Lithium Amidinate Research Articles

Reactions of lithium amidinates or guanidinates toward carbodiimides: Synthesis and characterization of multi-site triazapentadienyllithium compounds

Lithium amidinates or guanidinates form novel complexes 1–4 with N,N′-dicyclohexylcarbodiimide (CyN=C=NCy, DCC) or N,N′-diisopropylcarbodiimide (iPrN=C=NiPr, DIC). Their structures were characterized by spectroscopic and X-ray crystallographic method. The X-ray diffraction analysis revealed that heteroleptic complexes 1–3 were mononuclear with a four-co-ordinate metal center and homoleptic 4 was dimeric. Both the W-shaped 1,3,5-triazapentadienato lithium 1–3 and U-shaped 4 could be regarded as good intermediates en route to their metal complexes with varied substrates.

Synthesis and Crystal Structures of Three Thioether Functionalized Formamidines and Their Corresponding Lithium Formamidinates

AbstractThree thioether functionalized formamidines RNHC(H)NR (R=2‐SMe‐C6H4, 2‐StBu‐C6H4, 2‐SPh‐C6H4) were prepared from the corresponding amines RNH2 and triethyl orthoformate. X‐ray crystal structure determinations revealed the typical E configuration about the amidine C=N bond for all three compounds. The 2‐SMe and 2‐StBu derivatives exhibit the most frequently observed anti orientation of the RNH group while the 2‐SPh derivative displays the much more rarely encountered syn arrangement. All three compounds exhibit weak intramolecular N−H⋅⋅⋅S hydrogen bridges of the (5) type. Treatment of the amidines with n‐BuLi led to the formation of the corresponding lithium amidinates. X‐ray crystal structure determinations of the lithium amidinates revealed several molecular patterns ranging from the mononuclear complex [Li{2‐StBu‐C6H4N)2CH}2(THF)2] to the trimeric compound [Li3{(2‐SMe‐C6H4N)2CH}3].

Synthesis and Structural Characterization of a Series of Homoleptic First‐Row Transition Metal Tris(alkynyl‐amidinates)

AbstractA series of new homoleptic first‐row transition metal and yttrium tris(alkynylamidinate) complexes have been synthesized and fully characterized. The starting materials [c‐C3H5−C≡C−C(NR)2]Li⋅THF (1: R=iPr, 2: R=Cy; Cy=Cyclohexyl) were obtained in high yields by employing a modified literature procedure. In the course of this study, the unprecedented tetrameric, unsolvated lithium amidinate [Li{c‐C3H5−C≡C−C(NiPr)2}]4 (1 a) could be isolated and structurally characterized. In addition to the Li salts, two new potassium cyclopropylethinylamidinates, K[c‐C3H5−C≡C−C(NR)2]⋅THF (3: R=iPr, 4: R=Cy) were prepared by nucleophilic addition of potassium cyclopropylacetylide to N,N′‐di‐iso‐propylcarbodiimide or N,N′‐dicyclohexylcarbodiimide. The new homoleptic first‐row transition metal and yttrium complexes M[c‐C3H5−C≡C−C(NiPr)2]3 (M=Y (5), Cr (6), Fe (7)) and M[c‐C3H5−C≡C−C(NCy)2]3 (M=Y (8), Ti (9), V (10), Cr (11), Fe (12)) were found to be readily available by treatment of MCl3 precursors with 3 equiv. of the alkali metal cyclopropylethinylamidinates. An alternative synthetic route to the titanium(III) complex 9 was found in the reaction of trichloro(cyclopentadienyl)titanium(IV) and lithium amidinate 2 in a 1 : 3 molar ratio. Compounds 5–12 were fully characterized by the usual set of analytical and spectroscopic methods as well as single‐crystal X‐ray diffraction studies. All eight complexes represent unsolvated, homoleptic metal(III) tris(amidinates).

Synthesis of New Bulky Bis(amidine) with the Conformationally Rigid meta-Phenylene Bridge and Its Dilithium Derivative [1,3-C6H4{NC(Ph)N(2,6-iso-Pr2C6H3)}2]Li2(TMEDA)2

The reaction of 2,6-diisopropylaniline with m-phenylenedibenzimidoyl chloride 1,3-C6H4{N=C(Ph)Cl}2 in the presence of triethylamine in a toluene solution affords bis(amidine) 1,3-C6H4{NC(Ph)NH(2,6-iso-Pr2C6H3)}2 (H2L) in which two amidinate fragments are bound by the conformationally rigid m-phenylene linker. The metallation of bis(amidine) by n-butyllithium in the presence of tetramethylethylenediamine (TMEDA) occurs readily in a tetrahydrofuran solution at –70°С to form the corresponding lithium amidinate complex 1,3-C6H4{NC(Ph)N(2,6-iso-Pr2C6H3)}2Li2(TMEDA)2 (I). The X-ray structure analysis shows that complex I is monomeric (CIF file CCDC no. 1873201). Each amidinate fragment NCN is bound to one lithium atom via the κ2-N,N chelating mode.

Structural Investigation of New Lithium Amidinates and Guanidinates

A series of potentially useful lithium amidinates and guanidinates were prepared and fully characterized. Treatment of N,N′‐diisopropylcarbodiimide with phenyllithium in diethyl ether afforded the lithium amidinate [PhC(NiPr)2Li(OEt2)]2 (1). Similar treatment of N,N′‐diorganocarbodiimides R′–N=C=N–R′ [R′ = iPr, cyclohexyl (Cy)] with secondary lithium amides LiNR2 [R2 = Et2, iPr2, (CH2)4] followed by crystallization from THF or 1,4‐dioxane gave the lithium guanidinates [R2NC(NR′)2Li(S)]2 [2: R = Et, R′ = iPr, S = THF; 3: R2 = (CH2)4, R′ = iPr, S = THF; 4: R = R′ = iPr, S = ½ 1,4‐dioxane; 5: R2 = (CH2)4, R′ = Cy, S = 1,4‐dioxane] as crystalline solids. Reaction of N‐lithioaziridine with the corresponding carbodiimides afforded solvent‐deficient [{C2H4NC(NiPr2)2}2Li2(THF)]2 (6), and [C2H4NC(NEt)(NtBu)Li(THF)]2 (7). Crystal structure determination revealed the presence of common ladder‐type dimeric structures for 1–5. Compound 6 exists as a dimer of two ladder‐type dimers in the crystal, and 7 exhibits an unusual dimeric structure comprising an eight‐membered C2N4Li2 ring.

Alternative (κ1-N:η6-arene vs.κ2-N,N) coordination of a sterically demanding amidinate ligand: are size and electronic structure of the Ln ion decisive factors?

The amine elimination reaction of equimolar amounts of ansa-bis(amidine) C6H4-1,2-{NC(tBu)NH(2,6-iPr2C6H3)}2 (L1H) and [(Me3Si)2N]2Yb(THF)2 affords a bis(amidinate) YbII complex [C6H4-1,2-{NC(tBu)N(2,6-iPr2C6H3)}2]Yb(THF) (1) in 68% yield. Complex 1 features a rather rare η1-amido:η6-arene coordination of both amidinate fragments to the YbII ion, resulting in the formation of a bent bis(arene) structure. Oxidation of 1 by I2 regardless of the molar ratio of reagents (2 : 1 or 1 : 1) leads to the formation of the YbIII species [{(2,6-iPr2C6H3)[double bond, length as m-dash]NC(tBu)NH}-C6H4-1,2-{NC(tBu)N(2,6-iPr2C6H3)}]YbI2(THF)2 (2) in which only one amidinate fragment is coordinated to the ytterbium ion in κ2-N,N'-chelating coordination mode, while the second NCN fragment is protonated in the course of the reaction and is not bound to the metal ion. The outcome of the salt metathesis reaction of LaCl3 with lithium amidinates [C6H4-1,2-{NC(tBu)N(2,6-R2C6H3)}2Li2] (R = Me, iPr) is proven to be strongly affected by the substituent 2,6-R2C6H3 on the amidinate nitrogens. When R = iPr, the salt metathesis reaction occurs smoothly and results in the formation of an ate-chloro-amidinate complex [C6H4-1,2-{NC(tBu)N(2,6-iPr2C6H3)}2]La(μ2-Cl)Li(THF)(μ2-Cl)2Li(THF)2 (3) in which the LaIII ion is coordinated by both amidinate fragments in a "classic"κ2-N,N'-chelating fashion. In the case of R = Me, the reaction requires prolonged heating for completion. Moreover, the salt metathesis reaction is accompanied by the fragmentation of the ligand and affords a trinuclear chloro-amidinate complex [C6H4-1,2-{NC(tBu)N(2,6-Me2C6H3)}2]La{[(tBu)C(N-2,6-Me2C6H3)2]La(THF)}2(μ2-Cl)4(μ3-Cl)2 (4) containing one dianionic ansa-bis(amidinate) and two monoanionic [(tBu)C(N-2,6-Me2C6H3)2] amidinate fragments. DFT calculations are conducted to determine the factor that governs this change in coordination mode and, in particular, the effect of the metal oxidation state.

Neodymium dihalide complexes with a tridentate amidinate phosphine oxide ligand: synthesis, structure, and catalytic activity in isoprene polymerization

The deprotonation of amidine 2-[Ph2P(O)]C6H4NHC(But)=N(2,6-Me2C6H3) (1) with BunLi affords lithium amidinate {2-[Ph2P(O)]C6H4NLiC(But)=N(2,6-Me2C6H3)}2 (2) having a dimeric structure, as demonstrated by X-ray diffraction. New amidinate dihalide complexes {2-[Ph2P(O)]C6H4NC(But)N(2,6-Me2C6H3)}NdHal2(THF)2 (Hal = I (3), Cl (4)) were synthesized by exchange reactions of lithium and potassium amidinates with anhydrous neodymium halides NdHal3(THF)n (Hal = I, n = 3.5; Cl, n = 0). The X-ray diffraction studies showed that the new compounds are monomeric and the amidinate ligand is tridentate. Chloride complex 4 involved in the three- and four-component catalyst systems 4–AlR3–[Ph3C] [B(C6F5)4] (1: 10: 1; AlR3 = AlBui 3, AlMe3), 4–AlR3–PriOH (1: 10: 10; AlR3 = AlBui3, AlMe3), and 4–AlR3–[Ph3C][B(C6F5)4]–PriOH (1: 10: 1: 10; AlR3 = AlBui3, AlMe3) exhibits activity in stereospecific isoprene polymerization and allows the preparation of high-molecular-weight polyisoprene samples with exceptionally high cis-1,4-unit content (up to 99.4%).

Synthesis, structures of mononuclear and dinuclear iron(II) complexes supported by non-symmetric guanidinate(amidinate) ligands

A new family of Fe(II) compounds, 1–3, have been prepared, which are derived from the non-symmetric lithium guanidinate Li(L1) [L1 = N(Ph)C(R)N(SiMe3)] (R = 1-piperidino) or the lithium amidinates Li(L2) [L2 = N(Ph)C(Ph)N(SiMe3)] or Li(L3) [L3 = N(2,6-iPr2C6H3)C(Ph)N(SiMe3)]. Treatment of Li(L1), Li(L2) or Li(L3) with anhydrous FeCl2 afforded [(L1)4Fe2] (1), [(L2)4Fe2] (2) or [{L3}2Fe] (3), respectively. The molecular structures of 1–3 were determined by an X-ray diffraction study.

Direct access to non-symmetric lithium nitriloamidinate and disymmetric dilithium bisamidinate complexes from 1,3- or 1,4- dicyanobenzene and lithium amides

Non-symmetric lithium nitriloamidinate complexes of composition 3- or 4-(N≡C)C6H4[C(NSiMe3)(NAr)]Li(D)n where Ar is phenyl, 2,6-(CH3)2C6H3 (Dmp) or 2,6-[(CH3)2CH]2C6H3 (Dipp); D means coordinated solvent - THF or diethylether and n = 1 or 2, were prepared from 1,3- or 1,4-dicyanobenzene and one molar equivalent of appropriate trimethylsilylated lithium amide. Disymmetric dilithium bisamidinate complexes of 1, 3- or 1, 4-{[(NSiMe3)(NAr)C]Li(D)n}2C6H4 type were prepared by the same procedure using two molar equivalents of lithium amides. When the isolated lithium nitriloamidinate complexes were reacted with lithium amide of another type, asymmetric dilithium bisamidinates 3- or 4-{[(NSiMe3)(NAr)C]Li(D)n}{[(NSiMe3)(NAr')C]Li(D)n}C6H4 were obtained and characterized. The reaction period for essentially quantitative conversion of the starting material to desired bisamidinates is strongly dependent on the substitution pattern of parent lithium amides as well as the dinitrile going from hours to more than forty days in the case of Dipp-substituted amide and 1,3-dicyanobenzene combination. In the solid state, complexes bearing less bulky substituent - phenyl - tend to aggregate to dinuclear species for lithium nitriloamidinates or linear polymers for bisamidinates. Presence of more sterically demanding substituents directed the structure of prepared compounds to mononuclear species with isobidentate bonding fashion of amidinates and two molecules of solvent being extra-coordinated to the lithium atom. For all lithium amidinates prepared, the central lithium atom has distorted tetrahedral coordination geometry with ligands being in an anisobidenate or bidentate-bridging bonding fashion.

Amidinate bisborohydride complexes of rare-earth metals [6-Me-C5H3N-2-CH2C(NPri)2]Ln(BH4)2THF2 (Ln = Y, Nd): synthesis, structure, and catalytic activity in isoprene polymerization

Reactions of equimolar amounts of RN=C=NR (R = Pri, Cy) and 6-Me-C5H3N-2-CH2Li prepared in situ by metallation of 2,6-dimethylpyridine with n-butyllithium afforded corresponding lithium amidinates [Li{6-Me-C5H3N-2-CH2C(NPri)2}]•1/3THF (1) and [Li{6-MeC5H3N-2-CH2C(NCy)2}]4 (2) containing new tridentate amidinate ligands. The salt metathesis reactions of Ln(BH4)3(THF)3 (Ln = Y, Nd) with 1 (1: 1 molar ratio, THF) result in neutral amidinate bisborohydride complexes [Ln{6-Me-C5H3N-2-CH2C(NPri)2}(BH4)2(THF)2} (Ln = Y (3), Nd (4)). According to X-ray data, both compounds are monomeric, terminal borohydride ligands being coordinated to the rare earth metal atom in η3-fashion. Nitrogen atoms of the pyridine fragments of amidinate ligands are not involved in complexation with metal cations. Complexes 3 and 4 in combination with [Ph3C][B(C6F5)4] and AlBu 3 i (1: 1: 10 molar ratio) exhibit catalytic activity in isoprene polymerization.

Crystal and mol-ecular structures of two silver(I) amidinates, including an unexpected co-crystal with a lithium amidinate.

The silver(I) amidinates bis-[μ-N1,N2-bis-(propan-2-yl)benzamidinato-κ2N1:N2]disilver(I), [Ag2(C13H19N2)2] or [Ag{PhC(N i Pr)2}]2 (1), and bis-(μ-N1,N2-di-cyclohexyl-3-cyclo-propyl-propynamidinato-κ2N1:N2)disilver(I), [Ag2(C18H27N2)2] or [Ag{cyclo-C3H5-C≡C-C(NCy)2}]2 (2a), exist as centrosymmetric dimers with a planar Ag2N4C2 ring and a common linear coordination of the metal atoms in the crystalline state. Moiety 2a forms a co-crystal with the related lithium amidinate, namely bis-(μ-N1,N2-di-cyclo-hexyl-3-cyclo-propyl-propynamidinato-κ2N1:N2)disilver(I) bis-(μ-N1,N2-di-cyclo-hexyl-3-cyclo-propyl-propynamidinato-κ3N1,N2:N1)bis-(tetra-hydro-furan-κO)lithium(I) toluene monosolvate, [Ag2(C18H27N2)2][Li2(C18H27N2)2(C4H8O)2]·C7H8 or [Ag{cyclo-C3H5-C≡C-C(NCy)2}]2[Li{cyclo-C3H5-C≡C-C(NCy)2}(THF)]2·C7H8, composed as 2a × 2b × toluene. The lithium moiety 2b features a typical ladder-type dimeric structure with a distorted tetra-hedral coordination of the metal atoms. In the silver(I) derivatives 1 and 2a, the amidinate ligand adopts a μ-κN:κN' coordination, while it is a μ-κN:κN:κN'-coordination in the case of lithium derivative 2b.

Structure of non-symmetric lithium amidinate complexes prepared by addition of lithium amides to various nitriles

Lithium amidinate complexes were prepared by direct reactions from various nitriles - R1-CN (R = Ph, n-Bu, t-Bu) and trimethylsilyl-substituted lithium amides - R2(Me3Si)NLi (R2 = Ph, 2,6-(CH3)2C6H3 (Dmp) and 2,6-[(CH3)2CH]2C6H3 (Dipp)). All the reactions proceed only in coordinating solvents as diethylether or THF where the migration of the trimethylsilyl group to the nitrogen atom of the parent nitrile is favoured. In the case of t-BuCN, virtually no conversion to appropriate lithium amidinate was observed under the same reaction protocol. Only the adduct of the composition {(t-BuCN){2,6-[(CH3)2CH]2C6H3}(Me3Si)NLi]}2 was isolated from the reaction of t-BuCN with {2,6-[(CH3)2CH]2C6H3}(Me3Si)NLi]} carried out in hexane or toluene solution. Lithium atoms in this adduct appear in trigonal planar to pyramidal coordination neighborhoods. The structure of lithium amidinates in the solid state is strongly dependent on the substitution pattern, when the Dipp substituent is present, complexes always crystallize as mononuclear species with isobidentate bonding fashion of the amidinate and two molecules of solvent being extra-coordinated to the lithium atom. On contrary, smaller peripheral groups do not protect the lithium atom from further association and those complexes are described as di- or trinuclear adducts with less than two coordinated molecules of solvent per lithium atom. In all lithium amidinates prepared, the central lithium atom has distorted tetrahedral coordination geometry with ligands going from anisobidenate or bidentate-bridging to tridentate bonding fashion except the trinuclear complex bearing the smallest combination of ligands where one of the lithium atoms is found in the trigonal planar vicinity.

Bisborohydride yttrium complexes containing amidinate ligands [o-Me2NC6H4CH2C(NR)2]Y(BH4)2L n (R = Pri, L = DME, n = 1; R = Cy, L = THF, n = 2). Synthesis, structure, and catalytic activity in polymerization of rac-lactide and isoprene

A reaction of o-N,N-dimethyltoluidine lithium derivative (o-Me2NC6H4CH2Li) with carbodiimides (RN=C=NR, where R = Pri, Cy) in THF at room temperature leads to lithium complex of the general formula [{o-Me2NC6H4CH2C(NR)2}Li(THF)2]2 (R = Pri (1), Cy (2)) containing a new tridentate amidinate ligand. X-ray diffraction studies showed that complexes 1 and 2 are dimeric due to the coordination of the nitrogen atoms of the amidinate group with different lithium atoms. The nitrogen atoms of the aminobenzyl fragment are not involved in the complexation. The exchange reactions of Y(BH4)3(THF)3 with lithium amidinates 1 and 2 carried out with the equimolar ratio of reagents in solution in THF proceeded with the formation of neutral amidinatebisborohydride complexes of the general formula [o-Me2NC6H4CH2C(NR)2]Y(BH4)2Ln (3: R = Pri, L = DME (with added DME), n = 1; 4: R = Cy, L = THF, n = 2). According to the X-ray diffraction data, compounds 3 and 4 are monomeric, borohydride ligands are coordinated to the rare-earth metal atom by the η3- and η2-type. The donor NMe2 groups of the amidinate ligands are not involved in the metal—ligand interaction. Yttrium complexes 3 and 4 exhibit catalytic activity in polymerization of rac-lactide and isoprene.

Aluminum and Indium Complexes derived from Guanidines, Triazenes, and Amidines

Abstract The reaction of guanidines, triazenes, amidines, and lithium amidinates with trimethylamine alane ([AlH3(NMe3)]), lithium tetrahydridoaluminate, trimethylaluminum, aluminum trichloride, and indium trichloride is reported. Equimolar reactions utilising hindered N,N′‐bis(2, 6‐diisopropylphenyl)guanidines afford [{AlX2L}n] species through hydrogen elimination (X = H) from [AlH3(NMe3)] (n = 2) with HCGiso (1), HDGiso (2), or HDPiso (3) [CGiso = N,N′‐bis(2, 6‐disopropylphenyl)‐N′′‐dicyclohexylguanidinate, DGiso = N,N′,N′′‐tris(2, 6‐diisopropylphenyl)guanidinate, DPiso = N,N′‐bis(2, 6‐diisopropylphenyl)‐P‐2, 6‐diisopropylphenylphosphguanidinate], or through methane elimination (X = Me) from AlMe3 [n = 1, L = CGiso (5)]. The analogous reactions of the triazene HTiso with LiAlH4 and AlMe3 selectively afford [AlH(Tiso)2] (4) and [AlMe2(Tiso)] (6), respectively [Tiso = 1, 3‐bis(2, 6‐diisopropylphenyl)triazenide]. Reactions of N,N′‐bis(aryl)formamidines/ates with half an equivalent of AlMe3/AlCl3 result in [AlXL2] complexes [X = Me; L = Fxy (7) or Fet (8); X = Cl; L = Fet (9) or L = Fiso (10)] [Fxy = N,N′‐bis(2, 6‐dimethylphenyl)formamidinate, Fet = N,N′‐bis(2, 6‐diethylphenyl)formamidinate, Fiso = N,N′‐bis(2, 6‐diisopropylphenyl)formamidinate]. Treatment of 1 with one equivalent of I2 yields [AlI2(CGiso)] (11). Attempts to prepare [InCl2L] congeners of 11 with L = Fxy and Fet led to the isolation of prodigious quantities of [InCl3(HFxy)2] (12) and [InCl2(Fet)(HFet)] (13) due to adventitious water. The X‐ray crystal structures of 1–13 are reported.

Surprising reactivity of the unsymmetrically substituted amidinate anion [MeC(NEt)(NtBu)

Three unexpected products derived from the unsymmetrically substituted amidinate anion [MeC(NEt)(NtBu)]− are reported. Treatment of 1-tert-butyl-3-ethyl-carbodiimide, tBu-NCN–Et, with 1 equiv. of methyllithium in diethyl ether afforded colorless crystals of the unusual octanuclear lithium amidinate derivative {[LiN(Et)C(Me)N(tBu)]2⋅LiN(Et)C(CH2Li)N(tBu) Et2O}2 (1) in 57% yield instead of the expected lithium amidinate Li[MeC(NEt)(NtBu)]. In the molecule of 1, one central methyl group in a trimer of Li[MeC(NEt)(NtBu)] is deprotoned and two of these partially deprotonated trimers are linked through a central eight-membered [C–N–Li–CH2]2 ring to afford the octanuclear product 1. The same reaction carried out in 1,2-dimethoxyethane (DME) solution produced the oxygen-centered, heptanuclear lithium amidinate cluster {Li[MeC(NEt)(NtBu)]}5⋅Li2O (2) (21% yield). Treatment of anhydrous praseodymium trichloride with in situ-prepared Li[MeC(NEt)(NtBu)] in Et2O/THF afforded green (THF)Li[Pr{MeC(NEt)(NtBu)}4] (3) as the first anionic tetrakis(amidinato)lanthanide(III) complex in 55% isolated yield. The molecular and crystal structures of all three new compounds have been elucidated by X-ray diffraction.

Towards the Synthesis of Guanidinate- and Amidinate-Bridged Dimers of Mn and Ni

Reactions of Cp2M (Cp = cyclopentadienyl, M = Mn, Ni) with lithium amidinates and guanidinates are reported. The highly oxophilic nature of Mn leads to the isolation of the interstitial oxide Mn4O(MeN···CH···NMe)6 (4) in preference to the intended paddle-wheel homodimer Mn2(MeN···CH···NMe)4 when employing the sterically uncongested amidinate [MeN···CH···NMe]– ligand. In contrast, an analogous reaction using Cp2Ni yielded Ni2(MeN···CH···NMe)4 (5). The use of monoprotic guanidinate ligands also gave contrasting results for Mn and Ni. In the first case, the highly unusual spirocycle Mn{μ-NC(NMe2)2}4Li2·3THF (6) was produced in low yield. For M = Ni, use of the [hpp]– (1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidinate) ligand gives results comparable with the synthesis of 5, with Ni2(hpp)4 (7) isolated. In contrast to recent data obtained using Cp2Cr, the guanidinate ligands do not sequester coformed CpLi. Density functional theory analysis corroborates the view that the intermetal distance in each of the reported dinickel paddle-wheel complexes (2.4846(8) and 2.3753(5) Å in 5 and 7 respectively) is defined by the geometric parameters of the bidentate ligands and that intermetal bonding is not present.

Synthesis, Structural Characterization, and Reactivity of Mono(amidinate) Rare-Earth-Metal Bis(aminobenzyl) Complexes

Three kinds of solvated lithium amidinates with different coordination models were obtained via recrystallization of (PhC(NC6H4 i Pr2- 2,6)2)Li(THF) (1a )i n different solvents. Treatment of o-Me2NC6H4CH2Li with LLnCl2(THF)n (2; L = (PhC(NC6H4 i Pr2-2,6)2) � (NCN dipp ), (o-Me2NC6H4CH2C- (NC6H4 i Pr2-2,6)2) � (NCN dipp ')) formed in situ from reaction of LnCl3(THF)x with LLi(THF) gave the rare-earth-metal bis(aminobenzyl) complexes LLn- (CH2C6H4NMe2-o)2 (L = NCN dipp , Ln = Sc (3a), Y (3b), Lu (3c); L = NCN dipp ', Ln = Sc (3d), Lu (3e)) in high yields. Reactions of complexes 3 with CO2, PhNCO, 2,6-diisopropylaniline, and S have been explored. CO2 inserted into each LnC bond of complexes 3ac to form the dual-core complexes ((NCN dipp )Sc(μ- η 1 :η 1 -O2CCH2C6H4NMe2-o)2)2 (4a )a nd ((NCN dipp )Ln(μ-η 1 :η 2 - O2CCH2C6H4NMe2-o)(μ-η 1 :η 1 -O2CCH2C6H4NMe2-o))2 (Ln = Y (4b), Lu (4c)). The reaction of 3b,c,e with PhNCO produced LLu(OC(CH2C6H4NMe2- o)NPh)2(thf) (L = NCN dipp ,L n =Y( 5b), Lu (5c); L = NCN dipp ', Ln = Lu (5e)). Protonolysis of 3a,b by 2,6-diisopropylaniline formed straightforwardly the μ2-imido complexes ((NCN dipp )Ln(μ-NC6H4 i Pr2- 2,6))2 (Ln = Sc (6a), Lu (6c)). Reaction of 3e with S8 afforded the sulfur insertion products (NCN dipp ')Lu(CH2C6H4NMe2- o)(SCH2C6H4NMe2-o)(thf) (7e) and (NCN dipp ')Lu(SCH2C6H4NMe2-o)2(thf)2 (7f) in high yields, respectively, depending on the stoichiometric ratio. All of these complexes were fully characterized by elemental analysis, NMR spectroscopy, and X-ray structural determinations.

Lithium‐cyclopropylethinylamidinates

AbstractA series of six new lithium‐cyclopropylethinylamidinates, Li[c‐C3H5–C≡C–C(NR)2]·S (R = iPr, S = Et2O (2a), THF (2b), DME (2c); R = cyclohexyl (Cy), S = Et2O (3a), THF (3b), DME (3c)) were prepared and fully characterized. The synthetic protocol involves in situ‐deprotonation of commercially available cyclopropylacetylene followed by treatment with either N,N′‐diisopropylcarbodiimide or N,N′‐dicyclohexylcarbodiimide. The cyclopropyl substituent exerts a significant influence on the 13C NMR spectroscopic shift of the acetylenic carbon atom to which it is bound. X‐ray diffraction studies of 2b and 3b revealed that in the solid state the new lithium amidinates adopt ladder‐type dimeric molecular structures.

Aluminium(III) amidinates formed from reactions of `AlCl' with lithium amidinates

The disproportionation of AlCl(THF)n (THF is tetrahydrofuran) in the presence of lithium amidinate species gives aluminium(III) amidinate complexes with partial or full chloride substitution. Three aluminium amidinate complexes formed during the reaction between aluminium monochloride and lithium amidinates are presented. The homoleptic complex tris(N,N'-diisopropylbenzimidamido)aluminium(III), [Al(C13H19N2)3] or Al{PhC[N(i-Pr)]2}3, (I), crystallizes from the same solution as the heteroleptic complex chloridobis(N,N'-diisopropylbenzimidamido)aluminium(III), [Al(C13H19N2)2Cl] or Al{PhC[N(i-Pr)]2}2Cl, (II). Both have two crystallographically independent molecules per asymmetric unit (Z' = 2) and (I) shows disorder in four of its N(i-Pr) groups. Changing the ligand substituent to the bulkier cyclohexyl allows the isolation of the partial THF solvate chloridobis(N,N'-dicyclohexylbenzimidamido)aluminium(III) tetrahydrofuran 0.675-solvate, [Al(C19H27N2)2Cl]·0.675C4H8O or Al[PhC(NCy)2]2Cl·0.675THF, (III). Despite having a twofold rotation axis running through its Al and Cl atoms, (III) has a similar molecular structure to that of (II).

Alkyl-ended ansa-bis(amidinate) ligands from aliphatic primary amines and multinuclear lithium derivatives

A practical synthetic pathway to alkyl-ended ansa-bis(amidinate) ligands was developed via linking the freshly prepared aliphatic group substituted lithium amidinate and the subsequent deprotonation. The lithium complexes prepared by this method were characterized by NMR spectroscopy, elemental analysis and single-crystal X-ray diffraction analysis.