Alkali Metal Alkyl Research Articles

Structural, Spectroscopic, and Bonding Analyses of La(III)/Ce(III)-Tetrel Ate-Complexes.

In comparison with the research of transition-metal-tetrel complexes, the chemistry of lanthanide tetrel complexes, especially for these bearing heavier tetrel element ligands, is still relatively underexplored. In this research, K[Cp3Ln(III)CH2Ph], [(DME)3Li][Cp3Ln(III)GePh3], and [(DME)3Li][Cp3Ln(III)SnPh3] [Ln(III) = La(III), Ce(III)] have been synthesized by reacting [(DME)3Na][Cp3La(μ-Cl)LaCp3] or Cp3Ce(THF) with alkali metal alkyl, germyl, and stannyl reagents. Additionally, [(DME)3Li][Cp3Ce(III)SnPh3] is the first example of Ce(III)-Sn bond containing complex. All the obtained early Ln(III) tetrel ate-complexes were structurally analyzed by single-crystal X-ray diffraction. The formal shortness ratios of the Ln(III)-C, Ln(III)-Ge, and Ln(III)-Sn bonds are in the range of 1.03-1.11. Together with the previously reported [(DME)3Li][Cp3Ln(III)SiPh3], a group of tetrel (up to Sn) lanthanocene ate-complexes with an analogous coordination pattern are presented. Computational studies suggest the strongly polarized nature of the Ln(III)-E (E = C, Si, Ge, Sn) bonds in these complexes, with 77-85% atomic orbital contribution from tetrel elements and 15-23% atomic orbital contribution from Ln(III). The UV-vis measurements of this series of complexes show that the characteristic absorptions are hypsochromically shifted for Ln(III) heavier tetrel complexes in comparison to their lighter congeners. Moreover, the HOMOs, in which the Ln(III)-E σ-bonding orbitals are the dominant components, of these series complexes act as donor orbitals of the major electron transitions, as being disclosed by the time-dependent density functional theory analysis.

The quest for organo-alkali metal monomers: unscrambling the structure-reactivity relationship.

Organo-alkali metal reagents are essential tools in synthetic chemistry. Alkali metal organometallics aggregate in solution and solid-state forming clusters and polymers. The structure of these aggregates and their structure-reactivity relationship have been of great interest for many decades. This Perspective will look at the strategies that have been employed to isolate low aggregates and, in particular, monomeric complexes of the most common alkali metal alkyls (M = Li-Cs, R = methyl, trimethylsilylmethyl, bis/tris(trimethylsilylmethyl), butyls and benzyl) and the relationship between level of aggregation, structure and reactivity.

Alkali Metal Di-tert-butyl Phosphates: Single-Source Precursors for Homo- and Heterometallic Inorganic Phosphate Materials.

The reaction of alkali metal acetates, M(OAc)·nH2O (M = Li, Na, K), with thermally and hydrolytically unstable di-tert-butylphosphate ((tBuO)2PO2H, dtbp-H) in a 1:1 molar ratio in MeOH at room temperature leads to clean formation of group 1 metal phosphates [Li(μ-dtbp)]n (1), [Na(μ-dtbp)]n (2), and [K4(μ-dtbp)4(μ-H2O)3]n (3). All three compounds are essentially M/L 1:1 complexes. Owing to the presence of larger potassium ions, additional coordinated water molecules are found in 3, which has been further employed as a precursor for the synthesis of a mixed-metal phosphate polymer [CaK(μ-H2O)3(μ-dtbp)3]n (4) by reacting 3 with Ca(OAc)2. Compounds 1-4 have been characterized by various analytical and spectroscopic techniques. Molecular structures of 1-4 have been established in the solid state by single-crystal X-ray diffraction studies, which reveal them to be one-dimensional polymers, where the adjacent metal centers are connected through -O-P-O- bridges formed by the dtbp ligand. These complexes are rare examples of analytically pure alkali metal alkyl phosphates bearing no additional N-donor ligands (other than dtbp ligands, only water molecules are coordinated to the metal centers). Therefore, these compounds can be employed as single-source precursors (SSPs) for nano-sized ceramic phosphates. The thermogravimetric analysis of 1-4 reveals the loss of thermally labile tert-butyl substituents of the organophosphate ligands to form organic-free phosphate materials in the temperature range 300-500 °C. Solvothermal decomposition of 1-3 in boiling toluene leads to the formation of corresponding dihydrogen phosphates M(H2PO4) (M = Li, Na, and K). The thermal decomposition of heterometallic 4 in the temperature range 400-800 °C leads to the formation of phase-pure mixed-metal calcium potassium metaphosphate CaK(PO3)3.

Correlating axial and equatorial ligand field effects to the single-molecule magnet performances of a family of dysprosium bis-methanediide complexes.

Treatment of the new methanediide–methanide complex [Dy(SCS)(SCSH)(THF)] (1Dy, SCS = {C(PPh2S)2}2−) with alkali metal alkyls and auxillary ethers produces the bis-methanediide complexes [Dy(SCS)2][Dy(SCS)2(K(DME)2)2] (2Dy), [Dy(SCS)2][Na(DME)3] (3Dy) and [Dy(SCS)2][K(2,2,2-cryptand)] (4Dy). For further comparisons, the bis-methanediide complex [Dy(NCN)2][K(DB18C6)(THF)(toluene)] (5Dy, NCN = {C(PPh2NSiMe3)2}2−, DB18C6 = dibenzo-18-crown-6 ether) was prepared. Magnetic susceptibility experiments reveal slow relaxation of the magnetisation for 2Dy–5Dy, with open magnetic hysteresis up to 14, 12, 15, and 12 K, respectively (∼14 Oe s−1). Fitting the alternating current magnetic susceptibility data for 2Dy–5Dy gives energy barriers to magnetic relaxation (Ueff) of 1069(129)/1160(21), 1015(32), 1109(70), and 757(39) K, respectively, thus 2Dy–4Dy join a privileged group of SMMs with Ueff values of ∼1000 K and greater with magnetic hysteresis at temperatures >10 K. These structurally similar Dy-components permit systematic correlation of the effects of axial and equatorial ligand fields on single-molecule magnet performance. For 2Dy–4Dy, the Dy-components can be grouped into 2Dy–cation/4Dy and 2Dy–anion/3Dy, where the former have almost linear C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> DyC units with short average DyC distances, and the latter have more bent CDyC units with longer average DyC bonds. Both Ueff and hysteresis temperature are superior for the former pair compared to the latter pair as predicted, supporting the hypothesis that a more linear axial ligand field with shorter M–L distances produces enhanced SMM properties. Comparison with 5Dy demonstrates unusually clear-cut examples of: (i) weakening the equatorial ligand field results in enhancement of the SMM performance of a monometallic system; (ii) a positive correlation between Ueff barrier and axial linearity in structurally comparable systems.

Alkali-Metal Alkyl Complexes with the Tridentate Benzhydryl Ligand [2,2′-(4-MeC6H4NMe2)2CH]−

A series of alkali-metal alkyl complexes containing a tridentate benzhydryl ligand, [2,2′-(4-MeC6H4NMe2)2CH]Li(TMEDA) (1TMEDA), [2,2′-(4-MeC6H4NMe2)2CH]Na(THF)3 (2THF), {[2,2′-(4-MeC6H4NMe2)2CH]K(THF}2 (3THF), and [2,2′-(4-MeC6H4NMe2)2C(SiMe3)]K (5), were synthesized and structurally characterized. Smaller Li and Na ions form the monomeric complexes 1TMEDA and 2THF featuring η4-CCCN coordination of the [2,2′-(4-MeC6H4NMe2)2CH]− ligand, while the larger K affords the dimeric complex 3THF, in which two different types of metal–ligand bonding, μ-η5-pentadienyl-κ2-NN and μ-κ3-CNN:η6-arene are realized. Application of the Me3Si-substituited analogue [2,2′-(4-MeC6H4NMe2)2C(SiMe3)]− leads to the formation of the 1D coordination polymer {[2,2′-(4-MeC6H4NMe2)2C(SiMe3)]K}∞ (5) with μ-η3:η6 bridging coordination of the ligands to potassium ions.

Lutetium functionalities supported by a sterically encumbered β-diketiminate ligand

The sterically encumbered NacNac ligand, [HC(MeCNAr)2]− (Ar = 2,6-i-Pr2C6H3), was investigated as a platform for supporting Lu-halide complexes, sought for their potential capability of being further converted into hydrocarbyl derivatives via metathetical chemistries with alkali metal alkyls. These substituted analogs were targeted as potentially viable candidates for alkane elimination chemistries, with an eye towards the formation of an isolable Lu-alkylidene fragment.

Structural and Magnetic Diversity in Alkali-Metal Manganate Chemistry: Evaluating Donor and Alkali-Metal Effects in Co-complexation Processes.

By exploring co-complexation reactions between the manganese alkyl Mn(CH2SiMe3)2 and the heavier alkali-metal alkyls M(CH2SiMe3) (M=Na, K) in a benzene/hexane solvent mixture and in some cases adding Lewis donors (bidentate TMEDA, 1,4-dioxane, and 1,4-diazabicyclo[2,2,2] octane (DABCO)) has produced a new family of alkali-metal tris(alkyl) manganates. The influences that the alkali metal and the donor solvent impose on the structures and magnetic properties of these ates have been assessed by a combination of X-ray, SQUID magnetization measurements, and EPR spectroscopy. These studies uncover a diverse structural chemistry ranging from discrete monomers [(TMEDA)2 MMn(CH2SiMe3)3] (M=Na, 3; M=K, 4) to dimers [{KMn(CH2SiMe3)3 ⋅C6 H6}2] (2) and [{NaMn(CH2SiMe3)3}2 (dioxane)7] (5); and to more complex supramolecular networks [{NaMn(CH2SiMe3)3}∞] (1) and [{Na2Mn2 (CH2SiMe3)6 (DABCO)2}∞] (7)). Interestingly, the identity of the alkali metal exerts a significant effect in the reactions of 1 and 2 with 1,4-dioxane, as 1 produces coordination adduct 5, while 2 forms heteroleptic [{(dioxane)6K2Mn2 (CH2SiMe3)4(O(CH2)2OCH=CH2)2}∞] (6) containing two alkoxide-vinyl anions resulting from α-metalation and ring opening of dioxane. Compounds 6 and 7, containing two spin carriers, exhibit antiferromagnetic coupling of their S=5/2 moments with varying intensity depending on the nature of the exchange pathways.

Co-complexation Syntheses, Structural Characterization, and DFT Studies of a Novel Series of Polymeric Alkali-Metal Tetraorganogallates

Exploring the co-complexation reactions between the gallium alkyl Ga(CH2SiMe3)3 and alkali-metal alkyl MCH2SiMe3 (M = Li, Na, or K) using an arene/hexane solvent mixture has allowed the isolation of solvent-free alkali-metal tetraorganogallates [{MGa(CH2SiMe3)4}∞] (M = Li, 1; Na, 2) and related benzene adduct [{(C6H6)2KGa(CH2SiMe3)4}∞] (3). By combining X-ray crystallography, NMR spectroscopy, and DFT calculations, this study sheds new light on the constitution of these mixed-metal species. X-ray crystallographic studies reveal that all gallates exhibit novel polymeric arrangements, with 1 and 2 sharing the same linear chain structure, made up exclusively of M–C and Ga–C bonds, whereas 3 displays a significantly more open structural motif, where the K and Ga atoms are connected by a single alkyl bridge and propagation occurs via weaker K···Me electrostatic interactions of a methyl from a SiMe3 group of an alkyl ligand from one monomer to the potassium from a neighboring monomeric unit. Multinuclear NMR sp...

Synthesis and structures of the 2-(dimethylsila)pyrimidine derivatives (Ar = Ph, C 6H 4Bu t-4; X = H, SiMe 3, Li(hmpa) 2, K(thf) 3; n = 1, 2)

Five crystalline 2-(dimethylsila)pyrimidine derivatives ▪ ( Z) have been prepared in excellent 1– 4 or satisfactory 5 yield and characterised. The source of each was ultimately Li[CH(SiMe 2R)(SiMe 2OMe)] [R = Me ( B) or OMe ( I)]. Compound 1 ( Z with Ar = Ph, X = SiMe 3, n = 1) was obtained from Z [with Ar = Ph, X = Li(OEt 2), n = 4; previously isolated from B [P.B. Hitchcock, M.F. Lappert, X.-H. Wei, J. Organomet. Chem. 689 (2004) 1342]] and Me 3SiCl. The potassium salt 2 [ Z with Ar = C 6H 4Bu t -4; X = K(thf) 3, n = 2] was made from K[CH(SiMe 3)(SiMe 2OMe)] ( C) (via B) and 4-Bu t C 6H 4CN. Treatment of 2 with 1,2-dibromoethane afforded 3 ( Z with Ar = 4-Bu t C 6H 4; X = H, n = 1); which when reacted with successively n-butyllithium and Me 3SiCl produced 4 ( Z with Ar = 4-Bu t C 6H 4, X = SiMe 3, n = 1). Compound 5 [ Z with Ar = 4-Bu t C 6H 4, X = Li(hmpa) 2, n = 1] resulted from I with 4-Bu t C 6H 4CN and then OP(NMe 2) 3 (≡ hmpa). Plausible reaction pathways from the appropriate alkali metal alkyl C or I to 2 or 5, respectively, are suggested; these involve regiospecific 1,3-migrations of SiMe 2OMe from C → N and electrocyclic loss of Me 3SiOMe or SiMe 2(OMe) 2, respectively. The X-ray structures of crystalline 1, 2 and 5 are presented.

Synthesis and reactivity of neodymium(III) amido-tethered N-heterocyclic carbene complexes

Abstract The reaction of the heteroleptic Nd(III) iodide, [Nd(L′)(N″)(μ-I)] with the potassium salts of primary aryl amides [KN(H)Ar′] or [KN(H)Ar ∗ ] affords heteroleptic, structurally characterised, low-coordinate neodymium amides [Nd(L′)(N″)(N(H)Ar′)] and [Nd(L′)(N″)(N(H)Ar ∗ )] cleanly (L′ = t- BuNCH 2 CH 2 [C{NC(SiMe 3 )CHN t- Bu}], N″ = N(SiMe 3 ) 2 , Ar′ = 2,6-Dipp 2 C 6 H 3 , Dipp = 2,6-Pr i 2 C 6 H 3 , Ar ∗ = 2,6-(2,4,6-Pr i 3 C 6 H 2 ) 2 C 6 H 3 ). The potassium terphenyl primary amide [KN(H)Ar ∗ ] is readily prepared and isolated, and structurally characterised. Treatment of these primary amide-containing compounds with alkali metal alkyl salts results in ligand exchange to give alkali metal primary amides and intractable heteroleptic Nd(III) alkyl compounds of the form [Nd(L′)(N″)(R)] (R = CH 2 SiMe 3 , Me). Attempted deprotonation of the Nd-bound primary amide in [Nd(L′)(N″)(N(H)Ar ∗ )] with the less nucleophilic phosphazene superbase Bu t N P{N P(NMe 2 ) 3 } 3 resulted in indiscriminate deprotonations of peripheral ligand CH groups.

Reactivity control in anionic polymerization of ethylenic and heterocyclic monomers through formation of ‘ate’ complexes

AbstractThe reactivity and selectivity of active species are the key parameters in the design of living/controlled polymerizations. We have shown that alkyl metal derivatives, such as dialkylmagnesium or trialkylaluminum derivatives, when used as additives to conventional anionic polymerization systems, are very effective mediators for the polymerization control of both ethylenic and heterocyclic monomers. When added to alkali metal alkyl initiators, typically alkyl lithium, for styrene and dienes anionic polymerization they strongly retard the reactivity of the polystyryl and polybutadienyl propagating species and allow control of the polymerization of styrene under very unusual conditions (bulk, very high temperatures). On the contrary, when used in combination with quite similar alkali‐metal‐based initiators in the anionic polymerization of ethylene oxide or propylene oxide, these additives drastically enhance the reactivity and the selectivity of the involved propagating species, thus allowing a fast ‘living‐like’ polymerization to proceed at low temperatures in hydrocarbon media. Copyright © 2006 Society of Chemical Industry

New Perspectives in Living/Controlled Anionic Polymerization

AbstractSummary: Control of the reactivity and selectivity of active species remains a major challenge in the course of living/controlled polymerizations of vinyl and heterocyclic monomers. We have found that alkyl metal derivatives such as dialkylmagnesium or trialkylaluminum derivatives or the corresponding alkoxyakyl metal derivatives, when added to conventional anionic polymerization systems, are very effective mediators for the controlled anionic polymerization of both styrenic and oxirane monomers. When used as additives to alkali metal alkyl initiators (alkyl lithium, alkyl sodium) for the styrene anionic polymerizations, they strongly retard the reactivity of the propagating species and allow controlling the polymerization in very unusual conditions (bulk, very high temperature). On the contrary, when used in combination to the same alkali metal based initiators for the anionic polymerization of ethylene oxide or propylene oxide, these additives can drastically enhance the reactivity and the selectivity of the propagating species allowing a fast living‐like polymerization to proceed already at low temperature in hydrocarbon media.

Intercalation of alkali metal cations into layered organotitanium oxides.

Deprotonation of the complex [{Ti(η5-C5Me5)(μ-O)}3(μ3-CH)] with different alkali metal alkyl and amide reagents provides a method for the intercalation of alkali-metal ions into layered organometallic titanium oxides (see picture). The process and the structures were analyzed by DFT calculations.

Synthesis and structures of the heavier alkali metal alkyls; the X-ray structures of [Na(µ-R)]∞and [Rb(µ-R)(pmdeta)]2[R = CH(SiMe3)2, pmdeta =(Me2NCH2CH2)2NMe

The crystalline, hexane-soluble metal alkyls [Na(µ-R)∞1, [KR(pmedta)]m, and [Rb(µ-R)(pmdeta)]22[R = CH(SiMe3)2, pmdeta =(Me2NCH2CH2)2NMe] have been prepared from LiR with equimolar portions of NaOBut, KOBut+ pmdeta, and Rb(OC6H2But2-2,6-Me-4)+ pmdeta, respectively; 1has chains of alternating cations and planar R– anions which are approximately orthogonal to the chains, (Na–C)av 2.555(10)A, (Na–C–H)av 76(3) and (Na–C–Na)av 152(1)°, whereas 2 consists of discrete dimers, (Rb–C)av 3.412(9)A, Rb–C–Rb 75.3(2) and C–Rb–C 104.7(2)°.

The first X-ray crystal structural characterizations of alkali metal alkyl thiolates: X-ray crystal structures of [Li2(thf)4{SCH(SiMe3)2}2] and [Li2(thf)3.5{SC(SiMe3)3}2](thf = tetrahydrofuran)

The isolation and X-ray structural characterization of [Li2(thf)4{SCH(SiMe3)2}2](1) and [Li2(thf)3.5{SC(SiMe3)3}2](2)(thf = tetrahydrofuran) show them to be dimers with a central Li2S2 core (Li–S distances average 2.43 A); the lithium atoms have approximately tetrahedral co-ordination and each sulphur is three-co-ordinate, being pyramidal in (1) and almost planar in (2) where severe crowding is evident.

Some alkali metal alkyl amides as alkyne isomerization reagents: selective isomerization of one triple bond of a diynol

The lithium and sodium salts of 1,2-diaminoethane, 1,3-diaminopropane, n-butylamine, and the lithium salt of isobutylamine were studied as potential reagents for isomerization of triple bonds in alkyn-1-ols. The sodium salts of the diamines afforded high yields of the ω-alkyn-1-ol. Somewhat surprisingly, the sodium salt of n-butylamine also effects isomerization to the terminal position. The lithium salt of 1,3-diaminopropane gave the highest conversion of 2- to 3-alkyn-1-ol. A novel, selective rearrangement of one triple bond of a diynol, a 2, ω- to 3, ω-diyn-1-ol isomerization, was incorporated into a synthesis of the insect sex pheromone 3,13-octadecadienol acetate.

Polymerization of acrylonitrile in dimethylformamide induced by anionic catalysts

TH~ fact that there are comparatively few papers on homogeneous polymerization of acrylonitrile (AN) induced by anionic catalysts can be explained by the very limited choice of suitable solvents, inert to the catalysts used. In a study of the polymerization of AN in dimethylformamide (DMF) catalysed by sodiumdiphenyl, Tsukamote [1] states that sodiumdiphenyl does not react with the solvent at temperatures below --40 °. Zilkha and his collaborators [2-4] in studying the polymerization of AN under the influence of lithium butyl, C4H~Li, using DMF as the medium or as an electronating additive, did not take account of the possibility of reaction occurring between C4H~Li and DMF. Dimethylformamide reacts vigorously with alkali metal alkyls or aryls however. The products of the reaction after decomposition with water are aldehydes and amines [5]. We have been able to demonstrate that even at --70 ° D1KF reacts instantaneously with C4H~Li, and under carefully controlled reaction conditions the primary product is lithium butyl(dimethylamino)carbinolate [6]

石炭酸のアルキル炭酸アルカリ塩によるカルボキシル化反応

石炭酸のアルキル炭酸アルカリ塩によるカルボキシル化反応

Polymerization of higher aldehydes. IV. Crystalline isotactic polyaldehydes: Anionic and cationic polymerization

AbstractLow temperature polymerization of aldehydes in solvents of low dielectric constants yields crystalline isotactic polyaldehydes. Alkali metal alkoxides were found to be the best initiators; but alkali metals, alkali metal alkyls, Grignard reagents, lithium aluminum hydride, and aluminum organic compounds also work effectively. Isotactic polyaldehydes were also obtained by cationic initiation (stannic bromide, solid BF3 etherate). The stereoregularity increases with the increase of the space requirements of the side chain.

Mechanism of stereospecific polymerization of styrene with alkali metal alkyls

Journal of Polymer Science Part C: Polymer SymposiaVolume 4, Issue 1 p. 197-209 Mechanism and Kinetics of Stereospecific Polymerizations in Inhomogeneous Media Mechanism of stereospecific polymerization of styrene with alkali metal alkyls D. Braun, D. Braun Deutsches Kunststoff-Institut, Darmstadt, and Organisch-Chemisches Institut der Universität Mainz, GermanySearch for more papers by this authorW. Kern, W. Kern Deutsches Kunststoff-Institut, Darmstadt, and Organisch-Chemisches Institut der Universität Mainz, GermanySearch for more papers by this author D. Braun, D. Braun Deutsches Kunststoff-Institut, Darmstadt, and Organisch-Chemisches Institut der Universität Mainz, GermanySearch for more papers by this authorW. Kern, W. Kern Deutsches Kunststoff-Institut, Darmstadt, and Organisch-Chemisches Institut der Universität Mainz, GermanySearch for more papers by this author First published: 1963 https://doi.org/10.1002/polc.5070040118Citations: 8AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume4, Issue11963Pages 197-209 RelatedInformation