Synthesis, Structure, and Bonding of Actinide-Rhenium Polyhydrides.

The synthesis of actinide tetrarhenate complexes completes a series of iridate, osmate, and rhenate polyhydrides, allowing for structural and bonding comparisons to be made. Computational studies examine the bonding interactions, particularly between metals, in these complexes. Several factors─including metal oxidation state, coordination number, and dispersion effects─affect metal-metal distances and covalency in these actinide tetrametallates.

Reduction of CS to an ethanetetrathiolate by a hydride-bridged uranium-iridium heterobimetallic complex.

We report the synthesis of a heterobimetallic U(III)-Ir species which reacts with CS to form the novel ethanetetrathiolate fragment hydride insertion and C-C coupling. Computational studies suggest the formation of a radical intermediate, which may couple with another equivalent to form the final product.

CO cleavage by tantalum/M (M = iridium, osmium) heterobimetallic complexes.

A novel Ta/Os heterobimetallic complex, [Ta(CHBu)(μ-H)OsCp*], 2, is prepared by protonolysis of Ta(CHBu)(CHBu) with Cp*OsH. Treatment of 2 and its iridium analogue [Ta(CHBu)(μ-H)IrCp*], 1, with CO under mild conditions reveal the efficient cleavage of CO, driven by the formation of a tantalum oxo species in conjunction with CO transfer to the osmium or iridium fragments, to form Cp*Ir(CO)H and Cp*Os(CO)H, respectively. This bimetallic reactivity diverges from more classical CO insertion into metal-X (X = metal, hydride, alkyl) bonds.

Photolysis-driven bond activation by thorium and uranium tetraosmate polyhydride complexes.

Transition metal multimetallic complexes have seen intense study due to their unique bonding and potential for cooperative reactivity, but actinide-transition metal (An-TM) species are far less understood. We have synthesized uranium- and thorium-osmium heterometallic polyhydride complexes in order to study An-Os bonding and investigate the reactivity of An-Os interactions. Computational studies suggest the presence of a significant bonding interaction between the actinide center and the four coordinated osmium centers supported by bridging hydrides.

π-Bonding of Group 11 Metals to a Tantalum Alkylidyne Alkyl Complex Promotes Unusual Tautomerism to Bis-alkylidene and CO to Ketenyl Transformation.

A salt metathesis synthetic strategy is used to access rare tantalum/coinage metal (Cu, Ag, Au) heterobimetallic complexes. Specifically, complex [Li(THF)][Ta(CBu)(CHBu)], , reacts with (IPr)MCl (M = Cu, Ag, Au, IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) to afford the alkylidyne-bridged species [Ta(CHBu)(μ-CBu)M(IPr)] . Interestingly, π-bonding of group 11 metals to the Ta─C moiety promotes a rare alkylidyne alkyl to bis-alkylidene tautomerism, in which compounds are in equilibrium with [Ta(CHBu)(CHBu)(μ-CHBu)M(IPr)] .

An anthropocene-framed transdisciplinary dialog at the chemistry-energy nexus.

At the energy-chemistry nexus, key molecules include carbon dioxide (CO), hydrogen (H), methane (CH), and ammonia (NH). The position of these four molecules and that of the more general family of synthetic macromolecular polymer blends (found in plastics) were cross-analyzed with the planetary boundary framework, and as part of five scientific policy roadmaps for the energy transition. According to the scenarios considered, the use of some of these molecular substances will be drastically modified in the coming years.

Highly Selective and Efficient Perdeuteration of n-Pentane via H/D Exchange Catalyzed by a Silica-Supported Hafnium-Iridium Bimetallic Complex.

A Surface OrganoMetallic Chemistry (SOMC) approach is used to prepare a novel hafnium-iridium catalyst immobilized on silica, HfIr/SiO, featuring well-defined [≡SiOHf(CH Bu)(μ-H)IrCp*] surface sites. Unlike the monometallic analogous materials Hf/SiO and Ir/SiO, which promote n-pentane deuterogenolysis through C-C bond scission, we demonstrate that under the same experimental conditions (1 bar D, 250 °C, 3 h, 0.5 mol %), the heterobimetallic catalyst HfIr/SiO is highly efficient and selective for the perdeuteration of alkanes with D, exemplified on n-pentane, without substantial deuterogenolysis (<2 % at 95 % conversion).

Cooperative activation of carbon-hydrogen bonds by heterobimetallic systems.

The direct activation of C-H bonds has been a rich and active field of organometallic chemistry for many years. Recently, incredible progress has been made and important mechanistic insights have accelerated research. In particular, the use of heterobimetallic complexes to heterolytically activate C-H bonds across the two metal centers has seen a recent surge in interest.

A versatile strategy for the formation of hydride-bridged actinide-iridium multimetallics.

Reaction of the potassium pentamethylcyclopentadienyl iridate tris-hydride K[IrCp*H] with UCl and ThCl(DME) led to the complete replacement of the halide ligands to generate multimetallic complexes U{(μ-H)IrCp*} (1) and Th{[(μ-H)(H)IrCp*][(μ-H)IrCp*]} (2), respectively. These analogues feature a significant discrepancy in hydride bonding modes; 1 contains twelve bridging hydrides while 2 contains ten bridging hydrides and two terminal, Ir-bound hydrides. Use of a U(iii) starting material, UI(1,4-dioxane), resulted in the octanuclear complex {U[(μ-H)IrCp*][(μ-H)IrCp*]} (3).

Easy preparation of small crystalline PdSn nanoparticles in solution at room temperature.

We describe here a simple protocol yielding small (<2 nm) crystalline PdSn nanoparticles (NPs) along with Pd homologues for sake of comparison. These NPs were obtained an organometallic approach using Pd(dba)·dba (dba = dibenzylideneacetone) in THF with 2 equivalents of tributyltin hydride under 4 bars of H at room temperature. The Pd NP homologues were prepared similarly, using Pd(dba)·dba with 2 equivalents of -octylsilane.

Highly dispersed silica-supported iridium and iridium-aluminium catalysts for methane activation prepared surface organometallic chemistry.

The grafting of an iridium-aluminium precursor onto silica followed by thermal treatment under H yields small (<2 nm), narrowly distributed nanoparticles used as catalysts for methane H/D exchange. This Ir-Al/SiO catalyst demonstrated enhanced catalytic performances in comparison with the monometallic Ir/SiO analogue (TOFs of 339 h 117 h respectively), highlighting the promoting effect of aluminium. TON up to 900 is obtained after 9 hours, without evidence of catalyst deactivation, and identical performances are achieved after air exposure, underlining the good robustness of both Ir-Al/SiO and Ir/SiO catalytic materials.

Mn(CO) and UV light: a promising combination for regioselective alkene hydrosilylation at low temperature.

The low temperature regioselective hydrosilylation of various alkenes with (1,1,1,3,5,5,5-heptamethyltrisiloxane) MDM is described using Mn(CO) under UV irradiation with Mn loadings as low as 1 mol%, in the absence of additives and with excellent selectivity and yields. The generation of a manganese radical allowed the anti-Markovnikov hydrosilylation products to be selectively obtained in yields up to 99%.

Rational Preparation of Well-Defined Multinuclear Iridium-Aluminum Polyhydride Clusters and Comparative Reactivity.

We report an original alkane elimination approach, entailing the protonolysis of triisobutylaluminum by the acidic hydrides from Cp*IrH. This strategy allows access to a series of well-defined tri- and tetranuclear iridium aluminum polyhydride clusters, depending on the stoichiometry: [Cp*IrHAl(Bu)] (), [Cp*IrHAl(Bu)] (), [(Cp*IrH)Al(Bu)] (), and [(Cp*IrH)Al] (). Contrary to most transition-metal aluminohydride complexes, which can be considered as [AlH] aluminates and LnM moieties, the situation here is reversed: These complexes have original structures that are best described as [Cp*IrH] iridate units surrounding cationic Al(III) fragments.

Strongly Polarized Iridium-Aluminum Pairs: Unconventional Reactivity Patterns Including CO Cooperative Reductive Cleavage.

The iridium tetrahydride complex Cp*IrH reacts with a range of isobutylaluminum derivatives of general formula Al(Bu)(OAr) ( = 1, 2) to give the unusual iridium aluminum species [Cp*IrHAl(Bu)(OAr)] () via a reductive elimination route. The Lewis acidity of the Al atom in complex is confirmed by the coordination of pyridine, leading to the adduct [Cp*IrHAl(Bu)(OAr)(Py)] (). Spectroscopic, crystallographic, and computational data support the description of these heterobimetallic complexes and as featuring strongly polarized Al(III)-Ir(III) interactions.

A family of rhodium(i) NHC chelates featuring O-containing tethers for catalytic tandem alkene isomerization-hydrosilylation.

The rhodium complex Rh(HL)(COD)Cl, 1, L being a functionalized N-heterocyclic carbene (NHC) ligand with an oxygen-containing pendant arm, has been used as the entry point to synthesize a series of neutral and cationic Rh(i) O,C chelates. While the Rh-carbene interaction is similar in all these 16-electron complexes, structural analysis reveals that the strength of the Rh-O bond is greatly affected by the nature of the O-donor: R-O > R-OH > R-OBF. These subtle changes in the nature of the O-containing tether are found to be responsible for large differences in the alkene hydrosilylation catalytic activity of these compounds: the stronger the Rh-O interaction, the better the catalytic performances.

Mechanistic investigations via DFT support the cooperative heterobimetallic C-H and O-H bond activation across Ta[double bond, length as m-dash]Ir multiple bonds.

A rare heterobimetallic oxidative addition of X-H (X = C, O) bonds is reported. DFT suggests that steric constraints around the bimetallic core play a critical role to synergistically activate C-H bonds across the two metals and thus explains the exceptional H/D exchange catalytic activity of unhindered surface organometallic Ta/Ir species observed experimentally.

Developing a Highly Active Catalytic System Based on Cobalt Nanoparticles for Terminal and Internal Alkene Hydrosilylation.

This work describes the development of easy-to-prepare cobalt nanoparticles (NPs) in solution as promising alternative catalysts for alkene hydrosilylation with the industrially relevant tertiary silane 1,1,1,3,5,5,5-heptamethyltrisiloxane (MDM). The Co NPs demonstrated high activity when used at 30 °C for 3.5-7 h in toluene, with catalyst loadings 0.

Lability of Ta-NHC adducts as a synthetic route towards heterobimetallic Ta/Rh complexes.

We report the synthesis and characterization of a series of original tantalum/rhodium heterobimetallic species assembled by a bifunctional alkoxy-N-heterocyclic carbene (NHC) ligand platform (noted L). The heterotrimetallic [Ta(CH2tBu)(CHtBu)(μ-L)Rh2(COD)2Cl2]n, 2, and heterobimetallic [Ta(μ-L)(CHtBu)(CH2tBu)2Rh(COD)Cl], 4, complexes are obtained upon treatment of [Ta(L)(CHtBu)(CH2tBu)2], 1, with [Rh(COD)Cl]2. To avoid parasistic reactivity arising from the neopentylidene fragment in 1, the peralkyl compound {Ta(L)[OSi(OtBu)3](CH2tBu)3}, 5, resulting from the 1,2-addition of tris(tertbutoxysilanol) across the Ta[double bond, length as m-dash]C alkylidene motif, is prepared.

Metal-Metal Synergy in Well-Defined Surface Tantalum-Iridium Heterobimetallic Catalysts for H/D Exchange Reactions.

A novel heterobimetallic tantalum/iridium hydrido complex, [{Ta(CHBu)}{IrH(Cp*)}] , featuring a very short metal-metal bond, has been isolated through an original alkane elimination route from Ta(CHBu)(CHBu) and Cp*IrH. This molecular precursor has been used to synthesize well-defined silica-supported low-coordinate heterobimetallic hydrido species [≡SiOTa(CHBu){IrH(Cp*)}], , and [≡SiOTa(CHBu)H{IrH(Cp*)}], , using a surface organometallic chemistry (SOMC) approach. The SOMC methodology prevents undesired dimerization as encountered in solution and leading to a tetranuclear species [{Ta(CHBu)}(Cp*IrH)], .

Direct Synthesis of Cycloalkanes from Diols and Secondary Alcohols or Ketones Using a Homogeneous Manganese Catalyst.

A method for the synthesis of substituted cycloalkanes was developed using diols and secondary alcohols or ketones via a cascade hydrogen borrowing sequence. A non-noble and air-stable manganese catalyst (2 mol %) was used to perform this transformation. Various substituted 1,5-pentanediols (3-4 equiv) and substituted secondary alcohols (1 equiv) were investigated to prepare a collection of substituted cyclohexanes in a diastereoselective fashion.

Electrocatalytic Performance of Titania Nanotube Arrays Coated with MoS by ALD toward the Hydrogen Evolution Reaction.

The electrochemical splitting of water provides an elegant way to store renewable energy, but it is limited by the cost of the noble metals used as catalysts. Among the catalysts used for the reduction of water to hydrogen, MoS has been identified as one of the most promising materials as it can be engineered to provide not only a large surface area but also an abundance of unsaturated and reactive coordination sites. Using Mo[NMe] and HS as precursors, a desired thickness of amorphous MoS can be deposited on TiO nanotubes by atomic layer deposition.

On the alcoholysis of alkyl-aluminum(iii) alkoxy-NHC derivatives: reactivity of the Al-carbene Lewis pair versus Al-alkyl.

The reaction of a bifunctional hydroxy N-heterocyclic carbene (NHC-OH) ligand with alkyl-aluminum(iii) derivatives appears to be dependent on the precursor used. The expected alkoxy-NHC metallated product is indeed obtained with Al(Bu). In contrast, the sterically hindered [Al(Bu)(OAr)] (OAr = 2,6-di-tert-butyl-4-methylphenoxy) displays reactivity at the carbene and affords an imidazolium-aluminate zwitterion.

Early/Late Heterobimetallic Tantalum/Rhodium Species Assembled Through a Novel Bifunctional NHC-OH Ligand.

The straightforward synthesis of a new unsymmetrical hydroxy-tethered N-heterocyclic carbene (NHC) ligand, HL, is presented. The free ligand exhibits an unusual OH-carbene hydrogen-bonding interaction. This OH-carbene motif was used to yield 1) the first tantalum complex displaying both a Fischer- and Schrock-type carbene ligand and 2) a unique NHC-based early/late heterobimetallic complex.

A versatile route to homo- and hetero-bimetallic 5f-5f and 3d-5f complexes supported by a redox active ligand framework.

The salt-elimination reaction of the complex [NaU(bis-salophen)] with metal halides provides an entry to the synthesis of well-defined homobimetallic uranium-uranium and rare heterobimetallic uranium-cobalt and uranium-nickel complexes supported by a redox-active dinucleating ligand.

On the non-innocence of "Nacnacs": ligand-based reactivity in β-diketiminate supported coordination compounds.

While β-diketiminate (BDI or 'nacnac') ligands have been widely adopted to stabilize a wide range of metal ions in multiple oxidation states and coordination numbers, in several occurrences these ligands do not behave as spectators and participate in reactivity. Besides unwanted decomposition processes, BDI redox non-innnocence and unusual metal-ligand cooperative activation of substrates yielding attractive reactivity have been reported. This feature article will provide a comprehensive analysis of the various transformations involving BDI ligand platforms in coordination compounds across the periodic table.