Ytterbium(II) complex bearing a diaminobis(phenolate) ligand: synthesis, structure, and one-electron-transfer and epsilon-caprolactone polymerization reactions

The first divalent ytterbium complex supported by a diaminobis(phenolate) ligand, YbL(THF)2.0.5C7H8 (1; THF = tetrahydrofuran), was synthesized in good yield by the amine elimination reaction of Yb[N(SiMe3)2]2(THF)2 with H2L (L = [Me2NCH2CH2N(CH2-2-OC6H2-3,5-But2)2]) in a 1:1 molar ratio. X-ray structural determination shows complex 1 to be a THF-solvated monomer, which adopts a distorted octahedral coordination geometry around the Yb atom. Complex 1 can react with PhNCO and PhCCH, as a single electron-transfer reagent, to give the corresponding reduction coupling product [(YbLOCNPh)(THF)]2.4THF (2) and the alkynide complex YbLCCPh(DME) (3; DME = 1,2-dimethoxyethane). Complexes 2 and 3 have been characterized by X-ray crystal structural analysis. In complex 2, the dianionic oxamide ligand resulting from the reductive coupling of two phenyl isocyanate molecules coordinates to two Yb atoms in a mu,eta4 fashion. Complex 3 has a monomeric structure with a Yb-C(terminal phenylacetynide) bond length of 2.374(3) A. Complex 1 is also a highly efficient catalyst for ring-opening polymerization of epsilon-caprolactone.     

Reduction of carbodiimides by samarium(II) bis(trimethylsilyl)amides-formation of oxalamidinates and amidinates through C-C coupling or C-H activation

The reaction of [Sm{N(SiMe3)2}2(THF)2] (THF=tetrahydrofuran) with carbodiimides RN=C=NR (R=Cy, C6H3-2,6-iPr2) led to the formation of dinuclear SmIII complexes via differing C-C coupling processes. For R=Cy, the product [{(Me3Si)2N}2Sm(micro-C2N4Cy4)Sm{N(SiMe3)2}2] (1) has an oxalamidinate [C2N4Cy4]2- ligand resulting from coupling at the central C atoms of two CyNCNCy moieties. In contrast, for R=C6H3-2,6-iPr2, H transfer and an unusual coupling of two iPr methine C atoms resulted in a linked formamidinate complex, [{(Me3Si)2N}2Sm{micro-(RNC(H)N(Ar-Ar)NC(H)NR)}Sm{N(SiMe3)2}2] (2) (Ar-Ar=C6H3-2-iPr-6-C(CH3)2C(CH3)2-6'-C6H3-2'-iPr). Analogous reactions of RN=C=NR (R=Cy, C6H3-2,6-iPr2) with the SmII "ate" complex [Sm{N(SiMe2)3Na] gave 1 for R=Cy, but a novel C-substituted amidinate complex, [(THF)Na{N(R)C(NR)CH2Si(Me2)N(SiMe3)}Sm{N(SiMe3)2}2] (3), for R=C6H3-2,6-iPr2, via gamma C-H activation of a N(SiMe3)2 ligand.     

Synthesis and characterization of mono beta-diketiminatosamarium amides and hydrocarbyls

Reaction of SmCl3 with 1 eq of KL (L =[DippNC(Me)CHC(Me)NDipp]; Dipp = 2,6-i-Pr2C6H3) in THF afforded the dimeric samarium dichloride LSmCl2(THF)Cl2SmL (1) in high yield. Reactions of 1 with NaN(SiMe3)2, KNHAr (Ar = 2,4,6-t-Bu3C6H2), KBHEt3, and KCp*(Cp*= C5Me5) yielded various new complexes: LSmClN(SiMe3)2 (2), LSm[N(SiMe3)2]2 (3), LSmNHAr(HBEt3) (4), LSm(NHAr)2 (5), and LSmCp*Cl (6). Reaction of 1 with one eq of NaN(SiMe3)2 followed by treatment with excess AlMe3 afforded a unique bimetallic samarium tetramer Cl3L2Sm2(AlMe4)2Sm2L2Cl3 (7). Reaction of 6 with LiMe or LiCH2SiMe3 afforded LSmCp*Me (8) and LSmCp*CH2SiMe3 (9) in excellent yield. Methyl abstraction from with B(C6F5)3 in toluene yielded the cationic borate species (LSmCp*)[MeB(C6F5)3] (10). Molecular structures of 1-7 and 9 were determined by X-ray single crystal analysis.     

Cationic rare-earth metal trimethylsilylmethyl complexes supported by THF and 12-crown-4 ligands: synthesis and structural characterization

To expand the limited range of rare-earth metal cationic alkyl complexes known, a series of mono- and dicationic trimethylsilylmethyl complexes supported by THF and 12-crown-4 ligands with [BPh4]-, [BPh3(CH2SiMe3)]-, [B(C6F5)4]-, [B(C6F5)3(CH2SiMe3)]-, and [Al(CH2SiMe3)4]- anions were prepared from corresponding neutral precursors [Ln(CH2SiMe3)3Ln] (Ln = Sc, Y, Lu; L = THF, n = 2 or 3; L = 12-crown-4, n = 1) as solvent-separated ion pairs. The syntheses of the monocationic derivatives [Ln(CH2SiMe3)2(12-crown-4)n(THF)m]+[A]- are all high yielding and proceed rapidly in THF solution at room temperature. A "one pot" procedure using the neutral species directly for the syntheses of a number of lutetium and yttrium dicationic derivatives [Ln(CH2SiMe3)(12-crown-4)n(THF)m]2+[A]-2 with a variety of different anions, a class of compounds previously limited to just a few examples, is presented. When BPh3 is used to generate the ion triple, the presence of 12-crown-4 is required for complete conversion. Addition of a second equiv of 12-crown-4 and a third equiv of [NMe2PhH]+[B(C6F5)4]- abstracts a third alkyl group from [Ln(CH2SiMe3)(12-crown-4)2(THF)x]2+[B(C6F5)4]-2 (Ln = Y, Lu). X-ray crystallography and variable-temperature (VT) NMR spectroscopy reveal a structural diversity within the known series of neutral 12-crown-4 supported tris(trimethylsilylmethyl) complexes [Ln(CH2SiMe3)3(12-crown-4)] (Ln = Sc, Y, Sm, Gd-Lu) in the solid and solution states. The X-ray structure of [Sc(CH2SiMe3)3(12-crown-4)] exhibits incomplete 12-crown-4 coordination. VT NMR spectroscopy indicates fluxional 12-crown-4 coordination on the NMR time scale. X-ray crystallography of only the second structurally characterized dicationic rare-earth metal alkyl complex [Y(CH2SiMe3)(12-crown-4)(THF)3]2+[BPh4]-2 shows exocyclic 12-crown-4 coordination at the 8-coordinate metal center with well separated counteranions. 11B and 19F NMR spectroscopy of all mono- and dicationic rare-earth metal complexes reported demonstrate that the anions are symmetrical and noncoordinating on the NMR time scale. A series of trends within the 1H and 13C{1H} NMR resonances arising from the Ln-CH2 groups and, in the case of yttrium, the 1JYC coupling constants at the Y-CH2 group and the 89Y chemical shift values are discussed.     

The first structurally characterized cationic lanthanide-alkyl complexes

Reaction of rare earth metal-alkyl complexes [Ln(CH2SiMe3)3(THF)2](Ln = Y, Lu) with B(C6X5)3(X = H, F) in the presence of crown ethers gives crystallographically characterized ion pairs [Ln(CH2SiMe3)2(CE)(THF)n]+[B(CH2SiMe3)(C6X5)3]-(CE = [12]-crown-4, n = 1; CE = [15]-crown-5 and [18]-crown-6, n = 0).     

Synthetic and structural experiments on yttrium, cerium and magnesium trimethylsilylmethyls and their reaction products with nitriles; with a note on two cerium beta-diketiminates

The yttrium, cerium and magnesium bis(trimethylsilyl)methyls [Ln[CH(SiMe3)2]3][Ln = Y (1), Ce (2)], and the known compound Mg[[CH(SiMe3)2]2 (C) and [Mg(mu-Br)[CH(SiMe3)2](OEt2)]2 (D) formed the crystalline nitrile adducts [1(NCBut)2] (5), [2(NCPh)] (6), [C(NCR)2][R = But (8), Ph (9), C6H3Me2-2,6 (10)] and [Mg(mu-Br)[CH(SiMe3)2](NCR)]2 [R = But (11), Ph (12), C6H3Me2-2,6 (13)], rather than beta-diketiminato-metal insertion products. The beta-diketiminato-cerium complex [Ce[(N(SiMe3)C(C6H4But-4))2CH][N(SiMe3)2]2] (16) was obtained from [Ce[N(SiMe3)2]3] and the beta-diketimine H[[N(SiMe3)C(C6H4But-4)]2CH]]. The cerium alkyl 2 and [Ln[CH(SiMe3)(SiMe2OMe)]3][Ln = Y (3), Ce (4)] were obtained from the appropriate lithium alkyl precursor and [Ce(OC6H2But2-2,6-Me-4)3] or LnCl3, respectively. Heating complex 3 with benzonitrile in toluene afforded 2,2-dimethyl-4,6-diphenyl-5-trimethylsilyl-1,3-diaza-2-silahexa-1,3-diene (7), a member of a new class of heterocycles. The X-ray structures of the crystalline compounds, D, [Mg[CH(SiMe3)2]2(OEt2)2], the known [Ce(Cl)[(N(SiMe3)C(Ph))2CH]2] (E) and 16 are reported. The cerium alkyl (like 1) has one close Ce...C contact for each ligand, attributed to a gamma-C-Ce agostic interaction. The Ln alkyls and have a trigonal prismatic arrangement of the chelating ligands (each of the same chirality at Calpha) around the metal. In an arene solution at 313 K exists as two isomers, as evident from detailed NMR spectroscopic experiments.     

Synthesis and characterization of heterobimetallic oxo-bridged aluminum-rare earth metal complexes

Reaction of the aluminum hydroxide LAl(OH)[C(Ph)CH(Ph)] (1, L = HC[(CMe)(NAr)](2), Ar = 2,6-iPr(2)C(6)H(3)) with Y(CH(2)SiMe(3))(3)(THF)(2) yielded the oxo-bridged heterobimetallic yttrium dialkyl complex LAl[C(Ph)CH(Ph)](μ-O)Y(CH(2)SiMe(3))(2)(THF)(2) (2). Alkane elimination reaction of 2 with 2-(imino)pyrrole [NN]H ([NN]H = 2-(ArN═CH)-5-tBuC(4)H(2)NH) afforded the yttrium monoalkyl complex LAl[C(Ph)CH(Ph)] (μ-O)Y(CH(2)SiMe(3))[NN](THF)(2) (5). Alternatively, 5 can be prepared in high yield by reaction of 1 with [NN]Y(CH(2)SiMe(3))(2)(THF)(2) (3). The analogous samarium alkyl complex LAl[C(Ph)CH(Ph)](μ-O)Sm(CH(2)SiMe(3))[NN](THF)(2) (6) was prepared similarly. Reactions of 5 and 6 with 1 equiv of iPrOH yielded the corresponding alkoxyl complexes 7 and 8, respectively. The molecular structures of 3, 6, and 8 have been determined by X-ray single-crystal analysis. Complexes 2, 3, 5, 7, and 8 have been investigated as lactide polymerization initiators. The heterobimetallic alkoxyl 8 is highly active to yield high molecular weight (M(n) = 6.91 × 10(4)) polylactides with over 91% conversion at the lactide-to-initiator molar ratio of 2000.     

O(2) activation and hydrolysis of Salan rare-earth metal alkyl complexes

Salan ligated yttrium alkyl complex , L(1)Y(CH(2)SiMe(3))(THF) (Salan = L(1): [2-O-3,5-tBu(2)-C(6)H(2)CH(2)N(CH(3))CH(2)](2)), was exposed to an oxygen/nitrogen atmosphere to give a bimetallic alkoxide complex , [L(1)Y(mu-OCH(2)SiMe(3))](2). Whilst the lutetium counterparts (L(1)Lu(CH(2)SiMe(3))(THF)) and (L(2)Lu(CH(2)SiMe(3))(THF); L(2): [2-O-3-tBu-C(6)H(2)CH(2)N(CH(3))CH(2)](2)) were hydrolysed with moist nitrogen to afford mixed hydroxy/silyloxy complexes and ([L(1,2)Lu(mu-OSiMe(3))(mu-OH)LuL(1,2)]), respectively.     

Rare earth metal complexes bearing thiophene-amido ligand: synthesis and structural characterization

2,6-diisopropyl-N-(2-thienylmethyl)aniline (H2L) has been prepared, which reacted with equimolar rare earth metal tris(alkyl)s, Ln(CH2SiMe3)3(THF)2, afforded rare earth metal mono(alkyl) complexes, LLn(CH2SiMe3)(THF)3 (:Ln=Lu; :Ln=Y). In this process, H2L was deprotonated by one metal alkyl species followed by intramolecular C-H activation of the thiophene ring to generate dianionic species L2- with the release of two tetramethylsilane. The resulting L2- combined with three THF molecules and an alkyl unit coordinates to Y3+ and Lu3+ ions, respectively, in a rare N,C-bidentate mode, to generate distorted octahedron geometry ligand core. Whereas, with treatment of H2L with equimolar Sc(CH2SiMe3)3(THF)2, a heteroleptic complex (HL)(L)Sc(THF) () was isolated as the main product, where the dianionic L2- species bonds to Sc3+ via chelating N,C atoms whilst the monoanionic HL connects to Sc3+ in an S,N-bidentate mode. All complexes have been characterized by NMR spectroscopy and X-ray diffraction analysis.     

Tethered olefin studies of alkene versus tetraphenylborate coordination and lanthanide olefin interactions in metallocenes

The tethered olefin cyclopentadienyl ligand, [(C(5)Me(4))SiMe(2)(CH(2)CH=CH(2))](-), forms unsolvated metallocenes, [(C(5)Me(4))SiMe(2)(CH(2)CH=CH(2))](2)Ln (Ln = Sm, 1; Eu, 2; Yb, 3), from [(C(5)Me(4))SiMe(2)(CH(2)CH=CH(2))]K and LnI(2)(THF)(2) in good yield. Each complex in the solid state has both tethered olefins oriented toward the Ln metal center with the Ln-C(terminal alkene carbon) distances 0.2-0.3 A shorter than the Ln-C(internal alkene carbon) distances. The olefinic C-C bond distances in 2 and 3, 1.328(4) and 1.328(5) A, respectively, are normal. Like its permethyl analogue, (C(5)Me(5))(2)Sm(THF)(2), complex 1 reductively couples CO(2) to form the oxalate-bridged dimer [[(C(5)Me(4))SiMe(2)(CH(2)CH=CH(2))](2)Sm](2)(mu-eta(2):eta(2)-O(2)CCO(2)), 4, in which the tethered olefins are noninteracting substituents. Complex 1 reacts with AgBPh(4) to form an unsolvated cation that has the option of coordinating [BPh(4)](-) or a pendant olefin, a competition common in olefin polymerization catalysis. The structure of [[(C(5)Me(4))SiMe(2)(CH(2)CH=CH(2))](2)Sm][BPh(4)], 5, shows that both pendant olefins are located near samarium rather than the [BPh(4)](-) counterion.     

Homolysis of the Ln-N (Ln = Yb, Eu) bond. Synthesis, structural characterization and catalytic activity of ytterbium(II) and europium(II) complexes with methoxyethyl functionalized indenyl ligands

The interaction of methoxyethyl functionalized indene compounds (C(9)H(6)-1-R-3-CH(2)CH(2)OMe, R =t-BuNHSiMe(2)(1), Me(3)Si (2), H (3)) with [(Me(3)Si)(2)N](3)Ln(mu-Cl)Li(THF)(3)(Ln=Yb (4), Eu (5)) produced a series of new ytterbium(II) and europium(II) complexes via tandem silylamine elimination/homolysis of the Ln-N (Ln=Yb, Eu) bond. Treatment of the lanthanide(III) amides [(Me(3)Si)(2)N](3)Ln(mu-Cl)Li(THF)(3)(Ln=Yb (4), Eu (5) with 2 equiv. of, 1,2 and 3, respectively, produced, after workup, the ytterbium(II) complexes [eta5:eta1-Me(2)Si(MeOCH(2)CH(2)C(9)H(5))(NHBu-t)](2)Yb(II) (6), (eta5:eta1-MeOCH(2)CH(2)C(9)H(5)SiMe(3))(2)Yb(II) (7), (eta5:eta1-MeOCH(2)CH(2)C(9)H(6))(2)Yb(II)(8) and the corresponding europium(II) complexes [eta5:eta1-Me(2)Si(MeOCH(2)CH(2)C(9)H(5))(NHBu-t)](2)Eu(II)(9), (eta5:eta1-MeOCH(2)CH(2)C(9)H(5)SiMe(3))(2)Eu(II)(10) and (eta5:eta1-MeOCH(2)CH(2)C(9)H(6))(2)Eu(II)(11) in moderate to good yield. In contrast, interaction of the corresponding indene compounds 1, 2 or 3 with the lanthanide amides [(Me(3)Si)(2)N](3)Ln (Ln = Yb, Eu) was not observed, while addition of 0.5 equiv. of anhydrous LiCl to the corresponding reaction mixture produced, after workup, the corresponding ytterbium(II) or europium(II) complexes. All the new compounds were fully characterized by spectroscopic and elemental analyses. The structures of complexes, and were determined by single-crystal X-ray analyses. The catalytic activity of all the ytterbium(II) and europium(II) complexes on MMA polymerization was examined. It was found that all the ytterbium(II) and europium(II) complexes can function as single-component MMA polymerization catalysts. The temperature, solvent and ligand effects on the catalytic activity were studied.     

Synthesis and characterisation of lanthanide phenolate compounds and their catalytic activity towards ring-opening polymerisation of cyclic esters

Five new heteroleptic lanthanide(III) phenolate compounds have been synthesised in high yield, four via a transamination reaction between Ln(N(SiMe(3))2)3 and two equivalents of the phenol, HOC(6)H(2)(2,4-Bu(t))-6-CH(2)N(Me)CH(2)CH(2)NMe(2) [corrected] (LH) in thf {L(2)LnN(SiMe(3))2 where Ln = La (1); Nd (2); Sm (3); Yb (4)}. The fifth compound, [L(2)La][BPh(4)] 5 was formed by conversion of 1 by treatment with one equivalent of [Et(3)NH][BPh(4)] in toluene. Compound 3 was subjected to a single-crystal X-ray analysis and revealed a five-coordinate, distorted trigonal bipyramidal samarium(III) metal centre where each phenolate ligand is bidentate coordinating through the phenolate oxygen and nitrogen yielding six-membered chelate rings. Compound 1 exhibited fluxional behaviour in C(4)D(8)O solution which was temperature dependent. All five compounds were assessed as catalyst precursors towards the ring-opening polymerisation of both L-lactide and epsilon-caprolactone. These polymerisation studies revealed that catalysts containing larger lanthanide metals were more efficacious than those with smaller lanthanide metals. Furthermore, replacement of the [N(SiMe(3))2] initiating group in 1 with [BPh(4)] in 5 reduced catalytic activity by this compound. Detailed kinetics analysis of the ring-opening polymerisation of L-lactide by compound 1, the most efficacious catalyst precursor analysed in this study, revealed the following rate law: -d[LA]/dt = k[LA](2)[1](1) which is second order in lactide and first order in catalyst. End-group analysis by ESI mass spectrometry revealed the presence of phenolate end-groups and lactide cycles, the latter formed by intra-molecular, intrachain transesterification.     

Synthesis, characterization, and catalytic activity of rare earth metal amides supported by a diamido ligand with a CH2SiMe2 link

A series of four coordinate rare earth metal amides with general formula ((CH2SiMe2)[(2,6- IPr2C6H3)N]2)LnN(SiMe3)2(THF) [(Ln = Yb(2), Y (3), Dy (4), Sm (5), Nd (6)] containing a diamido ligand (CH2SiMe2)[(2,6-iPr2C6H3)N]2(2-) with a CH2SiMe2 link were synthesized in good yields via reaction of [(Me3Si)2N]3Ln(III)(mu-Cl)Li(THF)3 with the corresponding diamine (CH2SiMe2)[(2,6-iPr2C6H3)NH]2 (1). All compounds were fully characterized by spectroscopic methods and elemental analyses. The structures of complexes 2, 3, 4, 5, and 6 were determined by single-crystal X-ray analyses. Investigation of the catalytic properties of the complexes indicated that all complexes exhibited a high catalytic activity on the cyclotrimerization of aromatic isocyanates, which represents the first example of cyclopentadienyl-free rare earth metal complexes exhibiting a high catalytic activity and a high selectivity on cyclotrimerization of aromatic isocyanates. The temperatures, solvents, catalyst loading, and the rare earth metal effects on the catalytic activities of the complexes were examined.     

α'-三氟甲基-含氟β-二酮镧系螯合物的合成及其用作位移试剂的研究

本文合成了α'-三氟甲基-含氟β-二酮镧系螯合物Ln{CF3CF2[CF2OCF(CF3)]nCOCHCOC(CH3)3}3[n=1; Ln=Eu(1a), Pr(1b), Nd(1c),Sm(1d), Gd(1e), Tb(1f), Dy(1g), Er(1h). n=2; Ln=Eu(2a), Pr(2b), Nd(2c),Sm(2d), Gd(2e), Tb(2f), Dy(2g), Er(2h)], 并研究了它们的位移性能. 1a、1b、2a和2b在用作位移试剂时, 不仅具备Ln(fod)3(Ln=Eu, Pr)的所有优点, 而且还有另外两个优点: (1)在底物存在时, 试剂自身的叔丁基峰明显向高场迁移, 特别是在醇类化合物存在下, δ-Bu^t接近于0ppm, 因此, 1a和2a的t-Bu峰总是处于底物ω-甲基的高场, 不干扰图谱的解析. (2)1b和2b虽为镨类螯合物, 但与1a与2a一样, 都能得到非常清晰的一级图谱. c、f和g均使谱峰向高场迁移, 而h却使谱峰向低场迁移. c的位移能力略低于b. f、g和h的位移能力极强.     

Synthesis, structure and hydrosilylation activity of neutral and cationic rare-earth metal silanolate complexes

Rare-earth metal alkyl tri(tert-butoxy)silanolate complexes [Ln{mu,eta2-OSi(O(t)Bu)3}(CH2SiMe3)2]2 (Ln = Y (1), Tb (2), Lu (3)) were prepared via protonolysis of the appropriate tris(alkyl) complex [Ln(CH2SiMe3)3(thf)2] with tri(tert-butoxy)silanol in pentane. Crystal structure analysis revealed a dinuclear structure for with square pyramidal geometry at the yttrium centre. The silanolate ligand coordinates in an eta2-bridging coordination mode giving a 4-rung truncated ladder and non-crystallographic inversion centre. Addition of two equiv. of 12-crown-4 to a pentane solution of 1 or 3 respectively gave [Ln{OSi(O(t)Bu)(3)}(CH2SiMe3)2(12-crown-4)].12-crown-4 (Ln = Y (4), Lu (5)). Crystal structure analysis of 5 showed a slightly distorted octahedral geometry at the lutetium centre. The silanolate ligand adopts an eta(1)-terminal coordination mode, whilst the crown ether unit coordinates in an unusual kappa3-fashion. Reaction of 1-3 with [NEt3H]+[BPh4]- in thf yielded the cationic derivatives [Ln{OSi(O(t)Bu)3}(CH2SiMe3)(thf)4]+[BPh4]- (Ln = Y (6), Tb (7) and Lu (8)); coordination of crown ether led to compounds of the form [Ln{OSi(O(t)Bu)3}(CH2SiMe3)(L)(thf)n]+[BPh4]- (Ln = Y, Lu, L = 12-crown-4, n = 1 (9,10); Ln = Y, Lu, L = 15-crown-5, n = 0 (11,12)). Reaction of 1 with [NMe2PhH]+[B(C6F5)4]-, [Al(CH2SiMe3)3] or BPh3 in thf gave the ion pairs [Y{OSi(O(t)Bu)3}(CH2SiMe3)(thf)4]+[A]- ([A]- = [B(C6F5)4]- (13), [Al(CH2SiMe3)4]- (14), [BPh3(CH2SiMe3)]- (15)), whilst two equiv. [NMe2PhH]+[BPh4]- with 1 in thf produced the dicationic ion triple [Y{OSi(O(t)Bu)3}(thf)6]2+[BPh4]-2 (16). Crystal structure analysis revealed that 16 is mononuclear with pentagonal bipyramidal geometry at the yttrium centre. The silanolate ligand coordinates in an eta(1)-terminal fashion. All diamagnetic compounds have been characterized by NMR spectroscopy. 1, 3, 4, 6 and 13 were tested as olefin hydrosilylation pre-catalysts with a variety of substrates; 1 was found to be highly active in 1-decene hydrosilylation.     

Flexibility in the coordination chemistry of the 2,3-dimethylindolide ligand with potassium,yttrium, and samarium

The coordination chemistry of the 2,3-dimethylindolide anion (DMI), (Me(2)C(8)H(4)N)(-), with potassium, yttrium, and samarium ions is described. In the potassium salt [K(DMI)(THF)](n), 1, prepared from Me(2)C(8)H(4)NH and KH in THF, the dimethylindole anion binds and bridges potassium ions in three different binding modes, namely eta(1), eta(3), and eta(5), to form a two-dimensional extended structure. In the dimethoxyethane (DME) adduct [K(DMI)(DME)(2)](2), 2, prepared by crystallizing a sample of 1 from DME, DMI exists as a mu-eta(1):eta(1) ligand. Compound 1 reacts with SmI(2)(THF)(4) in THF to form the distorted octahedral complex trans-(DMI)(2)Sm(THF)(4), 3, in which the dimethyindolide anions are bound in the eta(1) mode to samarium. Reaction of 2,3-dimethylindole with Y(CH(2)SiMe(3))(3)(THF)(2) afforded the amide complex (DMI)(3)Y(THF)(2), 4, in which the dimethylindolide anions are also bound in the eta(1) mode to yttrium. Compound 1 also reacts with (C(5)Me(5))(2)LnCl(2)K(THF)(2) (Ln = Sm, Y) to form unsolvated amide complexes (C(5)Me(5))(2)Ln(DMI) (Ln = Sm, 5; Y, 6), in which DMI attaches primarily through nitrogen, although the edge of the arene ring is oriented toward the metals at long distances.     

Reactivity of calix-tetrapyrrole SmII and SmIII complexes with acetylene: isolation of an "N-confused" calix-tetrapyrrole ring

The nature of the substituents present on the calix-tetrapyrrole tetra-anion ligand [[R2C(C4H2N)]4]4- (R = [-(CH2)5-]0.5, Et) determines the type of reactivity of the corresponding SmII compounds with acetylene. With R = [-(CH2)5-]0.5, dehydrogenation occurred to yield the nearly colorless dinuclear diacetylide complex [[[[-(CH2)5-]4-calix-tetrapyrrole]SmIII]2(mu-C2Li4)].THF as the only detectable reaction product. Conversely, with R = Et, acetylene coupling in addition to dehydrogenation resulted in the formation of a dimeric butatrienediyl enolate derivative [[(Et8-calix-tetrapyrrole)SmIII[Li[Li(thf)]2(mu-OCH=CH2)]]2(mu,eta2,eta'2-HC=C=C=CH)]. Reaction of the trivalent hydride [(Et8-calix-tetrapyrrole)(thf)SmIII[(mu-H)[Li(thf)]]2 or of the terminally bonded methyl derivative [(Et8-calix-tetrapyrrole)(CH3)SmIII[[Li(thf)]2[Li(thf)2](mu3-Cl)]] with acetylene resulted in a mixture of the carbide [[(Et8-calix-tetrapyrrole)SmIII]2(mu-C2Li4)].Et2O with the dimerization product [[(Et8-calix-tetrapyrrole)SmIII[Li[Li(thf)]2(mu3-OCH=CH2)]]2-mu,eta2,eta'2-HC=C=C=CH)]. The same reaction also yielded a third product, a trivalent complex [[(Et8-calix-tetrapyrrole)SmIII[Li(thf)2]]2], in which the macrocycle was isomerized by shifting the ring attachment of one of the four pyrrole rings.     

Protonation of a lanthanum phosphide-alkyl occurs at the P-La not the C-La bond: isolation of a cationic lanthanum alkyl complex

Protonation of the heteroleptic, cyclometalated lanthanum phosphide complex [((Me3Si)2CH)(C6H4-2-CH2NMe2)P]La(THF)[P(C6H4-2-CH2NMe2)(CH(SiMe3)(SiMe2CH2))] with [Et3NH][BPh4] yields the cationic alkyllanthanum complex [(THF)4La[P(C6H4-2-CH2NMe2)(CH(SiMe3)(SiMe2CH2))]][BPh4].     

Divalent lanthanide complexes supported by the bridged bis(amidinates) L Me3SiN(Ph)CN(CH2)3NC(Ph)NSiMe3]: synthesis, molecular structures and one-electron-transfer reactions

Metathesis reactions of YbI(2) with Li(2)L (L = Me(3)SiN(Ph)CN(CH(2))(3)NC(Ph)NSiMe(3)) in THF at a molar ratio of 1:1 and 1:2 both afforded the Yb(II) iodide complex [{YbI(DME)(2)}(2)(μ(2)-L)] (1), which was structurally characterized to be a dinuclear Yb(II) complex with a bridged L ligand. Treatment of EuI(2) with Li(2)L did not afford the analogous [{EuI(DME)(2)}(2)(μ(2)-L)], or another isolable Eu(II) complex, but the hexanuclear heterobimetallic cluster [{Li(DME)(3)}(+)](2)[{(EuI)(2)(μ(2)-I)(2)(μ(3)-L)(2)(Li)(4)}(μ(6)-O)](2-) (2) was isolated as a byproduct in a trace yield. The rational synthesis of cluster 2 could be realized by the reaction of EuI(2) with Li(2)L and H(2)O in a molar ratio of 1:1.5:0.5. The reduction reaction of LLnCl(THF)(2) (Ln = Yb and Eu) with Na/K alloy in THF gave the corresponding Ln(II) complexes [Yb(3)(μ(2)-L)(3)] (3) and [Eu(μ(2)-L)(THF)](2) (4) in good yields. An X-ray crystal structure analysis revealed that each L in complex 3 might adopt a chelating ligand bonding to one Yb atom and each Yb atom coordinates to an additional amidinate group of the other L and acts as a bridging link to assemble a macrocyclic structure. Complex 4 is a dimer in which the two monomers [Eu(μ(2)-L)(THF)] are connected by two μ(2)-amidinate groups from the two L ligands. Complex 3 reacted with CyN═C═NCy and diazabutadienes [2,6-(i)Pr(2)C(6)H(3)N═CRCR═NC(6)H(3)(i)Pr(2)-2,6] (R═H, CH(3)) (DAD) as a one-electron reducing agent to afford the corresponding Yb(III) derivatives: the complex with an oxalamidinate ligand [LYb{(NCy)(2)CC(NCy)(2)}YbL] (5) and the complexes containing a diazabutadiene radical anion [LYb((i)Pr(2)C(6)H(3)NCRCRNC(6)H(3)(i)Pr(2))] (R = H (6), R = CH(3) (7)). Complexes 5-7 were confirmed by an X-ray structure determination.     

Regioselective C-H activation of lanthanide-bound N-heterocyclic carbenes

The reaction of Ln(L)N'2 (Ln = Nd, Ce; L = t-BuNCH2CH2[C{NCHCHNt-Bu}], N' = N(SiMe3)2) with trimethylsilyl iodide regiospecifically functionalises the carbene backbone at the C4-carbene ring position to afford the silylated complex Ln(L')N'I; Ln(L')N'2 is isolated after attempted reduction (L' = t-BuNCH2CH2[C{NC(SiMe3)CHNt-Bu}]) which allows a comparison of the structurally characterised complexes Nd(L)N'2, [Nd(L')N'I]2, and Nd(L')N'2.