Search

Expanding the library of structurally characterized lithium amidomanganates(II), here we report a general synthetic approach to access a new series of homoleptic complexes. In situ salt‐metathesis of commercially available reagents afforded tetrabutyl lithium manganate [(TMEDA)2Li2Mn(nBu)4] (1) (TMEDA=N,N,N',N'‐tetramethylethylendiamine) which could be used as a precursor for direct deprotonation of a selection of amines affording a family of homoleptic lithium amidomanganates. Complexes [{Li(THF)4}+{Mn(NPh2)3(THF)}‐] (2), [(THF)LiMn(NCy2)3] (3) (Cy=cyclohexyl), [(HNCy2)LiMn(NCy2)3] (4), [(THF)4Li2Mn(NHMes)4] (5) (Mes=2,4,6‐trimethylphenyl), and [(TMEDA)2Li2Mn(NHMes)4] (6) have been isolated and structurally characterized as main products. While it is evident that 1 possesses adequate basicity to effect deprotonation of both primary and secondary amines, the exact stoichiometry, constitution, and structural motif of newly generated lithium amidomanganates are governed by the steric and electronic variations of the amide ligands. [ABSTRACT FROM AUTHOR]

The kinetic stability provided by the sterically demanding {SiNDipp}2− dianion (SiNDipp = {CH2SiMe2NDipp}2; Dipp = 2,6-i-Pr2C6H3) is intrinsic to the isolation of not only the group 1 alumanyl reagents ([{SiNDipp}AlM]2; M = K, Rb, Cs) but also facilitates the completely selective oxidative addition of a C-H bond of 1,2-C2B10H12 to the aluminium centre. In each case, the resultant compounds comprise a four-coordinate o-carboranyl (hydrido)aluminate anion, [(SiNDipp)Al(H)(1,2-C2B10H11)]−, in which the carboranyl cage is bonded to aluminium by an Al-C σ bond. Although the anions further assemble as extended network structures based on Al-H∙∙∙M, B-H∙∙∙M, and C-H∙∙∙M interactions, each structure is unique due to the significant variation in M+ ionic radius as group 1 is descended. The potassium derivative crystallises as a one-dimensional polymer, its rubidium analogue is a dimer due to the polyhapto-sequestration of a molecule of benzene solvent within the alkali metal coordination sphere, and the caesium species is a two-dimensional assembly of hexameric aggregates. [ABSTRACT FROM AUTHOR]

The reactivity of [{SiNDipp}AlK]2, which comprises a formally anionic Al(I) centre, has been examined towards a variety of 1,3‐dienic molecules, including 2,3‐dimethylbutadiene, cyclooctatetraene, anthracene and tetracene. In each case, the alumanyl derivative experiences oxidative addition across the Al(I) centre to provide the corresponding potassium aluminacyclopentene, aluminacyclopropene or aluminanorbornadiene products of [4+1] cycloaddition. [ABSTRACT FROM AUTHOR]

The Mannich reaction of the zirconium MOF [Zr6 O4 (OH)4 (bdc-NH2 )6 ] (UiO-66-NH2 , bdc-NH2 =2-amino-1,4-benzenedicarboxylate) with paraformaldehyde and pyrazole, imidazole or 2-mercaptoimidazole led to post-synthetic modification (PSM) through C-N bond formation. The reaction with imidazole (Him) goes to completion whereas those with pyrazole (Hpyz) and 2-mercaptoimidazole (HimSH) give up to 41 and 36 % conversion, respectively. The BET surface areas for the Mannich products are reduced from that of UiO-66-NH2 , but the compounds show enhanced selectivity for adsorption of CO2 over N2 at 273 K. The thiol-containing MOFs adsorb mercury(II) ions from aqueous solution, removing up to 99 %. The Mannich reaction with pyrazole succeeds on [Zn4 O(bdc-NH2 )3 ] (IRMOF-3), but a similar reaction on [Zn2 (bdc-NH2 )2 (dabco)] (dabco=1,4-diazabicyclo[2.2.2]octane) gave [Zn3 (bdc-NH2 )1.32 (bdc-NHCH2 pyz)1.68 (dabco)]⋅2 C7 H8 5, whereas the reaction with imidazole gave the expected PSM product. Compound 5 forms via a dissolution-recrystallisation process that is triggered by the "free" pyrazolate nitrogen atom competing with dabco for coordination to the zinc(II) centre. In contrast, the "free" nitrogen atom on the imidazolate is too far away to compete in this way. Mannich reactions on [In(OH)(bdc-NH2 )] (MIL-68(In)-NH2 ) stop after the first step, and the product was identified as [In(OH)(bdc-NH2 )0.41 (bdc-NHCH2 OCH3 )0.30 (bdc-N=CH2 )0.29 ], with addition of the heterocycle prevented by steric interactions.

The Mannich reaction of the zirconium MOF [Zr6 O4 (OH)4 (bdc-NH2 )6 ] (UiO-66-NH2 , bdc-NH2 =2-amino-1,4-benzenedicarboxylate) with paraformaldehyde and pyrazole, imidazole or 2-mercaptoimidazole led to post-synthetic modification (PSM) through C-N bond formation. The reaction with imidazole (Him) goes to completion whereas those with pyrazole (Hpyz) and 2-mercaptoimidazole (HimSH) give up to 41 and 36 % conversion, respectively. The BET surface areas for the Mannich products are reduced from that of UiO-66-NH2 , but the compounds show enhanced selectivity for adsorption of CO2 over N2 at 273 K. The thiol-containing MOFs adsorb mercury(II) ions from aqueous solution, removing up to 99 %. The Mannich reaction with pyrazole succeeds on [Zn4 O(bdc-NH2 )3 ] (IRMOF-3), but a similar reaction on [Zn2 (bdc-NH2 )2 (dabco)] (dabco=1,4-diazabicyclo[2.2.2]octane) gave [Zn3 (bdc-NH2 )1.32 (bdc-NHCH2 pyz)1.68 (dabco)]⋅2 C7 H8 5, whereas the reaction with imidazole gave the expected PSM product. Compound 5 forms via a dissolution-recrystallisation process that is triggered by the "free" pyrazolate nitrogen atom competing with dabco for coordination to the zinc(II) centre. In contrast, the "free" nitrogen atom on the imidazolate is too far away to compete in this way. Mannich reactions on [In(OH)(bdc-NH2 )] (MIL-68(In)-NH2 ) stop after the first step, and the product was identified as [In(OH)(bdc-NH2 )0.41 (bdc-NHCH2 OCH3 )0.30 (bdc-N=CH2 )0.29 ], with addition of the heterocycle prevented by steric interactions.

[{SiNDipp}BeClM]2 ({SiNDipp} = {CH2SiMe2N(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 [{SiNDipp}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. [ABSTRACT FROM AUTHOR]

The dimeric β-diketiminato calcium hydride, [(BDI)CaH]2 (BDI = HC{(Me)CN-2,6-iPr2C6H3}2), reacts with ZnMe2 to afford the bimetallic calcium zincate complex, [(BDI)Ca(μ-CH3)2Zn(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. [ABSTRACT FROM AUTHOR]

The β-diketiminato calcium and magnesium complexes, [(BDI)MgnBu] and [(BDI)CaH]2 (BDI = HC{C(Me)NDipp}2; Dipp = 2,6-di-isopropylphenyl), react with ortho-carborane (o-C2B10H12) to provide the respective [(BDI)Ae(o-C2B10H11)] (Ae = Mg or Ca) complexes. While the lighter group 2 species is a monomer with magnesium in a distorted trigonal planar environment, the heavier analogue displays a puckered geometry at calcium in the solid state due to Ca⋯H–B intermolecular interactions. These secondary contacts are, however, readily disrupted upon addition of THF to provide the 4-coordinate monomer, [(BDI)Ca(THF)(o-C2B10H11)]. [(BDI)Mg(o-C2B10H11)] was reacted with [NHCIPrMCl] (NHCIPr = 1,3-bis(isopropyl)imidazol-2-ylidene; M = Cu, Ag, Au) to provide [NHCIPrM(o-C2B10H11)], rare C-bonded examples of coinage metal derivatives of unsubstituted (o-C2B10H11)− and confirming the alkaline earth compounds as viable reagents for the transmetalation of the carboranyl anion. [ABSTRACT FROM AUTHOR]

Liquid assisted ball milling of [NHC]HBr (NHC = N-heterocyclic carbene) salts with copper(I) chloride, and a range of alkali metal complexes was shown to efficiently produce (NHC)CuX (NHC = normal or RE-NHC, X = halide, alkoxide, amide, alkyl, aryl; RE-NHC = ring-expanded NHC). [ABSTRACT FROM AUTHOR]

Reaction of (6‐Dipp)CuOtBu (6‐Dipp=C{NDippCH2}2CH2, Dipp=2,6‐iPr2C6H3) with B2(OMe)4 provided access to (6‐Dipp)CuB(OMe)2 via σ‐bond metathesis. (6‐Dipp)CuB(OMe)2 was characterised by NMR spectroscopy and X‐ray crystallography and shown to be a monomeric acyclic boryl of copper. (6‐Dipp)CuB(OMe)2 reacted with ethylene and diphenylacetylene to provide insertion compounds into the Cu‐B bond which were characterised by NMR spectroscopy in both cases and X‐ray crystallography in the latter. It was also competent in the rapid catalytic deoxygenation of CO2 in the presence of excess B2(OMe)4. Alongside π‐insertion, (6‐Dipp)CuB(OMe)2 reacted with LiNMe2 to provide a salt metathesis reaction at boron, giving (6‐Dipp)CuB(OMe)NMe2, a second monomeric acyclic boryl, which also cuproborated diphenylacetylene. Computational interrogation validated these acyclic boryl species to be electronically similar to (6‐Dipp)CuBpin. [ABSTRACT FROM AUTHOR]

The dimeric β‐diketiminato calcium hydride, [(DippBDI)CaH]2 (DippBDI = HC{(Me)CN‐2,6‐i‐Pr2C6H3}2), reacts with ortho‐, meta‐ or para‐tolyl mercuric compounds to afford hydridoarylcalcium compounds, [(DippBDI)2Ca2(μ‐H)(μ‐o‐,m‐,p‐tolyl)], in which dimer propagation occurs either via μ2‐η1‐η1 or μ2‐η1‐η6 bridging between the calcium centers. In each case, the orientation and hapticity of the aryl units is dependent upon the position of the methyl substituent. While wholly organometallic meta‐ and para‐tolyl dimers, [(DippBDI)Ca(m‐tolyl)]2 and [(DippBDI)Ca(p‐tolyl)]2, can be prepared and are stable, the ortho‐tolyl isomer is prone to isomerization to a calcium benzyl analog. Computational analysis of this latter process with density functional theory (DFT) highlights an unusual mechanism invoking the generation of an intermediate dicalcium species in which the group 2 centers are bridged by a toluene dianion formed by the formal attachment of the original hydride anion to the initially generated ortho‐tolyl substituent. Use of a more sterically encumbered aryl substituent, {3,5‐t‐Bu2C6H3}, facilitates the selective formation of [(DippBDI)Ca(μ‐H)(μ‐3,5‐t‐Bu2C6H3)Ca(DippBDI)], which can be converted into the unsymmetrically‐substituted σ‐aryl calcium complexes, [(DippBDI)Ca(μ‐Ph)(μ‐3,5‐t‐Bu2C6H3)Ca(DippBDI)] and [(DippBDI)Ca(μ‐p‐tolyl)(μ‐3,5‐t‐Bu2C6H3)Ca(DippBDI)] by reaction with the appropriate mercuric diaryl. Conversion of [(DippBDI)Ca(H)(Ph)Ca(DippBDI)] to afford [{{(DippBDI)Ca}2(μ2‐Cl)}2(C6H5‐C6H5)], comprising a biphenyl dianion, is also reported. Although this latter transformation is serendipitous, AIM analysis highlights that, in a related manner to the ortho‐tolyl to benzyl isomerization, the requisite C–C coupling may be facilitated in an "across dimer" fashion by the experimentally‐observed polyhapto engagement of the aryl substituents with each calcium. [ABSTRACT FROM AUTHOR]