Preparation and crystal structures of a series of titanium(III) 9-BBN hydroborate complexes containing Ti...H agostic interactions

9-BBN hydroborate complexes Ti{(mu-H)2BC8H14}3(THF)2 (1), Ti{(mu-H)2BC8H14}3(OEt2) (2), and [K(OEt2)4]-[Ti{(mu-H)2BC8H14}4] (4) were formed from the reaction of TiCl4 with K[H2BC8H14] in diethyl ether or THF. Ti{(mu-H)2BC8H14}3(PhNH2) (3) was isolated from the reaction of 2 with aniline in diethyl ether. In the formation of these complexes, Ti(IV) is reduced to Ti(III). The coordinated diethyl ether in 2 can be displaced by the stronger bases THF and aniline, to form 1 and 3, respectively. All of the compounds were characterized by single-crystal X-ray diffraction analysis. In complex 1, which contains two coordinated THF ligands, the titanium possesses a 17 electron configuration and there is no evidence for agostic interaction. Complexes 2 and 3 contain only one coordinated ether or aniline ligand, and the titanium possesses a 15 electron configuration. In these compounds, a C-H hydrogen on an alpha carbon on the BC8H14 unit of a 9-BBN hydroborate ligand forms an agostic interaction with the titanium. Criteria for assessing the existence of agostic interactions are discussed. As the potassium salt, the anion of complex 4 is more stable than the complexes 1-3. Organometallic anions of the type [ML4]- for titanium(III) are rare.     

Europium(II) and ytterbium(II) cyclic organohydroborates: an europium(II) complex with an agostic interaction

Lanthanide bis((cyclooctane-1,5-diyl)dihydroborate) complexes (THF)(4)Ln[(micro-H)(2)BC(8)H(14)](2) (Ln = Eu, 1; Yb, 2) were synthesized by a metathesis reaction between (THF)(x)()LnCl(2) and K[H(2)BC(8)H(14)] in THF in a 1:2 molar ratio. Attempts to prepare the monosubstituted lanthanide cyclic organohydroborates (THF)(x)LnCl[(micro-H)(2)BC(8)H(14)] were unsuccessful. On the basis of the molecular structure and IR spectrum of 1, there is an agostic interaction between Eu(II) and one of the alpha-C-H hydrogens from the [(micro-H)(2)BC(8)H(14)] unit. No such interaction was observed for 2. The coordinated THF in 1 and 2 can be removed under dynamic vacuum, but the solvent ligands remain bound to Yb when 2 is directly dissolved in Et(2)O or toluene. In strong Lewis basic solvents, such as pyridine or CH(3)CN, attack of the Yb-H-B bridge bonds results. Decomposition of 2 to the 9-BBN dimer in CD(2)Cl(2) was observed by (11)B and (1)H NMR spectroscopies. Compound 2 was reacted with 2 equiv of the hydride ion abstracting reagent B(C(6)F(5))(3) to afford the solvent-separated ion pair [Yb(THF)(6)][HB(C(6)F(5))(3)](2) (3). Complexes 1, 2, and 3 were characterized by single-crystal X-ray diffraction analysis. Crystal data: 1 is orthorhombic, Pna2(1), a = 21.975(1) A, b = 9.310(1) A, c = 16.816(1) A, Z = 4; 2 is triclinic, P1, a = 9.862(1) A, b = 10.227(1) A, c = 10.476(1) A, alpha = 69.87(1) degrees, beta = 76.63(1) degrees, gamma = 66.12(1) degrees, Z = 1; 3.Et(2)O is triclinic, P1, a = 13.708(1) A, b = 14.946(1) A, c = 17.177(1) A, alpha = 81.01(1) degrees, beta = 88.32(1) degrees, gamma = 88.54(1) degrees, Z = 2.     

Controlled syntheses, characterization, and reactivity of neutral and anionic lanthanide amides supported by methylene-linked bis(phenolate) ligands

A series of neutral and anionic bis(phenolate) lanthanide amides were synthesized by general metathesis reactions, and their reactivity was explored. Protolytic ligand exchange reactions of MBMPH2 (MBMP = 2,2'-methylene bis(6-tert-butyl-4-methyl-phenolate)) with [Ln{N(TMS)2}2(mu-Cl)(THF)]2 (TMS = SiMe3) afforded the desired bridged bis(phenolate) lanthanide chlorides [(MBMP)Ln(mu-Cl)(THF)2]2 [Ln = Nd (1), Yb (2)] in high isolated yields. These lanthanide chlorides were found to be useful precursors for the synthesis of the corresponding lanthanide derivatives. Reactions of 1 and 2 with 2 equiv of NaN(TMS)2 in THF produced the expected neutral bis(phenolate) lanthanide amido complexes (MBMP)Ln[N(TMS)2](THF)2 [Ln = Nd (3), Yb (4)] in high yields. Whereas the reactions of 1 and 2 with LiN(TMS)2 in a 1:4 molar ratio gave the anionic bis(phenolate) lanthanide amides as discrete ion-pair complexes [Li(THF)4][(MBMP)Ln{N(TMS)2}2] [Ln = Nd (5), Yb (6)] in high isolated yields. Further study revealed that 5 and 6 can also be conveniently synthesized in high yields by the direct reactions of MBMPH2 with [Ln{N(TMS)2}2(mu-Cl)(THF)]2 in a 2:1 molar ratio, and then with 4 equiv of nBuLi. The reactivity of the neutral and anionic bis(phenolate) lanthanide amides was comparatively investigated. It was found that the insertion reactions of carbodiimide into the Ln-N bond of neutral lanthanide amido complexes 3 and 4 gave the anticipated bis(phenolate) lanthanide guanidinate complexes [(mu-O-MBMP)Nd{(iPrN)2CN(TMS)2}]2 (7) and (MBMP)Yb[(iPrN)2CN(TMS)2] (8), respectively, in high yields, whereas the similar reaction of carbodiimide with anionic amido complex 5 provided the unexpected ligand-redistributed products, and the homoleptic ion-pair bis(phenolate) neodymium complex [Li(DME)2(THF)][(MBMP)2Nd(THF)2] (9) was finally isolated as one of the products. Furthermore, the anionic bis(phenolate) lanthanide amides showed higher catalytic activity for the polymerization of epsilon-caprolactone than the neutral ones. All of the complexes were characterized with elemental analysis and IR spectra, and the definitive molecular structures of 1-3 and 5-9 were provided by single-crystal X-ray analyses.     

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.     

Carbon-bridged bis(phenolato)lanthanide alkoxides: syntheses, structures, and their application in the controlled polymerization of epsilon-caprolactone

A convenient method for the synthesis of lanthanide alkoxo complexes supported by a carbon-bridged bis(phenolate) ligand 2,2'-methylenebis(6-tert-butyl-4-methylphenoxo) (MBMP2-) is described. The reaction of (C5H5)3Nd with MBMPH2 in a 1:1 molar ratio in THF gave the bis(phenolato)lanthanide complex (C5H5)Nd(MBMP)(THF)2 (1) in a nearly quantitative yield. Complex 1 further reacted with 1 equiv of 2-propanol in THF to yield the bis(phenolato)lanthanide isopropoxide [(MBMP)2Nd(mu-OPr(i))(THF)2]2 (2) in high yield. Complex 2 can also be synthesized by the direct reaction of (C5H5)3Nd with MBMPH2 in a 1:1 molar ratio and then with 1 equiv of 2-propanol in situ in THF. Thus, the analogue bis(phenolato)lanthanide alkoxides [(MBMP)2Ln(mu-OR)(THF)2]2 [R = Pr(i), Ln = Yb (3); R = Me, Ln = Nd (4), Yb (5); R = CH2Ph, Ln = Nd (6), Yb (7)] were obtained by the reactions of (C5H5)3Ln (Ln = Nd, Yb) with MBMPH2 and then with 2-propanol, methanol, or benzyl alcohol, respectively. The ytterbium complex {[(MBMP)2Yb(THF)2]2(mu-OCH2Ph)(mu-OH)} (8) was also isolated as a byproduct. The single-crystal structural analyses of complexes 1-3 and 8 revealed that the coordination geometry around lanthanide metal can be best described as a distorted tetrahedron in complex 1 and as a distorted octahedron in complexes 2, 3, and 8. A O-H...Yb agostic interaction was observed in complex 8. Complexes 2-7 were shown to be efficient catalysts for the controlled polymerization of epsilon-caprolactone.     

Luminescence tuning of imidazole-based lanthanide(III) complexes [Ln = Sm, Eu, Gd, Tb, Dy

To tune the lanthanide luminescence in related molecular structures, we synthesized and characterized a series of lanthanide complexes with imidazole-based ligands: two tripodal ligands, tris{[2-{(1-methylimidazol-2-yl)methylidene}amino]ethyl}amine (Me(3)L), and tris{[2-{(imidazol-4-yl)methylidene}amino]ethyl}amine (H(3)L), and the dipodal ligand bis{[2-{(imidazol-4-yl)methylidene}amino]ethyl}amine (H(2)L). The general formulas are [Ln(Me(3)L)(H(2)O)(2)](NO(3))(3)·3H(2)O (Ln = 3+ lanthanide ion: Sm (1), Eu (2), Gd (3), Tb (4), and Dy (5)), [Ln(H(3)L)(NO(3))](NO(3))(2)·MeOH (Ln(3+) = Sm (6), Eu (7), Gd (8), Tb (9), and Dy (10)), and [Ln(H(2)L)(NO(3))(2)(MeOH)](NO(3))·MeOH (Ln(3+) = Sm (11), Eu (12), Gd (13), Tb (14), and Dy (15)). Each lanthanide ion is 9-coordinate in the complexes with the Me(3)L and H(3)L ligands and 10-coordinate in the complexes with the H(2)L ligand, in which counter anion and solvent molecules are also coordinated. The complexes show a screw arrangement of ligands around the lanthanide ions, and their enantiomorphs form racemate crystals. Luminescence studies have been carried out on the solid and solution-state samples. The triplet energy levels of Me(3)L, H(3)L, and H(2)L are 21?000, 22?700, and 23?000 cm(-1), respectively, which were determined from the phosphorescence spectra of their Gd(3+) complexes. The Me(3)L ligand is an effective sensitizer for Sm(3+) and Eu(3+) ions. Efficient luminescence of Sm(3+), Eu(3+), Tb(3+), and Dy(3+) ions was observed in complexes with the H(3)L and H(2)L ligands. Ligand modification by changing imidazole groups alters their triplet energy, and results in different sensitizing ability towards lanthanide ions.     

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..     

Chiral bridged aminotroponiminate complexes of the lanthanides

The enantiomerically pure bridged aminotroponimines, S,S- and R,R-H2{(iPrATI)2diph}, in which two amino-isopropyl-troponimine moieties are linked by 1,2-diamino-1,2-diphenylethane, were deprotonated with nBuLi to give the corresponding dilithium salts [{Li(THF)}2{(S,S)-(iPrATI)2diph)}] (1a) and [{Li(THF)}2{(R,R)-(iPrATI)2diph)}] (1b). The potassium salts [{K(THF)2}2{(S,S)-(iPrATI)2diph}] (2a) and [{K(THF)2}2{(R,R)-(iPrATI)2diph}] (2b) were obtained by a deprotonation reaction with KH. Transmetallation of 2a and 2b with anhydrous lanthanide trichlorides led to [(S,S)-{(iPrATI)2diph}LnCl(THF)] (Ln = Ho (3a), Er (4a)) and [(R,R)-{(iPrATI)2diph}LnCl(THF)] (Ln = Ho (3b), Er (4b), Yb (5b)), respectively. The corresponding Yb complex [(S,S)-{(iPrATI)2diph}YbCl(THF)] (5a) was obtained by treatment of 1a with YbCl3 at elevated temperature. Performing the same reaction at room temperature results in the metallate complex [(S,S)-{(iPrATI)2diph}YbCl2][Li(THF)4] (6). Reaction of NaC5H5 with afforded [(S,S)-{(iPrATI)2diph}Yb(eta5-C5H5)(THF)] (7). The structures of 1a, 3a, 4a, 5a, 5b, 6, and 7 were confirmed by single crystal X-ray diffraction in the solid-state.     

Synthesis and characterization of benzoxazine-functionalized amine bridged bis(phenolate) lanthanide complexes and their application in the ring-opening polymerization of cyclic esters

The synthesis and structures of lanthanide complexes supported by benzoxazine-functionalized amine bridged bis(phenolate) ligand 6,6'-(2-(8-tert-butyl-6-methyl-2H-benzo[e][1,3]oxazin-3(4H)-yl)ethylazanediyl)bis(methylene)bis(2-tert-butyl-4-methylphenolato) (L(2-)) are described. Salt metathesis reaction between lanthanide trichloride and 2 eq of LNa(2) in THF at room temperature afforded the corresponding "ate" complexes [L(2)LnNa(THF)(2)] (Ln[double bond, length as m-dash]Y (1), Nd (2), Er (3), Yb (4)). Further treatment of the product with 18-crown-6 afforded discrete ion-pair complexes [L(2)Ln][(18-crown-6)Na(THF)(2)] (Ln[double bond, length as m-dash]Y (5), Yb (6)). The single-crystal structural analyses of 1 and 3-6 revealed that the lanthanide cation and the sodium cation were bridged by two phenolate oxygen atoms in complexes 1, 3 and 4, while in complexes 5 and 6, the anion comprises a lanthanide cation coordinated by two L(2-) and the cation is comprised of a sodium cation surrounded by an 18-crown-6 and two THF molecules. These complexes were found to exhibit distinct activities towards the ring-opening polymerization of ε-caprolactone and l-lactide.     

Insight into substrate binding in Shibasaki's Li3(THF)n(BINOLate)3Ln complexes and implications in catalysis

Heterobimetallic Lewis acids M 3(THF) n (BINOLate) 3Ln [M = Li, Na, K; Ln = lanthanide(III)] are exceptionally useful asymmetric catalysts that exhibit high levels of enantioselectivity across a wide range of reactions. Despite their prominence, important questions remain regarding the nature of the catalyst-substrate interactions and, therefore, the mechanism of catalyst operation. Reported herein are the isolation and structural characterization of 7- and 8-coordinate heterobimetallic complexes Li 3(THF) 4(BINOLate) 3Ln(THF) [Ln = La, Pr, and Eu], Li 3(py) 5(BINOLate) 3Ln(py) [Ln = Eu and Yb], and Li 3(py) 5(BINOLate) 3La(py) 2 [py = pyridine]. Solution binding studies of cyclohexenone, DMF, and pyridine with Li 3(THF) n (BINOLate) 3Ln [Ln = Eu, Pr, and Yb] and Li 3(DMEDA) 3(BINOLate) 3Ln [Ln = La and Eu; DMEDA = N, N'-dimethylethylene diamine] demonstrate binding of these Lewis basic substrate analogues to the lanthanide center. The paramagnetic europium, ytterbium, and praseodymium complexes Li 3(THF) n (BINOLate) 3Ln induce relatively large lanthanide-induced shifts on substrate analogues that ranged from 0.5 to 4.3 ppm in the (1)H NMR spectrum. X-ray structure analysis and NMR studies of Li 3(DMEDA) 3(BINOLate) 3Ln [Ln = Lu, Eu, La, and the transition metal analogue Y] reveal selective binding of DMEDA to the lithium centers. Upon coordination of DMEDA, six new stereogenic nitrogen centers are formed with perfect diastereoselectivity in the solid state, and only a single diastereomer is observed in solution. The lithium-bound DMEDA ligands are not displaced by cyclohexenone, DMF, or THF on the NMR time scale. Use of the DMEDA adduct Li 3(DMEDA) 3(BINOLate) 3La in three catalytic asymmetric reactions led to enantioselectivities similar to those obtained with Shibasaki's Li 3(THF) n (BINOLate) 3La complex. Also reported is a unique dimeric [Li 6(en) 7(BINOLate) 6Eu 2][mu-eta (1),eta (1)-en] structure [en = ethylenediamine]. On the basis of these studies, it is hypothesized that the lanthanide in Shibasaki's Li 3(THF) n (BINOLate) 3Ln complexes cannot bind bidentate substrates in a chelating fashion. A hypothesis is also presented to explain why the lanthanide catalyst, Li 3(THF) n (BINOLate) 3La, is often the most enantioselective of the Li 3(THF) n (BINOLate) 3Ln derivatives.     

Structural and photophysical properties of coordination networks combining [Ru(bipy)(CN)4]2- anions and lanthanide(III) cations: rates of photoinduced Ru-to-lanthanide energy transfer and sensitized near-infrared luminescence

Co-crystallization of K2[Ru(bipy)(CN)4] with lanthanide(III) salts (Ln = Pr, Nd, Gd, Er, Yb) from aqueous solution affords coordination oligomers and networks in which the [Ru(bipy)(CN)4]2- unit is connected to the lanthanide cation via Ru-CN-Ln bridges. The complexes fall into two structural types: [{Ru(bipy)(CN)4}2{Ln(H2O)m}{K(H2O)n}] x xH2O (Ln = Pr, Er, Yb; m = 7, 6, 6, respectively), in which two [Ru(bipy)(CN)4]2- units are connected to a single lanthanide ion by single cyanide bridges to give discrete trinuclear fragments, and [{Ru(bipy)(CN)4}3{Ln(H2O)4}2] x xH2O (Ln = Nd, Gd), which contain two-dimensional sheets of interconnected, cyanide-bridged Ru2Ln2 squares. In the Ru-Gd system, the [Ru(bipy)(CN)4]2- unit shows the characteristic intense (3)metal-to-ligand charge transfer luminescence at 580 nm with tau = 550 ns; with the other lanthanides, the intensity and lifetime of this luminescence are diminished because of a Ru --> Ln photoinduced energy transfer to low-lying emissive states of the lanthanide ions, resulting in sensitized near-infrared luminescence in every case. From the degree of quenching of the Ru-based emission, Ru --> Ln energy-transfer rates can be estimated, which are in the order Yb (k(EnT) approximately 3 x 10(6) sec(-1), the slowest energy transfer) < Er < Pr < Nd (k(EnT) approximately 2 x 10(8) sec(-1), the fastest energy transfer). This order may be rationalized on the basis of the availability of excited f-f levels on the lanthanide ions at energies that overlap with the Ru-based emission spectrum. In every case, the lifetime of the lanthanide-based luminescence is short (tens/hundreds of nanoseconds, instead of the more usual microseconds), even when the water ligands on the lanthanide ions are replaced by D2O to eliminate the quenching effects of OH oscillators; we tentatively ascribe this quenching effect to the cyanide ligands.     

Lanthanide amido complexes incorporating amino-coordinate-lithium bridged bis(indolyl) ligands: synthesis, characterization, and catalysis for hydrophosphonylation of aldehydes and aldimines

Two series of new lanthanide amido complexes supported by bis(indolyl) ligands with amino-coordinate-lithium as a bridge were synthesized and characterized. The interactions of [(Me(3)Si)(2)N](3)Ln(III)(μ-Cl)Li(THF)(3) with 2 equiv of 3-(CyNHCH(2))C(8)H(5)NH in toluene produced the amino-coordinate-lithium bridged bis(indolyl) lanthanide amides [μ-{[η(1):η(1):η(1):η(1)-3-(CyNHCH(2))Ind](2)Li}Ln[N(SiMe(3))(2)](2)] (Cy = cyclohexyl, Ind = Indolyl, Ln = Sm (1), Eu (2), Dy (3), Yb (4)) in good yields. Treatment of [μ-{[η(1):η(1):η(1):η(1)-3-(CyNHCH(2))Ind](2)Li}Ln[N(SiMe(3))(2)](2)] with THF gave new lanthanide amido complexes [μ-{[η(1):η(1)-3-(CyNHCH(2))Ind](2)Li(THF)}Ln[N(SiMe(3))(2)](2)] (Ln = Eu (5), Dy (6), Yb (7)), which can be transferred to amido complexes 2, 3, and 4 by reflux the corresponding complexes in toluene. Thus, two series of rare-earth-metal amides could be reciprocally transformed easily by merely changing the solvent in the reactions. All new complexes 1-7 are fully characterized including X-ray structural determination. The catalytic activities of these new lanthanide amido complexes for hydrophosphonylation of both aromatic and aliphatic aldehydes and various substituted aldimines were explored. The results indicated that these complexes displayed a high catalytic activity for the C-P bond formation with employment of low catalyst loadings (0.1 mol?% for aldehydes and 1 mol?% for aldimines) under mild conditions. Thus, it provides a convenient way to prepare both α-hydroxy and α-amino phosphonates.     

Divalent lanthanide complexes: highly active precatalysts for the addition of N-H and C-H bonds to carbodiimides

Various divalent lanthanide complexes with the formula LnL2(sol)x (L = N(TMS)2, sol = THF, x = 3, Ln = Sm (I), Eu (II), Yb (III); L = MeC5H4, sol = THF, x = 2, Ln = Sm (IV); L = ArO(Ar = [2,6-((t)Bu)2-4-MeC6H2]), sol = THF, x = 2, Ln = Sm (V)), especially complexes I- III, serve as excellent catalyst precursors for catalytic addition of various primary and secondary amines to carbodiimides, efficiently providing the corresponding guanidine derivatives with a wide range of substrates under solvent-free condition. The reaction shows good functional groups tolerance. Complexes I- III are also excellent precatalysts for addition of terminal alkynes to carbodiimides yielding a series of propiolamidines. The active sequence of Yb < Eu < Sm for metal and MeC5H4 < ArO < N(TMS)2 for ligand around the metal was observed for both reactions. The first step in both reactions was supposed to include the formation of a bimetallic bisamidinate samarium species originating from the reduction-coupling reaction of carbodiimide promoted by lanthanide(II) complex. The active species is proposed to be a lanthanide guanidinate and a lanthanide amidinate.     

Synthesis and single-crystal x-ray diffraction examination of a structurally homologous series of tetracoordinate heteroleptic anionic lanthanide complexes: Ln[N[Si(CH3)2CH2CH2Si(CH3)2]]3(mu-Cl)Li(L)3 (Ln = Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb; (L)3 =(THF)3, (Et2O)3, (THF)2(Et2O)

Anhydrous lanthanide(III) chlorides (Ln = Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb) react with 3 equiv of lithium 2,2,5,5-tetramethyl-2,5-disila-1-azacyclopentanide, Li[N[Si(CH3)2CH2Ch2Si(CH3)2]], in THF or Et(2)O to afford the monomeric four-coordinate heteroleptic ate complexes Ln[N[Si(CH3)2CH2CH2Si(CH3)2]]3(mu-Cl)Li(THF/Et2O)3 (Ln = Sm (1), Eu (2), Gd (3), Tb (4), Dy (5), Ho (6), Er (7), Tm (8), Yb (9)), whose solid-state structures were determined by the single-crystal X-ray diffraction technique. All complexes additionally were characterized by melting point determination, elemental analyses, and mass spectrometry.     

Lanthanide-transition-metal carbonyl complexes: new [Co4(CO)11]2- clusters and lanthanide(II) isocarbonyl polymeric arrays

Two types of Ln(II)-Co(4) isocarbonyl polymeric arrays, [(Et(2)O)(3)(-)(x)()(THF)(x)()Ln[Co(4)(CO)(11)]]( infinity ) (1-3; x = 0, 1) and [(THF)(5)Eu[Co(4)(CO)(11)]]( infinity ) (4), were prepared and structurally characterized. Transmetalation involving Ln(0) and Hg[Co(CO)(4)](2) in Et(2)O yields [(Et(2)O)(3)Ln[Co(4)(CO)(11)]]( infinity ) (1, Ln = Yb; 2, Ln = Eu). Dissolution of the solvent-separated ion pairs [Ln(THF)(x)()][Co(CO)(4)](2) (Ln = Yb, x = 6; Ln = Eu) in Et(2)O affords [(Et(2)O)(2)(THF)Yb[Co(4)(CO)(11)]]( infinity ) (3) and [(THF)(5)Eu[Co(4)(CO)(11)]]( infinity ) (4). In these reactions, oxidation and condensation of the [Co(CO)(4)](-) anions result in formation of the new tetrahedral cluster [Co(4)(CO)(11)](2)(-). The two types of Ln(II)-Co(4) compounds contain different isomers of [Co(4)(CO)(11)](2)(-), and, consequently, the structures of the infinite isocarbonyl networks are distinct. The cluster in [(Et(2)O)(3)(-)(x)()(THF)(x)()Ln[Co(4)(CO)(11)]]( infinity ) (1-3) possesses pseudo C(3)(v)() symmetry (an apical Co, three basal Co atoms; one face-bridging, three edge-bridging, seven terminal carbonyls) and connects to Ln(II) centers through eta(2),micro(4)- and eta(2),micro(3)-carbonyls to generate a 2-D puckered sheet. In contrast, [(THF)(5)Eu[Co(4)(CO)(11)]]( infinity ) (4) incorporates a C(2)(v)() symmetric cluster (two unique Co environments; two face-bridging, one edge-bridging, eight terminal carbonyls), and isocarbonyl linkages (eta(2),micro(4)-carbonyls) to Eu(II) atoms create a 1-D zigzag chain. Complexes 1-4 contain the first reported eta(2),micro(4)-CO bridges between a Ln and a transition-metal carbonyl cluster. Infrared spectroscopic studies revealed that the isocarbonyl associations to Ln(II) persist in solution. The solution structure and dynamic behavior of the [Co(4)(CO)(11)](2)(-) cluster in 1 was investigated by variable-temperature (59)Co and (13)C NMR spectroscopies.     

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)].     

Metal-to-ligand charge-transfer sensitisation of near-infrared emitting lanthanides in trimetallic arrays M2Ln (M=Ru, Re or Os; Ln=Nd, Er or Yb)

The new pro-ligand 4-methyl-4'-(carbonylamino(2-(tert-butoxycarbonylamino)ethyl))-2,2'-bipyridyl (L1) has been prepared and used to synthesise the complex fac-Re(I)Cl(CO)3(L1) 1 and the complex salts [M(II)(bipy)2(L1)](PF6)2 (M=RuII 8 or OsII 15). Deprotection with trifluoroacetic acid affords the amine-functionalised derivatives fac-Re(I)Cl(CO)3(L2) 2, [M(II)(bipy)2(L2)](PF6)2 (M=RuII 9 or OsII 16) which react with the dianhydride of diethylenetriamine pentaacetic acid (DTPA) to give the binuclear complex {fac-Re(I)Cl(CO)3}2(L3) 3 and the complex salts [{M(II)(bipy)2}2(L3)](PF6)4 (M = RuII 10 or OsII 17). The latter react with salts Ln(OTf)3 to afford a series of 12 heterotrimetallic compounds that contain a lanthanide (Ln) ion in the DTPA binding site; {fac-Re(I)Cl(CO)3}2(L3)LnIII (Ln=Nd 4, Er 5, Yb 6 or Y 7) and [{M(II)(bipy)2}2(L3)LnIII](PF6)(OTf)3 (M=RuII, Ln=Nd 11, Er 12, Yb 13 or Y 14; M=OsII, Ln=Nd 18, Er 19, Yb 20 or Y 21). All of these trimetallic species display absorption bands ascribed to metal-to-ligand charge-transfer (MLCT) excitations, and luminescence measurements show that these excited states can be used to sensitise near-infrared emission from LnIII (Ln=Nd, Er or Yb) ions. Single crystal X-ray structures of L1 and [RuII(bipy)2(L2H)](H2PO4)3.(CH3)2CO.0.8H2O were obtained, the latter revealing the presence of H2PO4- counter anions, the source of which is presumed to be hydrolysis of PF6- ions.     

Postmetallocene lanthanide-hydrido chemistry: A new family of complexes [{Ln{(Me3Si)2NC(NiPr)2}2(mu-H)}2] (Ln = Y, Nd, Sm, Gd, Yb) supported by guanidinate ligands-synthesis, structure, and catalytic activity in olefin polymerization

The new family of Lewis base free hydrido complexes of rare-earth metals supported by guanidinate ligands [{Ln{(Me3Si)2NC(NiPr)2}2(mu-H)}2] (Ln = Y, Nd, Sm, Gd, Yb) was synthesized and structurally characterized. Single-crystal X-ray and solution NMR studies revealed that these complexes are dimeric in both solid state and in [D6]benzene. The dimeric hydrido complexes can adopt eclipsed (Nd, Sm, Gd) or staggered (Y, Yb, Lu) conformations depending on the metal-atom size. Catalytic activity of these [{Ln{(Me3Si)2NC(NiPr)2}2(mu-H)}2] complexes in the polymerization of ethylene, propylene, and styrene has been investigated. Complexes of Sm and Y have high catalytic activity in ethylene polymerization (1268 and 442 g mmol(-1) atm(-1) h(-1), respectively).     

Synthesis of Arenethiolate Complexes of Divalent and Trivalent Lanthanides from Metallic Lanthanides and Diaryl Disulfides: Crystal Structures of [{Yb(hmpa)(3)}(2)(&mgr;-SPh)(3)][SPh] and Ln(SPh)(3)(hmpa)(3) (Ln = Sm, Yb; hmpa = Hexamethylphosphoric Triamide)

A convenient and one-pot synthetic method of lanthanide thiolate compounds was developed. An excess of metallic samarium, europium, and ytterbium directly reacted with diaryl disulfides in THF to give selectively Ln(II) thiolate complexes, [Ln(SAr)(&mgr;-SAr)(thf)(3)](2) (1, Ln = Sm; 2, Ln = Eu; Ar = 2,4,6-triisopropylphenyl), Yb(SAr)(2)(py)(4) (3, py = pyridine), and [{Ln(hmpa)(3)}(2)(&mgr;-SPh)(3)][SPh] (6, Ln = Sm; 7, Ln = Eu; 8, Ln = Yb; hmpa = hexamethylphosphoric triamide). Reaction of metallic lanthanides with 3 equiv of disulfides afforded Ln(III) thiolate complexes, Ln(SAr)(3)(py)(n)()(thf)(3)(-)(n)() (9a, Ln = Sm, n = 3; 9b, Ln = Sm, n = 2; 10, Ln = Yb, n = 3) and Ln(SPh)(3)(hmpa)(3) (11, Ln = Sm; 12, Ln = Eu; 13, Ln = Yb). Thus, Ln(II) and Ln(III) thiolate complexes were prepared from the same source by controlling the stoichiometry of the reactants. X-ray analysis of 8 revealed that 8 has the first ionic structure composed of triply bridged dinuclear cation and benezenethiolate anion [8, orthorhombic, space group P2(1)2(1)2(1) with a = 21.057(9), b = 25.963(7), c = 16.442(8) ?, V = 8988(5) ?(3), Z = 4, R = 0.040, R(w) = 0.039 for 5848 reflections with I > 3sigma(I) and 865 parameters]. The monomeric structures of 11 and 13 were revealed by X-ray crystallographic studies [11, triclinic, space group P&onemacr; with a = 14.719(3), b = 17.989(2), c = 11.344(2) ?, alpha = 97.91(1), beta = 110.30(2), gamma = 78.40(1) degrees, V = 2751.9(9) ?(3), Z = 2, R = 0.045, R(w) = 0.041 for 7111 reflections with I > 3sigma(I) and 536 parameters; 13, triclinic, space group P&onemacr; with a = 14.565(2), b = 17.961(2), c = 11.302(1) ?, alpha = 97.72(1), beta = 110.49(1), gamma = 78.37(1) degrees, V = 2706.0(7) ?(3), Z = 2, R = 0.031, R(w) = 0.035 for 9837 reflections with I > 3sigma(I) and 536 parameters]. A comparison with the reported mononuclear and dinuclear lanthanide thiolate complexes has been made to indicate that the Ln-S bonds weakened by the coordination of HMPA to lanthanide metals have ionic character.     

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.