Reversible and Irreversible Regioselective Alkyne Insertion into a Silyl-Substituted Stannylene.

A range of aryl- and alkyl- substituted alkynes has been shown to insert regio-selectively into the Sn─Si bond of the electron-rich aryl(silyl)stannylene, ArSnSi(SiMe) (Ar = 2,6-MesCH, Mes = 2,4,6-MeCH) to generate a series of vinyl-stannylene products. In all cases, the product features a syn arrangement of Sn and Si-containing groups about the resulting carbon-carbon double bond; in the case of unsymmetrical alkynes, the more sterically bulky group is exclusively incorporated in the 1-position (i.e.

A mixed isocyanide Mn(I) complex and its reduction to a metallate.

A stepwise ligand exchange starting from [Mn(CO)Br] allows the synthesis of the heteroleptic isocyanide manganese(I) complex ,-[Mn(CN-FAr)(CNBu)Br] (DArF = 3,5-(CF)CH, Bu = -butyl). Subsequent reduction gave the first heteroleptic isocyanide manganese(-1) complex, [K(18-crown-6)][Mn(CN-FAr)(CNBu)], exhibiting a five-coordinate, trigonal bipyramidal coordination sphere.

Synthesis, and Structural and Spectroscopic Analysis of Trielyl-Derived Complexes of Iron.

The reactivity of group 13 anions of the form [(NON)E] (NON=4,5-bis(2,6-diisopropylanilido)-2,7-di-tert-butyl-9,9-dimethyl-xanthene, E=Al, Ga, In) towards Fe(CO) has been investigated. In the case of the aluminyl system, both reaction outcome and product structure are highly sensitive to the availability of the potassium counterion; sequestration by 18-crown-6 is necessary to yield a species featuring a direct, unsupported Al-Fe bond. 2.

Enabling nucleophilic reactivity in molecular calcium fluoride complexes.

Calcium fluoride is the ultimate source of all fluorochemicals. Current synthetic approaches rely on the use of HF, generated from naturally occurring fluorspar and sulfuric acid. Methods for constructing E-F bonds directly from CaF have long been frustrated by its high lattice energy, low solubility and impaired fluoride ion nucleophilicity.

Mercury-Group 13 Metal Covalent Bonds: A Systematic Comparison of Aluminyl, Gallyl and Indyl Metallo-ligands.

Bimetallic compounds containing direct metal-group 13 element bonds have been shown to display unprecedented patterns of cooperative reactivity towards small molecules, which can be influenced by the identity of the group 13 element. In this context, we present here a systematic appraisal of group 13 metallo-ligands of the type [(NON)E] (NON=4,5-bis(2,6-diisopropylanilido)-2,7-di-tert-butyl-9,9-dimethylxanthene) for E=Al, Ga and In, through a comparison of structural and spectroscopic parameters associated with the trans L or X ligands in linear d complexes of the types LM{E(NON)} and XM'{E(NON)}. These studies are facilitated by convenient syntheses (from the In(I) precursor, InCp) of the potassium indyl species [{K(NON)In}⋅KCp] (1) and [(18-crown-6)KCp] [(NON)In] (1'), and lead to the first structural characterisation of Ag-In and Hg-E (E=Al, In) covalent bonds.

Bis(Aluminyl)Magnesium: A Source of Nucleophilic or Radical Aluminium-Centred Reactivity.

The homoleptic magnesium bis(aluminyl) compound Mg[Al(NON)] (NON=4,5-bis(2,6-diisopropylanilido)-2,7-di-tert-butyl-9,9-dimethylxanthene) can be accessed from K[Al(NON)] and MgI and shown to possess a non-linear geometry (∠Al-Mg-Al=164.8(1)°) primarily due to the influence of dispersion interactions. This compound acts a four-electron reservoir in the reductive de-fluorination of SF, and reacts thermally with polar substrates such as MeI via nucleophilic attack through aluminium, consistent with the QT-AIM charges calculated for the metal centres, and a formal description as a Al(I)-Mg(II)-Al(I) trimetallic.

Boryl Ancillary Ligands: Influencing Stability and Reactivity of Amidinato-Silanone and Germanone Systems in Ammonia Activation.

While the nucleophilic addition of ammonia to ketones is an archetypal reaction in classical organic chemistry, the reactivity of heavier group 14 carbonyl analogues (RE=O; E=Si, Ge, Sn, or Pb) with NH remains sparsely investigated, primarily due to the synthetic difficulties in accessing heavier ketone congeners. Herein, we present a room-temperature stable boryl-substituted amidinato-silanone {(HCDippN)B}{PhC(tBuN)}Si=O (Dipp=2,6-iPrCH) (together with its germanone analogue), formed from the corresponding silylene under a NO atmosphere. This system reacts cleanly with ammonia in 1,2-fashion to give an isolable sila-hemiaminal complex {(HCDippN)B}{PhC(tBuN)}Si(OH)(NH).

A planar per-borylated digermene.

A tetraboryl digermene synthesized by the reaction between a dianionic digermanide nucleophile and a boron halide electrophile is dimeric both in the solid state and in hydrocarbon solution. It features both a planar 'alkene-like' geometry for the GeB core, and an exceptionally short GeGe double bond. These structural features are consistent with the known electronic properties of the boryl group, and with lowest energy () fragmentation into two triplet bis(boryl)germylene fragments.

Fluorochemicals from fluorspar via a phosphate-enabled mechanochemical process that bypasses HF.

All fluorochemicals-including elemental fluorine and nucleophilic, electrophilic, and radical fluorinating reagents-are prepared from hydrogen fluoride (HF). This highly toxic and corrosive gas is produced by the reaction of acid-grade fluorspar (>97% CaF) with sulfuric acid under harsh conditions. The use of fluorspar to produce fluorochemicals via a process that bypasses HF is highly desirable but remains an unsolved problem because of the prohibitive insolubility of CaF.

Reactivity of [AuF (SIMes)]: Pathway to Unprecedented Structural Motifs.

We report on a comprehensive reactivity study starting from [AuF (SIMes)] to synthesize different motifs of monomeric gold(III) fluorides. A plethora of different ligands has been introduced in a mono-substitution yielding trans-[AuF X(SIMes)] including alkynido, cyanido, azido, and a set of perfluoroalkoxido complexes. The latter were better accomplished via use of perfluorinated carbonyl-bearing molecules, which is unprecedented in gold chemistry.

Inducing Nucleophilic Reactivity at Beryllium with an Aluminyl Ligand.

The reactions of anionic aluminium or gallium nucleophiles {K[E(NON)]} (E = Al, ; Ga, ; NON = 4,5-bis(2,6-diisopropylanilido)-2,7-di-butyl-9,9-dimethylxanthene) with beryllocene (BeCp) led to the displacement of one cyclopentadienyl ligand at beryllium and the formation of compounds containing Be-Al or Be-Ga bonds (NON)EBeCp (E = Al, ; Ga, ). The Be-Al bond in the beryllium-aluminyl complex [2.310(4) Å] is much shorter than that found in the small number of previous examples [2.

Gold Teflates Revisited: From the Lewis Superacid [Au(OTeF ) ] to the Anion [Au(OTeF ) ].

A new synthetic access to the Lewis acid [Au(OTeF ) ] and the preparation of the related, unprecedented anion [Au(OTeF ) ] with inorganic or organic cations starting from commercially available and easy-to-handle gold chlorides are presented. In this first extensive study of the Lewis acidity of a transition-metal teflate complex by using different experimental and quantum chemical methods, [Au(OTeF ) ] was classified as a Lewis superacid. The solid-state structure of the triphenylphosphine oxide adduct [Au(OPPh )(OTeF ) ] was determined, representing the first structural characterization of an adduct of this highly reactive [Au(OTeF ) ].

Synthesis of Homo-Metallic Heavier Analogues of Cyclobutene and the Cyclobutadiene Dianion.

The reduction of the boryl-substituted Sn bromide {(HCDippN) B}Sn(IPrMe)Br with 1.5 equivalents of potassium graphite leads to the generation of the cyclic tetratin tetraboryl system K [Sn {B(NDippCH) } ], a homo-metallic heavier analogue of the cyclobutadiene dianion. This system is non-aromatic as determined by Nucleus Independent Chemical Shift Calculations (NICS(0)=-0.

Disproportionation and Ligand Lability in Low Oxidation State Boryl-Tin Chemistry.

Boryltin compounds featuring the metal in the+1 or 0 oxidation states can be synthesized from the carbene-stabilized tin(II) bromide (boryl)Sn(NHC)Br (boryl={B(NDippCH) }; NHC=C{(N PrCMe) }) by the use of strong reducing agents. The formation of the mono-carbene stabilized distannyne and donor-free distannide systems (boryl)SnSn(IPrMe)(boryl) (2) and K [Sn (boryl) ] (3), using Mg(I) and K reducing agents mirrors related germanium chemistry. In contrast to their lighter congeners, however, systems of the type [Sn(boryl)] are unstable with respect to disproportionation.

Taming Heavier Group 14 Imine Analogues: Accessing Tin Nitrogen [Sn=N] Double Bonds and their Cycloaddition/Metathesis Chemistry.

A systematic study to access stable stannaimines is reported, by combining different heteroleptic stannylenes with a range of organic azides. The reactions of terphenyl-/hypersilyl-substituted stannylenes yield the putative tin nitrogen double bond, but is directly followed by 1,2-silyl migration to give Sn systems featuring bulky silylamido ligands. By contrast, the transition from a two σ donor ligand set to a mixed σ-donor/π-donor scaffold allows access to three new stannaimines which can be handled at room temperature.

Structural Snapshots in Reversible Phosphinidene Transfer: Synthetic, Structural, and Reaction Chemistry of a Sn═P Double Bond.

The reaction of amido-substituted stannylenes with phospha-Wittig reagents (MePPR) results in release of hexamethyldisilazane and tethering of the resulting -CHPMePR fragment to the tin center to give P-donor stabilized stannylenes featuring four-membered ,,, heterocycles. Through systematic increases in steric loading, the structures of these systems in the solid state can be tuned, leading to successive P-P bond lengthening and Sn-P contraction and, in the most encumbered case, to complete P-to-Sn transfer of the phosphinidene fragment. The resulting stannaphosphene features a polar Sn═P double bond as determined by structural and computational studies.

Generation of a π-Bonded Isomer of [P ] by Aluminyl Reduction of White Phosphorus and its Ammonolysis to PH.

By employing the highly reducing aluminyl complex [K{(NON)Al}] (NON=4,5-bis(2,6-diisopropylanilido)-2,7-di-tert-butyl-9,9-dimethylxanthene), we demonstrate the controlled formation of P and P complexes from white phosphorus, and chemically reversible inter-conversion between them. The tetra-anion features a unique planar π-bonded structure, with the incorporation of the K cations implicit in the use of the anionic nucleophile offering additional stabilization of the unsaturated isomer of the P fragment. This complex is extremely reactive, acting as a source of P : exposure to ammonia leads to the release of phosphine (PH ) under mild conditions (room temperature and pressure), which contrast with those necessitated for the direct combination of P and NH (>5 kbar and >250 °C).

Trifluoromethylation of [AuF (SIMes)]: Preparation and Characterization of [Au(CF ) F (SIMes)] (x=1-3) Complexes.

Trifluoromethylation of [AuF (SIMes)] with the Ruppert-Prakash reagent TMSCF in the presence of CsF yields the product series [Au(CF ) F (SIMes)] (x=1-3). The degree of trifluoromethylation is solvent dependent and the ratio of the species can be controlled by varying the stoichiometry of the reaction, as evidenced from the F NMR spectra of the corresponding reaction mixtures. The molecular structures in the solid state of trans-[Au(CF )F (SIMes)] and [Au(CF ) (SIMes)] are presented, together with a selective route for the synthesis of the latter complex.

Investigation of Molecular Alkali Tetrafluorido Aurates by Matrix-Isolation Spectroscopy.

Molecular alkali tetrafluorido aurate ion pairs M[AuF ] (M=K, Rb, Cs) are produced by co-deposition of IR laser-ablated AuF and MF in solid neon under cryogenic conditions. This method also yields molecular AuF and its dimer Au F . The products are characterized by their Au-F stretching bands and high-level quantum-chemical calculations at the CCSD(T)/triple-ζ level of theory.

Tuning the Lewis acidity of difluorido gold(iii) complexes: the synthesis of [AuClF(SIMes)] and [AuF(OTeF)(SIMes)].

The synthesis and structural characterisation of the difluorido organo gold(iii) complexes [AuClF2(SIMes)] and [AuF2(OTeF5)(SIMes)] are presented. The substitution of a fluorido ligand in [AuF3(SIMes)] by an OTeF5 group increases the Lewis acidity of the Au moiety. A scale for carbene affinities is presented, which correlates calculated and experimental values for the Lewis acidity of the metal centre in akin compounds.

Stabilization of Lewis Acidic AuF as an N-Heterocyclic Carbene Complex: Preparation and Characterization of [AuF (SIMes)].

Two different reaction routes are described to access the unprecedented trifluoridoorganogold(III) complex [AuF (SIMes)]. The compound bears the N-heterocyclic carbene SIMes (1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene) as a ligand for a molecular Lewis acidic AuF unit and was characterized by NMR spectroscopy as well as X-ray crystallography. Apart from the use of a [AuF ] salt as precursor, the strong oxidizing compound AuF can be employed neat as starting material.

Taming the High Reactivity of Gold(III) Fluoride: Fluorido Gold(III) Complexes with N-Based Ligands.

The synthesis of [NMe ][AuF ] and [NEt ][AuF ], as well as an improved one-pot synthesis of Cs[AuF ], is reported. The new [AuF ] salts were structurally characterized by single crystal X-ray diffraction, NMR spectroscopy, vibrational spectroscopy, and mass spectrometry. These salts are the first gold(III) fluoride salts that can be isolated in pure form and are convenient to be used in usual organic solvents for subsequent synthesis.