Accurate crystal structures and chemical properties from NoSpherA2.

The relationship between the structure and the properties of a drug or material is a key concept of chemistry. Knowledge of the three-dimensional structure is considered to be of such importance that almost every report of a new chemical compound is accompanied by an X-ray crystal structure - at least since the 1970s when diffraction equipment became widely available. Crystallographic software of that time was restricted to very limited computing power, and therefore drastic simplifications had to be made. It is these simplifications that make the determination of the correct structure, especially when it comes to hydrogen atoms, virtually impossible. We have devised a robust and fast system where modern chemical structure models replace the old assumptions, leading to correct structures from the model refinement against standard in-house diffraction data using no more than widely available software and desktop computing power. We call this system NoSpherA2 (Non-Spherical Atoms in Olex2). We explain the theoretical background of this technique and demonstrate the far-reaching effects that the improved structure quality that is now routinely available can have on the interpretation of chemical problems exemplified by five selected examples.

Transition metal complexes of the pyridylphosphine ligand o-C6H4(CH2PPy2)2.

The synthesis and coordination behaviour of the pyridylphosphine ligand o-C6H4(CH2PPy2)2 (Py = 2-pyridyl) are reported. The phosphine selenide was synthesised and the 1JPSe value of 738 Hz indicates the phosphorus atoms have a similar basicity to PPh3. The ligand reacts with platinum(ii) and palladium(ii) complexes to give simple diphosphine complexes of the type [MX2(PP)] (M = Pt, X = Cl, I, Me, Et; M = Pd, X = Cl, Me). When the ligand is reacted with chloromethyl(hexa-1,5-diene)platinum the [PtClMe(PP)] complex results, from which a series of unsymmetrical platinum complexes of the type [PtMeL(PP)]+ (L = PPh3, PTA, SEt2 and pyridine) can be made. This enabled the comparison of the cis and trans influences of a range of ligands. The following cis influence series was compiled based on 31P NMR data of these complexes: Py ≈ Cl > SEt2 > PTA > PPh3. Reaction of [PtClMe(PP)] with NaCH(SO2CF3)2 and carbon monoxide slowly formed an acyl complex, where the CO had inserted in the Pt-Me bond. Attempts to achieve P,P,N chelation, through abstracting the chloride ligand in [PtClMe(PP)], were unsuccessful. When the ligand reacted with platinum(0), palladium(0) and silver(i) complexes the bis-chelated complexes [M(PP)2] (M = Pt, Pd) and [Ag(PP)2]+ were formed respectively. Reaction of the ligand with [Ir(COD)(µ-Cl)]2 formed [IrCl(PP)(COD)]. When the chloride ligand was abstracted, the pyridyl nitrogens were able to interact with the iridium centre facilitating the isomerisation of the 1,2,5,6-η4-COD ligand to a 1-κ-4,5,6-η3-C8H12 ligand. The X-ray crystal structure of [Ir(1-κ-4,5,6-η3-C8H12)(PPN)]BPh4 confirmed the P,P,N chelation mode of the ligand. In solution, this complex displayed hemilabile behaviour, with the pyridyl nitrogens exchanging at a rate faster than the NMR time scale at room temperature.

Crystal structure of bis-[1,3-bis-(di-phenyl-phosphan-yl)propane-κ(2) P,P']platinum(II) dichloride chloro-form penta-solvate.

In the title compound, [Pt{Ph2P(CH2)3PPh2}2]Cl2·5CHCl3, the Pt(II) cations, located on a centre of inversion, is coordinated by two chelating diphosphane ligands in a geometry which is close to square-planar. The chelate rings adopt a chair conformation. The Pt(II) cations are arranged in layers separated by Cl(-) anions as well as CHCl3 solvent mol-ecules. While this complex has been reported previously [Anderson et al. (1983 ▶). Inorg. Chim. Acta, 76, L251-L252], this is the first time a structure has been determined.

The coordination chemistry of pentafluorophenylphosphino pincer ligands to platinum and palladium.

The synthesis of electron-poor PCP pincer ligands 1,3-((C6F5)2PO)2C6H4, 1,3-((C6F5)2PCH2)2C6H4, and 1-((C6F5)2PO)-3-(tBu2PCH2)C6H4, and their coordination chemistry to platinum and palladium is described. The most electron-poor ligand 1,3-((C6F5)2PO)2C6H4 (POCOPH) reacts with Group 10 metal chloride precursors to form a range of unusual cis, trans-dimers of the type κ(2)-P,P-[(POCOPH)MCl(L)]2 (M = Pt, Pd; L = Cl, Me), which undergo metallation to form [(POCOP)MCl] pincer complexes only under prolonged thermolysis. The formation of such cis,trans-dimers during pincer complex formation can be mitigated through the use of starting materials with more strongly binding ancillary ligands, improving the overall rate of ligand metallation. Carbonyl complexes of the type [(PCP)M(CO)](+) were synthesised from the pincer chloride complexes by halide abstraction, and displayed large ν(C-O) values, from 2170-2111 cm(-1), confirming the electron-poor nature of the compounds. The [(PCP)Pd(CO)](+) complexes also demonstrated the ability to reversibly bind carbon monoxide both in solution and the solid state, with the rate of decarbonylation increasing with increasing wavenumber for the C-O stretch.

Synthesis and characterisation of novel o-xylene-based P,E ligands.

A range of novel hybrid ligands of the type, o-C6H4(CH2PBu(t)2)(CH2E) (E = P(C6F5)2, SBu(t), SPh, S(O)Bu(t), NR2, SiPh2H), have been synthesised in two or three steps from the common substrate, o-C6H4{CH2PBu(t)2(BH3)}(CH2Cl). The initial step involved treatment of the substrate with the appropriate nucleophilic reagent, or preparation of a Grignard reagent from o-C6H4{CH2PBu(t)2(BH3)}(CH2Cl) and reaction with the appropriate electrophile. In most cases, this versatile strategy produced air-stable crystalline ligand precursors. Phosphine deprotection was achieved via one of three methods, dependent upon the properties of the second functional group. An alternative synthesis of the known ligand, o-C6H4(CH2PBu(t)2)(CH2PPh2), is also presented.

Hot-injection synthesis of iron/iron oxide core/shell nanoparticles for T2 contrast enhancement in magnetic resonance imaging.

Here we report a new, bench-top synthesis for iron/iron oxide core/shell nanoparticles via the thermal decomposition of Fe(η(5)-C(6)H(3)Me(4))(2). The iron/iron oxide core/shell nanoparticles are superparamagnetic at room temperature and show improved negative contrast in T(2)-weighted MR imaging compared to pure iron oxides nanoparticles, and have a transverse relaxivity (r(2)) of 332 mM(-1) s(-1).

Synthesis and characterization of the dinuclear polyhydrides [Os(2)H(7)(PPh(i)Pr(2))(4)](+) and [Os(2)H(6)(PPh(i)Pr(2))(4)].

The dinuclear osmium polyhydride [Os(2)H(7)(PPh(i)Pr(2))(4)][HC(SO(2)CF(3))(2)] (1) was synthesized by the protonation of [OsH(6)(PPh(i)Pr(2))(2)] with bis(trifluoromethylsulfonyl)methane. Treatment with amine bases was not able to deprotonate 1, but reaction with potassium hydride gave the corresponding neutral polyhydride [Os(2)H(6)(PPh(i)Pr(2))(4)] (2). Single crystal X-ray diffraction revealed that 1 and 2 both crystallize in the P2(1)/c space group and are classical polyhydrides containing similar Os(mu-H)(3)Os cores with Os-Os distances of 2.5431(1) A and 2.5448(2) A, respectively. These structures represent rare examples of dinuclear osmium polyhydrides with six or more hydride ligands.