reflection
gasketsample reflection
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Results for [PdCl2([9]aneS3)]
Pd1 Cl1
S4
C3
C2S1C9
C8
S7
Cl2
C6
C5
D.R. Allan, A.J. Blake, D. Huang, T.J. Prior, M. Schröder, Chem. Commun. 2006, 4081-4083
Square planar +
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Response of [PdCl2([9]aneS3)]
Between ambient pressure and 76.8 kbar
• axial Pd…S 3.159(10) 2.771(13) Å • intermolecular Pd…S 3.525(8) 3.006(10) Å• intense colour change at 44 kbar• ligand conformation [234] → [1233]• unit cell volume contracts by 23%• density increases from 2.105 to 2.732 g cm-3
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[PdCl2([9]aneS3)]
- axial Pd…S1 distance contracts
3.009(5) Å 2.846(7) Å
42.5 kbar 46 kbar
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[PdCl2([9]aneS3)]
3.204(5) Å 3.117(8) Å
42.5 kbar 46 kbar
- intermolecular Pd…S contracts- distorted octahedral coordination- chain polymer formed
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[PdCl2([9]aneS3)]
42.5 kbar 46 kbar
[234] [1233]
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- ligand changes conformation
[PdCl2([9]aneS3)]
42.5 kbar 46 kbar
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- dramatic, reversible colour change
A short movie
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Increasing pressure now …
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Now decreasing pressure …
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“Based on a true story …”
The film you have just seen is based on real results, but does not represent an actual sequence of experiments.
“No animals …”
Unfortunately, several crystals were quite definitely harmed during the making of this film.
Disclaimers
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High Pressure Crystallography Laboratory in Nottingham
Oxford Diffraction (Agilent) SuperMovaII CCD diffractometer[Ancillary equipment for pressure measurement, etc.] 41
Diamond Light Source Oxfordshire, UK
Very high intensity synchrotron X-ray source on Beamline I19 (EH1 and EH2)
2008–date
HP work at SRS and Diamond
Synchrotron Radiation Source Daresbury Laboratory, Warrington, UK
High intensity synchrotron X-ray source on Stations 9.8 and 16.2SMX
2005–2008
[MX2([9]aneS3)] complexes studied at high pressure
Compound Shortaxial contact
Chain polymer formed
Ligand conformationchanges
Marked colourchange
Catenationinduced
[PdCl2([9]aneS3)]
[PtCl2([9]aneS3)]
[PdBr2([9]aneS3)] At 58 kbar
PtBr2([9]aneS3)] At 58 kbar
[PdI2([9]aneS3)] At 19 kbar
[PtI2([9]aneS3)] At 19 kbar
D. R. Allan, D. Bailey, N. Bird, A. J. Blake, N. R. Champness, D Huang, C. P. Keane, J. McMaster, T. J. Prior, J. P. Tidey & M. Schröder, Acta Crystallogr., Sect. B 2014, 70, 469−486.
Daniel Bailey
Cation at 0.001 kbar
Pressure-induced stacking and molecular deformation in [Pd([9]aneS3)(PPh3)2][PF6]2
… stacking
Pyramidalisation at C11 at 65.5 kbar
α = 149.3(8)⁰
Henry Wong
H. L. S. Wong, D. R. Allan, N. R. Champness, J. McMaster,M. Schröder & A. J. Blake, Angew. Chem. 2013, 52, 5093–5095.
Current work: [Pt([9]aneS3)(PPh3)2][PF6]2
• does not behave anything like the Pd analogue • pressure does not induce … stacking• no pyramidalisation at C11 under compression• edge-to-face interactions are more important• have preliminary results but need higher
precisionJeremiah Tidey
Current work: [PdCl2([9]aneS2O)]
α-[PdCl2([9]aneS2O)] - known phase:facially bound, endo macrocycleforms alternating sheets of Pd2 dimersHP study complete
γ-[PdCl2([9]aneS2O)] - new phase:equatorially bound, exo macrocycleproto-chains via intermolecular Pd···O HP study complete
2.985(16) Å
3.768(4) Å
3.213(15) Å
3.39(2) Å
3.405(4) Å
3.4937(8) Å
β-[PdCl2([9]aneS2O)] - new phase:equatorially bound, exo macrocyclesimilar Pd2 dimers as in the α formbut different packing of thesecutting transforms crystals to α form
Jeremiah Tidey
Current work: [PdCl2([9]aneS2O)]
β-[PdCl2([9]aneS2O)] is a possible “disappearing polymorph”see J. D. Dunitz & J. Bernstein, Acc. Chem. Res. 1995, 28, 193–200formation of the β form may be kinetically favouredthe γ polymorph may be more thermodynamically stableit may now be impossible to obtain the β form
Jeremiah Tidey
Multiple attempts over a year to regrow β-[PdCl2([9]aneS2O)]different solvents and solvent mixturesdifferent methods, techniques and variationsall such efforts were uniformly unsuccessful
Obtained stable crystals of β-[PtCl2([9]aneS2O)]isomorphous with β-[PdCl2([9]aneS2O)]
used as a seed for epitaxial growth of β-[PdCl2([9]aneS2O)]the disappearing polymorph has been recoveredhigh pressure studies are underway on both complexes
Future work
• Central facilitiesBeamline I19 at Diamond Light Source– for any difficult cases– for structures near pressure limits
• In-house high pressure laboratoryall preliminary studies will be done herealso most of the complete studies
• Main areas of investigation
[M([9]aneS3)1-2]x+ [M([9]aneS3)PP]x+
[MX2([9]aneS2O)] MOFs48
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Future work at Diamond
• Require the capabilities of EH2• Intensity, focussed beam, sample centring
• High pressure studies on our new flexible MOFs
• Focus on MOFs with interesting properties
• Working at the limits of sample quality
• Need to optimise experimental conditions
• Develop the best experimental approaches
Acknowledgements
Dr Dave AllanProfessor Martin SchröderProfessor Neil ChampnessDr Jon McMaster
Daniel BaileyHenry Wong
Alice O’ConnorJeremiah Tidey
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Dr Deguang HuangDr Tim Prior (Daresbury)
Tom McDonnellConal KeaneNigel BirdJoe Cavan
Dr John Warren (Daresbury)The Diamond I19 TeamProfessor Geoff Lawrance (Newcastle, AU)