Distinct reaction pathways of peralkylated LnIIAlIII heterobimetallic complexes with substituted phenols

The protonolysis reaction of heterobimetallic peralkylated complexes [Ln(AlR4)2]n (Ln=Sm, Yb; R=Me, Et) with 2 equiv of HOC 6H 2 tBu 2-2,6-Me-4 affords the bis(trialkylaluminum) adducts Ln[(micro-OArtBu,Me)(micro-R)AlR2]2 in good yields. Analogous reactions with the less sterically demanding iPr-substituted phenol result in ligand redistributions and formation of X-ray structurally evidenced Ln[(micro-OAriPr,H) 2AlR2]2 (Ln=Yb, R=Me; Ln=Sm, R=Et), Yb[(micro-OAriPr,H)(micro-Et)AlEt2]2(THF), and [Et2Al(micro-OAriPr,H) 2Yb(micro-Et)2AlEt2]2. The solid-state structures of serendipitous alumoxane complex Sm[(micro-OArtBu,Me)AlEt2OAlEt2(micro-OArtBu,Me)](toluene) and dimeric AlMe 3-adduct complex [(AlMe3)(micro-OArtBu,Me)Sm(micro-OArtBu,Me) 2Sm(micro-OArtBu,Me)(AlMe3)] were also determined by X-ray crystallography. While the former can be discussed as a typical hydrolysis product of Sm[(micro-OArtBu,Me)(micro-Et)AlEt2]2, the latter was isolated from the 1:1 reaction of [Sm(AlEt4)2]n with HOArtBu,Me.     

LnIIAlIII2(alkyl)8]x: donor addition instead of donor-induced cleavage

(SmAl2Me8)x and (SmAl2Et8)x are obtained via a silylamide elimination reaction from Sm[N(SiMe3)2]2(THF)2 and excess AlR3 (R = Me, Et); (LnAl2Et8)x (Ln = Sm, Yb) react with THF, pyridine, and 1,10-phenanthroline to form the first donor adducts of homoleptic peralkylated Ln-Al heterobimetallic complexes.     

Aluminum complexes incorporating bidentate amido phosphine ligands

A series of aluminum complexes supported by o-phenylene-derived amido phosphine ligands, N-(2-diphenylphosphinophenyl)-2,6-dimethylanilide ([Me-NP]-) and N-(2-diphenylphosphinophenyl)-2,6-diisopropylanilide ([iPr-NP]-), have been prepared. The reactions of trialkylaluminum with H[Me-NP] and H[iPr-NP], respectively, in refluxing toluene produced the corresponding dialkyl complexes [Me-NP]AlR(2) and [iPr-NP]AlR(2) (R = Me, Et). Deprotonation of H[Me-NP] with n-BuLi in THF at -35 degrees C followed by addition of AlCl(3) in toluene at -35 degrees C afforded [Me-NP]AlCl(2), which was subsequently reacted with 2 equiv of trimethylsilylmethyllithium in toluene to give [Me-NP]Al(CH(2)SiMe(3))(2). The aluminum complexes were all characterized by (1)H, (13)C, (31)P, and (27)Al NMR spectroscopy. The solid-state structures of monomeric, four-coordinate [Me-NP]AlEt(2) and [iPr-NP]AlMe(2) and five-coordinate [Me-NP]AlCl(2)(THF) were determined by X-ray crystallography. The (1)H NMR studies of [Me-NP]AlEt(2), [Me-NP]Al(CH(2)SiMe(3))(2), and [iPr-NP]AlEt(2) indicate diastereotopic alpha-hydrogen atoms in these molecules. Heteronuclear COSY and NOE experiments suggest that the phosphorus donor in [Me-NP]Al(CH(2)SiMe(3))(2) and [iPr-NP]AlEt(2) is coupled to only one of the diastereotopic alpha-hydrogen atoms that is virtually antiperiplanar with respect to the phosphorus atom.     

Synthesis and structural characterization of a series of lanthanide(II) amides: steric effect of amido ligand

The synthesis and structures of a series of lanthanide(II) and lanthanide(III) complexes supported by the amido ligand N(SiMe3)Ar were described. Several lanthanide(III) amide chlorides were synthesized by a metathesis reaction of LnCl3 with lithium amide, including {[(C6H5)(Me3Si)N]2YbCl(THF)}2.PhCH3 (1), [(C6H3-iPr2-2,6)(SiMe3)N]2YbCl(mu-Cl)Li(THF)3.PhCH3 (4), [(C6H3-iPr2-2,6)(SiMe3)N]YbCl2(THF)3 (6), and [(C6H3-iPr2-2,6)(SiMe3)N]2SmCl3Li2(THF)4 (7). The reduction reaction of 1 with Na-K alloy afforded bisamide ytterbium(II) complex [(C6H5)(Me3Si)N]2Yb(DME)2 (2). The same reaction for Sm gave an insoluble black powder. An analogous samarium(II) complex [(C6H5)(Me3Si)N]2Sm(DME)2 (3) was prepared by the metathesis reaction of SmI2 with NaN(C6H5)(SiMe3). The reduction reaction of ytterbium chloride 4 with Na-K alloy afforded monoamide chloride {[(C6H3-iPr2-2,6)(SiMe3)N]Yb(mu-Cl)(THF)2}2 (5), which is the first example of ytterbium(II) amide chloride, formed via the cleavage of the Yb-N bond. The same reduction reaction of 7 gave a normal bisamide complex [(C6H3-iPr2-2,6)(SiMe3)N]2Sm(THF)2 (8) via Sm-Cl bond cleavage. This is the first example for the steric effect on the outcome of the reduction reaction in lanthanide(II) chemistry. 5 can also be synthesized by the Na/K alloy reduction reaction of 6. All of the complexes were fully characterized including X-ray diffraction for 1-7.     

Synthesis and structural characterization of novel mixed-valent samarium and divalent ytterbium and europium complexes supported by amine bis(phenolate) ligands

The amine-elimination reactions of Ln[N(SiMe3)2]2(THF)2(Ln=Sm, Yb and Eu) with amine bis(phenol)s (L1H2=[BunN(CH(2)-2-OC6H(2)-3,5-But2)2]H2; L2H2=[Me2NCH2CH2N(CH(2)-2-OC6H(2)-3,5-But2)2]H2) were investigated. It was found that the number of heteroatom(s) in the ligands has a profound effect on the reaction outcome for the samarium systems. Reaction of the tetradentate diamino-bis(phenol)s L2H2 with Sm[N(SiMe3)2]2(THF)2 afforded a yellow solution, which indicated the complete oxidation of the SmII species, yellow being the characteristic color of SmIII species, while the same reaction with Eu[N(SiMe3)2]2(THF)2 gave a divalent complex with a dimeric structure (EuL2)2. Using the tridentate amine bis(phenol)s L1H2 as the reagent, the novel mixed-valent samarium complex SmIII2SmIIL1(4) was prepared by the same reaction. Both reactions of L1H2 with Yb[N(SiMe3)2]2(THF)2 and Eu[N(SiMe3)2]2(THF)2 yielded the normal divalent lanthanide complexes: monomeric complex for YbII, YbL1(THF)3 and dimeric complex for EuII, (EuL1)2. All of the complexes are well characterized with elemental analyses, IR and 1H NMR spectra for , and , as well as X-ray crystal structure determination in the cases of complexes , , and .     

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.     

Novel lanthanide(II) complexes supported by carbon-bridged biphenolate ligands: synthesis, structure and catalytic activity

[Ln[N(SiMe3)2]2(THF)2](Ln = Sm, Yb) reacts with 1 equiv. of carbon-bridged biphenols, 2,2'-methylene-bis(6-tert-butyl-4-methylphenol)(L1H2) or 2,2'-ethylidene-bis(4,6-di-tert-butylphenol)(L2H2), in toluene to give the novel aryloxide lanthanide(II) complexes [[LnL1(THF)n]2](Ln = Sm, n = 3 (1); Ln = Yb, n = 2 (2)) and [[LnL2(THF)3]2](Ln = Sm (5); Ln = Yb (6)) in quantitative yield, respectively. Addition of 2 equiv. of hexamethylphosphoric triamide (HMPA) to a tetrahydrofuran (THF) solution of 1, 2 and 5 affords the corresponding HMPA-coordinated complexes, [[LnL1(THF)m(HMPA)n]2(THF)y](Ln = Sm, n = 2, m = 0, y = 2 (3); Ln = Yb, m = 1, n = 1, y = 6 (4)) and [[SmL2(HMPA)2]2](7) in excellent yields. The single-crystal structural analyses of 3, 4 and 7 revealed that these aryloxide lanthanide(II) complexes are dimeric with two Ln-O bridges. The coordination geometry of each lanthanide metal can be best described as a distorted trigonal bipyramid. Complexes 1-3, 5 and 7 can catalyze the ring-opening polymerization of epsilon-caprolactone (epsilon-CL), and 1-3, along with 5 show moderate activity for the ring-opening polymerization of 2,2-dimethyltrimethylene carbonate (DTC) and the copolymerization of epsilon-CL and DTC to give random copolymers with high molecular weights and relatively narrow molecular weight distributions..     

Half-sandwich bis(tetramethylaluminate) complexes of the rare-earth metals: synthesis, structural chemistry, and performance in isoprene polymerization

The protonolysis reaction of [Ln(AlMe(4))(3)] with various substituted cyclopentadienyl derivatives HCp(R) gives access to a series of half-sandwich complexes [Ln(AlMe(4))(2)(Cp(R))]. Whereas bis(tetramethylaluminate) complexes with [1,3-(Me(3)Si)(2)C(5)H(3)] and [C(5)Me(4)SiMe(3)] ancillary ligands form easily at ambient temperature for the entire Ln(III) cation size range (Ln=Lu, Y, Sm, Nd, La), exchange with the less reactive [1,2,4-(Me(3)C)(3)C(5)H(3)] was only obtained at elevated temperatures and for the larger metal centers Sm, Nd, and La. X-ray structure analyses of seven representative complexes of the type [Ln(AlMe(4))(2)(Cp(R))] reveal a similar distinct [AlMe(4)] coordination (one eta(2), one bent eta(2)). Treatment with Me(2)AlCl leads to [AlMe(4)] --> [Cl] exchange and, depending on the Al/Ln ratio and the Cp(R) ligand, varying amounts of partially and fully exchanged products [{Ln(AlMe(4))(mu-Cl)(Cp(R))}(2)] and [{Ln(mu-Cl)(2)(Cp(R))}(n)], respectively, have been identified. Complexes [{Y(AlMe(4))(mu-Cl)(C(5)Me(4)SiMe(3))}(2)] and [{Nd(AlMe(4))(mu-Cl){1,2,4-(Me(3)C)(3)C(5)H(2)}}(2)] have been characterized by X-ray structure analysis. All of the chlorinated half-sandwich complexes are inactive in isoprene polymerization. However, activation of the complexes [Ln(AlMe(4))(2)(Cp(R))] with boron-containing cocatalysts, such as [Ph(3)C][B(C(6)F(5))(4)], [PhNMe(2)H][B(C(6)F(5))(4)], or B(C(6)F(5))(3), produces initiators for the fabrication of trans-1,4-polyisoprene. The choice of rare-earth metal cation size, Cp(R) ancillary ligand, and type of boron cocatalyst crucially affects the polymerization performance, including activity, catalyst efficiency, living character, and polymer stereoregularity. The highest stereoselectivities were observed for the precatalyst/cocatalyst systems [La(AlMe(4))(2)(C(5)Me(4)SiMe(3))]/B(C(6)F(5))(3) (trans-1,4 content: 95.6 %, M(w)/M(n)=1.26) and [La(AlMe(4))(2)(C(5)Me(5))]/B(C(6)F(5))(3) (trans-1,4 content: 99.5 %, M(w)/M(n)=1.18).     

Direct comparison of the magnetic and electronic properties of samarocene and ytterbocene terpyridine complexes

A new complex, Cp* 2Sm(tpy) ( 1, where Cp* = C 5Me 5, tpy = 2,2':6',2'-terpyridine) and its one-electron oxidized congener [Cp* 2Sm(tpy)]PF 6 ([ 1] (+)) have been synthesized and characterized with the aim of comparing their electronic and magnetic behavior to the known ytterbium analogues: Cp* 2Yb(tpy) ( 2) and [Cp* 2Yb(tpy)]OTf ([ 2] ( + )). These new samarium complexes have been characterized using single-crystal X-ray diffraction, (1)H NMR spectroscopy, cyclic voltammetry, optical spectroscopy, and bulk magnetic susceptibility measurements. All data for 1 indicate a Sm(III)-tpy* (-)[(4f) (5)-(pi*) (1)] ground-state electronic configuration similar to that found previously for 2 [(4f) (13)-(pi*) (1)]. Structural comparisons reveal that there are no significant changes in the overall geometries associated with the neutral and cationic samarium and ytterbium congeners aside from those anticipated based upon the lanthanide contraction. The redox potentials for the divalent Cp* 2Ln(THF) n precursors ( E 1/2(Sm (2+)) = -2.12 V, E 1/2(Yb (2+)) = -1.48 V) are consistent with established trends, the redox potentials (metal-based reduction and ligand-based oxidation) for 1 are nearly identical to those for 2. The correlation in the optical spectra of 1 and 2 is excellent, as expected for this ligand-radical based electronic structural assignment, but there does appear to be a red-shift ( approximately 400 cm (-1)) in all of the bands of 1 relative to those of 2 that suggests a slightly greater stabilization of the pi* level(s) in the samarium(III) complex compared to that in the ytterbium(III) complex. Similar spectroscopic overlap is observed for the monocationic complexes [ 1] (+) and [ 2] (+). Bulk magnetic susceptibility measurements for 1 reveal significantly different behavior than that of 2 due to differences in the electronic-state structure of the two metal ions. The implications of these differences in magnetic behavior are discussed.     

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.     

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.     

Stable heteroleptic complexes of divalent lanthanides with bulky pyrazolylborate ligands--iodides, hydrocarbyls and triethylborohydrides

The reaction of YbI(2) with KTp(Me2) gives (Tp(Me2))YbI(THF)(2) (1-Yb) as a thermally unstable product. Use of the more hindered KTp(tBu,Me) gave (Tp(tBu,Me))LnI(THF)(n) (Ln = Sm, n = 2, 2-Sm; Ln = Yb, n = 1, 2-Yb). The crystal structures of both these compounds are reported. Adducts with neutral ligands such as pyridines and isonitriles can be prepared and the crystal structures of [(Tp(tBu,Me))YbIL(n)] (L = CN(t)Bu, n = 1; L = 3,5-lutidine, n = 2) are described. 2-Sm can be oxidized using AgBPh(4) to give [(Tp(tBu,Me))SmI(THF)(2)]BPh(4). Compounds 2-Sm and 2-Yb are useful starting materials for the preparation of heteroleptic compounds by metathesis with appropriate potassium reagents. The preparations and characterization of the hydrocarbyls (Tp(tBu,Me))Ln{CH(SiMe(3))(2)} (Ln = Sm, 5-Sm; Yb, 5-Yb) and [(Tp(tBu,Me))Ln{CH(2)(SiMe(3))}(THF)] (Ln = Yb, 6a-Yb) and the triethylborohydrides [(Tp(tBu,Me))Ln(HBEt(3))(THF)(n)] (Ln = Sm, n = 0, 7-Sm; Yb, n = 1, 7-Yb) are reported, as well as the crystal structures of 5-Sm and 5-Yb, and the THF adducts 6a-Yb and [(Tp(tBu,Me))Sm{CH(SiMe(3))(2)}(THF)], 5a-Sm.     

Synthesis and structures of the first cationic perfluoroaryllanthanoid(II) complexes

Tetraphenylborate salts of solvated pentafluorophenyllanthanoid(II) cations [Ln(C(6)F(5))(thf)(n)](+) (Ln=Eu, n=6 (1); Ln=Yb, n=5 (2)) were readily synthesized in high yield by reactions of ytterbium or europium with HgPh(C(6)F(5)) and Me(3)NHBPh(4) in THF. The structures of 1.THF and 2 confirmed the existence of well-separated ions and both 1 and 2 show notable thermal stability at room temperature. The cation in 2 was also observed in the remarkable mixed-valent complex [Yb(II)(C(6)F(5))(thf)(5)][Yb(III)(C(6)F(5))(2)[N(SiMe(3))(2)](2)] (3), fortuitously isolated in low yield from a reaction of ytterbium metal, HgPh(C(6)F(5)), and HN(SiMe(3))(2) in THF, and which additionally has an unusual bis(pentafluorophenyl)bis[bis(trimethylsilyl)amido)]ytterbate(III) anion. (171)Yb-(19)F coupling has been observed in the low-temperature (171)Yb NMR spectra of 2 and [Yb(C(6)F(5))(2)(thf)(4)].     

Synthesis and solid-state structures of pyrazolylmethane complexes of the rare earths

In this paper, we report the first examples of trispyrazolylmethane complexes of rare earths. Reaction of LnCl3 with Tpm* (tris(3,5-dimethylpyrazolyl)methane) in THF or acetonitrile gives good yields of the [Ln(Tpm*)Cl3] (Ln = Y, Ce, Nd, Sm, Gd, Yb). Tpm* adducts of the lanthanide triflates [Ln(Tpm*)(OTf)3(THF)] (Ln = Y, Ho, Dy) may also be prepared. The X-ray crystal structures of [Y(Tpm*)Cl3], [Sm(Tpm*)Cl3(THF)], and [Ln(Tpm*)(OTf)3(THF)] (Ln = Y, Ho) are reported. The halide/triflate complexes may be used to prepare the aryloxide complexes [Ln(Tpm*)(OArMe2)3] (Ln = Y, Nd, Sm, Yb; ArMe2 = C6H3-2,6-(CH3)2), which are fluxional in solution as a result of interactions between the Tpm* and the aryloxide groups. The structures of the Nd and Sm complexes have been determined. Finally, the reaction of [Nd(BH4)3(THF)3] with Tpm* in THF results in the displacement of two THF molecules to give [Nd(Tpm*)(BH4)3(THF)]. Infrared spectra are consistent with tridentate borohydride coordination. The X-ray structures of these compounds indicate that the Tpm* ligand is less strongly bound than its anionic trispyrazolylborate analogues.     

Reactions of hypersilyl potassium with rare-earth metal bis(trimethylsilylamides): addition versus peripheral deprotonation

The scope of hypersilyl potassium, KHyp [Hyp = Si(SiMe3)3], as a silylation or deprotonation agent for some rare-earth bis(trimethylsilyl)amides has been explored. Thus, the reaction with Yb{N(SiMe3)2}2 affords the addition product [K][YbHyp{N(SiMe3)2}2] (2) in high yield, which contains a three-coordinate ytterbium atom, therefore representing the first example of a lanthanide silyl with a coordination number lower than 6. In contrast, deprotonation on the periphery is observed with the tris(amides) Ln{N(SiMe3)2}3 (Ln = Y, Yb) and compounds of the type [K][CH2Si(Me)2N(SiMe3)Ln{N(SiMe3)2}2] (Ln = Y (3), Yb (4)) are isolated. Crystallization of 3 from a mixture of benzene and heptane afforded the bis(benzene) solvate [(C6H6)2K][CH2Si(Me)2N(SiMe3)Y{N(SiMe3)2}2] (3a). The reaction between the strong bases nBuLi/tetramethylenediamine (TMEDA) or tBuLi with Y{N(SiMe3)2}3 or Yb{N(SiMe3)2}3 yielded the deprotonation product [(tmeda)Li][CH2Si(Me)2N(SiMe3)Y{N(SiMe3)2}2] (6) and the reduction product [LiYb{N(SiMe3)2}3] (7), respectively. Instead of the expected bimetallic product, the reaction between YbI(2) and 2 equiv of 3 gave the neutral complex [Y{CH2Si(Me)2N(SiMe3)}{N(SiMe3)2}(thf)] (8) in good yield. The compounds have been characterized by melting point, elemental analysis, IR spectroscopy, and X-ray crystallography and for selected species by 1H, 13C, 29Si, and 171Yb NMR spectroscopy. For 3a and 4, the nature of the bonding between the carbanionic centers and the lanthanide and potassium cations was studied by density functional theory calculations.     

Organolanthanide-based synthesis of 1,2,3-triazoles from nitriles and diazo compounds

The reaction of [(C5Me5)2Ln][(mu-Ph)2BPh2] complexes with the lithium salt of (trimethylsilyl)diazomethane, Li[Me3SiCN2], gave products formulated as the dimeric isocyanotrimethylsilyl amide complexes {(C5Me5)2Ln[mu-N(SiMe3)NC]}2 (Ln = Sm, 1; La, 2). Reactions of (C5Me5)2Sm and [(C5Me5)2Sm(mu-H)]2 with Me3SiCHN2 also form 1. Complexes 1 and 2 react with Me3CCN to form the 1,2,3-triazolato complexes (C5Me5)2Ln(NCCMe3)[NNC(SiMe3)C(CMe3)N] (Ln = Sm, 3; La, 4). Complex 2 reacts with Me3SiN3 to make the isocyanide ligated azide complex {(C5Me5)2La[CNN(SiMe3)2](mu-N3)}3, 5.     

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.     

Lanthanide-potassium wheels

Mixed potassium-lanthanide wheel-shaped-structured, hexanuclear coordination oligomers of composition [(eta5-C5H5)Ln(NPh2)2{N(PPh2)2}2K2(THF)4]2 (Ln = Er (1a), Yb (1b)) and an octanuclear coordination polymer of composition [(eta5-C5H5)Sm(NPh2)2{N(PPh2)2}K]infinity (2) were synthesized. All presented compounds can be obtained in moderate yields in a one-pot procedure, in which the potassium salts KNPh2 and [K(THF)(n)N(PPh2)2] as well as NaC5H5 are reacted with anhydrous samarium, erbium, and ytterbium trichloride in THF.     

Synthesis, structure and catalytic activity of alkali metal-free bent-sandwiched lanthanide amido complexes with calix[4]-pyrrolyl ligands

Simple silylamine elimination reactions of calix[4]-pyrrole [R(2)C(C(4)H(2)NH)](4) (R = Me (1), {-(CH(2))(5)-}(0.5) (2)) with 2 equiv. of [(Me(3)Si)(2)N](3)Ln(μ-Cl)Li(THF)(3) (Ln = Nd, Sm, Dy) in reflux toluene, afforded the novel dinuclear alkali metal-free trivalent lanthanide amido complexes (η(5):η(1):η(5):η(1)-R(8)-calix[4]-pyrrolyl){LnN(SiMe(3))(2)}(2) (R = Me, Ln = Nd (3), Sm (4), Dy (5); R = {-(CH(2))(5)-}(0.5), Ln = Nd (6), Sm(7)). The complexes were fully characterized by elemental analyses, spectroscopic analyses and single-crystal X-ray analyses. X-ray diffraction studies showed that each lanthanide metal was supported by bispyrrolyl anions in an η(5) fashion and along with three nitrogen atoms from N(SiMe(3))(2) and two other pyrroyl rings in η(1) modes formed the novel bent-sandwiched lanthanide amido bridged trivalent lanthanide amido complexes, similar to ansa-cyclopentadienyl ligand-supported lanthanide amides with respect to each metal center. The catalytic activities of these organolanthanide complexes as single component l-lactide polymerization catalysts were studied.     

Highly atom efficient guanylation of both aromatic and secondary amines catalyzed by simple lanthanide amides

It is demonstrated that the cyclopentadienyl-free simple lanthanide amides [(Me(3)Si)(2)N](3)Ln(mu-Cl)Li(THF)(3)(Ln = La, Sm, Eu, Y, Yb) and Ln[N(SiMe(3))(2)]3 (Ln = Y, Yb) are highly efficient catalysts for the guanylation of both aromatic and secondary amines with a high activity under mild conditions. It is found that these catalysts are compatible with a wide range of solvents and substrates.