Utilisation of a lithium boryl as a reducing agent in low oxidation state group 15 chemistry: synthesis and characterisation of an amido-distibene and a boryl-dibismuthene

Carbodiphosphorane-Activated Distibene and Dibismuthene Dications

Low-valent antimony and bismuth have emerged as novel platforms for achieving reversible small-molecule activation at main-group metals. Although various examples of oxidative addition reactions at monomeric Sb(I) and Bi(I) have been reported, the chemistry of the heavy group 15 Sb(I)═Sb(I)/Bi(I)═Bi(I) double bonds toward small molecules remains largely unexplored. In this study, we present a straightforward synthesis of distibene and dibismuthene dications coordinated with a neutral carbodiphosphorane (CDP) ligand. The nonbonding interactions between the occupied p-orbital at the CDP ligand and the π-bonding orbital of the Sb═Sb/Bi═Bi bonds yield compounds with exceptionally small HOMO-LUMO gaps. In addition, the reduction of steric hindrance compared to known neutral derivatives stabilized with bulky aryl groups allows for better accessibility of the double bonds. This high reactivity is demonstrated in the oxidative addition of distibene to diphenyldisulfide as well as in [2+2] cycloadditions to alkynes. Additionally, the Sb═Sb bond reversibly adds to 2,3-dimethylbutadiene in a [4+2] cycloaddition reaction.

Synthesis of bismuthanyl-substituted monomeric triel hydrides

The syntheses and characterizations of the first bismuthanylborane monomers stabilized only by a donor in D·BH2Bi(SiMe3)2 (D = DMAP 1a, IDipp 1b, IMe41c; DMAP = 4-dimethylaminopyridine, IDipp = 1,3-bis(2,6-diisopropylphenyl)-imidazolin-2-ylidene, IMe4 = 1,3,4,5-tetramethylimidazol-2-ylidene) are presented. All compounds were synthesized by salt metathesis reactions between D·BH2I and KBi(SiMe3)2(THF)0.3 and represent some of the extremely rare compounds featuring a 2c-2e B-Bi bond in a molecular compound. The products display high sensitivity towards air and light and slowly decompose in solution even at -80 °C. By the reaction of IDipp·GaH2(SO3CF3) with KBi(SiMe3)2(THF)0.3, the synthesis of the first bismuthanylgallane IDipp·GaH2Bi(SiMe3)2 (2) stabilized only by a 2-electron donor was possible, as evident from single crystal X-ray structure determination, NMR spectroscopy and mass spectrometry. Computational studies shed light on the stability of the products and the electronic nature of the compounds.

Carbene-Stabilized Phosphagermylenylidene: A Heavier Analog of Isonitrile

Phosphagermylenylidenes (R-P═Ge), as heavier analogs of isonitriles, whether in their free state or as complexes with a Lewis base, have not been previously identified as isolable entities. In this study, we report the synthesis of a stable monomeric phosphagermylenylidene within the coordination sphere of a Lewis base under ambient conditions. This species was synthesized by Lewis base-induced dedimerization of a cyclic phosphagermylenylidene dimer or via Me3SiCl elimination from a phosphinochlorogermylene framework. The deliberate integration of a bulky, electropositive N-heterocyclic boryl group at the phosphorus site, combined with coordination stabilization by a cyclic (alkyl)(amino)carbene at the low-valent germanium site, effectively mitigated its natural tendency toward oligomerization. Structural analyses and theoretical calculations have demonstrated that this unprecedented species features a P═Ge double bond, characterized by conventional electron-sharing π and σ bonds, complemented by lone pairs at both the phosphorus and germanium atoms. Preliminary reactivity studies show that this base-stabilized phosphagermylenylidene demonstrates facile release of ligands at the Ge atom, coordination to silver through the lone pair on P, and versatile reactivity including both (cyclo)addition and cleavage of the P═Ge double bond.

Triplet bismuthinidenes featuring unprecedented giant and positive zero field splittings

Isolation of triplet pnictinidenes, which bear two unpaired electrons at the pnictogen centers, has long been a great challenge due to their intrinsic high reactivity. Herein, we report the syntheses and characterizations of two bismuthinidenes MsFluindtBu-Bi (3) and MsFluind*-Bi (4) stabilized by sterically encumbered hydrindacene ligands. They were facilely prepared through reductions of the corresponding dichloride precursors with 2 molar equivalents of potassium graphite. The structural analyses revealed that 3 and 4 contain a one-coordinate bismuth atom supported by a Bi-C single σ bond. As a consequence, the remaining two Bi 6p orbitals are nearly degenerate, and 3 and 4 possess triplet ground states. Experimental characterizations with multinuclear magnetic resonance, magnetometry and near infrared spectroscopy coupled to wavefunction based ab initio calculations concurred to evidence that there exist giant and positive zero field splittings (>4300 cm-1) in their S = 1 ground states. Hence even at room temperature the systems almost exclusively populate the lowest-energy nonmagnetic Ms = 0 level, which renders them seemingly diamagnetic.

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

The reduction of the boryl-substituted SnII bromide {(HCDippN)2 B}Sn(IPrMe)Br with 1.5 equivalents of potassium graphite leads to the generation of the cyclic tetratin tetraboryl system K2 [Sn4 {B(NDippCH)2 }4 ], a homo-metallic heavier analogue of the cyclobutadiene dianion. This system is non-aromatic as determined by Nucleus Independent Chemical Shift Calculations (NICS(0)=-0.28, NICS(1)=-3.17), with the primary contributing resonance structures shown by Natural Resonance Theory (NRT) to involve a Sn=Sn double bond and 1,2-localized negative charges. Abstraction of the K+ cations or oxidation leads to contraction or cleavage of the Sn4 unit, respectively, while protonation generates the neutral dihydride 1,2-Sn4 {B(NDippCH)2 }4 H2 (a heavier homologue of cyclobutene) in a manner consistent with the predicted charge distribution in the [Sn4 {B(NDippCH)2 }4 ]2- dianion.

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)2 }; NHC=C{(Ni PrCMe)2 }) 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 K2 [Sn2 (boryl)2 ] (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)]n are unstable with respect to disproportionation. Carbene abstraction from 2 using BPh3 , and two-electron oxidation of 3 both result in the formation of a 2 : 1 mixture of the Sn(II) compound Sn(boryl)2 , and the hexatin cluster, Sn6 (boryl)4 (4). A viable mechanism for this rearrangement is shown by quantum chemical studies to involve a vinylidene intermediate (analogous to the isolable germanium compound, (boryl)2 Ge=Ge), which undergoes facile atom transfer to generate Sn(boryl)2 and trinuclear [Sn3 (boryl)2 ]. The latter then dimerizes to give the observed hexametallic product 4, with independent studies showing that similar trigermanium species aggregate in analogous fashion.

Synthesis of distibiranes and azadistibiranes by cycloaddition reactions of distibenes with diazomethanes and azides

Cycloaddition reactions of distibene [L(Me2N)GaSb]2 (L = HC[C(Me)NDipp]2; Dipp = 2,6-i-Pr2C6H3)[double bond, length as m-dash] with a series of organoazides RN3 (R = Ph, p-CF3Ph, 1-adamantyl (ada)) yielded azadistibiranes [L(Me2N)GaSb]2NR (R = Ph 1, p-CF3Ph 2, ada 3), whereas Me3SiN3 reacted with insertion into one Ga-Sb bond and formation of L(Me2N)GaSbSb(NSiMe3)Ga(NMe2)L (4). Analogous compounds 5 and 6 formed after heating of 1 and 2 above 60 °C. Prolonged heating of 5 resulted in a [2 + 2] cycloaddition accompanied by elimination of LGa(NMe2)2 and formation of tetrastibacyclobutane 7, while the reaction of 5 with a second equivalent of PhN3 gave heteroleptic azadistibirane 9, which isomerized at elevated temperature to distibene 10. Cycloaddition also occurred in reactions of [L(X)GaSb]2 (X = NMe2, OEt, Cl) with Me3Si(H)CN2, yielding distibiranes [L(X)GaSb]2C(H)SiMe3 (X = NMe211, OEt 12, Cl 13). Compounds 1-13 were characterized by IR, UV-Vis and NMR spectroscopy and sc-XRD. The mechanism of the reaction of [L(Me2N)GaSb]2 with PhN3 and Me3SiN3 and the electronic nature of the resulting compounds were studied by DFT calculations.

Sequential Reduction of Borylstibane to an Electronically Nonsymmetric Diboryldistibene Radical Anion

Understanding the formation of metal-metal bonds and their electronic structures is still a scientific task. We herein report on the stepwise synthesis of boryl-substituted antimony compounds in which the antimony atoms adopt four different oxidation states (+III, +II, +I, +I/0). Sb-C bond homolysis of Cp*[(HCNDip)₂B]SbCl (1; Cp* = C₅Me₅; Dip = 2,6-iPr₂C₆H₃) gave diboryldichlorodistibane [(HCNDip)₂BSbCl]₂ (2), which reacted with KC₈ to form diboryldistibene [(HCNDip)₂BSb]₂ (3) and traces of cyclotetrastibane [(HCNDip)₂B]₃Sb₄Cl (5). One-electron reduction of 3 yielded the potassium salt of the diboryldistibene radical anion [(HCNDip)₂BSb]₂̇^-, [K(18-c-6)(OEt₂)][{(HCNDip)₂BSb}₂] (4), which exhibits an unprecedented inequivalent spin localization on the Sb-Sb bond and hence an unsymmetric electronic structure. Compounds 1-4 were characterized by heteronuclear nuclear magnetic resonance (NMR) (¹H, ¹³C, ¹¹B), infrared (IR), ultraviolet-visible (UV-vis) spectroscopy (3, 4), and single crystal X-ray diffraction (sc-XRD, 1-5), while the bonding nature of 3 and 4 was analyzed by quantum chemical calculations. EPR spectroscopy resolves the dissimilar Sb hyperfine tensors of 4, reflecting the inequivalent spin distribution, setting 4 uniquely apart from all previously characterized dipnictene radical anions.

A Diarsene Radical Anion

The isolation of the first diarsene radical anion by reduction of a neutral diarsene is presented. Comprehensive characterisation in conjunction with DFT calculations reveal unpaired spin density residing in the...

Synthesis, structure and bonding nature of heavy dipnictene radical anions

Cyclic voltammetry (CV) studies of two L(X)Ga-substituted dipnictenes [L(R2N)GaE]2 (E = Sb, R = Me 1; E = Bi; R = Et 2; L = HC[C(Me)NDipp]2; Dipp = 2,6-i-Pr2C6H3) showed reversible reduction events. Single electron reduction of 1 and 2 with KC8 in DME in the presence of benzo-18-crown-6 (B-18-C-6) gave the corresponding dipnictenyl radical anions (DME)[K(B-18-C-6)][L(R2N)GaE]2 (E = Sb, R = Me 3; E = Bi, R = Et 4). Radical anions 3 and 4 were characterized by EPR, UV-vis and single crystal X-ray diffraction, while quantum chemical calculations gave deeper insight into the nature of the chemical bonding.

Dibismuthanes in catalysis: from synthesis and characterization to redox behavior towards oxidative cleavage of 1,2-diols

A family of aryl dinuclear bismuthane complexes has been successfully synthesized and characterized. The two bismuth centers are bonded to various xanthene-type backbones, which differ in ring-size and flexibility, resulting in complexes with different intramolecular BiBi distances. Moreover, their pentavalent Bi(v) analogues have also been prepared and structurally characterized. Finally, the synergy between bismuth centers in catalysis has been studied by applying dinuclear bismuthanes 5-8 to the catalytic oxidative cleavage of 1,2-diols. Unfortunately, no synergistic effects were observed and the catalytic activities of dinuclear bismuthanes and triphenylbismuth are comparable.

Carbodicarbene Bismaalkene Cations: Unravelling the Complexities of Carbene versus Carbone in Heavy Pnictogen Chemistry

We report a combined experimental and theoretical study on the first examples of carbodicarbene (CDC)-stabilized bismuth complexes, which feature low-coordinate cationic bismuth centers with C=Bi multiple-bond character. Monocations [(CDC)Bi(Ph)Cl][SbF6 ] (8) and [(CDC)BiBr2 (THF)2 ][SbF6 ] (11), dications [(CDC)Bi(Ph)][SbF6 ]2 (9) and [(CDC)BiBr(THF)3 ][NTf2 ]2 (12), and trication [(CDC)2 Bi][NTf2 ]3 (13) have been synthesized via sequential halide abstractions from (CDC)Bi(Ph)Cl2 (7) and (CDC)BiBr3 (10). Notably, the dications and trication exhibit C ⇉ Bi double dative bonds and thus represent unprecedented bismaalkene cations. The synthesis of these species highlights a unique non-reductive route to C-Bi π-bonding character. The CDC-[Bi] complexes (7-13) were compared with related NHC-[Bi] complexes (1, 3-6) and show substantially different structural properties. Indeed, the CDC ligand has a remarkable influence on the overall stability of the resulting low-coordinate Bi complexes, suggesting that CDC is a superior ligand to NHC in heavy pnictogen chemistry.

Reactivity of a magnesium diboranate with organic nitriles

A series of complexes generated through reactions of the β-diketiminato magnesium diboranate species, [(BDI)Mg{(n-Bu)pinB-Bpin}] (BDI = HC{(Me)CNDipp}2; Dipp = 2,6-di-iso-propylphenyl), and a variety of organic nitriles are reported. Although, in every case, the diboranate anion acts as a surrogate source of the {Bpin} nucleophile, resulting in B-C bond formation at the electrophilic sp-hydridised nitrile carbon, the resultant compounds display a variable propensity to undergo subsequent reaction with additional nitrile equivalents. This behaviour is rationalised to be a consequence of substituent-dependent modulation in the basicity and resultant electrophilicity of magnesium-coordinated nitrile intermediates.

Stabilization of a bismuth–bismuth double bond by anionic N-heterocyclic carbenes

Anionic N-heterocyclic carbenes have been employed for the isolation of the first dicarbene–dibismuth complex; the resulting dibismuthene features a trans-bent geometry with a Bi–Bi double bond and short intramolecular Bi–C_ipso contacts.

Synthesis and Characterization of a Magnesium Boryl and a Beryllium-Substituted Diazaborole

Reaction of a lithium boryl, [(THF)₂ Li{B(DAB)}] (DAB=[(DipNCH)₂ ]^2- , Dip=2,6-diisopropylphenyl), with a dinuclear magnesium(I) compound [{(^Mes Nacnac)Mg}₂ ] (^Mes Nacnac=[HC(MeCNMes)₂ ]^- , Mes=mesityl) unexpectedly afforded a rare example of a terminal magnesium boryl species, [(^Mes Nacnac)(THF)Mg{B(DAB)}]. Attempts to prepare the magnesium boryl via a salt metathesis reaction between the lithium boryl and a β-diketiminato magnesium iodide compound, instead led to an intractable mixture of products. Similarly, reaction of the lithium boryl with a β-diketiminato beryllium bromide precursor, [(^Dep Nacnac)BeBr] (Dep=2,6-diethylphenyl) did not give a beryllium boryl, but instead afforded an unprecedented example of a beryllium substituted diazaborole heterocycle, [{(^Dep Nacnac)Be(4-DAB^-H )}BBr]. For sake of comparison, the same group 2 halide precursor compounds were treated with a potassium gallyl analogue of the lithium boryl, viz. [(tmeda)K{:Ga(DAB)}] (tmeda=N,N,N',N'-tetramethylethylenediamine), but no reactions were observed.

Ligand Effects on the Electronic Structure of Heteroleptic Antimony-Centered Radicals

We report on the structures of three unprecedented heteroleptic Sb-centered radicals [L(Cl)Ga](R)Sb^. (2-R, R=B[N(Dip)CH]₂ 2-B, 2,6-Mes₂ C₆ H₃ 2-C, N(SiMe₃ )Dip 2-N) stabilized by one electropositive metal fragment [L(Cl)Ga] (L=HC[C(Me)N(Dip)]₂ , Dip=2,6-i-Pr₂ C₆ H₃ ) and one bulky B- (2-B), C- (2-C), or N-based (2-N) substituent. Compounds 2-R are predominantly metal-centered radicals. Their electronic properties are largely influenced by the electronic nature of the ligands R, and significant delocalization of unpaired-spin density onto the ligands was observed in 2-B and 2-N. Cyclic voltammetry (CV) studies showed that 2-B undergoes a quasi-reversible one-electron reduction, which was confirmed by the synthesis of [K([2.2.2]crypt)][L(Cl)GaSbB[N(Dip)CH]₂ ] ([K([2.2.2]crypt)][2-B]) containing the stibanyl anion [2-B]^- , which was shown to possess significant Sb-B multiple-bonding character.

Distibanes and Distibenes from Reduction of Sb(NONR )Cl by using MgI Reagents

The bis(amidodimethyl)disiloxane antimony chlorides Sb(NON^R )Cl (NON^R =[O(SiMe₂ NR)₂ ]^2- ; R=tBu, Ph, 2,6-Me₂ C₆ H₃ =Dmp, 2,6-iPr₂ C₆ H₃ =Dipp, 2,6-(CHPh₂ )₂ -4-tBuC₆ H₂ =tBu-Bhp) are reduced to Sb^II and Sb^I species by using Mg^I reagents, [Mg(BDI^R' )]₂ (BDI=[HC{C(Me)NR'}₂ ]^- ; R'=2,4,6-Me₃ C₆ H₂ =Mes, Dipp). Stoichiometric reactions with Sb(NON^R )Cl (R=tBu, Ph) form dimeric Sb^II stibanes [Sb(NON^R )]₂ , shown crystallographically to contain Sb-Sb single bonds. The analogous distibane with R=Dmp substituents has an exceptionally long Sb-Sb interaction and exhibits spectroscopic and reactivity properties consistent with radical character in solution. When R=Dipp, reductions with Mg^I reagents directly give distibenes [Sb(μ-NON^Dipp )Mg(BDI^R' )(THF)_n ]₂ (R'=Mes, n=1; R'=Dipp, n=0). Crystallographic analysis shows a trans-substitution of the Sb=Sb double bond, with bridging NON^Dipp -ligands between the Sb^I and Mg^II centres. An attempt to access the NON^Ph -analogue using the same protocol afforded the polystibide cluster Sb₈ [μ₄ ,η^2:2:2:2 -Mg(BDI^Mes )]₄ , which co-crystallized with the ligand transfer product, [Mg(BDI^Mes )]₂ (μ-NON^Ph ).

Snapshots of magnesium-centred diborane heterolysis by an outer sphere SN2 process

Reactions of a magnesium diboranate as a source of [Bpin]^– anions are initiated by ‘outer sphere’ attack of C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> N bonded substrates.

Reactions of the β-diketiminato magnesium diboranate derivative, [(BDI)Mg{pinB(n-Bu)Bpin}] (BDI = HC{(Me)CNDipp}₂; Dipp = 2,6-i-Pr₂C₆H₃), 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 Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> 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.

Intramolecular Metal⋅⋅⋅π-Arene Interactions in Neutral and Cationic Main Group Compounds

The role of intramolecular metal⋅⋅⋅π-arene interactions has been investigated in the solid-state structures of a series of main group compounds supported by the bulky amide ligands, [N(^tBu Ar^≠ )(SiR₃ )]^- (^tBu Ar^≠ =2,6-(CHPh₂ )₂ -4-tBuC₆ H₂ , R=Me, Ph). The lithium and potassium amide salts showed different patterns of solvation and demonstrated that the SiPh₃ substituent is able to be involved in stabilizing the electrophilic metal. These group 1 metal compounds served as ligand transfer reagents to access a series of bismuth(III) halides. Chloride extraction from Bi(N{^tBu Ar^≠ }{SiPh₃ })Cl₂ using AlCl₃ afforded the 1:1 salt [Bi(N{^tBu Ar^≠ }{SiPh₃ })Cl][AlCl₄ ]. This was accompanied by a significant rearrangement of the stabilizing π-arene contacts in the solid-state. Attempted preparation of the corresponding tetraphenylborate salt resulted in phenyl-transfer and generation of the neutral Bi(N{^tBu Ar^≠ }{SiPh₃ })(Ph)Cl.

Isolation of Cyclic(Alkyl)(Amino) Carbene-Bismuthinidene Mediated by a Beryllium(0) Complex

The long-sought carbene-bismuthinidene, (CAAC)Bi(Ph), has been synthesized. Notably, this represents both the first example of a carbene-stabilized subvalent bismuth complex and the extension of the carbene-pnictinidene concept to a non-toxic metallic element (Bi). The bonding has been investigated by single-crystal X-ray diffraction studies and DFT calculations. This report also highlights the hitherto unknown reducing and ligand transfer capability of a beryllium(0) complex.

Diborane heterolysis and P(v) reduction by Ph3PO coordination to magnesium

Inner sphere attack of Ph₃PO provides a terminal magnesium boryl, which is a potent reagent for the deoxygenation of P(v).

Diborane heterolysis: breaking and making B-B bonds at magnesium

Reaction of the dimeric β-diketiminato magnesium hydride [(BDI)MgH]2 (BDI = HC{(Me)CN-2,6-i-Pr2C6H3}2) with bis-pinacolatodiborane (B2pin2) resulted in B-O bond activation and formation of a magnesium complex of an unusual borylborohydride anion. In contrast, similar treatment of the mononuclear organomagnesium [{BDI}Mg(n-Bu)] with 4,4,4',4',6,6'-hexamethyl-2,2'-bi(1,3,2-dioxaborinane) (B2hex2) provided a B(sp2)-B(sp3) diborane anion, [(hex)BB(n-Bu)(hex)]-, with a constitution which is analogous to that formed in the previously reported reaction with bis(pinacolato)diboron (B2pin2). Subsequent addition of 4-dimethylaminopyridine to a solution of this compound induced alkylborane displacement and provided a magnesium boryl derivative containing a terminal Mg-B(hex) interaction (Mg-B 2.319(3) Å), a result which reinforces the generality of this approach for the synthesis of boryl anions by B-B bond heterolysis. Further studies of the reactivity of the initially formed B(sp2)-B(sp3) anions with diborane small molecules also resulted in alkylborane displacement and the production of triboron anions, which are propagated by contiguous and electron precise (2c-2e) B-B-B interactions.

Redox transmetallation approaches to the synthesis of extremely bulky amido-lanthanoid(ii) and -calcium(ii) complexes

Redox transmetallation protolysis and direct redox transmetallation reactions have been employed to access a variety of extremely bulky amido-lanthanoid(ii), and related calcium(ii) complexes which cannot be prepared using classical salt metathesis pathways.

Easy access to nucleophilic boron through diborane to magnesium boryl metathesis

Organoboranes are some of the most synthetically valuable and widely used intermediates in organic and pharmaceutical chemistry. Their synthesis, however, is limited by the behaviour of common boron starting materials as archetypal Lewis acids such that common routes to organoboranes rely on the reactivity of boron as an electrophile. While the realization of convenient sources of nucleophilic boryl anions would open up a wealth of opportunity for the development of new routes to organoboranes, the synthesis of current candidates is generally limited by a need for highly reducing reaction conditions. Here, we report a simple synthesis of a magnesium boryl through the heterolytic activation of the B–B bond of bis(pinacolato)diboron, which is achieved by treatment of an easily generated magnesium diboranate complex with 4-dimethylaminopyridine. The magnesium boryl is shown to act as an unambiguous nucleophile through its reactions with iodomethane, benzophenone and N,N′-di-isopropyl carbodiimide and by density functional theory.

Organoboranes are widely employed in organic synthesis and typically are prepared using electrophilic boron sources. Here the authors report a route to nucleophilic boryl anions via organomagnesium-driven cleavage of boron-boron bonds.

Boryl substituted group 13 metallylenes: complexes with an iron carbonyl fragment

The first examples of boryl substituted aluminylene and gallylene complexes, [(DAB)B(THF)Al{Fe(CO)₃(μ-CO)}]₂ and [(DAB)BGa{μ-Fe(CO)₄}]₂ (DAB = {(C₆H₃Prⁱ₂-2,6)NCH}₂) have been prepared by reduction of MX₂(THF){B(DAB)} (M = Al or Ga, X = Cl or Br) with K₂[Fe(CO)₄]. Spectroscopic and crystallographic analyses of the compounds show them to be structurally distinct dimers, the latter of which possesses a close GaGa separation that computational analyses reveal has negligible bonding character.

A Boryl-Substituted Diphosphene: Synthesis, Structure, and Reaction with n-Butyllithium To Form a Stabilized Adduct by pπ-pπ Interaction

A boryl-substituted diphosphene was synthesized through the nucleophilic borylation of PCl3 with a borylzinc reagent, followed by a reduction with Mg. A combined analysis of the resulting diboryldiphosphene by single-crystal X-ray diffraction, DFT calculations, and UV/Vis spectroscopy revealed a σ-electron-donating effect for the boryl substituent that was slightly weaker than that of the 2,4,6-tri-tert-butylphenyl (Mes*) ligand. The reaction of this diboryldiphosphene with (n) BuLi afforded a boryl-substituted phosphinophosphide that was, in comparison with the thermally unstable Mes*-substituted diaryldiphosphene, stabilized by a π-electron-accepting effect of the boryl substituent.

Paddlewheel 1,2,4-diazaphospholide distibines with the shortest antimony-antimony single bonds

One-electron reduction of SbCl3 with the non-innocent 1,2,4-diazaphospholide anion [3,5-R2dp](-) produced straightforwardly three unprecedented paddlewheel distibines [L2(Sb-Sb)L2] (L = η(1),η(1)-3,5-R2dp, R = tBu (4), iPr (5α, 5β), or Cy (6)) with very short Sb-Sb bond lengths (2.6691(8)-2.7451(8) Å). The novel structures were rationalized by DFT calculations.