Salt Elimination Reactions Research Articles

2-chloro-azaborolyl anion: a source of 1,2-azaborole isosteric to cyclopentadienylidene.

Azaborolyl anions, the five-membered BN heterocycles, have attracted a considerable attention due to their aromaticity and isoelectronic relationship with ubiquitous cyclopentadienyl ligands. Besides their syntheses and applications in the preparation of metal complexes, the other aspects of their chemistry have been virtually unexplored. Reduction of the azabutadienyl chelate boron dichloride [ArNC(R)CHC(R)]BCl2 (2, Ar=2,6-Me2 C6 H3 , R=tBu) with two equivalents of potassium yielded the novel 2-chloro-azaborolyl anion [ArNC(R)CHC(R)BCl]K(thf) (3) as a stable product in good yield. Reaction of 3 with 1,3,4,5-tetramethylimidazol-2-ylidene (NHC) yielded the first NHC-azaborole adduct with the elimination of KCl. The salt elimination reaction was also observed in the reactions with H2 O and the organic azide ArN3 , leading to the formation of an oxo-bridged 3H-1,2-diazaborole and an intramolecular donor-stabilized iminoborane, demonstrating that 3 is a source of the unexplored 1,2-azaborole isosteric to cyclopentadienylidene.

Iron(II) Dihydrocarbyls Supported by a Biphenyl-Linked Bis(benzimidazol-2-ylidene) Ligand: Syntheses and Characterization

The use of a biphenyl-linked bis(benzimidazol-2-ylidene) ligand enables the access of dialkyl-, diaryl-, and diallyliron(II) species with bis(NHC) ligation. Deprotonation of the biphenyl-linked bis(benzimidazolium) salt (1) with 2 equiv of KH affords the biphenyl-linked dibenzotetraazafulvalene 2 in high yield. Treatment of 2 with 0.5 equiv of [(TMEDA)FeCl2]2 leads to the formation of the biphenyl-linked bis(benzimidazol-2-ylidene)iron(II) dichloride 3. Further salt elimination reactions between 3 and 2 equiv of TMSCH2Li, C6H5CH2K, PhMgBr, 3,5-(CF3)2C6H3MgBr, C3H5MgCl, and 2-Me-C3H4MgCl yield the corresponding biphenyl-linked bis(benzimidazol-2-ylidene)iron(II) dihydrocarbyls, denoted as [bis(NHC)FeR2] (R = CH2TMS (4), CH2Ph (5), Ph (6), C6H3-3,5-(CF3)2 (7), η3-CH2CHCH2 (8), η3-CH2C(Me)CH2 (9)). Compounds 2–9 have been fully characterized by NMR spectroscopy, absorption spectroscopy, solution magnetic susceptibility measurements, elemental analysis, and X-ray crystallography, revealing that 3–7 are four-c...

Syntheses and Structures of 10‐Trimethylelement‐Substituted 1,8‐Dichloroanthracenes

1,8-Dichloroanthracenes bearing EMe3 substituents at the 10-position (E = Si, Ge, Sn) have been synthesised by salt elimination reactions. The key compound, 10-bromo-1,8-dichloroanthracene (2), was quantitatively obtained by conversion of 1,8-dichloroanthracene with elemental bromine in dichloromethane. The EMe3-substituted anthracene compounds 1,8-dichloro-10-(trimethylsilyl)- (3), 1,8-dichloro-10-(trimethylgermyl)- (4) and 1,8-dichloro-10-(trimethylstannyl)anthracene (5) were completely characterised by multinuclear NMR spectroscopy and mass spectrometry. Their molecular structures in the crystalline state were analysed by X-ray diffraction experiments and compared with the crystal structure of 10-tert-butyl-1,8-dichloroanthracene (1). It was found that the level of deformation of the anthracene backbone continuously increases along the series of anthracene substituents SnMe3 < GeMe3 < SiMe3 < CMe3. Owing to the good agreement of experimental structural parameters with the results of quantum chemical calculations, the molecular deformations can be regarded as inherent molecular properties.

Siloxane-bridged [n]troticenophanes: Syntheses, structures and ring-opening reactions

Salt elimination reactions between dilithiotroticene [(η7–C7H6Li)Ti(η5–C5H4Li)]∙pmdta (1) (pmdta = N,N′,N′,N″,N″-pentamethyldiethylenetriamine) and siloxane dichlorides ClMe2Si-(OSiMe2)m-Cl (m = 1–3) at low temperature allowed the synthesis and isolation of the siloxane-bridged [n]troticenophanes [(η7–C7H6)Ti(η5–C5H4)](OSiMe2)m(SiMe2) (2, m = 1; 3, m = 2; 4, m = 3) as blue crystalline solids in moderate yield. The compounds were characterized by 1H, 13C and 29Si NMR spectroscopy, elemental and single-crystal X-ray diffraction analyses. The molecular structures of 2 and 3 showed a low degree of strain indicated by the dihedral (α = 4.8° for 2; 4.9/3.7° for 3) and distortion (δ = 176.2° for 2; 174.3/176.3° for 3) angles between the two rings. The structure of 4 was severely disordered. Compounds 2–4 are thermally resistant to ring-opening polymerization, as revealed by differential scanning calorimetry studies, with 2 exhibiting the higher melting temperature. Moreover, the observation of two endotherms in the DSC spectrum of 2 suggests a solid state transition as a result of polymorphism. The reactions of 2–4 with basic initiators such as potassium siloxanolate, ammonium siloxanolate or n-BuLi and analysis of the product distribution by electron ionization mass spectrometry revealed the formation of oligotroticenylsiloxanes incorporating one or more troticenyl units, ring-opened troticenes and ring-expanded troticenophanes [(η7–C7H6)Ti(η5–C5H4)](OSiMe2)r(SiMe2) (r > m). Similar cleavage and extension of the ring were observed by treatment of 2–4 with the acidic initiator Purolite CT-175, and ring-opened troticenes having mixed terminal –OH and –SiMe3 groups were detected. Attempts to copolymerize 2–4 and cyclotrisiloxane with n-BuLi afforded essentially the monomeric and polymeric siloxanes [Me2SiO]w (w = 7, 8), Me2(nBu)Si[OSiMe2]yOSiMe2 (y = 3–6) and Me2(n-Bu)Si[OSiMe2]zOH (z = 1–7), together with the ring-opened and ring-expanded products mentioned above.

Hydroalumination versus Deprotonation of Alkynes with Sterically Demanding Substituents

Abstract Treatment of sterically highly shielded terminal alkynes, H-C≡C-aryl, with dialkylaluminium and dialkylgallium hydrides, R2E-H, afforded by hydrogen release dimeric dialkylelement alkynides with a four-membered E2C2 heterocycle independent of the bulk of the aryl groups. A rare example of a monomeric alkynylaluminium compound was only obtained with very bulky CH(SiMe3)2 groups attached to the metal atoms and by salt elimination reaction. The steric shielding by the bulky aryl groups did not prevent condensation reactions. Hydroalumination of 1-(trimethylsilyl)-2-(2,6- dimethylphenyl)ethyne using Me2Al-H resulted in a divinyl compound by elimination of trimethylaluminium

Synthesis, structure and electrochemical properties of TCNQ lanthanide complexes

Five TCNQ (TCNQ = 7,7,8,8-tetracyano-p-quinodimethane) lanthanide complexes, namely, [Gd2(TCNQ)2(DMF)4(H2O)12][(TCNQ)4]·4H2O (1), [Gd(TCNQ)2(H2O)7][TCNQ]·6H2O·EtOH (2), [Gd2(TCNQ)4(H2O)8(CH3OH)2][(TCNQ)2]·2H2O (3), [Ln(TCNQ)2(H2O)6][TCNQ]·H2O·2MeOH [Ln = Ho (4), Ln = Yb (5)], have been synthesized by salt-elimination reactions. X-ray crystallographic analysis shows that 1–5 are discrete ionic complexes with monomer and dimer structure. Cyclic voltammograms, differential pulse voltammograms and the 1st–10th cycles CV for complexes 1–5 show the reversible one-electron oxidation and reversible one-electron reduction within the electrochemical window of CH3CN. Their electrochemical HOMO–LOMO gap and the reversibility are discussed.

Three alkaline-earth metal complexes with 3D networks constructed from a 7,7,8,8-tetracyanoquinodimethane ligand: synthesis, structure and electrochemical properties

Three new 7,7,8,8-tetracyanoquinodimethane (TCNQ) alkaline-earth metal complexes, namely {[M2(TCNQ)3(H2O)6]·TCNQ}n (M = Ca (1), Sr (2) and Ba (3)) have been synthesized by salt elimination reactions. X-ray crystallographic analysis reveals that complexes 1, 2 and 3 are isomorphic featuring a unique 3D structure. Cyclic and differential pulse voltammograms for complexes 1-3 show a reversible one-electron oxidation and a reversible one-electron reduction within the electrochemical window of CH3CN. Their electrochemical HOMO-LUMO gap and reversibility are examined.

Homoleptic Gadolinium Amidinates as Precursors for MOCVD of Oriented Gadolinium Nitride (GdN) Thin Films

Five new homoleptic gadolinium tris-amidinate complexes are reported, which were synthesized via the salt-elimination reaction of GdCl(3) with 3 equiv of lithiated symmetric and asymmetric amidinates at ambient temperature. The Gd-tris-amidinates [Gd{(N(i)Pr)(2)CR}(3)] [R = Me (1), Et (2), (t)Bu (3), (n)Bu (4)] and [Gd{(NEt)(N(t)Bu)CMe}(3)] (5) are solids at room temperature and sublime at temperatures of about 125 °C (6 × 10(-2) mbar) with the exception of compound 4, which is a viscous liquid at room temperature. According to X-ray diffraction analysis of 3 and 5 as representative examples of the series, the complexes adopt a distorted octahedral structure in the solid state. Mass spectrometric (MS) data confirmed the monomeric structure in the gas phase, and high-resolution MS allowed the identification of characteristic fragments, such as [{(N(i)Pr)(2)CR}GdCH(3)](+) and [{(N(i)Pr)(2)CR}GdNH](+). The alkyl substitution patterns of the amidinate ligands clearly show an influence on the thermal properties, and specifically, the introduction of the asymmetric carbodiimide leads to a lowering of the onset of volatilization and decomposition. Compound 5, which is the first Gd complex with an asymmetric amidinate ligand system to be reported, was, therefore, tested for the MOCVD of GdN thin films. The as-deposited GdN films were capped with Cu in a subsequent MOCVD process to prevent postdeposition oxidation of the films. Cubic GdN on Si(100) substrates with a preferred orientation in the (200) direction were grown at 750 °C under an ammonia atmosphere and exhibited a columnar morphology and low levels of C or O impurities according to scanning electron microscopy, Rutherford backscattering, and nuclear reaction analysis.

Luminescence of unique 1D tube-like lactate lanthanide coordination polymers

Two lactate lanthanide coordination polymers, {[LnNa(lactate)4]·2(H2O)}n (Ln = Sm (1) and Eu (2)), have been synthesized through the salt elimination reactions. X-ray diffraction analysis reveals that complexes 1 and 2 are isomorphic featured 1D tube-like structure incorporating with two distinct coordination models of lactate. Further, the alternative coordinated LnIII and NaI ions with lactate forms a novel coordination framework. The XRD spectra demonstrate that the complex decomposes step by step with the increasing temperature. Complex 2 exhibits essential characteristic luminescence of EuIII ion.

Early–Late Heterobimetallic Complexes with a Ta–Ir Multiple Bond: Bimetallic Oxidative Additions of C–H, N–H, and O–H Bonds

A heterobinuclear transition metal complex with a Ta–Ir multiple bond, Cp*(Me3SiCH2)2Ta–IrCp*(H)2 (1), was synthesized using a salt elimination reaction. The isolable complex was characterized by NMR, IR, UV–vis spectroscopy, and X-ray crystallography. Compound 1 features an exceptionally short intermetallic distance (Ta–Ir 2.4457(3) A). DFT calculation for 1 revealed the presence of a highly covalent bonding nature in spite of the involvement of such disparate d elements. Oxidative additions of C–H, N–H, and O–H bonds to 1 were also investigated.

New Routes to Soluble Magnesium Amidoborane Complexes

AbstractSeveral new synthetic routes to the known and new magnesium amidoborane complexes, [{(Nacnac)Mg(NH2BH3)}2] and [(Nacnac)Mg(NH2BH3)(THF)] (Nacnac = DipNacnac, [{N(Dip)C(Me)}2CH]–, or tBuNacnac, [{N(Dip)C(tBu)}2CH]–; Dip = C6H3iPr2‐2,6), are reported. These include the reductive dehydrogenation reaction of NH3BH3 (AB) with the magnesium(I) dimer, [{(DipNacnac)Mg}2], and the salt elimination reaction of [(DipNacnac)MgI(OEt2)] with Li(NH2BH3). Moreover, the reaction of ammonia–borane with two magnesium(II) hydride complexes, [{(Nacnac)Mg(μ‐H)}2], or an alkylmagnesium(II) complex [{(DipNacnac)Mg(μ‐nBu)}2], have been shown to yield well defined parent amidoborane complexes of magnesium for the first time. The crystal structures of all prepared complexes were obtained and shown to be similar to those previously reported for related compounds.

Synthesis, Reactivity and Ring‐Opening Polymerization of a Tin‐Bridged ansa‐Cycloheptatrienyl‐Cyclopentadienyl Titanium Sandwich Complex

AbstractThe tBu2Sn‐bridged [1]troticenophane [(η7‐C7H6)Ti(η5‐C5H4)]SntBu2 (2) has been synthesized by low‐temperature salt elimination reaction between stoichiometric amounts of the dilithiated troticene [(η7‐C7H6Li)Ti(η5‐C5H4Li)]·pmdta (1; pmdta = N,N′,N′,N″,N″‐pentamethyltriethylenetriamine) and tBu2SnCl2. Compound 2 was isolated as a blue‐green crystalline solid in moderate yield and characterized by multinuclear 1H, 13C and 119Sn NMR spectroscopy, UV/Vis spectroscopy and elemental analysis. Compound 2 and the co‐crystal 2·[(pmdta)LiCl] were characterized in the solid state by X‐ray diffraction analyses. The dihedral angles between the planes of the C5H4 and C7H6 rings are 16.3(3) and 17.2(1)°, respectively, for 2 and its co‐crystal. Compound 2 is the first monocrystalline structurally characterized heteroleptic stanna[1]troticenophane. The reaction of 2 with [Pt(PEt3)3] afforded the platinastanna[2]troticenophane 3, in which the Pt0 fragment was inserted by regioselective cleavage of the ipso‐C7H6–Sn bond, as evidenced by 13C NMR spectroscopy and X‐ray diffraction analysis. Compound 2 underwent thermal ring‐opening polymerization in the solid state to form poly(troticenylstannane) 4. In solution and in the presence of nBuLi as initiator, 2 opens and reassembles to form the metallopolymer 5. The polymeric nature of both 4 and 5 was determined by gel permeation chromatography.

Metal-Enriched [3]Trochrocenophanes: Bimetallic Metalloarenophanes by Coordination to Chelating Bis(phosphanyls)

The first 1,1′-bis(phosphanyl)trochrocene derivatives (1–3) have been prepared in reasonable isolated yields by salt elimination reactions of monochlorophosphines (ClPPh2, ClPCy2, and ClPMe2) with ...

Compounds with Direct Gallium–Lanthanum and Gallium–Zinc Bonds

The reduction of digallane (dpp-Bian)Ga–Ga(dpp-Bian) (1) {dpp-Bian = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene} with 2 equiv of sodium in Et2O affords complex (dpp-Bian)Ga–Na(Et2O)3 (2), containing a gallium–sodium direct bond. The gallium–zinc complex with a chiral amido–imino ligand, (dpp-Bian)Ga–Zn{dpp-Bian(nBu)} (4), has been prepared by the salt elimination reaction between 2 and [{dpp-Bian(nBu)}ZnCl]2 (3). Reduction of complex (dpp-Bian)Ga–Zn(dpp-Bian) (5) with 1 equiv of potassium gave the gallium–zinc complex [(dpp-Bian)Ga–Zn(dpp-Bian)][K(thf)5.5] (6). Lanthanum dicyclopentadienides [(C5Me4Et)2LaCl2][K(thf)2] (7) and [(C5Me5)2LaCl2][Na(Et2O)2] (8) react with 2 to give the first complexes with gallium–lanthanum bonds, (dpp-Bian)Ga–La(C5Me4Et)2(thf) (9) and (dpp-Bian)Ga–La(C5Me5)2(thf) (10), respectively. The newly prepared complexes 4, 6, 9, and 10 have been characterized by 1H nuclear magnetic resonance and infrared spectroscopy; the molecular structures of 4, 6, and 9 have been determined...

Synthesis and Characterization of an Amidinate-Stabilized Siladithiocarboxylate and Its Germanium(II) Complex

The synthesis and characterization of the amidinate-stabilized potassium siladithiocarboxylate [{LSi(S)2}K(THF)2]2 (2, L = PhC(NBut)2) are described. Compound 2 was synthesized by the reaction of [LSiCl] (1) with two equivalents of elemental sulfur and KC8 in THF. X-ray crystallography and DFT calculations show that the Si–S bond lengths in 2 are intermediate between the Si═S double and Si–S single bond lengths. There is a weak electronic delocalization along the “Si(S)2” skeleton. Compound 2 underwent a salt elimination reaction with GeCl2·dioxane to form [{LSi(S)2}2Ge:] (3), which contains two “LSi(S)2–” moieties chelating to the germanium(II) atom in an anisobidentate manner.

Selective Dilithiation of [Ti(η5-C5H5)(η8-C8H8)] and Subsequent Conversion into Neutral and Cationic ansa-Complexes

Selective dimetalation of a sandwich complex featuring the cyclooctatetraene ligand has been accomplished for the first time. The isolation of the dilithiated species 1 subsequently enabled the isolation of a paramagnetic [2]stannatitanoarenophane (2) via salt elimination reaction. Chemical oxidation resulted in the formation of a rare example of a cationic ansa-complex (3).

Synthesis, Structure, and Reactivity of Organo-Iron(II) Complexes with N-Heterocyclic Carbene Ligation

The synthesis, structure, and reactivity of some organo-iron complexes with monodentate N-heterocyclic carbene (NHC) ligation were studied. Mononuclear ferrous complexes [(IEt)2FeR2] (IEt = 2,5-diethyl-3,4-dimethylimidazol-1-ylidene, R = Me (2a), CH2TMS (2b)) and [(IPr)FeMes2] (3, IPr = 2,5-diisopropyl-3,4-dimethylimidazol-1-ylidene) were prepared in good yields via salt elimination reactions of [(NHC)2FeCl2] (1) with alkylation reagents. The interaction of 1 with PhLi gave a mixture of dinuclear complexes [Cl(IEt)Fe(IEt′)2Fe(IEt)Cl] (4a) and [Ph(IEt)Fe(IEt′)2Fe(IEt)Ph] (4b) (IEt′ = 3-Et-4,5-Me2-2-ylideneimidazolyl anion), in which N−C(ethyl) bond cleavage of the NHC ligand was involved. Complexes 2a−4b were characterized by 1H NMR, elemental analyses, and single-crystal X-ray diffraction studies. Solution magnetism measurement by Evan’s method revealed the high-spin electronic configuration for the mononuclear organo-iron(II) complexes 2a, 2b, and 3. Reactivity studies showed the tetrahedral complex 2a was inert toward many unsaturated organic substrates, whereas the trigonal-planar complex 3 could react with CO and carbodiimide PriN═C═NPri to yield dimesityl ketone and [(IPr)Fe(Mes)(η2-PriNC(Mes)NPri)] (5), respectively. Relevant to iron-catalyzed Kumada couplings, both complexes 2b and 3 were found reactive with PhI to yield the corresponding carbon−carbon bond formation products Ph−CH2TMS and Ph−Mes.

Synthesis and X-ray Crystal Structures of Tetranuclear Zincamidinate Complexes

Polynuclear amidinate zinc halide complexes of the general type{C[C(Ni-Pr)2ZnX]4} [X = Cl, 2; Br, 3; I, 4] were prepared in high yields via methyl/halide exchange reaction of {C[C(Ni-Pr)2ZnMe]4} (1a) with AlX3. 2−4 were characterized by elemental analysis, multinuclear NMR, and IR spectroscopy and single-crystal X-ray diffraction. Computational calculations of halide-substituted complexes {C[C(Ni-Pr)2ZnX]4} [X = F−I] were performed to clarify the influence of the halide atom on the structural parameters of the complexes and to elucidate their electronic structure and bonding situation. The capability of these halide-substituted complexes to serve as suitable starting reagents for further salt elimination reactions was proven by reaction of 2 with LiR (R = Me, n-Bu) and EtMgBr, which yielded the corresponding Zn-alkyl species {C[C(Ni-Pr)2ZnR]4} [R = Me, 1a; n-Bu, 5; Et, 6].

Bulky guanidinato and amidinato zinc complexes and their comparative stabilities

The preparation of a series of amidinato and guanidinato zinc halide complexes incorporating ligands of varying steric bulk is described, and their thermal stabilities compared. Salt elimination reactions between [M(Giso)] (M = K or Li; Giso = [(ArN)(2)CNCy(2)](-), Ar = 2,6-diisopropylphenyl, Cy = cyclohexyl) and ZnX(2) (X = I or Br) have yielded the monomeric complexes [(Giso)ZnI] and [(Giso)Zn(mu-Br)(2)Li(OEt(2))(2)]. Both have been crystallographically characterised and the former shown to slowly decompose in solution at ambient temperature to give the carbodiimide, ArN[double bond, length as m-dash]C[double bond, length as m-dash]NAr. In contrast, reactions between alkali metal complexes of a less bulky guanidinate, [M(Priso)] (Priso = [(ArN)(2)CNPr(i)(2)](-)) and ZnX(2) have yielded [(IZn)(2)(mu-NPr(i)(2)){mu-N,N'-(NAr)(2)CH}] and [(Priso)Zn(mu-Br)(2)Li(OEt(2))(2)]. The latter decomposes in solution at ambient temperature, generating ArN[double bond, length as m-dash]C[double bond, length as m-dash]NAr, which was also produced in the preparation of the former. Analogies are drawn between the decomposition of [(Priso)Zn(mu-Br)(2)Li(OEt(2))(2)] and the carbonic anhydrase catalysed dehydration of bicarbonate. Two bulky amidinato zinc complexes, [{(Piso)Zn(mu-Br)}(2)] and [Zn(Piso)(2)] (Piso = [(ArN)(2)CBu(t)](-)) have been prepared, structurally characterised and shown to be markedly more thermally stable than the zinc guanidinate compounds. Attempts to reduce several of the zinc(ii) halide complexes to dimeric zinc(i) compounds were so far unsuccessful, in all cases leading to the deposition of zinc metal.

Some reactions of an η3-tetracyanobutadienyl-ruthenium complex

In the eta(3)-butadienyl complex Ru{eta(3)-C(CN)(2)CPhC=C(CN)(2)}(PPh(3))Cp 1, which is formed from Ru(C[triple bond]CPh)(PPh(3))(2)Cp and tcne, a CN group reacts with MeO(-) to give the methoxy-amide Ru{NH=C(OMe)C(CN)=CCPh=C(CN)(2)}(PPh(3))Cp 2, in which the NH has displaced the C=C from the Ru centre with formation of a RuC(3)N ring. "Click addition" of azide to a CN group in 1 gives the oligomeric tetrazolato complex Ru{N(3)N[Na(OEt(2))]=CC(CN)=CCPh=C(CN)(2)}(PPh(3))Cp 3, also containing a RuC(3)N ring. Salt-elimination reactions of 3 with MeOTf, FeCl(dppe)Cp, RuCl(dppe)Cp* and trans-PtCl(2){P(tol)(3)}(2) result in selective substitution at one nitrogen atom of the RuC(3)N ring. Geometries of 1 and the anion in 3 were computed by DFT methods. Preferences for CN groups attacked in the nucleophilic and cycloaddition reactions of 1 are supported by NBO calculations. Alkylation of 1 in reactions with 1,2-dimethoxyethane gave two isomers of Ru{N(3)[CH(CH(2)OMe)(OMe)]N=CC(CN)=CCPh=C(CN)(2)}(PPh(3))Cp 8 and 9, differing in the sites of attachment of the alkyl group, likely by radical processes. The molecular structures of eight complexes are reported, including a re-determination of 1. Computed NMR chemical shifts are used to reassign the butadienyl carbon resonances in the (13)C NMR spectrum of 1.