Synthesis and Characterisation of Phosphino-Aryloxide Rare Earth Complexes.

A series of homoleptic rare earth (RE) complexes bearing phosphino-aryloxide ligands (, ) has been prepared. The complexes have been characterised using multinuclear NMR and IR spectroscopy, X-ray crystallography and elemental analysis. Structural characterisation highlighted the different RE-P interactions as a result of differing Lewis acidity and ionic size across the series, hinting at the possibility of FLP-type activity.

-Silanide f-Block Complexes: Insights into Paramagnetic Influence on NMR Chemical Shifts.

The paramagnetism of f-block ions has been exploited in chiral shift reagents and magnetic resonance imaging, but these applications tend to focus on H NMR shifts as paramagnetic broadening makes less sensitive nuclei more difficult to study. Here we report a solution and solid-state (ss) Si NMR study of an isostructural series of locally -symmetric early f-block metal(III) -hypersilanide complexes, [M{Si(SiMe)}(THF)] (; M = La, Ce, Pr, Nd, U); were also characterized by single crystal and powder X-ray diffraction, EPR, ATR-IR, and UV-vis-NIR spectroscopies, SQUID magnetometry, and elemental analysis. Only one SiMe signal was observed in the Si ssNMR spectra of , while two SiMe signals were seen in solution Si NMR spectra of and .

Reactivity of Tetrel-Functionalized Heptaphosphane Clusters toward Azides.

In this work, the reactivity of tetrel-functionalized phosphorus clusters toward organoazides is probed. Clusters (MeSi)P () and (MeGe)P () were reacted with benzyl azide, phenyl azide, and 4-bromophenyl azide, and it was found that the [RN] (R = benzyl, phenyl, and 4-bromophenyl) unit from the azide inserted into the phosphorus-tetrel bonds on the cluster, accompanied by N elimination. Through control of the azide stoichiometry, the mono-, bis-, and tris-inserted products could be observed, consistent with these insertions proceeding in a stepwise manner.

Zintl Clusters as a Platform for Lewis Acid Catalysis.

Clusters of the main group elements phosphorus and arsenic, commonly categorized as Zintl clusters, have been known for over a century. And, only now is the application of these systems as catalysts for organic synthesis being investigated. In this work, boranes are tethered via an aliphatic linker to Zintl-based clusters and their Lewis acidity is examined experimentally, by the Gutmann-Beckett test and competency in the hydroborative reduction of six organic substrates, as well as computationally, by fluoride ion affinity and hydride ion affinity methods.

Zintl Ions and Phases Promote the Catalytic Hydrophosphination of Alkynes, Alkenes, and Imines.

Although Zintl ions and phases have been known for more than a century, their application as tools to build organic molecules is underdeveloped. Here, a range of Zintl ions and phases were surveyed in the hydrophosphination of alkynes, alkenes, and imines with diphenylphosphine to afford useful organophosphine products. Further investigations with diphenylphosphine in the absence of the unsaturated organic substrates revealed the formation of the diphenylphosphide anion, allowing for the conclusion that the role of the Zintl species is as an initiator in these transformations.

Comparison of group 4 and thorium M(IV) substituted cyclopentadienyl silanide complexes.

We report the synthesis and characterisation of a series of M(IV) substituted cyclopentadienyl hypersilanide complexes of the general formula [M(Cp){Si(SiMe)}(X)] (M = Hf, Th; Cp = Cp', {CH(SiMe)} or Cp'', {CH(SiMe)-1,3}; X = Cl, CH). The separate salt metathesis reactions of [M(Cp)(Cl)] (M = Zr or Hf, Cp = Cp'; M = Hf or Th, Cp = Cp'') with equimolar K{Si(SiMe)} gave the respective mono-silanide complexes [M(Cp'){Si(SiMe)}(Cl)] (M = Zr, 1; Hf, 2), [Hf(Cp'')(Cp'){Si(SiMe)}(Cl)] (3) and [Th(Cp''){Si(SiMe)}(Cl)] (4), with only a trace amount of 3 presumably formed silatropic and sigmatropic shifts; the synthesis of 1 from [Zr(Cp')(Cl)] and Li{Si(SiMe)} has been reported previously. The salt elimination reaction of 2 with one equivalent of allylmagnesium chloride gave [Hf(Cp'){Si(SiMe)}(η-CH)] (5), whilst the corresponding reaction of 2 with equimolar benzyl potassium yielded [Hf(Cp')(CHPh)] (6) together with a mixture of other products, with elimination of both KCl and K{Si(SiMe)}.

Electronic structure comparisons of isostructural early d- and f-block metal(iii) bis(cyclopentadienyl) silanide complexes.

We report the synthesis of the U(iii) bis(cyclopentadienyl) hypersilanide complex [U(Cp''){Si(SiMe)}] (Cp'' = {CH(SiMe)-1,3}), together with isostructural lanthanide and group 4 M(iii) homologues, in order to meaningfully compare metal-silicon bonding between early d- and f-block metals. All complexes were characterised by a combination of NMR, EPR, UV-vis-NIR and ATR-IR spectroscopies, single crystal X-ray diffraction, SQUID magnetometry, elemental analysis and calculations. We find that for the [M(Cp''){Si(SiMe)}] (M = Ti, Zr, La, Ce, Nd, U) series the unique anisotropy axis is conserved tangential to ; this is governed by the hypersilanide ligand for the d-block complexes to give easy plane anisotropy, whereas the easy axis is fixed by the two Cp'' ligands in f-block congeners.

Synthesis and Characterization of Yttrium Methanediide Silanide Complexes.

The salt metathesis reactions of the yttrium methanediide iodide complex [Y(BIPM)(I)(THF)] (BIPM = {C(PPhNSiMe)}) with the group 1 silanide ligand-transfer reagents MSiR (M = Na, R = BuMe or Bu; M = K, R = (SiMe)) gave the yttrium methanediide silanide complexes [Y(BIPM)(SiBuMe)(THF)] (), [Y(BIPM)(SiBu)(THF)] (), and [Y(BIPM){Si(SiMe)}(THF)] (). Complexes provide rare examples of structurally authenticated rare earth metal-silicon bonds and were characterized by single-crystal X-ray diffraction, multinuclear NMR and ATR-IR spectroscopies, and elemental analysis. Density functional theory calculations were performed on to probe their electronic structures further, revealing predominantly ionic Y-Si bonding.

Mapping boron catalysis onto a phosphorus cluster platform.

Clusters of main group elements, such as phosphorus, arsenic, germanium, and tin - called Zintl clusters - have been known for more than a century. However, their application in main group catalysis is largely unknown. Here, we tether boranes to a seven-atom phosphorus cluster ({CH}BCHCHSiMe)P (2) and we demonstrate Lewis acid catalysis as proof-of-principle that boron chemistry can be mapped onto clusters using this method.

Si NMR Spectroscopy as a Probe of s- and f-Block Metal(II)-Silanide Bond Covalency.

We report the use of Si NMR spectroscopy and DFT calculations combined to benchmark the covalency in the chemical bonding of s- and f-block metal-silicon bonds. The complexes [M(SiBu)(THF)(THF)] (: M = Mg, Ca, Yb, = 0; M = Sm, Eu, = 1) and [M(SiBuMe)(THF)(THF)] (: M = Mg, = 0; M = Ca, Sm, Eu, Yb, = 1) have been synthesized and characterized. DFT calculations and Si NMR spectroscopic analyses of and (M = Mg, Ca, Yb, No, the last due to experimental unavailability) together with known {Si(SiMe)}-, {Si(SiMeH)}-, and {SiPh}-substituted analogues provide 20 representative examples spanning five silanide ligands and four divalent metals, revealing that the metal-bound Si NMR isotropic chemical shifts, δ, span a wide (∼225 ppm) range when the metal is kept constant, and direct, linear correlations are found between δ and computed delocalization indices and quantum chemical topology interatomic exchange-correlation energies that are measures of bond covalency.

f-Element silicon and heavy tetrel chemistry.

The last three decades have seen a significant increase in the number of reports of f-element carbon chemistry, whilst the f-element chemistry of silicon, germanium, tin, and lead remain underdeveloped in comparison. Here, in this perspective we review complexes that contain chemical bonds between f-elements and silicon or the heavier tetrels since the birth of this field in 1985 to present day, with the intention of inspiring researchers to contribute to its development and explore the opportunities that it presents. For the purposes of this perspective, f-elements include lanthanides, actinides and group 3 metals.

Polarised covalent thorium(IV)- and uranium(IV)-silicon bonds.

We report the synthesis and characterisation of isostructural thorium(iv)- and uranium(iv)-silanide actinide (An) complexes, providing an opportunity to directly compare Th-Si and U-Si chemical bonds. Quantum chemical calculations show significant and surprisingly similar An%:Si%, 7s-, 6d-, and 5f-orbital contributions from both elements in polarised covalent An-Si bonds, and marginally greater covalency in the U-Si vs. Th-Si linkages.

Heteroleptic Samarium(III) Chalcogenide Complexes: Opportunities for Giant Exchange Coupling in Bridging σ- and π-Radical Lanthanide Dichalcogenides.

The introduction of (N) radicals into multinuclear lanthanide molecular magnets raised hysteresis temperatures by stimulating strong exchange coupling between spin centers. Radical ligands with larger donor atoms could promote more efficient magnetic coupling between lanthanides to provide superior magnetic properties. Here, we show that heavy chalcogens (S, Se, Te) are primed to fulfill these criteria.

Heteroleptic samarium(iii) halide complexes probed by fluorescence-detected L-edge X-ray absorption spectroscopy.

The addition of various oxidants to the near-linear Sm(ii) complex [Sm(N)] (1), where N is the bulky bis(triisopropylsilyl)amide ligand {N(SiPr)}, afforded a family of heteroleptic three-coordinate Sm(iii) halide complexes, [Sm(N)(X)] (X = F, 2-F; Cl, 2-Cl; Br, 2-Br; I, 2-I). In addition, the trinuclear cluster [{Sm(N)}(μ-I)(μ-I)] (3), which formally contains one Sm(ii) and two Sm(iii) centres, was isolated during the synthesis of 2-I. Complexes 2-X are remarkably stable towards ligand redistribution, which is often a facile process for heteroleptic complexes of smaller monodentate ligands in lanthanide chemistry, including the related bis(trimethylsilyl)amide {N(SiMe)} (N'').