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[{SiN Dipp }BeClM] 2 ({SiN Dipp } = {CH 2 SiMe 2 N(Dipp)} 2 ; M = Li, Na, K, Rb) are converted to ionic species by treatment with a crown ether. Whereas the lithium derivative reacts with Na or K to provide [{SiN Dipp }BeCl] - [M(12-cr-4) 2 ] + (M = Na, K), the resultant sodium species is resistant to reduction by potassium. These observations are rationalised by a hybrid experimental/theoretical analysis.

The dimeric β-diketiminato calcium hydride, [(BDI)CaH] 2 (BDI = HC{(Me)CN-2,6- i Pr 2 C 6 H 3 } 2 ), reacts with ZnMe 2 to afford the bimetallic calcium zincate complex, [(BDI)Ca(μ-CH 3 ) 2 Zn(μ-H)] 2 , which subsequently undergoes an intramolecular reaction to effect the formation of [(BDI)CaMe] 2 , a notable omission from the homologous series of β-diketiminato alkylcalcium derivatives.

Reduction of [Mg(NON)] 2 ([NON] 2- = [O(SiMe 2 NDipp) 2 ] 2- , Dipp = 2,6-iPr 2 C 6 H 3 ) affords Mg(I) species containing NON- and NNO-ligands ([NNO] 2- = [N(Dipp)SiMe 2 N(Dipp)SiMe 2 O] 2- ). The products of reactions with iPrNCNiPr and CO are consistent with the presence of reducing Mg(I) centres. Extraction with THF affords [K(THF) 2 ] 2 [(NNO)Mg-Mg(NNO)] with a structurally characterised Mg-Mg bond that was examined using density functional theory.

The hypercoordinate [SiH 6 ] 2- anion is not stable in solution. Here, we report the room temperature, solution stable molecular [SiH 6 ] 2- complex, [{KCa(NON)(OEt 2 )} 2 ][SiH 6 ] (NON=4,5-bis(2,6-diisopropylanilido)-2,7-di-tert-butyl-9,9-dimethyl-xanthene)), where the [SiH 6 ] 2- anion is stabilised within a supramolecular assembly that mimics the solid-state environment of the anion in the lattice of K 2 SiH 6 . Solution-state reactivity of the complex towards carbon monoxide, benzaldehyde, azobenzene and acetonitrile is reported, yielding a range of reduction and C-C coupled products., (© 2024 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Reactions of β-diketiminato alkaline earth alkyldiboranate derivatives [(BDI)Ae{pinBB(R)pin}] (BDI = HC{(Me)CNDipp} 2 ; Dipp = 2,6-i-Pr 2 C 6 H 3 ; Ae = Mg, R = n -Bu or Ae = Ca, R = n -hexyl) with t -BuNC provide access to the respective group 2 derivatives of unprecedented diborata-allyl, {(pinB) 2 CNBpin( t -Bu)} - , anions. Although the necessary mode of B-C bond cleavage implicated in these transformations could not be elucidated, further studies of the reactivity of magnesium triboranates toward isonitriles delivered a more general and rational synthetic access to analogous anionic moieties. Extending this latter reactivity to a less symmetric triboranate variant also provided an isomeric Mg-C-bonded dibora-alkyl species and sufficient experimental insight to prompt theoretical evaluation of this reactivity. DFT calculations, thus, support a reaction pathway predicated on initial RNC attack at a peripheral boron centre and the intermediacy of such dibora-alkyl intermediates., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The bimetallic species, [{SiN Dipp }MgNa] 2 [{SiN Dipp } = {CH 2 SiMe 2 N(Dipp)} 2 ; (Dipp = 2,6- i -Pr 2 C 6 H 3 )], is shown to be a potent reducing agent, able to effect one- or two-electron reduction of either dioxygen, TEMPO, anthracene, benzophenone, or diphenylacetylene. In most cases, the bimetallic reaction products imply that the dissimilar alkaline metal centers react with a level of cooperativity. EPR analysis of the benzophenone-derived reaction and the concurrent isolation of [{SiN Dipp }Mg(OCPh 2 ) 2 ], however, illustrate that treatment with such reducible, but O -basic, species can also result in reactivity in which the metals provide independent reaction products. The notable E -stereochemistry of the diphenylacetylene reduction product prompted a computational investigation of the PhC≡CPh addition. This analysis invokes a series of elementary steps that necessitate ring-opening via Mg + → Na + amido group migration of the SiN Dipp ligand, providing insight into the previously observed lability of the bidentate dianion and its consequent proclivity toward macrocyclization., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

The application of Mg[Ph 4 Pn] (L = 1,5-cyclooctadiene, norbornadiene, ethylene; Li·K[Ph 4 Pn] in transmetalation reactions to a range of Rh(I) precursors led to the formation of "half-baguette" anti -[Rh I (L) n ] 2 [μ:η 5 :η 5 Ph 4 Pn] (L = 1,5-cyclooctadiene, norbornadiene, ethylene; n = 1, 2) and syn -[Rh I (CO) 2 ] 2 [μ:η 5 :η 5 Ph 4 Pn] complexes as well as the related iridium complex anti -[Ir I (COD)] 2 [μ:η 5 :η 5 Ph 4 Pn] . With CO exclusive syn metalation was obtained even when using mono-nuclear Rh(I) precursors, indicating an electronic preference for syn metalation. DFT analysis showed this to be the result of π overlap between the adjacent M(CO) 2 units which overcompensates for d z 2 repulsion of the metals, an effect which can be overridden by steric clash of the auxiliary ligands to yield anti -configuration as seen in the larger olefin complexes. syn -[Rh I (CO) 2 ] 2 [μ:η 5 :η 5 Ph 4 Pn] is a rare example of a twinned organometallic where the two metals are held flexibly in close proximity, but the two d 8 Rh(I) centres did not show signs of M-M bonding interactions or exhibit Lewis basic behaviour as in some related mono-nuclear Cp complexes due to the acceptor properties of the ligands. The ligand substitution chemistry of syn -[Rh I (CO) 2 ] 2 [μ:η 5 :η 5 Ph 4 Pn] was investigated with a series of electronically and sterically diverse donor ligands (P(OPh) 3 , P(OMe) 3 , PPh 3 , PMe 3 , dppe) yielding new mono- and bis-substituted complexes, with E-syn -[Rh I (CO)(P{OR}) 3 ] 2 [μ:η 5 :η 5 Ph 4 Pn] (R = Me, Ph) characterised by XRD.

The aluminacyclopropane K[Al(NON)(η-C 2 H 4 )] ([NON] 2- = [O(SiMe 2 NDipp) 2 ] 2- , Dipp = 2,6-iPr 2 C 6 H 3 ) reacts with CO 2 and iPrNCNiPr to afford ring-expanded products of C-C bond formation. The latter system undergoes a 1,3-silyl retro-Brook rearrangement of the NON-group, to afford the [NNO] 2- ligand ([NNO] 2- = [N(Dipp)SiMe 2 N(Dipp)SiMe 2 O] 2- ). The mechanism of transformation was examined by density functional theory (DFT).

A simple sequential addition protocol for the reductive coupling of ketones and aldehydes by a potassium aluminyl grants access to unsymmetrical pinacolate derivatives. Isolation of an aluminium ketyl complex presents evidence for the accessibility of radical species. Product release from the aluminium centre was achieved using an iodosilane, forming the disilylated 1,2-diol and a neutral aluminium iodide, thereby demonstrating the steps required to generate a closed synthetic cycle for pinacol (cross) coupling at an aluminyl anion., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

The reaction of 9-diazo-9H-fluorene (fluN 2 ) with the potassium aluminyl K[Al(NON)] ([NON] 2- =[O(SiMe 2 NDipp) 2 ] 2- , Dipp=2,6-iPr 2 C 6 H 3 ) affords K[Al(NON)(κN 1 ,N 3 -{(fluN 2 ) 2 })] (1). Structural analysis shows a near planar 1,4-di(9H-fluoren-9-ylidene)tetraazadiide ligand that chelates to the aluminium. The thermally induced elimination of dinitrogen from 1 affords the neutral aluminium ketimide complex, Al(NON)(N=flu)(THF) (2) and the 1,2-di(9H-fluoren-9-yl)diazene dianion as the potassium salt, [K 2 (THF) 3 ][fluN=Nflu] (3). The reaction of 2 with N,N'-diisopropylcarbodiimide (iPrN=C=NiPr) affords the aluminium guanidinate complex, Al(NON){N(iPr)C(N=CMe 2 )N(CHflu)} (4), showing a rare example of reactivity at a metal ketimide ligand. Density functional theory (DFT) calculations have been used to examine the bonding in the newly formed [(fluN 2 ) 2 ] 2- ligand in 1 and the ketimide bonding in 2. The mechanism leading to the formation of 4 has also been studied using this technique., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Counter to synthetic convention and expectation provided by the relevant standard reduction potentials, the chloroberyllate, [{SiN Dipp }BeClLi] 2 [{SiN Dipp } = {CH 2 SiMe 2 N(Dipp)} 2 ; Dipp = 2,6-i-Pr 2 C 6 H 3 )], reacts with the group 1 elements (M = Na, K, Rb, Cs) to provide the respective heavier alkali metal analogues, [{SiN Dipp }BeClM] 2 , through selective reduction of the Li + cation. Whereas only [{SiN Dipp }BeClRb] 2 is amenable to reduction by potassium to its nearest lighter congener, these species may also be sequentially interconverted by treatment of [{SiN Dipp }BeClM] 2 by the successively heavier group 1 metal. A theoretical analysis combining density functional theory (DFT) with elemental thermochemistry is used to rationalise these observations, where consideration of the relevant enthalpies of atomisation of each alkali metal in its bulk metallic form proved crucial in accounting for experimental observations., (© 2023. The Author(s).)

The study of sub-valent Group 2 chemistry is a relatively new research field, being established in 2007 with the report of the first Mg(I) dimers. These species are stabilized by the formation of a Mg-Mg covalent bond; however, the extension of this chemistry to heavier alkaline earth (AE) metals has been frustrated by significant synthetic challenges, primarily associated with the instability of heavy AE-AE interactions. Here we present a new blueprint for the stabilization of heavy AE(I) complexes, based upon the reduction of AE(II) precursors with planar coordination geometries. We report the synthesis and structural characterisation of homoleptic trigonal planar AE(II) complexes of the monodentate amides {N(SiMe 3 ) 2 } - and {N(Mes)(SiMe 3 )} - . DFT calculations showed that the LUMOs of these complexes all show some d-character for AE = Ca-Ba. DFT analysis of the square planar Sr(II) complex [Sr{N(SiMe 3 ) 2 }(dioxane) 2 ] ∞ revealed analogous frontier orbital d-character. AE(I) complexes that could be accessed by reduction of these AE(II) precursors were modelled computationally, revealing exergonic formation in all cases. Crucially, NBO calculations show that some d-character is preserved in the SOMO of theoretical AE(I) products upon reduction, showing that d-orbitals could play a crucial role in achieving stable heavy AE(I) complexes., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Like the previously reported potassium-based system, rubidium and cesium reduction of [{SiN Dipp }AlI] ({SiN Dipp } = {CH 2 SiMe 2 NDipp} 2 ) with the heavier alkali metals [M = Rb and Cs] provides dimeric group 1 alumanyl derivatives, [{SiN Dipp }AlM] 2 . In contrast, similar treatment with sodium results in over-reduction and incorporation of a formal equivalent of [{SiN Dipp }Na 2 ] into the resultant sodium alumanyl species. The dimeric K, Rb, and Cs compounds display a variable efficacy toward the C-H oxidative addition of arene C-H bonds at elevated temperatures (Cs > Rb > K, 110 °C) to yield (hydrido)(organo)aluminate species. Consistent with the synthetic experimental observations, computational (DFT) assessment of the benzene C-H activation indicates that rate-determining attack of the Al(I) nucleophile within the dimeric species is facilitated by π-engagement of the arene with the electrophilic M + cation, which becomes increasingly favorable as group 1 is descended., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

We disclose herein our detailed investigation into the Barton copper-promoted C3-arylation of indoles using triarylbismuth bis(trifluoroacetates). The arylation of unsubstituted 1H-indole using Barton's conditions gave a low yield of the C3-arylated indole, along with small amounts of the product of double C2/C3-arylation and traces of the product of C2 arylation. On the contrary, the arylation of indoles blocked at the C2 position is highly efficient, affording the desired products of C3-arylation in good to excellent yields. The reaction operates under simple conditions, shows good substrate scope, excellent functional group compatibility, and allows the transfer of electron-neutral or deficient aryl groups. Computational studies propose a mechanism involving a trifluoroacetate-assisted C-H activation step., (© 2023 The Authors. ChemPlusChem published by Wiley-VCH GmbH.)

We report the reaction of the potassium aluminyl, K[Al(NON)] ([NON] 2- = [O(SiMe 2 NDipp) 2 ] 2- , Dipp = 2,6-iPr 2 C 6 H 3 ) with a series of isocyanide substrates (R-NC). In the case of t Bu-NC, degradation of the isocyanide was observed generating an isomeric mixture of the corresponding aluminium cyanido-κ C and -κ N compounds, K[Al(NON)(H)(CN)]/K[Al(NON)(H)(NC)]. The reaction with 2,6-dimethylphenyl isocyanide (Dmp-NC), gave a C 3 -homologation product, which in addition to C-C bond formation showed dearomatisation of one of the aromatic substituents. In contrast, using adamantyl isocyanide Ad-NC allowed both the C 2 - and C 3 -homologation products to be isolated, allowing a degree of control to be exercised over the chain growth process. These data also show that the reaction proceeds through a stepwise addition, supported in this study by the synthesis of the mixed [(Ad-NC) 2 (Dmp-NC)] 2- product. Computational analysis of the bonding within the homologised products confirm a high degree of multiple bond character in the exocyclic ketenimine units of the C 2 - and C 3 -products. In addition, the mechanism of chain growth was investigated, identifying different possible pathways leading to the observed products, and highlighting the importance of the potassium cation in formation of the initial C 2 -chain., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

[{SiN Dipp }MgNa] 2 ({SiN Dipp } = {CH 2 SiMe 2 N(Dipp)} 2 ; Dipp = 2,6-i-Pr 2 C 6 H 3 ) reacts directly with H 2 to provide a heterobimetallic hydride. Although the transformation is complicated by the simultaneous disproportionation of magnesium, computational density functional theory (DFT) studies suggest that this reactivity is initiated by orbitally-constrained and interactions between the frontier MOs of both H 2 and the tetrametallic core of [{SiN Dipp }MgNa] 2 .

Organosodium chemistry is underdeveloped compared with organolithium chemistry, and all the reported organosodium complexes exhibit similar, if not identical, reactivity patterns to their lithium counterparts. Herein, we report a rare organosodium monomeric complex, namely, [Na(CH 2 SiMe 3 )(Me 6 Tren)] ( 1 -Na) (Me 6 Tren: tris[2-(dimethylamino)ethyl]amine) stabilized by a tetra -dentate neutral amine ligand Me 6 Tren. Employing organo-carbonyl substrates (ketones, aldehydes, amides, ester), we demonstrated that 1 -Na features distinct reactivity patterns compared with its lithium counterpart, [Li(CH 2 SiMe 3 )(Me 6 Tren)] ( 1 -Li). Based on this knowledge, we further developed a ligand-catalysis strategy to conduct ketone/aldehyde methylenations, using [NaCH 2 SiMe 3 ] ∞ as the CH 2 feedstock, replacing the widely used but hazardous/expensive C═O methylenation methods, such as Wittig, Tebbe, Julia/Julia-Kocieński, Peterson, and so on.

The copper(i) alumanyl derivative, [{SiN Dipp }Al-Cu(NHC iPr )] (SiN Dipp = {CH 2 SiMe 2 NDipp} 2 ; Dipp = 2,6-di-isopropylphenyl; NHC iPr = N , N '-di-isopropyl-4,5-dimethyl-2-ylidene), reacts in a stepwise fashion with up to three equivalents of various terminal alkynes. This reactivity results in the sequential formation of cuprous (hydrido)(alkynyl)aluminate, (alkenyl)(alkynyl)aluminate and bis(alkynyl)aluminate derivatives, examples of which have been fully characterised. The process of alkene liberation resulting from the latter reaction step constitutes a unique case of alkyne transfer semi-hydrogenation in which the C-H acidic alkyne itself acts as a source of proton, with the Cu-Al bond providing the requisite electrons to effect reduction. This reaction sequence is validated by DFT calculations, which rationalise the variable stability of the initially formed heterobimetallic hydrides., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Analogous to the ubiquitous alkoxide ligand, metal boroxide and boryloxy complexes are an underexplored class of hard anionic O - ligand. A new series of amine-stabilized Li, Sn(II), and Zn boryloxy complexes, comprising electron-rich tetrahedral boron centers have been synthesized and characterized. All complexes have been characterized by one-dimensional (1D), two-dimensional (2D), and DOSY NMR, which are consistent with the solid-state structures unambiguously determined via single-crystal X-ray diffraction. Electron-rich μ 2 - (Sn and Zn) and μ 3 - (Li) boryloxy binding modes are observed. Compounds 6 - 9 are the first complexes of this class, with the chelating bis- and tris-phenol ligands providing a scaffold that can be easily functionalized and provides access to the boronic acid pro-ligand, hence allowing facile direct synthesis of the resulting compounds. Computational quantum chemical studies suggest a significant enhancement of the π-donor ability of the amine-stabilized boryloxy ligand because of electron donation from the amine functionality into the p-orbital of the boron atom.

Ionic compounds containing sodium cations are notable for their stability and resistance to redox reactivity unless highly reducing electrical potentials are applied. Here we report that treatment of a low oxidation state {Mg 2 Na 2 } species with non-reducible organic bases induces the spontaneous and completely selective extrusion of sodium metal and oxidation of the Mg I centers to the more conventional Mg II state. Although these processes are also characterized by a structural reorganisation of the initially chelated diamide spectator ligand, computational quantum chemical studies indicate that intramolecular electron transfer is abetted by the frontier molecular orbitals (HOMO/LUMO) of the {Mg 2 Na 2 } ensemble, which arise exclusively from the 3s valence atomic orbitals of the constituent sodium and magnesium atoms., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Treatment of [Ru(PPh 3 )(C 6 H 4 PPh 2 ) 2 H][Li(THF) 2 ] with AlMe 2 Cl and SnMe 3 Cl leads to elimination of LiCl and CH 4 and formation of the heterobimetallic complexes [Ru(C 6 H 4 PPh 2 ) 2 {PPh 2 C 6 H 4 AlMe(THF)}H] 5 and [Ru(PPh 3 )(C 6 H 4 PPh 2 )(PPh 2 C 6 H 4 SnMe 2 )] 6 , respectively. The pathways to 5 and 6 have been probed by variable temperature NMR studies, together with input from DFT calculations. Complete reaction of H 2 occurs with 5 at 60 °C and with 6 at room temperature to yield the spectroscopically characterized trihydride complexes [Ru(PPh 2 ) 2 {PPh 2 C 6 H 4 AlMe}H 3 ] 7 and [Ru(PPh 2 ) 2 {PPh 2 C 6 H 4 SnMe 2 }H 3 ] 8 . In the presence of CO, 6 forms the acylated phosphine complex, [Ru(CO) 2 (C(O)C 6 H 4 PPh 2 )(PPh 2 C 6 H 4 SnMe 2 )] 9 , through a series of intermediates that were identified by NMR spectroscopy in conjunction with 13 CO labeling. Complex 6 undergoes addition and substitution reactions with the N-heterocyclic carbene 1,3,4,5-tetramethylimidazol-2-ylidene (IMe 4 ) to give [Ru(IMe 4 ) 2 (PPh 2 C 6 H 4 )(PPh 2 C 6 H 4 SnMe 2 )] 10 , which converted via rare N-Me group C-H activation to [Ru(IMe 4 )(PPh 3 )(IMe 4 )'(PPh 2 C 6 H 4 SnMe 2 )] 11 upon heating at 60 °C and to a mixture of [Ru(IMe 4 ) 2 (IMe 4 )'(PPh 2 C 6 H 4 SnMe 2 )] 12 and [Ru(PPh 3 )(PPh 2 C 6 H 4 )(IMe 4 -SnMe 2 )'] 13 at 120 °C., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

The reaction of compounds containing Al-Mg and Al-Zn bonds with N 2 O enabled isolation of the corresponding Al(μ-O)M complexes. Electronic structure analysis identified largely ionic Al-O and O-M bonds, featuring an anionic μ-oxo centre. Reaction with CO 2 confirmed that these species correspond to the proposed intermediates in the formation of μ-carbonate compounds.

Thermolysis of a 1,3-dioxa-2-phospholane supported by the terphenyl ligand Ar iPr4 (Ar iPr4 =[C 6 H 3 -2,6-(C 6 H 3 -2,6-iPr 2 )]) at 150 °C gives [Ar iPr4 PO 2 ] 2 via loss of ethene. [Ar iPr4 PO 2 ] 2 was characterised by X-ray crystallography and NMR spectroscopy; it contains a 4-membered P-O-P-O ring and is the isostructural oxygen analogue of Lawesson's and Woollins' reagents. The dimeric structure of [Ar iPr4 PO 2 ] 2 was found to persist in solution through VT NMR spectroscopy and DOSY, supported by DFT calculations. The addition of DMAP to the 1,3-dioxa-2-phospholane facilitates the loss of ethene to give Ar iPr4 (DMAP)PO 2 after days at room temperature, with this product also characterised by X-ray crystallography and NMR spectroscopy. Replacement of the DMAP with pyridine induces ethene loss from the 1,3-dioxa-2-phospholane to provide gram-scale samples of [Ar iPr4 PO 2 ] 2 in 75 % yield in 2 days at only 100 °C., (© 2022 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Multiply-bonded main group metal compounds are of interest as a new class of reactive species able to activate and functionalize a wide range of substrates. The aluminium sulfido compound K[Al(NON Dipp )(S)] (NON Dipp = [O(SiMe 2 NDipp) 2 ] 2- , Dipp = 2,6- i Pr 2 C 6 H 3 ), completing the series of [Al(NON Dipp )(E)] - anions containing Al-E{16} multiple bonds (E{16} = O, S, Se, Te), was accessed via desulfurisation of K[Al(NON Dipp )(S 4 )] using triphenylphosphane. The crystal structure showed a tetrameric aggregate joined by multiple K⋯S and K⋯π(arene) interactions that were disrupted by the addition of 2.2.2-cryptand to form the separated ion pair, [K(2.2.2-crypt)][Al(NON Dipp )(S)]. Analysis of the anion using density functional theory (DFT) confirmed multiple-bond character in the Al-S group. The reaction of the sulfido and selenido anions K[Al(NON Dipp )(E)] (E = S, Se) with CO 2 afforded K[Al(NON Dipp )(κ 2 E , O -EC{O}O)] containing the thio- and seleno-carbonate groups respectively, consistent with a [2 + 2]-cycloaddition reaction and C-E bond formation. An analogous cycloaddition reaction took place with benzophenone affording compounds containing the diphenylsulfido- and diphenylselenido-methanolate ligands, [κ 2 E , O -EC{O}Ph 2 ] 2- . In contrast, when K[Al(NON Dipp )(E)] (E = S, Se) was reacted with benzaldehyde, two equivalents of substrate were incorporated into the product accompanied by formation of a second C-E bond and complete cleavage of the Al-E{16} bonds. The products contained the hitherto unknown κ 2 O , O -thio- and κ 2 O , O -seleno-bis(phenylmethanolate) ligands, which were exclusively isolated as the cis -stereoisomers. The mechanisms of these cycloaddition reactions were investigated using DFT methods., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The stoichiometric reactivity of a β-diketiminato (BDI) magnesium silanide towards a variety of organic isocyanates has been assessed. While the primary outcome of reactions of t -BuNCO, DippNCO and CyNCO was the production of β-diketiminato magnesium siloxide adducts of the isonitrile resulting from isocyanate deoxygenation, analogous treatment with i -PrNCO led to multiple products, four of which have been positively identified. Although the specificity of this latter reaction was hampered by competitive isocycanate addition at the γ-methine carbon of the BDI supporting ligand, the identification of [{ i -PrNCO}CH{(Me)CNDipp}Mg{Me 2 PhSi}C(O)N i -Pr] 6 provided corroborative evidence for the likely generation of sila-amidate intermediates in all four reactions under study. The formation of [{Me 2 PhSi}C(O)NR] - anions as the most likely initial species formed en route to isonitrile and siloxide formation was, therefore, validated by a computational density functional theory (DFT) study.

We report the [Al(NON Dipp )(Te)(THF)] - anion containing a terminal aluminium telluride bond. DFT calculations confirm appreciable Al-Te multiple bond character and reaction with CO 2 proceeds via a double insertion to afford the previously unknown tellurodicarbonate ligand.

Oxoborane carbamate and carboxylate analogues result from the in situ trapping of [BO 2 ] - produced by elimination of 2,3-dimethyl-2-butene from a pinacolatoboryl anion., (© 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

The reaction of diphenyltin dihydride with LiAlH4 gives access to a set of charged tin cages as their lithium salts. Variation in the ratio of reactants provides a perstannabicyclooctane dianion and a perstannanorbornane as the di- and monoanions. These compounds can be synthesised selectively by careful stoichiometric control and have been characterised by single crystal X-ray diffractometry, NMR and UV-vis spectroscopy. Computational exploration of the electronic structures of these compounds was undertaken and, in agreement with structural and spectroscopic features, indicated significant σ-delocalisation in the tin skeletons.

Reaction of a magnesium diboranate complex with triphenylphosphine oxide provides a terminal magnesium boryl, which is itself a potent reagent for the deoxygenative reduction of Ph 3 PO. Computational analysis with density functional theory (DFT) indicates that B-B bond activation results from initial coordination of the P[double bond, length as m-dash]O bond of the phosphine oxide to magnesium.

Reactions of the β-diketiminato magnesium diboranate derivative, [(BDI)Mg{pinB( n -Bu)Bpin}] (BDI = HC{(Me)CNDipp} 2 ; Dipp = 2,6-i-Pr 2 C 6 H 3 ), with N , N '-dialkyl and N , N '-diaryl carbodiimides provided the corresponding C-borylated magnesium borylamidinates. This reactivity occurs with the displacement of n -BuBpin and with the apparent addition of a nucleophilic {Bpin} anion to the electrophilic unsaturated carbodiimide carbon centres. In contrast, while analogous reactions of [(BDI)Mg{pinB( n -Bu)Bpin}] with N -alkyl or N -aryl aldimines and ketimines also resulted in facile displacement of n -BuBpin, they provided the organomagnesium products of {Bpin} addition to the imine nitrogen atom rather than the more electrophilic trigonal imine carbon. Computational assessment by density functional theory (DFT) indicated that, although the energetic differences are marginal, the organomagnesium products may be considered as the kinetic outcome of these reactions with respect to the generation of alternative amidomagnesium regioisomers. This latter deduction was borne out by the thermally-induced conversion of two such organomagnesium species to their C-borylated amidomagnesium isomers, both of which occur with negligible entropies of activation indicative of purely intramolecular processes. Detailed analysis by DFT of the reaction of [(BDI)Mg{pinB( n -Bu)Bpin}] with PhN[double bond, length as m-dash]CHPh indicated that B-N bond formation is initiated by attack of the imine nitrogen at the three-coordinate boron atom of the diboranate anion rather than the more crowded magnesium centre. Consistent with an effectively spontaneous reaction, the resultant cleavage of the B-B bond of the diboranate unit is accomplished via the traversal of two very modest barriers of only 8.3 and 6.7 kcal mol -1 . This analysis was also supportive of a subsequent intramolecular B-N to B-C isomerisation process. Of greater general significance, however, the addition of the {Bpin} - anion to the reducible aldimine is best rationalised as a consequence of the electrophilic character of this three-coordinate boron centre rather than any intrinsic nucleophilicity associated with the B-B bond of the [pinBB( n -Bu)pin] - anion., (This journal is © The Royal Society of Chemistry 2019.)

Reactions of a magnesium-based pinacolatoboryl nucleophile with the electrophilic organoboranes, 9-BBN and Ph 3 B, provide facile B-B' single bond formation. Although the Ph 3 B derivative is thermally stable, when heated, the unsymmetrical diborane(5) anion derived from 9-BBN is found to isomerize to two regioisomeric species via a proposed mechanism involving dehydroboration of the borabicyclo[3.3.1]nonane and syn-diboration of the resultant alkenyl carbocycle., (© 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

The para-selective C-H alkylation of aniline derivatives furnished with a pyrimidine auxiliary is herein reported. This reaction is proposed to take place via an N-H-activated cyclometalate formed in situ. Experimental and DFT mechanistic studies elucidate a dual role of the ruthenium catalyst. Here the ruthenium catalyst can undergo cyclometalation by N-H metalation (as opposed to C-H metalation in meta-selective processes) and form a redox active ruthenium species, to enable site-selective radical addition at the para position., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)