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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.

A series of neutral, bulky diazabutadienediyl-substituted beryllacycles [Be(DipDAB)(L)] (DipDAB = [(DipNCH)2]2–, Dip = 2,6-diisopropylphenyl; L = OEt2, THF, :C(RNCH)2; R = Me (TMC), Pri (IPriMe)) h...

Reaction of several N-heterocyclic carbenes, a carbodiphosphorane, and bis(diphenylphosphino)ethane (DPPE) with [BeX2(OEt2)2] (X = Br or I) have yielded a variety of beryllium dihalide adduct complexes, all of which were crystallographically characterised. Attempts to reduce the compounds to low oxidation state beryllium complexes using a variety of reducing agents have been carried out, but were of limited success. However, reaction of [(IPr)BeBr2] (IPr = :C{(DipNCH)2}; Dip = 2,6-diisopropylphenyl) with the aluminium(I) heterocycle, [:Al(DipNacnac)] (DipNacnac = [HC(MeCNDip)2]−) afforded the adduct complex, [{(IPr)(Br)Be(μ-H)}2], while reduction of [(IPr)BeBr2] with potassium naphthalenide gave the beryllium naphthalenediyl complex, [(IPr)Be(C10H8)]. Furthermore, reaction of [{(DPPE)BeI2}∞], with [:Al(DipNacnac)] led to insertion of the Al centre of the heterocycle into a Be–I bond, and formation of a rare example of an Al–Be bonded complex, [(DPPE)(I)Be–Al(I)(DipNacnac)].

Dititanoxycarbene [(TiX3)2(μ-CO2)] (X = N[tBu](3,5-Me2C6H3)) and B(C6F5)3 cleaved dihydrogen under ambient conditions to give the zwitterionic formate [(TiX3)2(μ-OCHO-κO:κO′)(B(C6F5)3)] and the hydrido borate [Ti(N[tBu]Ar)3][HB(C6F5)3].

Reactions of two magnesium(I) compounds, [{(Ar Nacnac)Mg}2 ] (Ar Nacnac=[HC(MeCNAr)2 ]- ; Ar=mesityl (Mes) or o-xylyl (Xyl)), with CO in the presence of [Mo(CO)6 ] lead to the reductive hexamerization of CO, and formation of magnesium benzenehexolate complexes, [{(Ar Nacnac)Mg}6 (C6 O6 )]. [Mo(CO)6 ] is not consumed in these reactions, but is apparently required to initiate (or catalyze) the CO hexamerizations. A range of studies were used to probe the mechanism of formation of the benzenehexolate complexes. The magnesium(I) reductive hexamerizations of CO are closely related to Liebig's reduction of CO with molten potassium (to give K6 C6 O6 , amongst other products), originally reported in 1834. As the mechanism of that reaction is still unknown, it seems reasonable that magnesium(I) reductions of CO could prove useful homogeneous models for its elucidation, and for the study of other C-C bond forming reactions that use CO as a C1 feedstock (e.g. the Fischer-Tropsch process).

Reactions of two magnesium(I) compounds, [{(

Reactions of the beryllium dihalide complexes [BeX2 (OEt2 )2 ] (X=Br or I) with N,N,N',N'-tetramethylethylenediamine (TMEDA), a series of diazabutadienes, or bis(diphenylphosphino)methylene (DPPM) have yielded the chelated complexes, [BeX2 (TMEDA)], [BeX2 {(RN=CH)2 }] (R=tBu, mesityl (Mes), 2,6-diethylphenyl (Dep) or 2,6-diisopropylphenyl (Dip)), and the non-chelated system, [BeI2 (κ1 -P-DPPM)2 ]. Reactions of lithium or potassium salts of a variety of β-diketiminates have given both three-coordinate complexes, [{HC(RCNAr)2 }BeX] (R=H or Me; Ar=Mes, Dep or Dip; X=Br or I); and four-coordinate systems, [{HC(MeCNPh)2 }BeBr(OEt2 )] and [{HC(MeCNDip)(MeCNC2 H4 NMe2 }BeI]. Alkali metal salts of ketiminate, guanidinate, boryl/phosphinosilyl amide, or terphenyl ligands, lead to dimeric [{BeI{μ-[(OCMe)(DipNCMe)]CH}}2 ], and monomeric [{iPr2 NC(NMes)2 }BeI(OEt2 )], [κ2 -N,P-{(HCNDip)2 B}(PPh2 SiMe2 )NBeI(OEt2 )] and [{C6 H3 Ph2 -2,6}BeBr(OEt2 )], respectively. Compound [{HC(MeCNPh)2 }BeBr(OEt2 )] undergoes a Schlenk redistribution reaction in solution, affording the homoleptic complex, [{HC(MeCNPh)2 }2 Be]. The majority of the prepared complexes have been characterized by X-ray crystallography and multi-nuclear NMR spectroscopy. The structures and stability of the complexes are discussed, as is their potential for use as precursors in poorly developed low oxidation state beryllium chemistry.

The alkali metal halide supported alkali metal materials, ca. 5% w/w Na/NaCl and 5% w/w K/KI, are prepared without specialist equipment by rapidly stirring molten alkali metal with finely ground al...

This work focuses on nucleophilic activation of CO2 at the anionic terminal oxo titanium tris(anilide) complexes [(Solv)n M][OTi(N[t Bu]Ar)3 ]m with M=Li, Na, K, Mg, MgMe, AlCl2 , AlI2 ; Ar=3,5-Me2 C6 H3 ; Solv=Et2 O, THF, 12-crown-4, 2,2,2-cryptand; n, m=1-2. The CO2 binding strength to the terminal oxo ligand of [OTi(N[t Bu]Ar)3 ]- ([1]- ) and the stability of the resulting carbonate moiety [O2 COTi(N[t Bu]Ar)3 ]- ([2]- ) are highly dependent on the Lewis acidity of the countercation. We report herein on CO2 binding as a function of countercation and countercation coordination environment, and comment in this respect on the bottom and upper limits of the cation Lewis acidity. Thermodynamic parameters are provided for oxo complexes with lithium as countercation, that is, [(Et2 O)2 Li][1] and [(12-c-4)Li][1].

Chemistry freshmen learn to distinguish between nitrate NO 3 − and nitrite NO 2 − or sulfate SO 4 2− and sulfite SO 3 2− , but how many would know about carbonite CO 2 2− in contrast to carbonate CO 3 2− ? This is not surprising for an anion that has never been observed in solution. However, it might be a crucial intermediate in the reductive activation of CO 2 . This review will track back carbonite and reflect on its relevance to carbon dioxide binding in metal complexes.

Deprotonation of a formato ligand by a cis-coordinated propylidyne ligand in a tungsten(vi) complex [(OSSO)W([triple bond, length as m-dash]CEt)(OCHO)] (3) that contains a tetradentate bis(phenolato) ligand (OSSO = {1,4-dithiabutanediyl-2,2'-bis(4,6-di-tert-butyl-phenolato)}) gave the dioxo complex [(OSSO)WO2] (4) along with CO, ethylene and propylene as major products of decomposition.

A critical survey on the literature on CO2 metal complexes is provided. A re-evaluation of all known CO2 complexes reveals the existence of several bonding modes, which have not been recognized as separate classes so far. This review further provides suggestions on alternative interpretations of the bonding in reported complexes. The accurate classification of the bonding situation as well as the oxidation states of carbon and the metals involved in binding CO2 allowed for establishing a generalized summary of all known synthetic methods. Finally, a short overview of reductive carbon dioxide transformations at metal centers is given.

Additions of beryllium-halide bonds in the simple beryllium dihalide adducts, [BeX2 (tmeda)] (X=Br or I, tmeda=N,N,N',N'-tetramethylethylenediamine), across the metal center of a neutral aluminum(I) heterocycle, [:Al(Dip Nacnac)] (Dip Nacnac=[(DipNCMe)2 CH]- , Dip=2,6-diisopropylphenyl), have yielded the first examples of compounds with beryllium-aluminum bonds, [(Dip Nacnac)(X)Al-Be(X)(tmeda)]. For sake of comparison, isostructural Mg-Al and Zn-Al analogues of these complexes, viz. [(Dip Nacnac)(X)Al-M(X)(tmeda)] (M=Mg or Zn, X=I or Br) have been prepared and structurally characterized. DFT calculations reveal all compounds to have high s-character metal-metal bonds, the polarity of which is consistent with the electronegativities of the metals involved. Preliminary reactivity studies of [(Dip Nacnac)(Br)Al-Be(Br)(tmeda)] are reported.

International audience; This study details syntheses of unsymmetrical magnesium(I) adduct complexes, [((Ar)Nacnac)-(D)Mg-Mg ((Ar)Nacnac)] ((Ar)Nacnac = [(ArNC-Me)(2)CH](-)), Ar = xylyl (Xyl), mesityl (Mes), 2,6-diethylphenyl (Dep), or 2,6-diisopropylphenyl (Dip); D = N-heterocyclic carbene or 4-dimethylaminopyridine, DMAP), which X-ray crystallographic studies show to have markedly elongated Mg-Mg bonds. Two of these highly reactive species are shown to reductively trimerize CO to yield rare crystallographically characterized examples of the planar, aromatic deltate dianion, incorporated in the complexes [{((DiP)Nacnac)(D)Mg(mu-C3O3)Mg((DiP)Nacnac)}(2)] (D = DMAP or :C{N(Me)C-(Me)}(2)). DFT calculations suggest that these complexes form via stepwise two-electron reductions of three CO molecules, resulting in the formation of three C C bonds within the cyclic deltate unit. This work highlights the utility of activated magnesium(I) adduct complexes as soluble organometallic models for the study of reductive C C bond-forming events in, for example, the heterogeneously catalyzed Fischer-Tropsch process.

The terminal formate complex [(OCHO)Ti(N3N)] (3) containing the trianionic triamido-amine ligand (Me3SiNCH2CH2)3N3− (N3N) was prepared via salt metathesis of [ClTi(N3N)] (1) with sodium formate or alternatively by treatment of the alkyl complex [nBuTi(N3N)] (2) with ammonium formate [HNEt3][OCHO]. Deprotonation of 3 with potassium hexamethyldisilazide gave a polymeric helical chain of the oxo complex {K[OTi(N3N)]}n (4). Reaction of 2 with the trityl salt [Ph3C][B(3,5-Cl2C6H3)4] or the Bronsted acid [HNEt3][B(C6F5)4] gave [(Et2O)Ti(N3N)][BR4] (6[BR4]·Et2O) with R = 3,5-Cl2C6H3 or C6F5. The diethyl ether ligand was easily replaced by other L-type donor ligands such as tetrahydrofuran, pyridine, and 4-dimethylaminopyridine to give 6[BR4]·L with L = thf, py, and dmap. Reaction of 6[BR4]·Et2O with a stoichiometric amount of CO2 gave the dimeric, dicationic bis(carbamate)-bridged complexes [Ti{N(CH2CH2NSiMe3)2(CH2CH2NSiMe3(μ-CO2-ηO:ηO′))}]2[BR4]2 (7[BR4]2) through insertion of one CO2 into one of the titanium-amido bonds. Addition of pyridine to 7[B(C6F5)4]2 formed the monomeric carbamate complex [(py)Ti{((O2C-κ2O,O′)NSiMe3CH2CH2)N(CH2CH2NSiMe3)2}][B(C6F5)4] (8[B(C6F5)4]·py). The cationic formate-bridged species [(Ti(N3N))2(μ-OCHO-ηO:ηO′)][BR4] (10[BR4]) readily formed when the terminal formate complex 3 was reacted with the cationic 6[BR4]. The reactivity of triamido-amine stabilized titanium(IV) complexes is shown to differ considerably from that of related titanium tris(anilide) complexes.

We describe the stable and isolable dimetalloxycarbene [(TiX3 )2 (μ2 -CO2 -κ(2) C,O:κO')] 5, where X=N-(tert-butyl)-3,5-dimethylanilide, which is stabilized by fluctuating μ2 -κ(2) C,O:κ(1) O' coordination of the carbene carbon to both titanium centers of the dinuclear complex 5, as shown by variable-temperature NMR studies. Quantum chemical calculations on the unmodified molecule indicated a higher energy of only +10.5 kJ mol(-1) for the μ2 -κ(1) O:κ(1) O' bonding mode of the free dimetalloxycarbene compared to the μ2 -κ(2) C,O:κ(1) O' bonding mode of the masked dimetalloxycarbene. The parent cationic bridging formate complex [(TiX3 )2 (μ2 -OCHO-κO:κO')][B(C6 F5)4], 4[B(C6 F5)4], was simply deprotonated with the strong base K(N(SiMe3 )2 ) to give 5. Complex 5 reacts smoothly with CO2 to generate the bridging oxalate complex [(TiX3 )2 (μ2 -C2 O4 -κO:κO'')], 6, in a C-C bond formation reaction commonly anticipated for oxalate formation by reductive coupling of CO2 on low-valent transition-metal complexes.

Wir beschreiben ein stabiles, isolierbares Dimetalloxycarben [(TiX3)2(μ2-CO2-κ2C,O:κO′)], 5 (X=N-(tert-Butyl)-3,5-dimethylanilid), das NMR-spektroskopischen Studien bei variabler Temperatur zufolge durch fluktuierende μ2-κ2C,O: κ1O′-Koordination des Carben-C-Atoms an beide Ti-Zentren des zweikernigen Komplexes 5 stabilisiert wird. Quantenchemische Rechnungen am unmodifizierten Molekul lassen auf eine hohere Energie von nur +10.5 kJ mol−1 fur den μ2-κ1O: κ1O′-Bindungsmodus des freien Dimetalloxycarbens gegenuber dem μ2-κ2C,O:κ1O′-Bindungsmodus des maskierten Dimetalloxycarbens schliesen. Der kationische Ausgangskomplex [(TiX3)2(μ2-OCHO-κO:κO′)][B(C6F5)4], 4[B(C6F5)4], mit verbruckendem Formiatliganden wurde einfach mit der starken Base K(N(SiMe3)2) zu 5 deprotoniert. Komplex 5 reagiert glatt mit CO2 zum verbruckten Oxalatkomplex [(TiX3)2(μ2-C2O4-κO:κO′′)], 6, in einer C-C-bindungsbildenden Reaktion, die allgemein fur die Oxalatbildung durch reduktive Kupplung von CO2 an niedervalenten Ubergangsmetallkomplexen erwartet wird.

A safer route than that previously published for the synthesis of [BeI2(OEt2)2] has been developed. Reactions of beryllium dihalide complexes [BeX2(OEt2)2] (X=Br or I) with either LiMe or LiBun lead to mixtures of products, which have been shown to act as sources of ‘BeR2’ (R=Me or Bun) in previous synthetic studies. Here, a titration method has been developed to determine the quantity of metal alkyl residues in these ‘BeR2’ mixtures that are available for subsequent alkane elimination reactions. Treating ‘BeMe2’ mixtures with N,N,N′,N′-tetramethylethylenediamine (tmeda) gave two lithium tetramethylberyllate compounds, [{(tmeda)Li}2(μ-BeMe4)] and [{[(tmeda)Li](BeMe4)(μ-Li)}∞], which were crystallographically characterised. Treatment of insitu-generated ‘BeR2’ solutions with several β-diketimines (HC{C(Me)=NR}{=C(Me)N(H)R}, NacnacH, R=aryl or alkyl) yielded a series of β-diketiminato beryllium alkyl complexes, [(Nacnac)BeR], including the first chiral example of such a compound. Crystallographic studies of these reveal them to be monomeric, with planar three-coordinate beryllium centres.