Molybdenum(III) Amidinate: Synthesis, Characterization, and Vapor Phase Growth of Mo-Based Materials.

The synthesis, characterization, and thermogravimetric analysis of tris(,'-di-isopropylacetamidinate)molybdenum(III), Mo(iPr-AMD), are reported. Mo(iPr-AMD) is a rare example of a homoleptic mononuclear complex of molybdenum(III) and fills a longstanding gap in the literature of transition metal(III) trisamidinate complexes. Thermogravimetric analysis (TGA) reveals excellent volatilization at elevated temperatures, pointing to potential applications as a vapor phase precursor for higher temperature atomic layer deposition (ALD), or chemical vapor deposition (CVD) growth of Mo-based materials.

Electronic Structure of Re(OCR)Cl Complexes (R = H, CMe) and Reassignment of the Electronic Absorption Spectrum of Re(OCCMe)Cl.

Electronic structure calculations on two dinuclear rhenium(III) carboxylate complexes, Re(OCH)Cl and Re(OCCMe)Cl, are presented and discussed. Allowed electronic transitions for both molecules were calculated using time-dependent density functional theory (TDDFT). The results for the pivalate dimer, Re(OCCMe)Cl, are compared with previously reported single-crystal polarized absorption spectra obtained by Martin and co-workers (Inorg.

Multimetallic Permethylpentalene Hydride Complexes.

The synthesis and characterization of group 4 permethylpentalene (Pn* = CMe) hydride complexes are explored; in all cases, multimetallic hydride clusters were obtained. Group 4 lithium metal hydride clusters were obtained when reacting the metal dihalides with hydride transfer reagents such as LiAlH, and these species featured an unusual hexagonal bipyramidal structural motif. Only the zirconium analogue was found to undergo hydride exchange in the presence of deuterium.

Comment on "In Defence of Oxidation States" by N. C. Norman and P. G. Pringle, Dalton Transactions, 2022, 51, DOI: 10.1039/D0DT03914D.

The evolution of the Covalent Bond Classification as a pedagogical tool for classifying an element's chemistry is described.

Synthesis, characterisation and redox properties of anti-bimetallic permethylpentalene complexes.

We report a series of anti-bimetallic transition metal complexes based on the permethylpentanyl (Pn*, C8Me6) ligand: anti-(MCpR5)2Pn* (where M = Fe, Co and Ni and R = H or Me). Compounds (FeCp*)2Pn* (1), (CoCp*)2Pn* (2), (NiCp*)2Pn* (3), (CoCp)2Pn* (4) and (NiCp)2Pn* (5) were fully characterised by NMR spectroscopy, X-ray crystallography, DFT calculations and cyclic voltammetry. All anti-(MCpR5)Pn* structures have diamagnetic ground states.

Reversible coordination of N and H to a homoleptic = 1/2 Fe(i) diphosphine complex in solution and the solid state.

The synthesis and characterisation of the = 1/2 Fe(i) complex [Fe(depe)][BArF4] ([][BArF4]), and the facile reversible binding of N and H in both solution and the solid state to form the adducts [·N] and [·H], are reported. Coordination of N in THF is thermodynamically favourable under ambient conditions (1 atm; Δ = -4.9(1) kcal mol), while heterogenous binding is more favourable for H than N by a factor of ∼300.

Bis(pentalene)dititanium chemistry: C-H, C-X and H-H bond activation.

The reaction of the bis(pentalene)dititanium complex Ti2(μ:η5,η5-Pn†)2 (Pn† = C8H4(1,4-SiiPr3)2) (1) with the N-heterocyclic carbene 1,3,4,5-tetramethylimidazol-2-ylidene results in intramolecular C-H activation of an isopropyl substituent to form a tucked-in hydride (3). Whilst pyridine will also effect this cyclometallation reaction to form (5), the pyridine analogue of (3), the bases 1,2,4,5-tetramethyl-imidazole, 2,6-lutidine, DABCO or trimethylphosphine are ineffective. The reaction of (1) with 2,6-dichloro-pyridine affords crystallographically characterised (6) which is the product of oxidative addition of one of the C-Cl bonds in 2,6-dichloro-pyridine across the Ti-Ti double bond in (1).

Fe-Catalyzed Conversion of N to N(SiMe) via an Fe-Hydrazido Resting State.

The catalytic conversion of N to N(SiMe) by homogeneous transition metal compounds is a rapidly developing field, yet few mechanistic details have been experimentally elucidated for 3 d element catalysts. Herein we show that Fe(PP)(N) (PP = RPCHCHPR; R = Me, 1; R = Et, 1) are highly effective for the catalytic production of N(SiMe) from N (using KC/MeSiCl), with the yields being the highest reported to date for Fe-based catalysts. We propose that N fixation proceeds via electrophilic N silylation and 1e reduction to form unstable Fe(NN-SiMe) intermediates, which disproportionate to 1 and hydrazido Fe[N-N(SiMe)] species (3); the latter act as resting states on the catalytic cycle.

Geoff Cloke at 65: a pioneer in organometallic chemistry.

Professor Geoff Cloke FRS celebrates his 65th birthday in 2018. In a career spanning four decades, his research endeavours have accounted for some of the most innovative synthetic chemistry of the modern era, with his many publications describing truly exceptional compounds and experimental methods that portray a unique chemical imagination. In addition to his scientific accomplishments, Cloke can be particularly proud of his successful mentoring, a level of dedication that propelled many students and post-docs on to become research leaders in their own right.

Trimerisation of carbon suboxide at a di-titanium centre to form a pyrone ring system.

The reaction of the -bimetallic bis(pentalene)dititanium complex Ti(μ:η,η-Pn) (Pn = CH(1,4-SiPr)) with carbon suboxide (O[double bond, length as m-dash]C[double bond, length as m-dash]C[double bond, length as m-dash]C[double bond, length as m-dash]O, CO) results in trimerisation of the latter and formation of the structurally characterised complex [{Ti(μ:η,η-Pn)}{μ-CO}]. The trimeric bridging CO unit in the latter contains a 4-pyrone core, a key feature of both the hexamer and octamer of carbon suboxide which are formed in the body from trace amounts of CO and are, for example, potent inhibitors of Na/K-ATP-ase. The mechanism of this reaction has been studied in detail by DFT computational studies, which also suggest that the reaction proceeds the initial formation of a mono-adduct of with CO.

Correction: C-H and H-H activation at a di-titanium centre.

Correction for 'C-H and H-H activation at a di-titanium centre' by Nikolaos Tsoureas et al., Chem. Commun.

C-H and H-H activation at a di-titanium centre.

The reaction of the bis(pentalene)dititanium complex Ti(μ:η,η-Pn) (Pn = CH(1,4-SiPr)) with the N-heterocyclic carbene 1,3,4,5-tetramethylimidazol-2-ylidene results in intramolecular C-H activation of one of the Pr methyl groups of a Pn ligand and formation of a "tucked-in" bridging hydride complex. The "tuck-in" process is reversed by the addition of hydrogen, which yields a dihydride featuring terminal and bridging hydrides.

Cationic silyldiazenido complexes of the Fe(diphosphine)(N) platform: structural and electronic models for an elusive first intermediate in N fixation.

The first cationic Fe silyldiazenido complexes, [Fe(PP)(NN-SiMe)][BAr] (PP = dmpe/depe), have been synthesised and thoroughly characterised. Computational studies show the compounds to be useful structural and electronic surrogates for the more elusive [Fe(PP)(NN-H)], which are postulated intermediates in the H/e mediated fixation of N by Fe(PP)(N) species.

Synthesis, Structure, and Bonding for Bis(permethylpentalene)diiron.

The synthesis of the first homoleptic double metallocene complex of iron, Fe2Pn*2 (Pn* = permethylpentalene, C8Me6) is described. The structural and electronic properties of Fe2Pn*2 have been characterized by NMR and EPR spectroscopy, single crystal X-ray diffraction, magnetic measurements, cyclic voltammetry, and DFT calculations. Fe2Pn*2 adopts a Ci symmetry in the solid state with a Fe-Fe distance of 2.

Bonding in Complexes of Bis(pentalene)dititanium, Ti(CH).

Bonding in the bis(pentalene)dititanium "double-sandwich" species TiPn (Pn = CH) and its interaction with other fragments have been investigated by density functional calculations and fragment analysis. TiPn with symmetry has two metal-metal bonds and a low-lying metal-based empty orbital, all three frontier orbitals having a symmetry. The latter may be regarded as being derived by symmetric combinations of the classic three frontier orbitals of two bent bis(cyclopentadienyl) metal fragments.

The Reductive Activation of CO Across a Ti=Ti Double Bond: Synthetic, Structural, and Mechanistic Studies.

The reactivity of the bis(pentalene)dititanium double-sandwich compound TiPn () (Pn = 1,4-{SiPr}CH) with CO is investigated in detail using spectroscopic, X-ray crystallographic, and computational studies. When the CO reaction is performed at -78 °C, the 1:1 adduct is formed, and low-temperature spectroscopic measurements are consistent with a CO molecule bound symmetrically to the two Ti centers in a μ:η,η binding mode, a structure also indicated by theory. Upon warming to room temperature the coordinated CO is quantitatively reduced over a period of minutes to give the bis(oxo)-bridged dimer and the dicarbonyl complex .

Group 9 bimetallic carbonyl permethylpentalene complexes.

We describe the synthesis, structure and bonding of the first iridium and rhodium permethylpentalene complexes, syn-[M(CO)2]2(μ:η(5):η(5)-Pn*) (M = Rh, Ir). In fact, [Ir(CO)2]2(μ:η(5):η(5)-Pn*) is the first iridium pentalene complex. An interesting preference for the isolation of the sterically more demanding syn-isomer is observed and substantiated by DFT analysis.

Polarization dependent high energy resolution X-ray absorption study of dicesium uranyl tetrachloride.

Dicesium uranyl tetrachloride (Cs2UO2Cl4) has been a model compound for experimental and theoretical studies of electronic structure of U(VI) in the form of UO2(2+) (uranyl ion) for decades. We have obtained angle-resolved electronic structure information for oriented Cs2UO2Cl4 crystal, specifically relative energies of 5f and 6d valence orbitals probed with extraordinary energy resolution by polarization dependent high energy resolution X-ray absorption near edge structure (PD-HR-XANES) and compare these with predictions from quantum chemical Amsterdam density functional theory (ADF) and ab initio real space multiple-scattering Green's function based FEFF codes. The obtained results have fundamental value but also demonstrate an experimental approach, which offers great potential to benchmark and drive improvement in theoretical calculations of electronic structures of actinide elements.

Variable photon energy photoelectron spectroscopy of tris-cyclopentadienyl lanthanides.

The gas phase photoelectron (PE) spectra of LnCp3 (Cp = η-C5H5; Ln = Pr, Nd, Sm), measured with a wide range of photon energy, are reported. Resonances observed in the photon energy regions of 4d to 4f excitation enable identification of ion states resulting from 4f ionization. For all three compounds molecular ion states characteristic of both 4f(n) and 4f(n-1) configurations are observed (Pr, n = 2; Nd, n = 3; Sm, n = 6).

Indium-bridged [1]ferrocenophanes.

Indium-bridged [1]ferrocenophanes ([1]FCPs) and [1.1]ferrocenophanes ([1.1]FCPs) were synthesized from dilithioferrocene species and indium dichlorides.

Exploring Pathways for Activation of Carbon Monoxide by Palladium Iminophosphines.

DFT calculations on palladium(II) methyl complexes incorporating P/N ligands demonstrate that CO activation in the presence of competing ligands, such as CH CN or C H , occurs through an associative mechanism involving CO/ligand exchange, followed by migratory insertion of CO into the PdMe bond. Recent investigations into the Pd coordination of CO and C H and their subsequent insertion into the PdMe bonds of complexes of the type [PdMe(iminophosphine)(NCMe)] are reported.

Bis(pentalene)di-titanium: a bent double-sandwich complex with a very short Ti-Ti bond.

The novel bimetallic bis(pentalene) complex Ti2(μ:η(5),η(5)-Pn(†))2 (Pn(†) = C8H4{Si(i)Pr3-1,4}2) has been synthesised and structurally characterised. Structural data show a Ti-Ti distance of 2.399(2) Å, consistent with a strong metal-metal interaction, which DFT calculations best describe as a double bond with σ and π components.

140 H/D isotopomers identified by long-range NMR hyperfine shifts in ruthenium(III) ammine complexes. Hyperconjugation in Ru-NH3 bonding.

(1)H NMR spectra of the paramagnetic cyanide-bridged mixed-valence compound [(η(5)-C5H5)Fe(CO)2(μ-CN)Ru(NH3)5](CF3SO3)3 (I) have been obtained in several solvents. When traces of partially deuterated water are present, instead of a single cyclopentadienyl (Cp) resonance shifted by the hyperfine interaction, numerous well-resolved resonances are observed. The spectra were simulated satisfactorily by giving the appropriate statistical weight to 140 possible H/D isotopomers formed by deuteration in the five ruthenium(III) ammine ligands.

The occurrence and representation of three-centre two-electron bonds in covalent inorganic compounds.

Although compounds that feature 3-centre 2-electron (3c-2e) bonds are well known, there has been no previous effort to classify the interactions according to the number of electrons that each atom contributes to the bond, in a manner analogous to the classification of 2-centre 2-electron (2c-2e) bonds as either normal covalent or dative covalent. This article provides an extension to the Covalent Bond Classification (CBC) method by categorizing 3c-2e interactions according to whether (i) the two electrons are provided by one or by two atoms and (ii) the central bridging atom provides two, one, or zero electrons. Class I 3c-2e bonds are defined as those in which two atoms each contribute one electron to the 3-centre orbital, while Class II 3c-2e bonds are defined as systems in which the pair of electrons are provided by a single atom.

Understanding the reactivity of strained sandwich compounds with aluminum or gallium in bridging positions: experiments and DFT calculations.

The aluminum and gallium dichlorides (Mamx)ECl(2)1a (E = Al; 82%) and 1b (E = Ga; 79%) (Mamx = 2,4-di-tert-butyl-6-[(dimethylamino)methyl]phenyl) reacted with dilithioferrocene or dilithioruthenocene to give [1]ferrocenophanes (2a, 2b) and [1]ruthenocenophanes (3a, 3b), respectively. The galla[1]ruthenocenophane 3b could be isolated from the reaction mixture through precipitation into hexane (50%), while 2a, 2b, and 3a underwent ring-opening polymerization under the reaction conditions of their formation reactions to give metallopolymers (M(w) (DLS) between 8.07 and 106 kDa).