Amido Ligands Research Articles

Rare-earth metal methylidene complexes with Ln3(μ3-CH2)(μ3-Me)(μ2-Me)3 core structure.

Trinuclear rare-earth metal methylidene complexes with a Ln3(μ3-CH2)(μ3-Me)(μ2-Me)3 structural motif were synthesized by applying three protocols. Polymeric [LuMe3]n (1-Lu) reacts with the sterically demanding amine H[NSiMe3(Ar)] (Ar = C6H3iPr2-2,6) in tetrahydrofuran via methane elimination to afford isolable monomeric [NSiMe3(Ar)]LuMe2(thf)2 (4-Lu). The formation of trinuclear rare-earth metal tetramethyl methylidene complexes [NSiMe3(Ar)]3Ln3(μ3-CH2)(μ3-Me)(μ2-Me)3(thf)3 (7-Ln; Ln = Y, Ho, Lu) via reaction of [LnMe3]n (1-Ln; Ln = Y, Ho, Lu) with H[NSiMe3(Ar)] is proposed to occur via an "intermediate" species of the type [NSiMe3(Ar)]LnMe2(thf)x and subsequent C-H bond activation. Applying Lappert's concept of Lewis base-induced methylaluminate cleavage, compounds [NSiMe3(Ar)]Ln(AlMe4)2 (5-Ln; Ln = Y, La, Nd, Ho) were converted into methylidene complexes 7-Ln (Ln = Y, Nd, Ho) in the presence of tetrahydrofuran. Similarly, tetramethylgallate complex [NSiMe3(Ar)]Y(GaMe4)2 (6-Y) could be employed as a synthesis precursor for 7-Y. The molecular composition of complexes 4-Ln, 5-Ln, 6-Y and 7-Ln was confirmed by elemental analyses, FTIR spectroscopy, (1)H and (13)C NMR spectroscopy (except for holmium derivatives) and single-crystal X-ray diffraction. The Tebbe-like reactivity of methylidene complex 7-Nd with 9-fluorenone was assessed affording oxo complex [NSiMe3(Ar)]3Nd3(μ3-O)(μ2-Me)4(thf)3 (8-Nd). The synthesis of 5-Ln yielded [NSiMe3(Ar)]2Ln(AlMe4) (9-Ln; Ln = La, Nd) as minor side-products, which could be obtained in moderate yields when homoleptic Ln(AlMe4)3 were treated with two equivalents of K[NSiMe3(Ar)].

A bis(amido) ligand set that supports two-coordinate chromium in the +1, +2, and +3 oxidation states

The amido ligand -N(Si(i)Pr3)DIPP (DIPP = 2,6-diisopropylphenyl) has been used to prepare two-coordinate complexes of Cr(I), Cr(II), and Cr(III). The two-coordinate Cr(II) complex has also been used to prepare a three-coordinate Cr(III) iodide complex, which can be used to access a stable Cr(III) methyl species.

Synthesis, structures and stability of amido gold(iii) complexes with 2,2':6',2''-terpyridine.

Three gold(iii) complexes with terminal amido ligands were prepared by the reaction of [Au(III)(trpy)(OH)](ClO4)2 and primary amines having electron-withdrawing groups such as 2-amino-4-chloropyrimidine, 2-amino-5-chloro-pyridine, and 2-aminopyrimidine. Conversion of the amido ligands into the imido or amine ligands resulted in the decomposition of the complexes by intramolecular redox reaction or the release of amine ligands, respectively.

Synthesis, structure, and reactivity of platinum compounds featuring terminal amido and phosphido ligands

Using the sterically encumbered 1,2-bis(di-tert-butylphosphino)ethane (dtbpe) ligand, a family of terminal anilido compounds of the general form (dtbpe)PtX(NHAr) (X=Cl, 2; Me, 6; Ph, 7; Ar=2,6-di-isopropylphenyl) as well as (dtbpe)Pt(NHPh)2 (8) were prepared in high isolated yields via salt metathesis using (dtbpe)PtCl2. Likewise, new sterically encumbered terminal phosphido compounds were prepared of the general form (dtbpe)PtX(PHAr) (X/Ar=Cl/dmp, 9; Cl/Mes∗, 10; Me/Mes∗, 11; where dmp=2,6-dimesitylphenyl, Mes∗=2,4,6-tri-tert-butylphenyl). Both families of compounds resist attempts to deprotonate the amido or phosphido ligand with either external bases or through alkane or arene elimination. Compound 11 reacts with various acids to afford salts having the cation [(dtbpe)PtMe(PH2Mes∗)]+ [12]+. Compounds 6, 9·0.5Et2O, 10·Et2O, 11·Et2O, and the salt [12][BArf4] were structurally characterized.

Mixed‐Donor Amido–Siloxo Actinide(IV) Halide and Alkyl Complexes with an Aryl Cipso Interaction

AbstractThe synthesis and characterisation of a series of new actinide(IV) complexes supported by the mixed‐donor amido–amino–siloxo framework [RN(Li)SiMe2N(R)SiMe2OLi] ([RNNO]Li2; R = 2,4,6‐Me3Ph, 2,6‐iPr2Ph) are presented. The reaction of 1 equiv. of [RNNO]Li2 with ThCl4·2DME (DME = 1,2‐dimethoxyethane) in DME generated {Li·nDME}{[RNNO]2Th2Cl5} (1: R = 2,4,6‐Me3Ph, n = 2; 2: R = 2,6‐iPr2Ph, n = 3) in high yield, and the addition of [NNO]Li2 to UCl4 in tetrahydrofuran (THF) resulted in the formation of {[NNO]UCl3Li·THF}2 (3). The structures of 1–3 indicate that they retain LiCl as “ate” complexes. The addition of 2 equiv. of [NNO]Li2 to ThCl4·2DME and UCl4 gives the bis‐ligated complexes [NNO]2ThClLi (4) and [NNO]2U (5), respectively. In 1–5, the [RNNO]2– ligands all coordinate through the amido and siloxo donors as well as the ipso carbon atom of the phenyl group of the amido ligand but not through the central amino group. Complex 3 can be alkylated through the addition of 2 equiv. of LiCH2SiMe3 to give [NNO]U(CH2SiMe3)2 (6) or NaCp (Cp = cyclopentadienyl) to give [NNO]UCp2 (7); the latter has been structurally characterised.

Computational Studies Explain the Importance of Two Different Substituents on the Chelating Bis(amido) Ligand for Transfer Hydrogenation by Bifunctional Cp*Rh(III) Catalysts

A computational approach (DFT-B3PW91) is used to address previous experimental studies (Chem. Commun. 2009, 6801) that showed that transfer hydrogenation of a cyclic imine by Et3N·HCO2H in dichloromethane catalyzed by 16-electron bifunctional Cp*Rh III(XNC6H4NX') is faster when XNC 6H4NX' = TsNC6H4NH than when XNC6H4NX' = HNC6H4NH or TsNC 6H4NTs (Cp* = η5-C5Me 5, Ts = toluenesulfonyl). The computational study also considers the role of the formate complex observed experimentally at low temperature. Using a model of the experimental complex in which Cp* is replaced by Cp and Ts by benzenesulfonyl (Bs), the calculations for the systems in gas phase reveal that dehydrogenation of formic acid generates CpRhIIIH(XNC 6H4NX'H) via an outer-sphere mechanism. The 16-electron Rh complex + formic acid are shown to be at equilibrium with the formate complex, but the latter lies outside the pathway for dehydrogenation. The calculations reproduce the experimental observation that the transfer hydrogenation reaction is fastest for the nonsymmetrically substituted complex CpRh III(XNC6H4NX') (X = Bs and X' = H). The effect of the linker between the two N atoms on the pathway is also considered. The Gibbs energy barrier for dehydrogenation of formic acid is calculated to be much lower for CpRhIII(XNCHPhCHPhNX') than for CpRh III(XNC6H4NX') for all combinations of X and X'. The energy barrier for hydrogenation of the imine by the rhodium hydride complex is much higher than the barrier for hydride transfer to the corresponding iminium ion, in agreement with mechanisms proposed for related systems on the basis of experimental data. Interpretation of the results by MO and NBO analyses shows that the most reactive catalyst for dehydrogenation of formic acid contains a localized Rh-NH π-bond that is associated with the shortest Rh-N distance in the corresponding 16-electron complex. The asymmetric complex CpRhIII(BsNC6H4NH) is shown to generate a good bifunctional catalyst for transfer hydrogenation because it combines an electrophilic metal center and a nucleophilic NH group.

Comparison of reactivity of C,N-chelated and Lappert’s stannylenes with trimethylsilylazide

Two mixed amido-azido tin(IV) species bearing either C,N-chelating or bulky amido ligands were prepared by the reaction of the corresponding stannylene (e.g., Sn[N(SiMe3)2]2 (1) or (LCN)2Sn (2, LCN = 2-(N,N-dimethylaminomethyl)phenyl)) with Me3SiN3. Both products of the oxidative addition, Sn[N(SiMe3)2]3N3 (3) and (LCN)2Sn[N(SiMe3)2]N3 (5), respectively, were fully characterized by both multinuclear NMR spectroscopy and XRD analysis. Heating of a mixture of 2 and Me3SiN3 up to 100 °C lead to the formation of a novel dimeric species (LCN)2Sn(μ-NSiMe3)2Sn(LCN)2 (4), where the two tin atoms are bridged by two NSiMe3 ligands, thus forming a four-membered diazadistannacycle. DFT calculations were also carried out to support the proposed reaction mechanisms.

Tetrylenes chelated by bifunctional β‐diketiminate ligand: structure and possible applications

The synthesis and structure of heteroleptic tetrylenes containing bifunctional β‐diketiminate ligand are reported. Compounds were prepared via a protolytic reaction of free β‐diketimine {N‐[(2‐MeO)C6H5]}N═C(Me)CH═C(Me)N(H){N′‐[(2‐MeO)C6H5]} (LCOH) and {N‐[(2‐MeO)C6H5]}NCHCHCHN(H){N′‐[(2‐MeO)C6H5]} (LHOH), respectively, with corresponding bis(amide) – M[N(SiMe3)2]2 (M = Ge, Sn, Pb) – in equimolar ratio or via the salt elimination route from lithium precursors generated from LHOH/LCOH species and slight excess of SnCl2 or GeCl2.dioxane complex. Only heteroleptic complexes were obtained by the mentioned methods. Products were characterized by multinuclear NMR spectroscopy techniques and structures of four of them have been determined by X‐ray diffraction methods. Complexes LHOGeCl and LCOSnN(SiMe3)2 crystallize as monomers with the three‐coordinated metal centres by one chloro or amido ligand and one bidentate β‐diketiminato unit, in contrast to the structure of LCOSnCl, which reveals a dimeric character and compound LCOPbN(SiMe3)2, where the central atom of lead is five‐coordinated by methoxy groups of the ligand. Complex LCOSnN(SiMe3)2 was tested as a catalyst for polymerization of various epoxides. Copyright © 2014 John Wiley & Sons, Ltd.

Trinuclear alkyl hydrido rare-earth complexes supported by amidopyridinato ligands: synthesis, structures, C-Si bond activation and catalytic activity in ethylene polymerization.

The reaction of Ap(9Me)Lu(CH2SiMe3)2(thf) (Ap(9Me) = (2,4,6-trimethylphenyl)[6-(2,4,6-triisopropylphenyl)pyridine-2-yl]amido ligand) with two molar equivalents of PhSiH3 affords a trinuclear alkyl-hydrido cluster [(Ap(9Me)Lu)3(μ(2)-H)3(μ(3)-H)2(CH2SiMe3)(thf)2]. The analogous reactions with Ap(9Me)Ln(CH2SiMe3)2(thf) (Ln = Y, Yb) are more complex and result in the formation of mixtures of two types of trinuclear alkyl-hydrido complexes [(Ap(9Me)Ln)3(μ(2)-H)3(μ(3)-H)2(CH2SiMe3)(thf)2] and [(Ap(9Me)Ln)3(μ(2)-H)3(μ(3)-H)2(CH2SiH2Ph)(thf)2] differing in the alkyl group. The DFT calculations of [(Ap*Y)3(μ(2)-H)3(μ(3)-H)2(CH2SiMe3)(thf)2] (Ap* = (2,6-diisopropylphenyl)[6-(2,4,6-triisopropylphenyl)pyridine-2-yl]amido ligand) confirm localization of the HOMO on the Ap*-Y(1A)-CH2SiMe3 fragment, thus explaining its enhanced reactivity. Analysis of the electron density distribution reveals the Y-H and H-H bonding interactions in the (Y)3(μ(2)-H)3(μ(3)-H)2 moiety. The NMR studies of diamagnetic complexes [(Ap(9Me)Lu)3(μ(2)-H)3(μ(3)-H)2(CH2SiMe3)(thf)2] and [(Ap*Y)3(μ(2)-H)3(μ(3)-H)2(CH2SiMe3)(thf)2] demonstrated that the trinuclear cores are retained in the solution and revealed exchange between μ(3)- and μ(2)-bridging hydrido ligands. Complexes [(Ap*Ln)3(μ(2)-H)3(μ(3)-H)2(CH2SiMe3)(thf)2], the cationic yttrium hydrido cluster [(Ap*Y)3(μ(2)-H)3(μ(3)-H)2(thf)3](+)[B(C6F5)4](-) as well as [(Ap(9Me)Ln)3(μ(2)-H)3(μ(3)-H)2(CH2SiMe3)(thf)2] proved to be active in catalysis of ethylene polymerization under mild conditions.

Probing the metallating ability of a polybasic sodium alkylmagnesiate supported by a bulky bis(amido) ligand: deprotomagnesiation reactions of nitrogen-based aromatic substrates

Exploring the reactivity of sodium butylmagnesiate reagent [{Na(THF)6}(+){(Ph2Si(NAr*)2)Mg(Bu)(THF)}(-)] (1) supported by the bulky chelating silyl(bisamido) ligand {Ph2Si(NAr*)2}(2-) (Ar* = 2,6-iPr2-C6H3) towards N-methylbenzimidazole (bIm(Me)), pyrrole and 2,6-diisopropylaniline (NH2Ar*), this study provides new insights into the ability of this bimetallic base to facilitate direct Mg-H exchange reactions as well as to exhibit polybasicity. Thus 1 effectively promotes the deprotomagnesiation of bIm(Me) under mild reaction conditions to give the α-metallated intermediate [{Na(THF)5}2(+){(Ph2Si(NAr*)2)Mg(bIm(Me)*)}2(-)] (2) (bIm(Me)* = 2-N-methylbenzimidazolyl). Analysis of crystallographic and NMR data of 2 combined with DFT calculations show that the metallated C in the bIm(Me)* ligands possesses a significant carbenic character. Contrasting with previous studies of benzothiazole (btz), 1 does not react with an excess of bIm(Me) even under forcing refluxing conditions. Contrastingly, the amination reactions of equimolar amounts of 1 with pyrrole and 2,6-diisopropylaniline allowed the isolation of [{(Ph2Si(NAr*)(NHAr*))Mg(NC4H4)2(THF)Na(THF)2}] (3) and [{Na(THF)6}(+){(Ph2Si(NAr*)(NHAr*))Mg(NHAr*)2(THF)}(-)] (4) respectively as crystalline solids. Highlighting the ability of 1 to act as a polybasic reagent, 3 and 4 are formed as the result of the deprotonation of two molecules of the relevant amine via its butyl group and one amido arm of the silyl(bisamido) ligand. Similarly, the reactions of 1 with 3 molar equivalents of the relevant amine yielded homoleptic tris(amido) compounds [(THF)2NaMg(NC4H4)3] (5) and [{Na(THF)6}(+){Mg(NHAr*)3}(-)] (7), with the concomitant formation of bis(amine) Ph2Si(NHAr)2, as a result of the complete amination of 1 using its three basic sites. The structures in the solid state of 3 and 4 were elucidated by X-ray crystallography. Despite their similar constitution, these heteroleptic tris(amido)magnesiates adopt contrasting structures, with the former displaying a contacted ion-pair structure, where Na and Mg are connected by two bridging pyrrolyl anions, whereas the latter gives rise to a solvent-separated ion pair motif. To the best of our knowledge 3 represents the first crystallographically characterized magnesium compound containing an anionic non-substituted form of pyrrole. Noticeably, Mg interacts exclusively with the N atoms of the pyrrolyl ligands, forming strong σ-bonds, whereas Na prefers to engage with the π-systems of both NC4-rings.

Aluminum complexes with bidentate amido ligands: synthesis, structure and performance on ligand-initiated ring-opening polymerization of rac-lactide.

A series of mononuclear aluminum dimethyl complexes bearing bidentate N-[2-(1-piperidinyl)benzyl]anilino or N-(2-morpholinobenzyl)anilino ligands were synthesized via reactions of the corresponding proligands with trimethylaluminum upon heating, while at ambient temperature two trimethylaluminum adducts with neutral N-[2-(1-piperidinyl)benzyl]aniline proligands were obtained. These complexes were well characterized by NMR spectroscopy, elemental analysis and occasionally by EI-HRMS. The molecular structures of the typical trimethylaluminum adduct 2b and aluminum dimethyl complex 3b were further confirmed by X-ray diffraction studies. All the aluminum dimethyl complexes could effectively initiate the ring-opening polymerization (ROP) of rac-lactide in a well-controlled manner to afford PLAs with narrow molecular weight distributions (PDI = 1.06-1.18). The polymer samples obtained are systematically end-capped with the bidentate ancillary ligands as characterized by (1)H NMR and ESI-TOF mass spectroscopy. Moreover, the introduction of substituent(s) at the ortho-position(s) of the anilino moiety in the ligand results in an obvious decrease in the catalytic activity of the corresponding aluminum complex, and complexes with meta-chloro substituted anilino units show higher activities likely due to the enhanced electrophilicity of the metal centers induced by the anilino groups.

Synthesis, stability and reactivity of the first mononuclear nonheme oxoiron(IV) species with monoamido ligation: a putative reactive species generated from iron-bleomycin.

The preparation and characterisation of an oxoiron(IV) species with monoamido ligation are described. Reactivity studies revealed the important role of the amido ligand in enhancing the ability of oxoiron(IV) complexes to promote hydrogen atom transfer from external alkanes.

Copolymerization of Ethylene with Isobutylene and Limonene Catalyzed by Titanium Complexes with Various ansa-(Fluorenyl)(alkylamido) Ligand

A series of titanium complexes bearing ansa-(fluorenyl)(amido) ligands with cyclohexylamido, isopropylamido, and isobutylamido groups were synthesized and their catalytic behaviors for the copolymerization of ethylene with isobutylene were compared with those with cyclododecylamido and tert-butylamido groups. The effects of cocatalyst on the ethylene-isobutylene copolymerization by a titanium complex having ansa-(fluorenyl)(cyclododecylamido) ligand were examined. The catalytic activity of the titanium complex for ethylene-limonene copolymerization was also further investigated.

New azido-substituted tantalum compounds: syntheses and DFT examination of nitrogen-rich mono-, di-, and trinuclear tantalum(v) compounds

The syntheses of new tantalum compounds containing an ancillary azido ligand(s) are described. The tantalum compound with the composition Ta(NMe2)4(N3) has been synthesized in high yield from the reaction of TaCl(NMe2)4 with NaN3 in THF. The solid-state structure reveals a dimeric architecture based on Ta2(NMe2)8(μ-N3)2 (), where the eight-membered dimetallocyclic ring possesses a chair-like conformation with bridging azido ligands binding the two Ta(NMe2)4 moieties. Solution molecular weight measurements and electronic structure calculations predict to exist as a monomer at room temperature. reacts with the formamidine (i)PrNC(H)NH(i)Pr to furnish fac-Ta(NMe2)3(η(1)-N3)[(i)PrNC(H)N(i)Pr] () and Me2NH; compound has been characterized by IR and (1)H NMR spectroscopy and X-ray diffraction analysis. Treatment of with p-toluidine affords the trinuclear compound Ta3(NMe2)5(μ-NMe2)(μ-NC6H4Me-4)2(NC6H4Me-4)(μ-N3)2(η(1)-N3) (). Compound contains three non-bonded tantalum atoms that are ligated by edge-bridging imido, amido, and azido ligands. The molecular structure of has been determined by X-ray crystallography, and the unprecedented presence of terminal and bridging imido, amido, and azido ligands in a single tantalum compound confirmed. The bonding in has been examined by DFT, and these data are discussed relative to the crystallographic structure. Compounds represent the first structurally characterized examples of heteroleptic tantalum compounds that possess an all-nitrogen coordination sphere with at least one azido ligand.

Unprecedented Calcium Metalla‐macrocycle Having Phosphinoselenoic Amide and Diphenylphosphinate in the Coordination Sphere

AbstractAn eight‐membered calcium metalla‐macrocycle of the composition [Ca{Ph2P(Se)N(Ar)}{Ph2P(O)O}(THF)2]2 (2) (Ar = 2, 6‐dimethylphenyl) can be isolated with a good yield by the reaction of neutral phosphinoselenoic amide [Ph2P(Se)NH(Ar)] (1) and calcium bis(trimethylsilyl)amides [Ca{N(SiMe3)2}2(THF)2] in toluene followed by crystallization in air. The homoleptic calcium phosphinoselenoic amido complex of the composition [Ca{Ph2P(Se)N(Ar)}2(THF)2] (3) can also be obtained through two synthetic routes. In the first route, [Ca{N(SiMe3)2}2(THF)2] is treated with phosphinoselenoic amide [Ph2P(Se)NH(Ar)] (1) at an ambient temperature followed by re‐crystallization in an inert atmosphere to give complex 3 of high purity. In the second route, a one‐pot reaction is carried out involving 1, calcium diiodide, CaI2, and potassium bis(trimethylsilyl)amide [K{N(SiMe3)2}] in toluene in an inert atmosphere. When complex 3 is treated with diphenylphosphinic acid in THF, compound 2 is also obtained with a good yield. Both complexes are confirmed using single‐crystal X‐ray diffraction analysis. The solid‐state structure of complex 2 reveals an eight‐membered macrocycle formed by two diphenylphosphinate groups and two calcium ions. In addition, a four‐membered calcium metallacycle around each calcium atom is formed by the phosphinoselenoic amido ligand through coordination between the nitrogen and selenium atoms. In complex 3, the calcium atom is coordinated by two phosphinoselenoic amido groups and a direct metal selenium bond is observed.

Donor‐Stabilized Silylenes with Guanidinato Ligands

AbstractThe first donor‐stabilized silylenes with guanidinato ligands, compounds 4 and 6, were synthesized and structurally characterized in the solid state and in solution. As demonstrated by single‐crystal X‐ray diffraction studies, compound 4 contains a bidentate and a monodentate guanidinato ligand of the type [iPrNC(NiPr2)NiPr]–, and compound 6 contains the bidentate guanidinato ligand [ArNC(NMe2)NAr]– (Ar = 2,6‐diisopropylphenyl) and the monodentate amido ligand [(Me3Si)2N]–. Both silicon(II) complexes exist also in solution.

A Structurally Rigid Bis(amido) Ligand Framework in Low-Coordinate Ni(I), Ni(II), and Ni(III) Analogues Provides Access to a Ni(III) Methyl Complex via Oxidative Addition

A structurally persistent bis-amido ligand framework capable of supporting nickel compounds in three different oxidation states has been identified. A highly unusual, isolable Ni(III) alkyl species has been prepared and characterized via a rare example of a two-electron oxidative addition of MeI to Ni(I).

Reactivity of Scorpionate-Anchored Yttrium Alkyl Primary Amido Complexes toward Carbodiimides. Insertion Selectivity of Y–NHAr and Y–CH2Ph Bonds

The TpMe2-supported yttrium dialkyl TpMe2Y(CH2Ph)2(THF) (TpMe2 = tri(3,5-dimethylpyrazolyl)borate) reacted with 1 equiv of ArNH2 in THF at room temperature to afford the yttrium alkyl primary amido complexes TpMe2YNHAr(CH2Ph)(THF) (Ar = Ph (1), C6H3-iPr2-2,6 (2)) in 84% and 88% isolated yields, respectively. Complex 1 reacted with iPrN═C═NiPr in THF at room temperature to give a yttrium dianionic guanidinate complex, TpMe2Y[(iPrN)2C═NPh](THF)2 (3, 74%). However, the reaction of 1 with ArN═C═NAr (Ar = C6H3-iPr2-2,6) in the same conditions produced a Y–C bond insertion product, TpMe2Y[(ArN)2CCH2Ph](NHPh) (4, 87%). Moreover, treatment of 2 with 1 equiv of iPrN═C═NiPr in THF at room temperature afforded two yttrium complex, TpMe2Y[(iPrN)C═NAr](THF) (5) and TpMe2Y[(iPrN)2CCH2Ph](NHAr) (6), in 58% and 19% isolated yields, respectively. These results indicated that carbodiimide can selectively insert into the Y–CH2Ph and Y–NHAr σ-bonds of TpMe2-supported yttrium alkyl primary amido complexes TpMe2YNHAr(CH2Ph)(THF), and this selectivity depends on the steric hindrance of the substituent groups R of cabodiimides and the primary amido ligands. All these new complexes were characterized by elemental analysis and spectroscopic methods, and their solid-state structures except 1 were also confirmed by single-crystal X-ray diffraction analysis.

Yttrium half-sandwich complexes bearing the 2-(N,N-dimethylamino)ethyl-tetramethylcyclopentadienyl ligand

The synthesis of bis(dimethylsilyl)amide and dimethyl half-sandwich complexes of yttrium bearing the 2-(N,N-dimethylamino)ethyl-tetramethylcyclopentadienyl ligand revealed unusual Si‒H activation reactions and ate complex formation, respectively. Protonolysis of complex Y[N(SiHMe2)2]3(thf)2 with cyclopentadiene C5Me4HCH2CH2NMe2 (HCpNMe2) at elevated temperature yielded complex CpNMe2Y[η2-SiMe2(NSiHMe2)2](thf) featuring a four-membered metallacycle. The bis(amido) ligand [η2-SiMe2(NSiHMe2)2]2− is shown to form via separation of H2SiMe2. In contrast, the salt metathesis reaction of YCl3(thf)3 with LiN(SiHMe2)2 and LiCpNMe2 in a 1/2/1 ratio at ambient temperature generated the non-activated complex CpNMe2Y[N(SiHMe2)2]2, exhibiting a distinct ligand activation at elevated temperatures, as evidenced by a comprehensive NMR spectroscopic study. Application of a sequential salt metathesis protocol involving YCl3(thf)3, LiCpNMe2, and LiMe led to the isolation of ate complexes [CpNMe2YCl2]2[LiCl(thf)2] and [CpNMe2YMe2(LiMe)]2. Aforementioned half-sandwich complexes were all characterized by X-ray structure analyses and the respective silylamido and methyl derivatives are demonstrated to produce the half-sandwich yttrium bis(tetramethylaluminate) complex [CpNMe2AlMe3Y(AlMe4)2] in the presence of excess trimethylaluminium, by NMR spectroscopic studies.

2,6-Diisopropylphenylamides of Potassium and Calcium: A Primary Amido Ligand in s-Block Metal Chemistry with an Unprecedented Catalytic Reactivity

Transamination of KN(SiMe3)2 with 2,6-diisopropylphenylamine (2,6-diisopropylaniline) in toluene at ambient temperature yields [K{N(H)Dipp}·KN(SiMe3)2] (1) regardless of the applied stoichiometry. Recrystallization of 1 in the presence of tetramethylethylenediamine (TMEDA) and tetrahydrofuran (THF) leads to the formation of [(μ-thf)K2{N(H)Dipp}2]∞ (2), whereas potassium bis(trimethylsilyl)amide remains in solution. Addition of pentamethyldiethylenetriamine (PMDETA) gives [(pmdeta)K{N(H)Dipp}]2 (3). In contrast to the thf and pmdeta adducts, which lead to dissociation of 1 into homoleptic species, addition of bidentate dimethoxyethane maintains the mixed complex [(dme)K{μ-N(SiMe3)2}{μ-N(H)Dipp}K]2 (4). A complete transamination of 2,6-diisopropylaniline with KN(SiMe3)2 in toluene at 100 °C yields [K{N(H)Dipp}] (5), which reacts with CaI2 to give [(thf)nCa{N(H)Dipp}2] (6), [(pmdeta)Ca{N(H)Dipp}2] (7), and [(dme)2Ca{N(H)Dipp}2] (8), depending on the solvents and coligands. Excess potassium 2,6-diisopropylphe...