New luminescent solids in the Ln-W(Mo)-Te-O-(Cl) systems

Solid-state reactions of lanthanide(III) oxide (and/or lanthanide(III) oxychloride), MoO3 (or WO3), and TeO2 at high temperature lead to eight new luminescent compounds with four different types of structures, namely, Ln2(MoO4)(Te4O10) (Ln = Pr, Nd), La2(WO4)(Te3O7)2, Nd2W2Te2O13, and Ln5(MO4)(Te5O13)(TeO3)2Cl3 (Ln = Pr, Nd; M = Mo, W). The structures of Ln2(MoO4)(Te4O10) (Ln = Pr, Nd) feature a 3D network in which the MoO4 tetrahedra serve as bridges between two lanthanide(III) tellurite layers. La2(WO4)(Te3O7)2 features a triple-layer structure built of a [La2WO4]4+ layer sandwiched between two Te3O72- anionic layers. The structure of Nd2W2Te2O13 is a 3D network in which the W2O108- dimers were inserted in the large tunnels of the neodymium(III) tellurites. The structures of Ln5(MO4)(Te5O13)(TeO3)2Cl3 (Ln = Pr, Nd; M = Mo, W) feature a 3D network structure built of lanthanide(III) ions interconnected by bridging TeO32-, Te5O136-, and Cl- anions with the MO4 (M = Mo, W) tetrahedra capping on both sides of the Ln4 (Ln = Pr, Nd) clusters and the isolated Cl- anions occupying the large apertures of the structure. Luminescent studies indicate that Pr2(MoO4)(Te4O10) and Pr5(MO4)(Te5O13)(TeO3)2Cl3 (M = Mo, W) are able to emit blue, green, and red light, whereas Nd2(MoO4)(Te4O10), Nd2W2Te2O13, and Nd5(MO4)(Te5O13)(TeO3)2Cl3 (M = Mo, W) exhibit strong emission bands in the near-IR region.     

Simulated annealing and density functional theory calculations of structural and energetic properties of the ammonium chloride clusters (NH4Cl)n, (NH4+)(NH4Cl)n, and (Cl-)(NH4Cl)n, n = 1-13

Simulated annealing Monte Carlo conformer searches using the "mag-walking" algorithm are employed to locate the global minima of molecular clusters of ammonium chloride of the types (NH(4)Cl)(n), (NH(4)(+))(NH(4)Cl)(n), and (Cl(-))(NH(4)Cl)(n) with n = 1-13. The M06-2X density functional theory method is used to refine and predict the structures, energies, and thermodynamic properties of the neutral, cation, and anion clusters. For selected small clusters, the resulting structures are compared to those obtained from a variety of models and basis sets, including RI-MP2 and B3LYP calculations. M06-2X calculations predict enhanced stability of the (NH(4)(+))(NH(4)Cl)(n) clusters when n = 3, 6, 8, and 13. This prediction corresponds favorably to anomalies previously observed in thermospray mass spectroscopy experiments. The (NH(4)Cl)(n) clusters show alternations in stability between even and odd values of n. Clusters of the type (Cl(-))(NH(4)Cl)(n) display a magic number distribution different from that of the cation clusters, with enhanced stability predicted for n = 2, 6, and 11. None of the observed cluster structures resemble the room-temperature CsCl structure of NH(4)Cl(s), which is consistent with previous work. Numerous clusters have structures reminiscent of the higher-temperature, rock-salt phase of the solid ammonium halides.     

Systematics and anomalies in rare earth/aluminum bromide vapor complexes: thermodynamic properties of the vapor complexes LnAl3Br12 from Ln = Sc to Ln = Lu

Systematics and anomalies in the rare earth/aluminum bromide vapor complexes have been investigated by the phase equilibrium-quenching experiments. The measurements suggest that the LnAl3Br12 complexes are the predominant vapor complexes for the 16 rare earth elements Ln = Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu in the temperature range 601-833 K and pressure range 0.01-0.22 MPa, which is different from the rare earth/aluminum chloride systems, where the predominant vapor complexes are LnAl3Cl12 from Ln = La to Ln = Lu, but LnAl2Cl9 for Ln = Sc and Y are roughly in the same ranges, which indicates the importance of the halogen anion radius on the rare earth vapor complex formation. In the temperature and pressure ranges, gaseous Al2Br6 and AlBr3 are dominant species and the molar fraction of LnAl3Br12 is normally less than 0.01. Thermodynamic functions of the reactions LnBr3(s) + (3/2)Al2Br6(g) = LnAl3Br12(g) were calculated from the measurements for the 16 rare earth elements and then smoothly interpolated for the radioelement Ln = Pm. The standard molar enthalpies and standard molar entropies show significant Gd divergences from LaAl3Br12 to LuAl3Br12 when plotted as functions of the rare earth atomic number. They also suggest nearly linear manner for ScAl3Br12, LuAl3Br12, YAl3Br12, and LaAl3Br12 when plotted as functions of the rare earth ionic radius.     

A series of 3d-4f heterometallic frameworks comprising 2D lanthanide-organic layers and diverse Cu-complex pillars

Six novel 3D layer-pillared lanthanide-transition metal coordination polymers,LnCuX(IN)2(Ac)(H2O)(Ln = Tb,X = Br(1);Ln = Er,X = Cl(2)),[LnCuCl(IN)2(Ac)].H2O(Ln = Gd(3);Ln = Eu(4)),and [LnCu2Br2(IN)2(Ac)(H2O)].nH2O(Ln = Dy,n =0(5);Ln = Gd,n = 0.5(6))(IN = isonicotinate,Ac = acetate),have been obtained by linking Ln-organic layers and diverse Cu-complex pillars under hydrothermal conditions.1 and 2 are isostructural and formed by 2D Ln-IN-Ac layers and CuX(IN)2 pillars(X = Br(1),X= Cl(2));3 and 4 are isomorph...     

Elevated-temperature metathesis syntheses of structurally novel alkali-metal tetrakis(3,5-di-tert-butylpyrazolato)lanthanoidate(III) complexes: toluene-coordinated discrete bimetallic complexes and supramolecular chains

Sodium and potassium tetrakis(3,5-di-tert-butylpyrazolato)lanthanoidate(III) complexes [M[Ln(tBu(2)pz)(4)]] have been prepared by reaction of anhydrous lanthanoid trihalides with alkali metal 3,5-di-tert-butylpyrazolates at 200-300 degrees C, and a 1,2,4,5-tetramethylbenzene flux for M=K. On extraction with toluene (or occasionally directly from the reaction tube) the following complexes were isolated: [Na(PhMe)[Ln(tBu(2)pz)(4)]] (1 Ln; 1 Ln=1 Tb, 1 Ho, 1 Er, 1 Yb), [K(PhMe)[Ln(tBu(2)pz)(4)]].2 PhMe (2 Ln; 2 Ln=2 La, 2 Sm, 2 Tb, 2 Ho, 2 Yb, 2 Lu), [Na[Ln(tBu(2)pz)(4)]](n) (3 Ln; 3 Ln=3 La, 3 Tb, 3 Ho, 3 Er, 3 Yb), [K[Ln(tBu(2)pz)(4)]](n) (4 Ln; 4 Ln=4 La, 4 Nd, 4 Sm, 4 Tb, 4 Ho, 4 Er, 4 Yb, 4 Lu), with the last two classes generally being obtained by loss of toluene from 1 Ln or 2 Ln, and [Na(tBu(2)pzH)[Ln(tBu(2)pz)(4)]].PhMe (5 Ln; 5 Ln=5 Nd, 5 Er, 5 Yb). Extraction with 1,2-dimethoxyethane (DME) after isolation of 2 Ho yielded [K(dme)[Ho(tBu(2)pz)(4)]] (6 Ho). X-ray crystal structures of 1 Ln (=1 Tb, 1 Ho; P2(1)/c), 2 Ln (=2 La, 2 Sm, 2 Tb, 2 Yb, 2 Lu; Pnma), 3,4 Ln (=3 La, 3 Er, 4 Sm; P2(1)/m), and 5 Ln (=5 Nd, 5 Er, and 5 Yb; P1) show each group to be isomorphous regardless of the size of the Ln(3+) ion. All complexes contain eight-coordinate [Ln(eta(2)-tBu(2)pz)(4)] units. These are further linked to the alkali metal by bridging through two (1,2,5 Ln) or three (3,4 Ln) tBu(2)pz groups which show striking coordination versatility. Sodium is coordinated by an eta(4)-PhMe, a micro-eta(2):eta(2)-tBu(2)pz, and a micro-eta(4)(Na):eta(2)(Ln)-tBu(2)pz ligand in 1 Ln, and by one eta(1)-tBu(2)pzH and two micro-eta(3)(Na):eta(2)(Ln) ligands in 5 Ln. By contrast, potassium has one eta(6)-PhMe and two micro-eta(5)(K):eta(2)(Ln) ligands in 2 Ln. Classes 3,4 Ln form polymeric chains with the alkali metal bonded by two micro-eta(3)(NNC-M):eta(2)(Ln)-tBu(2)pz ligands within [MLn(tBu(2)pz)(4)] units which are joined together by eta(1)(C)-tBu(2)pz-Na, K linkages.     

Two-dimensional lanthanide heteropolyvanadates of manganese(IV) and nickel(IV) containing two types of heteropoly anions with 1:13 and 1:12 stoichiometry

Reactions of 1:13 heteropoly anions [MV13O38](7-) (M = Mn, Ni) and lanthanide cations Ln3+ (Ln = La, Ce, or Pr) produce five isomorphic compounds, which are crystallized in the triclinic crystal system, space group P1, and formulated as [Ln6(H2O)25(MV12O38)(HMV13O38)].nH2O ((1) Ln = La, M = Mn, and n approximately 31; (2) Ln = Ce, M = Mn, and n approximately 29; (3) Ln = Pr, M = Mn, and n approximately 31; (4) Ln = La, M = Ni, and n approximately 28; (5) Ln = Pr, M = Ni, and n approximately 33). These compounds are two-dimensional polymeric structures constructed by hydrated lanthanide cations and two types of heteropoly anions, [MV13O38](7-) and [MV12O38](12-). In contrast to the previous reported 1:13 heteropoly anions, all with disordered structures, [MV13O38](7-) clusters in 1-5 are non-disordered with a distinct mode. The second kind of anionic cluster [MV12O38](12-) with O(h) symmetry, which consists of 13 entire edge-sharing MO(6) (M = V, Mn or Ni) octahedra, has not been reported hitherto. The emergence of the new cluster may be correlated to the six capping lanthanide cations surrounding it with a stabilization effect. In this paper, the syntheses and structures of the five polymeric lanthanide heteropolyvanadates of manganese(IV) and nickel(IV) have been presented.     

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.     

Synthesis and structures of the C5Me4SiMe3-supported polyhydride complexes over the full size range of the rare earth series

The acid-base reaction of [Ln(CH(2)SiMe(3))(3)(thf)(2)] with Cp'H gave the corresponding half-sandwich rare earth dialkyl complexes [(Cp')Ln(CH(2)SiMe(3))(2)(thf)] (1-Ln: Ln=Sc, Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu; Cp'=C(5)Me(4)SiMe(3)) in 62-90% isolated yields. X-ray crystallographic studies revealed that all of these complexes adopt a similar overall structure, in spite of large difference in metal-ion size. In most cases, the hydrogenolysis of the dialkyl complexes in toluene gave the tetranuclear octahydride complexes [{(Cp')Ln(μ-H)(2)}(4)(thf)(x)] (2-Ln: Ln=Sc, x=0; Y, x=1; Er, x=1; Tm, x=1; Gd, x=1; Dy, x=1; Ho, x=1) as the only isolable product. However, in the case of Lu, a trinuclear pentahydride [(Cp')(2)Lu(3)(μ-H)(5)(μ-CH(2)SiMe(2)C(5)Me(4))(thf)(2)] (3), in which the C-H activation of a methyl group of the Me(3)Si unit on a Cp' ligand took place, was obtained as a major product (66% yield), in addition to the tetranuclear octahydride [{(Cp')Lu(μ-H)(2)}(4)(thf)] (2-Lu, 34%). The use of hexane instead of toluene as a solvent for the hydrogenolysis of 1-Lu led to formation of 2-Lu as a major product (85%), while a similar reaction in THF yielded 3 predominantly (90%). The tetranuclear octahydride complexes of early (larger) lanthanide metals [{Cp'Ln(μ-H)(2)}(4)(thf)(2)] (2, Ln=La, Ce, Pr, Nd, Sm) were obtained in 38-57% isolated yields by hydrogenolysis of the bis(aminobenzyl) species [Cp'Ln(CH(2)C(6)H(4)NMe(2)-o)(2)], which were generated in-situ by reaction of [Ln(CH(2)C(6)H(4)NMe(2)-o)(3)] with one equivalent of Cp'H. X-ray crystallographic studies showed that the fine structures of these hydride clusters are dependent on the size of the metal ions.     

Synthesis and ligand-based mixed valency of cis- and trans-Cr(III)(X(4)SQ)(X(4)Cat)(L)(n) (X = Cl and Br,n = 1 or 2) complexes: effects of solvent media on intramolecular charge distribution and ligand dissociation of Cr(III)(X(4)SQ)(3)

The treatment of Cr(III)(X(4)SQ)(3) (SQ = o-semiquinonate; X = Cl and Br) with acetonitrile affords trans-Cr(III)(X(4)SQ)(X(4)Cat)(CH(3)CN)(2) (X = Cl (1) and Br (2)). In the presence of 2,2'-bipyridine (bpy) or 3,4,7,8-tetramethyl-1,10-phenanthrene (tmphen), the reaction affords Cr(III)(X(4)SQ)(X(4)Cat)(bpy).nCH(3)CN (X = Cl, n = 1 (3); X = Br, n = 0.5 (4)) or Cr(III)(X(4)SQ)(X(4)Cat)(tmphen) (X = Cl (5) and Br (6)), respectively. All of the complexes show a ligand-based mixed-valence (LBMV) state with SQ and Cat ligands. The LBMV state was confirmed by the presence of the interligand intervalence charge-transfer band. Spectroscopic studies in several solvent media demonstrate that the ligand dissociation included in the conversion of Cr(III)(X(4)SQ)(3) to 1-6 occurs only in solvents with relatively high polarity. On the basis of these results, the effects of solvent media were examined and an equilibrium, Cr(III)(X(4)SQ)(3) <--> Cr(III)(X(4)BQ)(X(4)SQ)(X(4)Cat) (BQ = o-benzoquinone), is proposed by assuming an interligand electron transfer induced by solvent polarity.     

Contribution of spin and anisotropy to single molecule magnet behavior in a family of bell-shaped Mn11Ln2 coordination clusters

The synthesis, structures, and magnetic properties of a family of isostructural "bell-shaped" heterometallic coordination clusters [Mn(III)(9)Mn(II)(2)La(III)(2)(μ(4)-O)(7)(μ(3)-O)(μ(3)-OH)(2)(piv)(10.8)(O(2)CC(4)H(3)O)(6.2)(NO(3))(2)(OH(2))(1.5)(MeCN)(0.5)]·12CH(3)CN·2H(2)O (1) and [Mn(III)(9)Mn(II)(2)Ln(2)(μ(4)-O)(7)(μ (3)-O)(μ(3)-OH)(2)(piv)(10.6)(O(2)CC(4)H(3)O)(6.4)(NO(3))(2)(OH(2))]·nCH(3)CN·H(2)O (Ln = Pr(III), n = 8 (2); Ln = Nd(III), n = 10 (3); Ln = Eu(III), n = 17 (4); Ln = Gd(III), n = 13 (5); piv = pivalate) are reported. The complexes were obtained from the reaction of [Mn(III)(2)Mn(II)(4)O(2)(piv)(10)(4-Me-py)(2.5)(pivH)(1.5)] and Ln(NO(3))(3)·6H(2)O in the presence of 2-furan-carboxylic acid (C(4)H(3)OCOOH) in CH(3)CN. Compounds 1-5 are isomorphous, crystallizing in the triclinic space group P1 with Z = 2. The Mn(III) and Mn(II) centers together form the shell of the bell, while the two Ln(III) centers can be regarded as the bell's clapper. The magnetic properties of 1-4 reveal dominant antiferromagnetic interactions between the magnetic centers leading to small spin ground states; while those of 5 indicate similar antiferromagnetic interactions between the manganese ions but with unusually strong ferromagnetic interactions between the Gd(III) ions leading to a large overall spin ground state of S = 11-12. While ac and dc magnetic measurements confirmed that Mn(11)Gd(2) (5) is a single-molecule magnet (SMM) showing hysteresis loops at low temperatures, compounds 1-4 do not show any slow relaxation of the magnetization, indicating that the S = 7 spin of the ferromagnetic Gd(2) unit in 5 is a necessary contribution to its SMM behavior.     

溴化稀土冠醚配合物LnBr3(18-C-6)·nH2O的振动光谱与结构

本文合成了溴化稀土冠醚配合物, 测定了3500—100 cm~(-1)的付里叶红外和激光喇曼光谱, 并由振动光谱推断LnBr_3(18-C-6)·nH_2O的可能分子结构。     

Equilibria and structure of the lanthanide(III)-2-hydroxy-1,3-diaminopropane-N,N,N',N'-tetraacetate complexes: formation of alkoxo-bridged dimers in solid state and solution

The complex formed between 1,3-diamino-2-hydroxypropane-N,N,N',N'-tetraacetic acid (H4L-OH) and Nd3+ at pH 7.5 was found to be a dinuclear dimer in the solid state by X-ray crystallography. In the complex K4[Nd2(L-O)2(H2O)2].14H2O each ligand is coordinated to both Nd3+ atoms with an iminodiacetate group (the Nd3+-Nd3+ distance is 3.9283(8) A). The alcoholic OH groups are deprotonated, and the alkoxo oxygens are coordinated to both Nd3+ in a bridging position. The Nd3+ ions are nine-coordinated with one water molecule per Nd(III) ion in the inner sphere. The complex K4[Nd2(L-O)2(H2O)2].14H2O has an inversion center, and the space group is P1. Two of the K+ counterions are six-coordinated, while the other two K+ ions are eight-coordinated; polar polymeric water-K+ layers are formed between the apolar ligand layers via the bridging water molecules. The dinuclear dimer complexes are also present in aqueous solution. The proton relaxivities of the Gd3+ complex decrease with the increase of pH, and at pH > 6, the low relaxivity values indicate the probable absence of H2O in the inner sphere and the predominance of the eight-coordinated dimer species [Gd2(L-O)2].4- The results of ESI-TOF MS studies of the complexes of La3+, Nd3+, and Lu3+ proved the formation of dinuclear dimers in dilute (0.25 mM) solutions. pH-potentiometric titrations indicate the formation of complexes with 1:1 (Ln(L-OH)-, Ln(HL-OH), and Ln2(L-O)24-) and 2:1 (Ln2(L-O)+) metal-to-ligand ratios. The stability constants of the Ln(L-OH)- species increase from La3+ (log K = 10.19) to Lu3+ (log K = 14.08). The alcoholic OH group of the Ln(L-OH)- species dissociates at unusually low pH values. The pH range of dissociation shifts to lower and lower pH's with the increasing atomic number of the lanthanides. This pH range is about 4-7 for the La3+ complex and 1-4 for the Lu3+ complex. The results of 1D and 2D 1H and 13C NMR studies of the La3+ complex, the number and multiplicity of signals, and the values of coupling constants are in agreement with the dinuclear dimer structure of the complex in solution.     

Catalytic addition of amine N-H bonds to carbodiimides by half-sandwich rare-earth metal complexes: efficient synthesis of substituted guanidines through amine protonolysis of rare-earth metal guanidinates

Reaction of [Ln(CH(2)SiMe(3))(3)(thf)(2)] (Ln=Y, Yb, and Lu) with one equivalent of Me(2)Si(C(5)Me(4)H)NHR' (R'=Ph, 2,4,6-Me(3)C(6)H(2), tBu) affords straightforwardly the corresponding half-sandwich rare-earth metal alkyl complexes [{Me(2)Si(C(5)Me(4))(NR')}Ln(CH(2)SiMe(3))(thf)(n)] (1: Ln = Y, R' = Ph, n=2; 2: Ln = Y, R' = C(6)H(2)Me(3)-2,4,6, n=1; 3: Ln = Y, R' = tBu, n=1; 4: Ln = Yb, R' = Ph, n=2; 5: Ln = Lu, R' = Ph, n=2) in high yields. These complexes, especially the yttrium complexes 1-3, serve as excellent catalyst precursors for the catalytic addition of various primary and secondary amines to carbodiimides, efficiently yielding a series of guanidine derivatives with a wide range of substituents on the nitrogen atoms. Functional groups such as C[triple chemical bond]N, C[triple chemical bond]CH, and aromatic C--X (X: F, Cl, Br, I) bonds can survive the catalytic reaction conditions. A primary amino group can be distinguished from a secondary one by the catalyst system, and therefore, the reaction of 1,2,3,4-tetrahydro-5-aminoisoquinoline with iPrN==C==NiPr can be achieved stepwise first at the primary amino group to selectively give the monoguanidine 38, and then at the cyclic secondary amino unit to give the biguanidine 39. Some key reaction intermediates or true catalyst species, such as the amido complexes [{Me(2)Si(C(5)Me(4))(NPh)}Y(NEt(2))(thf)(2)] (40) and [{Me(2)Si(C(5)Me(4))(NPh)}Y(NHC(6)H(4)Br-4)(thf)(2)] (42), and the guanidinate complexes [{Me(2)Si(C(5)Me(4))(NPh)}Y{iPrNC(NEt(2))(NiPr)}(thf)] (41) and [{Me(2)Si(C(5)Me(4))(NPh)}Y{iPrN}C(NC(6)H(4)Br-4)(NHiPr)}(thf)] (44) have been isolated and structurally characterized. Reactivity studies on these complexes suggest that the present catalytic formation of a guanidine compound proceeds mechanistically through nucleophilic addition of an amido species, formed by acid-base reaction between a rare-earth metal alkyl bond and an amine N--H bond, to a carbodiimide, followed by amine protonolysis of the resultant guanidinate species.     

Catalytic Hydrolysis of Phosphate Diesters by Lanthanide(III) Cryptate (2.2.1) Complexes

Lanthanide(III) Cryptate (2.2.1) chlorides (Ln(2.2.1)Cl(3); Ln = La (1a), Ce(1b), and Eu(1c); (2.2.1) = 4,7,13,16,21-pentaoxa-1,10-diazabicyclo[8.8.5]tricosane) are effective for the catalytic hydrolysis of bis(4-nitrophenyl) phosphate. Kinetic studies reveal that the europium(III) complex (1c) catalyzes the hydrolysis to produce 6 equiv of 4-nitrophenol with a significant rate (k(1) = 1.5 x 10(-)(4) s(-)(1) at 0.40 mM) at pH 8.5 and 50 degrees C. The catalytic activity of the complexes is increased with decreasing the ionic size, i.e, La < Ce < Eu. While the use of hydrogen peroxide further increase the activity of 1b (k(1) = 1.6 x 10(-)(3) s(-)(1) at 0.40 mM), the presence of molecular oxygen does not affect the activity at all. Crystal of 1a.CH(3)OH([La(2.2.1)(Cl)(2)](Cl)(CH(3)OH)) belongs to the space group Pnma with a = 17.072(3) ?, b = 19.037(3) ?, c = 14.725(2) ?, V = 4786(1) ?(3), Z = 8, D(x)() = 1.691 g cm(-)(3), &mgr; = 21.7 cm(-)(1). The encryptated metal ion is nine-coordinated, and all the heteroatoms of the cryptate (2.2.1) ligand coordinate the metal center to form a bowl-shaped structure. Two coordinating chloride anions are located on the open face with a cis geometry. The existence of coordinated water to the europium(III) complex 1c in the aqueous solution was confirmed by time-resolved Eu(III) luminescence spectroscopy. From the decay constants in H(2)O and D(2)O, the numbers of coordinated water molecules (q) are found to be 3.02 at pH of 5.0. The above kinetic and spectroscopic observation are supportive of mechanisms in which the metal complexes act as a center for binding and activation as well as a source of nucleophilic metal hydroxides.     

Homoleptic rare-earth metal(III) tetramethylaluminates: structural chemistry, reactivity, and performance in isoprene polymerization

The complexes [Ln(AlMe4)3] (Ln=Y, La, Ce, Pr, Nd, Sm, Ho, Lu) have been synthesized by an amide elimination route and the structures of [Lu{(micro-Me)2AlMe2}3], [Sm{(micro-Me)2AlMe2}3], [Pr{(micro-Me)2AlMe2}3], and [La{(micro-Me)2AlMe2}2{(micro-Me)3AlMe}] determined by X-ray crystallography. These structures reveal a distinct Ln3+ cation size-dependency. A comprehensive insight into the intrinsic properties and solution coordination phenomena of [Ln(AlMe4)3] complexes has been gained from extended dynamic 1H and 13C NMR spectroscopic studies, as well as 1D 89Y, 2D 1H/89Y, and 27Al NMR spectroscopic investigations. [Ce(AlMe4)3] and [Pr(AlMe4)3] have been used as alkyl precursors for the synthesis of heterobimetallic alkylated rare-earth metal complexes. Both carboxylate and siloxide ligands can be introduced by methane elimination reactions that give the heterobimetallic complexes [Ln{(O2CAriPr)2(micro-AlMe2)}2(AlMe4)(C6H14)n] and [Ln{OSi(OtBu)3}(AlMe3)(AlMe4)2], respectively. [Pr{OSi(OtBu)3}(AlMe3)(AlMe4)2] has been characterized by X-ray structure analysis. All of the cerium and praseodymium complexes are used as precatalysts in the stereospecific polymerization of isoprene (1-3 equivalents of Et2AlCl as co-catalyst) and compared to the corresponding neodymium-based initiators reported previously. The superior catalytic performance of the homoleptic complexes leads to quantitative yields of high-cis-1,4-polyisoprene (>98%) in almost all of the polymerization experiments. In the case of the binary catalyst mixtures derived from carboxylate or siloxide precatalysts quantitative formation of polyisoprene is only observed for nLn:nCl=1:2. The influence of the metal size is illustrated for the heterobimetallic lanthanum, cerium, praseodymium, neodymium, and gadolinium carboxylate complexes, and the highest activities are observed for praseodymium as a metal center in the presence of one equivalent of Et2AlCl.     

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).     

Cationic methyl complexes of the rare-earth metals: an experimental and computational study on synthesis, structure, and reactivity

Synthesis, structure, and reactivity of two families of rare-earth metal complexes containing discrete methyl cations [LnMe(2-x)(thf)n]((1+x)+) (x = 0, 1; thf = tetrahydrofuran) have been studied. As a synthetic equivalent for the elusive trimethyl complex [LnMe3], lithium methylates of the approximate composition [Li3LnMe6(thf)n] were prepared by treating rare-earth metal trichlorides [LnCl3(thf)n] with 6 equiv of methyllithium in diethyl ether. Heteronuclear complexes of the formula [Li3Ln2Me9L(n)] (Ln = Sc, Y, Tb; L = Et2O, thf) were isolated by crystallization from diethyl ether. Single crystal X-ray diffraction studies revealed a heterometallic aggregate of composition [Li3Ln2Me9(thf)n(Et2O)m] with a [LiLn2Me9](2-) core (Ln = Sc, Y, Tb). When tris(tetramethylaluminate) [Ln(AlMe4)3] (Ln = Y, Lu) was reacted with less than 1 equiv of [NR3H][BPh4], the dimethyl cations [LnMe2(thf)n][BPh4] were obtained. The coordination number as well as cis/trans isomer preference was studied by crystallographic and computational methods. Dicationic methyl complexes of the rare-earth metals of the formula [LnMe(thf)n][BAr4]2 (Ln = Sc, Y, La-Nd, Sm, Gd-Lu; Ar = Ph, C6H4F-4) were synthesized, by protonolysis of either the ate complex [Li3LnMe6(thf)n] (Ln = Sc, Y, Gd-Lu) or the tris(tetramethylaluminate) [Ln(AlMe4)3] (Ln = La-Nd, Sm, Dy, Gd) with ammonium borates [NR3H][BAr4] in thf. The number of coordinated thf ligands varied from n = 5 (Ln = Sc, Tm) to n = 6 (Ln = La, Y, Sm, Dy, Ho). The configuration of representative examples was determined by X-ray diffraction studies and confirmed by density-functional theory calculations. The highly polarized bonding between the methyl group and the rare-earth metal center results in the reactivity pattern dominated by the carbanionic character and the pronounced Lewis acidity: The dicationic methyl complex [YMe(thf)6](2+) inserted benzophenone as an electrophile to give the alkoxy complex [Y(OCMePh2)(thf)5](2+). Nucleophilic addition of the soft anion X(-) (X(-) = I(-), BH4(-)) led to the monocationic methyl complexes [YMe(X)(thf)5](+).     

Organometallic early lanthanide clusters: syntheses and X-ray structures of new monocyclopentadienyl complexes

The reaction of Ln(BH(4))(3)(THF)(3) or LnCl(3)(THF)(3) with 1 equiv of KCp*' ligand (Cp' = C(5)Me(4)n-Pr) afforded the new monocyclopentadienyl complexes Cp*'LnX(2)(THF)(n) (X = BH(4), Ln = Sm, n = 1, 1a, Ln = Nd, n = 2, 1b; X = Cl, Ln = Sm, n = 1, 3a) and [Cp*'LnX(2)](n') (X = BH(4), n' = 6, Ln = Sm, 2a, Ln = Nd, 2b; X = Cl, Ln = Nd, 4b). All these compounds were characterized by elemental analysis and (1)H NMR. Crystals of mixed borohydrido/chloro-bridged [Cp*'(6)Ln(6)(BH(4))(12-x))Cl(x)(THF)(n')] (x = 10, n' = 4, Ln = Sm, 2a', Ln = Nd, 2b'; x = 5, n = 2, Ln = Sm, 2a' ') were also isolated. Compounds 2a, 2b, 2a', 2b', and 2a' were structurally characterized; they all exhibit a hexameric structure in the solid state containing the [Cp*(3)Ln(3)X(5)(THF)] building block. The easy clustering of THF adducts first isolated is illustrative of the well-known bridging ability of the BH(4) group. Hexameric 2a was found to be unstable in the presence of THF vapors; this may be correlated to the opening of unsymmetrical borohydride bridges observed in the molecular structure.     

A series of three-dimensional architectures constructed from lanthanide-substituted polyoxometalosilicates and lanthanide cations or lanthanide-organic complexes as linkers

Six 3D architectures based on lanthanide-substituted polyoxometalosilicates, KLn[(H(2)O)(6)Ln](2)[(H(2)O)(4)LnSiW(11)O(39)](2)·nH(2)O (Ln = La 1, n = 42; Ce 2, n = 40), H[(H(2)O)(6)Nd](2)[(H(2)O)(7)Nd][(H(2)O)(4)NdSiW(11)O(39)][(H(2)O)(3)NdSiW(11)O(39)]·13H(2)O (3), H(2)K(2)[(Hpic)(H(2)O)(5)Ln](2)[(H(2)O)(4)LnSiW(11)O(39)](2)·nH(2)O (Ln = La 4, n = 18.5; Ce 5, n = 35; Nd 6, n = 36; Hpic = 4-picolinic acid), have been synthesized and characterized by elemental analysis, IR and UV-vis spectroscopy, TG analysis, powder X-ray diffraction and single crystal X-ray diffraction. Compounds 1 and 2 are isostructural, built up of lanthanide-substituted polyoxoanions [{(H(2)O)(4)Ln(SiW(11)O(39))}(2)](10-) linked by Ln(3+) cations to form a 3D open framework with 1D channels. The polyoxoanion [{(H(2)O)(4)Ln(SiW(11)O(39))}(2)](10-) consists of two α(1)-type mono-Ln-substituted Keggin anions. When Nd(3+) ion was used instead of La(3+) or Ce(3+) ions, compound 3 with a different structure was obtained, containing two kinds of polyoxoanions [{(H(2)O)(4)Nd(SiW(11)O(39))}(2)](10-) and [{(H(2)O)(3)Nd(SiW(11)O(39))}(2)](10-) which are connected together by Nd(3+) ions to yield a 3D framework. When 4-picolinic acid was added to the reaction system of 1-3, isostructural compounds 4-6 were obtained, constructed from the polyoxoanions [{(H(2)O)(4)Ln(SiW(11)O(39))}(2)](10-) linked by picolinate-chelated lanthanide centers to form a 3D channel framework. From a topological viewpoint, the 3D nets of 1, 2, 4, 5 and 6 exhibit a (3,6)-connected rutile topology, whereas the 3D structure of 3 possesses a rare (3,3,6,10)-connected topology. The magnetic properties of 2, 3, 5 and 6 have been studied by measuring their magnetic susceptibilities in the temperature range 2-300 K.     

Structure and dissociation characteristics of metal chloride anion clusters containing redox-active metal ions studied by laser desorption and electrospray ionization mass spectrometry and ab initio calculations

Copper chloride anion clusters with both copper oxidation states can be made by laser desorption of CuCl(2) crystals. We have used this method to study the dissociation characteristics of such cluster ions. The stability and the structure of the observed complexes were probed by ab initio calculations. These calculations show that many of these complexes are bridged structures. Thus, for the Cu(2)Cl(4) dimer anion, formally [ClCu-Cl-CuCl(2)](-) , with putative mixed copper oxidation states, the two copper ions become equivalent through bridging. Such bridging does not occur when redox inactive metal ions are present as in [ClCu-Cl-CaCl(2)](-) . By observing the dissociation characteristics of a variety of metal chloride cluster anions produced from binary mixtures, the following Cl(-) affinity order is obtained: FeCl(3) > CuCl > CaCl(2) > FeCl(2) > AgCl ≈ CuCl(2) ≈ ZnCl(2) > LiCl. Ab initio calculations on the Cl(-) affinity of selected chlorides confirm this order as do Cl(-) affinity estimates from the experimentally known vertical electron detachment energies of the superhalogens CaCl(3)(-) and LiCl(2)(-) . An equimolar mixture of CuCl(2) and FeCl(3) produces an intense cluster ion, which, from (65)Cu labeling experiments, is best described as FeCl(4)(-)···Cu(+)···(-)Cl(4) Fe, a Cu(+) bound superhalogen FeCl(4)(-) dimer. The Cu(+) ion can be replaced by the redox inactive alkali cations and by Ag(+) but these metal ion bound FeCl(4)(-) dimers show an entirely different fragmentation behavior which is attributed to the absence of bridging. Electrospray ionization (ESI) of CuCl(2) produces an extended series of (CuCl(2))(n) Cl(-) anions (n = 1-11) and so in ESI very limited reduction of Cu(2+) takes place. The (CuCl(2))(n) Cl(-) anions show an abundant dissociation via loss of neutral Cu(2)Cl(4) which according to our ab initio calculations is 9 kcal/mol more stable than two CuCl(2).