The reactions of iron chlorides with mesityl Grignard reagents and tetramethylethylenediamine (TMEDA) under catalytically relevant conditions tend to yield the homoleptic "ate" complex [Fe(mes)3 ](-) (mes=mesityl) rather than adducts of the diamine, and it is this ate complex that accounts for the catalytic activity. Both [Fe(mes)3 ](-) and the related complex [Fe(Bn)3 ](-) (Bn=benzyl) react faster with representative electrophiles than the equivalent neutral [FeR2 (TMEDA)] complexes. Fe(I) species are observed under catalytically relevant conditions with both benzyl and smaller aryl Grignard reagents. The X-ray structures of [Fe(Bn)3 ](-) and [Fe(Bn)4 ](-) were determined; [Fe(Bn)4 ](-) is the first homoleptic σ-hydrocarbyl Fe(III) complex that has been structurally characterized.

Some porous crystalline solids change their structure upon guest inclusion. Unlocking the potential of these solids for a wide variety of applications requires full characterisation of the response to adsorption and the underlying framework–guest interactions. Here, we introduce an approach to understanding gas uptake in porous metal-organic frameworks (MOFs) by loading liquefied gases at GPa pressures inside the Zn-based framework ZIF-8. An integrated experimental and computational study using high-pressure crystallography, grand canonical Monte Carlo (GCMC) and periodic DFT simulations has revealed six symmetry-independent adsorption sites within the framework and a transition to a high-pressure phase. The cryogenic high-pressure loading method offers a different approach to obtaining atomistic detail on guest molecules. The GCMC simulations provide information on interaction energies of the adsorption sites allowing to classify the sites by energy. DFT calculations reveal the energy barrier of the transition to the high-pressure phase. This combination of techniques provides a holistic approach to understanding both structural and energetic changes upon adsorption in MOFs.

Protonation of MeRNH·BH3 (R = Me or H) with HX (X = B(C6F5)4, OTf, or Cl), followed by immediate, spontaneous H2 elimination, yielded the amine-boronium cation salt [MeRNH·BH2(OEt2)][B(C6F5)4] and related polar covalent analogs, MeRNH·BH2X (X = OTf or Cl). These species can be deprotonated to conveniently generate reactive aminoborane monomers MeRN=BH2 which oligomerize or polymerize; in the case of MeNH2·BH3, the two step process gave poly(N-methylaminoborane), [MeNH-BH2]n.

Selective, robust and cost-effective chemical sensors for detecting small volatile-organic compounds (VOCs) have widespread applications in industry, healthcare and environmental monitoring. Here we design a Pt(II) pincer-type material with selective absorptive and emissive responses to methanol and water. The yellow anhydrous form converts reversibly on a subsecond timescale to a red hydrate in the presence of parts-per-thousand levels of atmospheric water vapour. Exposure to methanol induces a similarly-rapid and reversible colour change to a blue methanol solvate. Stable smart coatings on glass demonstrate robust switching over 104 cycles, and flexible microporous polymer membranes incorporating microcrystals of the complex show identical vapochromic behaviour. The rapid vapochromic response can be rationalised from the crystal structure, and in combination with quantum-chemical modelling, we provide a complete microscopic picture of the switching mechanism. We discuss how this multiscale design approach can be used to obtain new compounds with tailored VOC selectivity and spectral responses.

Photocrystallography is a rapidly developing technique that enables the full three-dimensional structure of a molecule in a metastable or excited state to be elucidated when a single crystal of the complex is photoactivated by visible or UV light.[1] Pioneering work in the areas of both molecular and macromolecular photocrystallography has allowed the crystallographic characterization of species with microsecond and sub-microsecond lifetimes. [2, 3] Of equal importance are the detailed studies on the identification and stabilization of metastable species [4,5] because of potential photorefractive applications, including data storage and optical switching. [6] This area has been pioneered by Coppens et al., and they, and others, have now successfully determined the structures of a number of metastable species including several transitionmetal-nitrosyl, -nitro, and -SO 2 complexes. [7][8][9] A major limitation in the study of these systems has been the relatively low level of conversion from the ground state to the metastable state that can be achieved in the single crystal. Controlled, complete reversible interconversion is desirable if these materials are to find real applications as optical switches or in data-storage devices. Examples of high conversions into metastable species are rare; however, notable studies include the first example of a reversible 100 % conversion of the nickel(II)-nitro complex [Ni(dppe)(h 1 -NO 2 )Cl] (dppe = 1,2-bis(diphenylphosphino)ethane) into the nitrito isomer [Ni-(dppe)(h 1 -ONO)Cl] when irradiated with UV light-emitting diodes (LEDs) [10] at temperatures below 160 K. A 92 % lightinduced conversion from the h 1 -NO isomer to the h 1 -ON

The mononuclear complex [(EtO 2 C-C^N^C)Pt(dmpyz)] (1) (dmpyz = 2,5-dimethylpyrazine) has been synthesised by reaction of [(EtO 2 C-C^N^C)Pt(dmso)] (A) with dmpyz in 1:1 molar ratio in dichloromethane. Complex 1 is the precursor for preparing the homodinuclear complex [{(EtO 2 C-C^N^C)Pt} 2 (-dmpyz)] (2) and the heterotrinuclear clusters [{(EtO 2 C-C^N^C)Pt(dmpyz)} 2 M]X (M= Cu, X= PF 6 (3); M= Ag, X= BF 4 (4)). Compounds 1, 2 and 4 were studied by X-ray diffraction methods. In the crystal packing of 1 and 2, the molecules display short intermolecular ••• contacts, which control the solid state emissive behavior. X-ray study on 4 shows two [Pt 2 Ag] sandwich-type clusters in the asymmetric unit, both with the two square-planar "(R-CNC)Pt(dmpyz)" moieties stabilized by two Pt→Ag donoracceptor bonds as well as by  1-and  2-Ag-C interactions. Intramolecular - contacts were found between the pyridine rings of the CNC ligands within the same Pt 2 Ag cluster. 1 H and 195 Pt NMR studies confirm that the Pt 2 M cluster is also retained in solution at room temperature. 195 Pt NMR spectra of 3 and 4 show signals shifted significantly downfield when comparing to that for the monomer (1), which is attributed to presence of Pt-M dative bonds. At lower temperatures (T = 193 K), the copper derivative definitely falls apart, whereas the silver one still holds up unbroken. In solid state at 77 K, compounds 1-4 give red emissions arising from 3  excited states due to the intra-or intermolecular - contacts observed in the crystal structures. As expected, in glassy solutions (77 K), compound 3 displays analogous emissions to those from the starting material (1). Complexes 1 and 2 show structured emission bands which are particularly sensitive to the ex (HE and LE). In contrast, 4 displays an unstructured emission at 680 nm with a shoulder at 556 nm, both are not dependent on the ex. DFT and TDDFT computational studies have been performed on 1 and 2 which support the conclusions drawn from the photophysical studies.

The solid-state, low-temperature linkage isomerism in a series of five square planar group 10 phosphino nitro complexes have been investigated by a combination of photocrystallographic experiments, Raman spectroscopy and computer modelling. The factors influencing the reversible solid-state interconversion between the nitro and nitrito structural isomers have also been investigated, providing insight into the dynamics of this process. The cis-[Ni(dcpe)(NO2)2] (1) and cis-[Ni(dppe)(NO2)2] (2) complexes show reversible 100 % interconversion between the η1-NO2 nitro isomer and the η1-ONO nitrito form when single-crystals are irradiated with 400 nm light at 100 K. Variable temperature photocrystallographic studies for these complexes established that the metastable nitrito isomer reverted to the ground-state nitro isomer at temperatures above 180 K. By comparison, the related trans complex [Ni(PCy3)2(NO2)2] (3) showed 82 % conversion under the same experimental conditions at 100 K. The level of conversion to the metastable nitrito isomers is further reduced when the nickel centre is replaced by palladium or platinum. Prolonged irradiation of the trans-[Pd(PCy3)2(NO2)2] (4) and trans-[Pt(PCy3)2(NO2)2] (5) with 400 nm light gives reversible conversions of 44 and 27 %, respectively, consistent with the slower kinetics associated with the heavier members of group 10. The mechanism of the interconversion has been investigated by theoretical calculations based on the model complex [Ni(dmpe)Cl(NO2)].

The synergistic combination of high pressure techniques with ab initio methods creates a powerful tool to understand giant magnetic anisotropy.