High-pressure studies of palladium and platinum thioether macrocyclic dihalide complexes

Switching On/Off of a Solvent Coordination in a Au(I)-Pb(II) Complex: High Pressure and Temperature as External Stimuli

The benzonitrile solvate {[{Au(C6F5)2}2{Pb(terpy)}]·NCPh}n (1) (terpy = 2,2':6',2″-terpyridine) displays reversible reorientation and coordination of the benzonitrile molecule to lead upon external stimuli. High-pressure X-ray diffraction studies between 0 and 2.1 GPa reveal a 100% of conversion without loss of symmetry, which is totally reversible upon decompression. By variable-temperature X-ray diffraction studies between 100 and 285 K, a partial coordination is achieved.

Hydrogen bonding and fluorous weak interactions in the non-isomorphous {4,4'-bis[(2,2,3,3-tetrafluoropropoxy)methyl]-2,2'-bipyridine-κ2N,N'}dibromidopalladium and -platinum complexes

The polyfluorinated title compounds, [MBr₂(C₁₈H₁₆F₈N₂O₂)] or [4,4'-(HCF₂CF₂CH₂OCH₂)₂-2,2'-bpy]MBr₂, (1) (M = Pd and bpy is bipyridine) and (2) (M = Pt), have -CH_(α)2OCH_(β)2CF₂CF₂H side chains with methylene H-atom donors at the α and β sites, and methine H-atom donors at the terminal sites, in addition to aromatic H-atom donors. In contrast to the original expectation of isomorphous structures, (1) crystallizes in the space group C2/c and (2) in P2₁/n, with similar unit-cell volumes and Z = 4. The asymmetric unit of (1) is one half of the molecule, which resides on a crystallographic twofold axis. Both (1) and (2) display stacking of the molecules, indicating a planar (bpy)MBr₂ skeleton in each case. The structure of (1) exhibits columns with C-H_(β)...Br hydrogen bonds between consecutive layers which conforms to a static (β,β) linkage between layers. In the molecular plane, (1) shows double C-H_(α)...Br hydrogen bonds self-repeating along the b axis, the planar molecules being connected into infinite belts. Compound (2) has no crystallographic symmetry and forms π-dimer pairs as supermolecules, which then stack parallel to the a axis. The π-dimer-pair supermolecules exhibit (Pt-)Br...Br(-Pt) contacts [3.6937 (7) Å] to neighbouring π-dimer pairs crosslinking the columns. The structure of (2) reveals many C-H...F(-C) interactions between F atoms and aromatic C-H groups, in addition to those between F atoms and methylene C-H groups.

Phase transition in metal–organic complex trans-PtCl2(PEt3)2 under pressure: insights into the molecular and crystal structure

Molecular reorientations result in structural phase transition in trans-PtCl₂(PEt₃)₂ under pressure, leading to a hydrogen bond assisted supramolecular architecture.

High-pressure studies of three polymorphs of a palladium(II) oxathioether macrocyclic complex

The three reported phases of the mononuclear macrocyclic Pd(II) complex [PdCl2([9]aneS2O)] [(1); [9]aneS2O = 1-oxa-4,7-dithiacyclononane] were each studied up to pressures exceeding 9 GPa using high-pressure single-crystal X-ray diffraction. The α- and γ-phases both exhibit smooth compression of the unit-cell parameters with third-order Birch-Murnaghan bulk moduli of 14.4 (8) and 7.6 (6) GPa, respectively. Between 6.81 and 6.87 GPa β-[PdCl2([9]aneS2O)] was found to undergo a reversible transition to a phase denoted as β' and characterized by a tripling of the unit-cell volume. Across the phase transition, rearrangement of the conformation of the bound macrocycle at two of the resulting three unique sites gives rise to an extensively disordered structure.

Structural aspects of metal-organic framework-based energy materials research at Diamond

Large-scale central facilities such as Diamond Light Source fulfil an increasingly pivotal role in many large-scale scientific research programmes. We illustrate these developments by reference to energy-centred projects at the University of Nottingham, the progress of which depends crucially on access to these facilities. Continuing access to beamtime has now become a major priority for those who direct such programmes.

Epitaxial Retrieval of a Disappearing Polymorph

Recrystallization of [PdCl2([9]aneS2O)] ([9]aneS2O = 1-oxa-4,7-dithiacyclononane), 1, and [PtCl2([9]aneS2O)], 2, by diffusion of Et2O vapor into solutions of the complexes in MeNO2 yielded three phases of 1 and two phases of 2. The known phase of 1, herein designated α-1, was obtained under ambient conditions. A second phase, designated β-1, was initially also obtained by this method; however, following the advent of a third phase, γ-1, all subsequent efforts over a period of a year to crystallize β-1 yielded either γ-1, obtained by carrying out the recrystallization at elevated temperature, or α-1, commonly found throughout the study. This persistent absence of a phase which could initially be crystallized with ease led us to the conclusion that β-1 was an example of a "disappearing polymorph". The first phase obtained of 2, designated α-2, was obtained by recrystallization under ambient conditions and is isomorphous and isostructural with α-1. The second phase β-2 was obtained by slight elevation of the recrystallization temperature and was found to be isomorphous and isostructural with β-1. Subsequently, β-2 was used to seed the growth of the disappearing polymorph β-1. No third phase of 2 (γ-2) has been isolated thus far.