Royston C. B. Copley

Exo-π-bonding to an ortho-carborane hypercarbon atom: systematic icosahedral cage distortions reflected in the structures of the fluoro-, hydroxy- and amino-carboranes, 1-X-2-Ph-1,2-C2B10H10 (X = F, OH or NH2) and related anions

The structures of derivatives of phenyl-ortho-carborane bearing on the second cage hypercarbon atom a pi-donor substituent (F, OH, O-, NH2, NH- and CH2-) were investigated by NMR, X-ray crystallography and computational studies. The molecular structures of these compounds, notably their cage C1-C2 distances and the orientations of their pi-donor substituents (OH, NH2, NH- and CH2-) show remarkable and systematic variations with the degree of exo pi-bonding, which varies as expected with the pi-donor characteristics of the substituent.

Studying the Origin of the Antiferromagnetic to Spin‐Canting Transition in the β‐p‐NCC6F4CNSSN. Molecular Magnet

The crystal structure of the spin-canted antiferromagnet beta-p-NCC(6)F(4)CNSSN* at 12 K (reported in this work) was found to adopt the same orthorhombic space group as that previously determined at 160 K. The change in the magnetic properties of these two crystal structures has been rigorously studied by applying a first-principles bottom-up procedure above and below the magnetic transition temperature (36 K). Calculations of the magnetic exchange pathways on the 160 K structure reveal only one significant exchange coupling (J(d1)=-33.8 cm(-1)), which generates a three-dimensional diamond-like magnetic topology within the crystal. The computed magnetic susceptibility, chi(T), which was determined by using this magnetic topology, quantitatively reproduces the experimental features observed above 36 K. Owing to the anisotropic contraction of the crystal lattice, both the geometry of the intermolecular contacts at 12 K and the microscopic J(AB) radical-radical magnetic interactions change: the J(d1) radical-radical interaction becomes even more antiferromagnetic (-43.2 cm(-1)) and two additional ferromagnetic interactions appear (+7.6 and +7.3 cm(-1)). Consequently, the magnetic topologies of the 12 and 160 K structures differ: the 12 K magnetic topology exhibits two ferromagnetic sublattices that are antiferromagnetically coupled. The chi(T) curve, computed below 36 K at the limit of zero magnetic field by using the 12 K magnetic topology, reproduces the shape of the residual magnetic susceptibility (having subtracted the contribution to the magnetization arising from spin canting). The evolution of these two ferromagnetic J(AB) contributions explains the change in the slope of the residual magnetic susceptibility in the low-temperature region.

The novel structure of the [Au11(PMePh2)10]3+ cation: crystal structures of [Au11(PMePh2)10][C2B9H12]3·4thf and [Au11(PMePh2)10][C2B9H12]3(thf = tetrahydrofuran)

Crystal structure analyses of [Au11(PMePh2)10][C2B9H12]3·4thf (thf = tetrahydrofuran) and [Au11(PMePh2)10][C2B9H12]3 showed the metal framework of the [Au11(PMePh2)10]3+ cation to approximate to a centred bicapped square antiprism, with idealized D4d symmetry. Symmetry-related cage distances and angles have similar mean values but different ranges in the two structures, with the latter having greater consistency in the peripheral bond lengths but more distortion in the squares of the antiprism. It is suggested that these differences are directly related to the ligand packing around the metal skeletons. The cations of the two clusters cannot be superimposed in any orientation. It is possible to relate a centred bicapped square antiprism to the previously reported undecagold cage geometry, although they belong to different symmetry point groups. The largest differences between the idealized C3v and D4d frameworks centre around three adjacent peripheral sites. The movements required to interconvert the geometries take place about a common mirror plane and appear to be closely related to those of the diamond–square–diamond rearrangement mechanism. Fluxional interconversions of this type provide a possible explanation for the 31P-{1H} NMR spectra of the Au11 cluster compounds.

Molybdenum(VI) complexes containing differing cis multiply-bonded ligands: Some structural consequences of competing π-donor groups

Abstract The mixed bis(imido) molybdenum complex Mo(N-2,6-Pr2iC6H3)N-But)Cl2(dme) ( 1 ; dme = 1,2- dimthoxyethane ) is accessible in multi-gram quantities upon treatment of Na2MoO4 with equimolar quantities of H2N-2,6-Pr2iC6H3 and ButNH2 in the presence of excess NEt3 and chlorotrimethylsilane. Treatment of Na2MoO4 with one equivalent of 1-adamantamine under analogous conditions afforded Mo(N-1-adamantyl)(O)Cl2(dme) (2). The molecular structures of 1 and 2 are reported. A rationale for the orientation of the imido aryl substituent based on electronic considerations is proposed.

Crystallographic evidence for the diene character of C2B10H10C4H4(‘benzocarbonae’) and a Diels–Alder reaction of its anionic nido-analogue, [C2B9H10C4H4]–: crystal structures of C2B10H10C4H4 and C2B10H10C4H6

Single-crystal X-ray diffraction studies on [C2B10H10C4H4](‘benezocarborane’) and C2B10H10C4H6(‘dihydrobenzocarborane’) show that the C6 rings of each posses localised double bonds and this has been confirmed by bond-order calculations: the nido-anion. [C2B9H10C4H4]– synthesised from C2B10H10C4H4, with maleic anhydride forms a Diels-Alder adduct.

Synthesis and structural characterization of [Au9Ag4Cl4(PMePh2)8][C2B9H12]·H2O·0.5CH2Cl2: the first example of an icosahedral silver–gold cluster

The compound [Au9Ag4Cl4(PMePh2)8][C2B9H12]·H2O·0.5CH2Cl2 has been synthesised in high yield from [Au11(PMePh2)10]3+ and [Ag(PMePh2)Cl] in CH2Cl2 and its centred icosahedral geometry has been confirmed by single-crystal X-ray diffraction measurements.

Structural-magnetic correlations on the first dinuclear spin crossover d4 system.

The triple decker dinuclear Cr(II) salt [(η5-C5Me5)Cr(μ2:η5-P5)Cr(η5-C5Me5)]+ (SbF6)− has been structurally characterised by multiple temperature X-ray diffraction experiments from 290 K to 12 K. This material shows changes in its structural features which correlate with its magnetic response, including a structural transition with a change of symmetry from the orthorhombic space group Fddd to the monoclinic I2/a at ∼160 K and an abrupt rearrangement of electron density at ∼23 K

General method for the description, visualization and comparison of metal coordination spheres: geometrical preferences, deformations and interconversion pathways

The coordination sphere geometry of metal atoms (M) in their complexes with organic and inorganic ligands (L) is often compared with the geometry of archetypal forms for the appropriate coordination number, n in ML(n) species, by use of the k = n( n- 1)/2 L-M-L valence angles subtended at the metal centre. Here, a Euclidean dissimilarity metric, R(c)(x), is introduced as a one-dimensional comparator of these k-dimensional valence-angle spaces. The computational procedure for R(c)(x), where x is an appropriate archetypal form (e.g. an octahedron in ML(6) species), takes account of the atomic permutational symmetry inherent in ML(n) systems when no distinction is made between the individual ligand atoms. It is this permutational symmetry, of order n!, that precludes the routine application of multivariate analytical techniques, such as principal component analysis (PCA), to valence angle data for all but the lowest metal coordination numbers. It is shown that histograms of R(c)(x) values and, particularly, scatterplots of R(c)(x) values computed with respect to two or more different appropriate archetypal forms (e.g. tetrahedral and square-planar four-coordinations), provide information-rich visualizations of the observed geometrical preferences of metal coordination spheres retrieved from, e.g. the Cambridge Structural Database. These mappings reveal the highly populated clusters of similar geometries, together with the pathways that map their geometrical interconversions. Application of R(c)(x) analysis to the geometry of four- and seven-coordination spheres provides information that is at least comparable to, and in some cases is more complete than, that obtained by PCA.

Synthesis and characterization of the centred icosahedral cluster series [Au9MIB4Cl4(PMePh2)8][C2B9H12], where MIB= Au, Ag or Cu

The compounds [Au9MIB4Cl4(PMePh2)8][C2B9H12](MIB= Au, Ag or Cu) have been prepared from solutions of [Au11(PMePh2)10][C2B9H12]3 by the addition or formation in situ of [MIBCl(PMePh2)]. The reaction is believed to take place via the intermediate cations [Au11MIB2Cl2(PMePh2)10]3+ and [Au10MIB3Cl3(PMePh2)9]2+. The final products have been characterized by FAB mass spectrometry, electronic spectroscopy and 31P-{1H}, 11B-{1H} and 1H NMR spectroscopy. Single-crystal X-ray diffraction studies on [Au9Ag4Cl4(PMePh2)8][C2B9H12]·H2O·0.5CH2Cl2 and [Au9Cu4Cl4(PMePh2)8][C2B9H12]·CH2Cl2 have been carried out. The cations of these compounds contain centred icosahedral metal frameworks and in both cases the cages have approximate C2v symmetry: the silver and copper atoms, associated with the halide ligands, occupy identical positions. A gold atom sits at the interstitial site. The cations cannot be superimposed due to differences in the ligand packing. Comparable Au–Au bond lengths in the two structures are very similar and, given the large differences that are seen between the Au–Ag and the Au–Cu bond lengths, the Ag–Cl and Cu–Cl moieties can be visualized as moving relative to one another along radial vectors.

1,4,7-Triazacyclononane-1,4,7-triyltrimethylenetris-(phenylphosphinate) enforces octahedral geometry: crystal and solution structures of its metal complexes and comparative biodistribution studies of radiolabelled indium and gallium complexes

1,4,7-Triazacyclononane-1,4,7-triyltrimethylenetris(phenylphosphinate) formed C3-symmetric complexes with the divalent ions of Co. Ni, Cu and Zn and structurally similar complexes with the trivalent ions of Fe, Co, Ga and In. For each of the eight crystal structures examined, the ligand adopts the same rigid conformation and a single chiral diastereoisomer is formed (RRR or SSS at each stereogenic phosphorus centre). The geometry around the metal centre is slightly distorted octahedral. The copper(II) complex only undergoes a Jahn–Teller distortion below 100 K, and the pink cobalt(II) complex only slowly oxidises to the dark blue cobalt(III) complex. The chiral gallium(III) complex may be resolved by preparative HPLC, and its 1H NMR spectrum has been fully assigned with the aid of two-dimensional methods. The indium-111 and gallium-67 complexes have been examined in vivo and exhibit selective biliary clearance associated with their lipophilic nature.