Heterometallic europium disiloxanediolates: synthesis, structural diversity, and photoluminescence properties.

This contribution presents a full account of a structurally diverse class of heterometallic europium disiloxanediolates. The synthetic protocol involves in situ metalation of (HO)SiPh2OSiPh2(OH) (1) with either (n)BuLi or KN(SiMe3)2 followed by treatment with EuCl3 in suitable solvents such as 1,2-dimethoxyethane (DME) or tetrahydrofuran (THF). Reaction of EuCl3 with 2 equiv of (LiO)SiPh2OSiPh2(OLi) in DME afforded the Eu(III) bis(disiloxanediolate) "ate" complex [{(Ph2SiO)2O}2{Li(DME)}3]EuCl2 (2), which upon attempted reduction with Zn gave the tris(disiloxanediolate) [{(Ph2SiO)2O}3{Li(DME)}3]Eu (3). Treatment of EuCl3 with (LiO)SiPh2OSiPh2(OLi) in a molar ratio of 1:2 yielded both the ate complex [{(Ph2SiO)2O}3Li{Li(THF)2}{Li(THF)}]EuCl·Li(THF)3 (4) and the LiCl-free europium(III) complex [{(Ph2SiO)2O}2{Li(THF)2}2]EuCl (5). Compound 5 was found to exhibit a brilliant red triboluminescence. When (KO)SiPh2OSiPh2(OK) was used as starting material in a 3:1 reaction with EuCl3, the Eu(III) tris(disiloxanediolate) [{(Ph2SiO)2O}3{K(DME)}3]Eu (6) was isolated. Attempted ligand transfer between 5 and (DAD(Dipp))2Ba(DME) (DAD(Dipp) = N,N'-bis(2,6-diisopropylphenyl)-1,4-diaza-1,3-butadiene) afforded the unique mixed-valent Eu(III)/Eu(II) disiloxanediolate cluster [(Ph2SiO)2O]6Eu(II)4Eu(III)2Li4O2Cl2 (7). All new complexes were structurally characterized by X-ray diffraction. Photoluminescence studies were carried out for complex 5 showing an excellent color quality, due to the strong (5)D0→(7)F2 transition, but a weak antenna effect.

Crystal structure of the high-energy-density material guanylurea dipicryl-amide.

The title compound, 1-carbamoylguanidinium bis-(2,4,6-tri-nitro-phen-yl)amide [H2NC(=O)NHC(NH2)2](+)[N{C6H2(NO2)3-2,4,6}2](-) (= guanylurea dipicryl-amide), was prepared as dark-red block-like crystals in 70% yield by salt-metathesis reaction between guanylurea sulfate and sodium dipicryl-amide. In the solid state, the new compound builds up an array of mutually linked guanylurea cations and dipicryl-amide anions. The crystal packing is dominated by an extensive network of N-H⋯O hydrogen bonds, resulting in a high density of 1.795 Mg m(-3), which makes the title compound a potential secondary explosive.

Unexpected formation and crystal structure of tetra-kis-(1H-pyrazole-κN (2))-palladium(II) dichloride.

The title salt, [Pd(C3H4N2)4]Cl2, was obtained unexpectedly by the reaction of palladium(II) dichloride with equimolar amounts of 1-chloro-1-nitro-2,2,2-tris-(pyrazol-yl)ethane in methanol solution. The Pd(2+) cation is located on an inversion centre and has a square-planar coordination sphere defined by four N atoms of four neutral pyrazole ligands. The average Pd-N distance is 2.000 (2) Å. The two chloride anions are not coordinating to Pd(2+). They are connected to the complex cations through N-H⋯Cl hydrogen bonds. In addition, C-H⋯Cl hydrogen bonds are observed, leading to a three-dimensional linkage of cations and anions.

Homoleptic gadolinium amidinates as precursors for MOCVD of oriented gadolinium nitride (GdN) thin films.

Five new homoleptic gadolinium tris-amidinate complexes are reported, which were synthesized via the salt-elimination reaction of GdCl(3) with 3 equiv of lithiated symmetric and asymmetric amidinates at ambient temperature. The Gd-tris-amidinates [Gd{(N(i)Pr)(2)CR}(3)] [R = Me (1), Et (2), (t)Bu (3), (n)Bu (4)] and [Gd{(NEt)(N(t)Bu)CMe}(3)] (5) are solids at room temperature and sublime at temperatures of about 125 °C (6 × 10(-2) mbar) with the exception of compound 4, which is a viscous liquid at room temperature. According to X-ray diffraction analysis of 3 and 5 as representative examples of the series, the complexes adopt a distorted octahedral structure in the solid state. Mass spectrometric (MS) data confirmed the monomeric structure in the gas phase, and high-resolution MS allowed the identification of characteristic fragments, such as [{(N(i)Pr)(2)CR}GdCH(3)](+) and [{(N(i)Pr)(2)CR}GdNH](+). The alkyl substitution patterns of the amidinate ligands clearly show an influence on the thermal properties, and specifically, the introduction of the asymmetric carbodiimide leads to a lowering of the onset of volatilization and decomposition. Compound 5, which is the first Gd complex with an asymmetric amidinate ligand system to be reported, was, therefore, tested for the MOCVD of GdN thin films. The as-deposited GdN films were capped with Cu in a subsequent MOCVD process to prevent postdeposition oxidation of the films. Cubic GdN on Si(100) substrates with a preferred orientation in the (200) direction were grown at 750 °C under an ammonia atmosphere and exhibited a columnar morphology and low levels of C or O impurities according to scanning electron microscopy, Rutherford backscattering, and nuclear reaction analysis.

5-Bromo-4-(3,5-di-bromo-2-hy-droxy-phen-yl)-2-(piperidin-1-yl)-1,3-di-thiol-2-ylium bromide.

In the title salt, C14H13Br3NOS2 (+)·Br(-), synthesized by bromination of mesoionic 2-[2-(piperidin-1-yl)-1,3-di-thiol-2-ylium-4-yl]phenolate in glacial acetic acid, the dihedral angle between the 1,3-di-thiol-ium ring and the phenolic substituent ring is 45.9 (3)° due to the steric influence of the ortho-Br group on the 1,3-di-thiol-ium ring. The piperidine ring adopts a chair conformation. In the crystal, the cation and anion are linked by an O-H⋯Br hydrogen bond.

rac-1-(5-Bromo-2-hy-droxy-phen-yl)-1-oxopropan-2-yl morpholine-4-carbo-dithio-ate.

In the racemic title compound, C14H16BrNO3S2, synthesized from the corresponding ω-bromo-propio-phenone, the dihedral angle between the plane of the phenol group and that of the planar section [maximum deviation = 0.040 (2) Å] of the morpholine-4-carbodi-thiol-ate moiety is 76.36 (10)°. A strong intra-molecular phenol O-H⋯O hydrogen bond if present in the mol-ecule. In the crystal, only weak C-H⋯S and C-H⋯O inter-actions are found.

4-Bromo-2-[5-methyl-2-(morpholin-4-yl)-1,3-thia-zol-4-yl]phenol.

In the title compound, C14H15BrN2O2S, synthesized by the reaction of the corresponding phenacyl thio-cyanate with morpholine, the dihedral angle between the 1,3-thia-zole ring and the phenolic substituent ring is 23.46 (10)° as a result of the steric influence of the ortho-methyl group on the thia-zole ring. A strong intra-molecular phenolic O-H⋯N hydrogen bond is present in the mol-ecule. In the crystal, a weak C-H⋯Ophenol hydrogen bond gives rise to chains lying parallel to [20-1]. A short inter-molecular Br⋯Omorpholine inter-action is also present [3.1338 (19) Å].

Di-µ-oxido-bis-[bis-(diiso-propyl-aceta-midinato)-κN;κ(2) N,N'-germanium(IV)].

The title compound, [Ge2(C8H17N2)4O2], crystallizes with imposed twofold symmetry, which allows the monodentate amidinate ligands to be arranged in a cisoid fashion. The independent Ge-O distances within the central Ge2O2 ring, which is essentially planar (r.m.s. deviation = 0.039 Å), are 1.7797 (8) and 1.8568 (8) Å. The germanium centres adopt a distorted trigonal-bipyramidal geometry, being coordinated by the two O atoms and by one bidentate and one monodentate amidinate ligand (three N atoms). One N-isopropyl group is disordered over two positions; these are mutually exclusive because of 'collisions' between symmetry-equivalent methyl groups and thus each has 0.5 occupancy.

Ruthenium-catalyzed functionalization of pyrroles and indoles with propargyl alcohols.

Several ruthenium-catalyzed atom-economic transformations of propargyl alcohols with pyrroles or indoles leading to alkylated, propargylated, or annulated heteroaromatics are reported. The mechanistically distinct reactions are catalyzed by a single ruthenium(0) complex containing a redox-coupled dienone ligand. The mode of activation regarding the propargyl alcohols determines the reaction pathway and depends on the alcohols' substitution pattern. Secondary substrates form alkenyl complexes by a 1,2-hydrogen shift, whereas the transformation of tertiary substrates involves allenylidene intermediates. 1-Vinyl propargyl alcohols are converted by a cascade allylation/cyclization sequence. The environmentally benign processes are of broad scope and allow the selective synthesis of highly functionalized pyrroles and indoles generating water as the only waste product.

Bromidobis[3-(1H-pyrazol-1-yl-κN(2))propionamide-κO]copper(II) bromide methanol monosolvate.

The title copper(II) N-pyrazolylpropanamide (PPA) complex, [CuBr(PPA)(2)]Br, was obtained in 78% yield by treatment of CuBr(2) with an excess of the ligand in methanol. Crystallization from the mother liquid afforded the title compound, i.e. the methanol solvate [CuBr(C(6)H(9)N(3)O)(2)]Br·CH(3)OH or [CuBr(PPA)(2)]Br·MeOH, as bright green crystals. In the solid state, the title salt comprises isolated [CuBr(PPA)(2)](+) cations, separated bromide ions and methanol of crystallization. In the cation, the central Cu(II) ion is coordinated by two N,O-chelating PPA ligands and one Br(-) ion. The coordination geometry around the Cu(II) ion is distorted trigonal-bipyramidal with the bromide ligand and the amide O atoms occupying the equatorial positions [Cu-Br = 2.4443 (4) Å; Cu-O = 2.035 (2) and 2.179 (2) Å], while the pyrazole N atoms coordinate in the axial positions [Cu-N = 1.975 (2) and 1.976 (2) Å]. In the crystal, the three constituents are linked by N-H⋯Br, O-H⋯Br, and N-H⋯O hydrogen bonds, forming a three-dimensional network.

Unprecedented bending and rearrangement of f-element sandwich complexes induced by superbulky cyclooctatetraenide ligands.

The use of the superbulky cyclooctatetraenide dianion ligand [C(8)H(6)(SiPh(3))(2)](2-) (= COT(BIG)) in organo-f-element chemistry leads to unprecedented effects such as the formation of a significantly bent anionic Ce(III) sandwich complex, a novel cerocene formed by sterically induced SiPh(3) group migration, as well as the first example of a bent uranocene.

Carboranylamidinates.

Carboranylamidinate anions are readily accessible via addition of N,N'-dialkylcarbodiimides to lithio-ortho-carborane. They represent a novel difunctional boron-rich ligand system for main group and transition elements (Li, Sn, Cr). Initial structural investigations revealed an unexpected N,C-coordination mode instead of N,N'-chelation.

Facile access to tetravalent cerium compounds: one-electron oxidation using iodine(III) reagents.

Readily accessible and easy-to-use phenyliodine(III) dichloride, PhICl(2), has been established as an innovative and superior reagent for the one-electron oxidation of cerium(III) complexes, comprising amide, amidinate, and cyclopentadienyl derivatives. Its use allowed the successful synthesis and structural characterization of the first members of three new classes of chloro-functionalized (organo)cerium(IV) compounds, including the long sought-after Cp(3)CeCl.

Rare-earth metal alkyl, amido, and cyclopentadienyl complexes supported by imidazolin-2-iminato ligands: synthesis, structural characterization, and catalytic application.

The rare earth metal dichlorides [(1)MCl(2)(THF)(3)] (2a, M = Sc; 2b, M = Y; 2c, M = Lu) and the gadolinium complex [(1)GdCl(2)(THF)(2)] x [LiCl(THF)(2)] (2d), containing the 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-iminato ligand 1, proved to be versatile starting materials for the preparation of trimethylsilylmethyl ("neosilyl") and bis(trimethylsilyl)amido complexes [(1)M(CH(2)SiMe(3))(2)(THF)(2)] (3a-3d) and [(1)M(HMDS)(2)(THF)] [4a-4d, HMDS = hexamethyldisilazide, N(SiMe(3))(2)] and for the preparation of the benzyl complex [(1)Lu(CH(2)Ph)(2)(THF)(2)] (5c) by the reaction with LiCH(2)SiMe(3), Na[N(SiMe(3))(2)], and KCH(2)Ph, respectively. Treatment of 2a-2c with KCp* afforded the mono(pentamethylcyclopentadienyl) complexes [(1)Sc(Cp*)Cl(THF)] (6a), [(1)Y(Cp*)Cl(THF)(2)] (6b), and [(1)Lu(Cp*)Cl(THF)] (6c). In contrast, the gadolinocene complex [(1)Gd(Cp*)(2)(THF)] (7) was isolated from the reaction of 2d with 2 equiv of KCp*. The molecular structures of 3a-3d, 4b.THF, 4d, 5c, 6a, 6c, and 7 x THF were determined by X-ray diffraction analyses, revealing the presence of exceptionally short metal-nitrogen bonds. The neosilyl complexes 3b and 3c showed high catalytic activity in the intramolecular hydroamination of aminoalkenes and aminoalkynes and in the hydrosilylation of 1-hexene and 1-octene with PhSiH(3).

Bis({tris[2-(3,5-di-tert-butyl-2-oxido-benzylideneamino)ethyl]amine}cerium(III)) diethyl ether solvate.

The title compound, 2[Ce(C(51)H(75)N(4)O(3))]·C(4)H(10)O, was obtained in high yield (92%) by reduction of (TRENDSAL)Ce(IV)Cl [TRENDSAL is N,N',N''-tris-(3,5-di-tert-butyl-salicyl-ide-natoamino)-triethyl-amine] with potassium in THF. The bulky tripodal TRENDSAL ligand effectively encapsulates the central Ce(III) cation with a Ce-N(imine) distance of 2.860 (2) Šand an average C-N(amine) distance of 2.619 Šwithin a distorted monocapped octahedral coordination.

Bis(1H-pyrazole-κN)bis-(2,4,6-tri-isopropyl-benzoato-κO)cobalt(II).

The title compound, [Co(C(16)H(23)O(2))(2)(C(3)H(4)N(2))(2)] or (C(3)H(4)N(2))(2)Co(O(2)CC(6)H(2) (i)Pr(3)-2,4,6), is a rare example of a tetra-coordinate cobalt(II) carboxyl-ate stabilized by ancillary N-heterocyclic ligands. The Co(II) ion resides on a crystallographic twofold axis so that the asymmetric unit comprises one half-mol-ecule. Due to the steric bulk of the 2,4,6-triisopropyl-phenyl substituents, the carboxyl-ate ligands are both coordinated in a monodentate fashion despite the low coordination number. The coordination geometry around the central Co(II) ion is distorted tetra-hedral with angles at Co ranging from 92.27 (18)° to 121.08 (14)°.

Tris(N,N'-diisopropyl-benzamidinato)cerium(III).

The title compound, [Ce(C(13)H(19)N(2))(3)], was obtained in moderate yield (67%) by treatment of anhydrous cerium trichloride with three equivalents of Li[PhC(N(i)Pr)(2)] in tetra-hydro-furan. It is the first homoleptic lanthanide complex of this amidinate ligand. The central Ce(III) ion is coordinated by three chelating benzamidinate anions in a distorted octa-hedral fashion, with Ce-N distances in the narrow range 2.482 (2)-2.492 (2) Å. The dihedral angles between the phenyl rings and the chelating N-C-N units are in the range 73.3-87.9°, thus preventing conjugation between the two π-systems. The mol-ecule is located on a twofold rotation axis, and one of the phenyl rings is equally disordered over two alternative symmetry-equivalent positions around this axis.

[N,N'-Bis(2,6-diisopropyl-phen-yl)methanimidamidato][η-1,4-bis-(tri-methyl-sil-yl)cyclo-octa-tetra-enyl](tetra-hydro-furan)-samarium(III) toluene monosolvate.

The title compound, [Sm(C(25)H(35)N(2))(C(14)H(24)Si(2))(C(4)H(8)O)]·C(7)H(8), was prepared by treatment of anhydrous samarium trichloride with a 1:1 mixture of in situ-prepared Li(DippForm) [DippFormH = N,N'-bis-(2,6-diisopropyl-phen-yl)methanimidamide] and Li(2)(COT'') [COT'' = 1,4-bis-(trimethyl-sil-yl)cyclo-octa-tetra-enyl] in tetra-hydro-furan (THF). Despite the presence of two very bulky ligands (COT'' and DippForm), the mol-ecule still contains one coordinated THF ligand. The overall coordination geometry around the Sm(III) atom resembles a three-legged piano-stool with the COT'' ligand being η(8)-coordinated and the DippForm(-) anion acting as an N,N'-chelating ligand [Sm-N = 2.5555 (15) and 2.4699 (15) Å]. The asymmetric unit also contains a disordered mol-ecule of toluene, the refined ratio of the two components being 0.80 (4):0.20 (4).

Secondary interactions in phosphane-functionalized group 4 cycloheptatrienyl-cyclopentadienyl sandwich complexes.

Twice as reactive: The coordination chemistry of phosphane-functionalized Zr and Hf cycloheptatrienyl-cyclopentadienyl complexes gives rise to unusual secondary interactions associated with the presence of Lewis acidic 16-electron sandwich moieties. These structures can develop weak dative bonds as exemplified by the noncovalent Pd-->Zr interaction in the heterobimetallic {Zr(2)Pd} complex (see picture). Phosphane-functionalized cycloheptatrienyl-cyclopentadienyl Group 4 metal complexes of the type [(eta(7)-C(7)H(7))M(eta(5)-C(5)H(4)PR(2))] (M=Ti (9); M=Zr (10); M=Hf (11); R=Ph (a); R=iPr (b)) have been prepared by the reduction of [(eta(5)-C(5)H(4)PR(2))TiCl(3)] or [(eta(5)-C(5)H(4)PR(2))(2)MCl(2)] (M=Zr, Hf) with magnesium in the presence of cycloheptatriene (C(7)H(8)). In the solid state, the Ti complex 9 a and the complex 11 b are monomeric, whereas 10 a, 10 b, and 11 a form dimers, in which the sandwich units are linked by long Zr-P or Hf-P bonds. Density-functional theory (DFT) calculations indicate that the metal-phosphane interaction is weak, and accordingly, both the Ti complex 9 b and the Zr complex 10 b act as monodentate phosphane ligands upon reaction with [{(cod)RhCl}(2)] (cod=eta(4)-1,5-cyclooctadiene). The X-ray crystal structures of [(cod)Rh(9 b)Cl] (12) and [(cod)Rh(10 b)Cl] (13) reveal that only the latter exhibits a secondary intramolecular Cl-metal interaction. The complex [(10 b)(2)Pd] (14) was obtained by reaction of [(eta(5)-C(5)H(5))Pd(eta(3)-C(3)H(5))] with two equivalents of 10 b. The solid-state structure of 14 reveals a T-shaped Pd(0) center with a long Pd-Zr bond of 2.9709(3) A, which can be interpreted as a weak noncovalent Pd(0)-->Zr(+IV) bond, as indicated by the calculated relaxed force constant of 5.68 N m(-1).

Imidazolin-2-iminato complexes of rare earth metals with very short metal-nitrogen bonds: experimental and theoretical studies.

The reactions of 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-imine (Im(Dipp)NH, 1-H) with trimethylsilylmethyl lithium (LiCH(2)SiMe(3)) and anhydrous rare earth metal trichlorides MCl(3) afforded the imidazolin-2-iminato complexes [(1)MCl(2)(THF)(3)] (2a, M = Sc; 2b, M = Y; 2c, M = Lu) and [(1)GdCl(2)(THF)(2)] x [LiCl(THF)(2)] (2d). Treatment of complexes 2 with dipotassium cyclooctatetradienide, K(2)(C(8)H(8)) resulted in the formation of two- or three-legged piano-stool complexes of the type [(eta(8)-C(8)H(8))M(1)(THF)(n)] (3a, M = Sc, n = 1; 3b, M = Y, n = 2; 3c, M = Lu, n = 2; 3d, M = Gd, n = 2). X-ray diffraction analyses of all eight complexes 2 and 3 revealed the presence of very short metal-nitrogen bonds, which are among the shortest ever observed for these elements. [(eta(8)-C(8)H(8))Sc(1)(THF)] (3a) reacted with 2,6-dimethylphenyl isothiocyanate (Xy-NCS) to form the [2 + 2]-cycloaddition product 4, which contains a thioureato-N,N' moiety. The related COT-titanium complex [(eta(8)-C(8)H(8))TiCl(1)] (6) could be obtained from [(1)TiCl(3)] (5) by reaction with K(2)(C(8)H(8)) and was structurally characterized. As a theoretical analysis of the nature of the metal-nitrogen bond, density functional theory (DFT) calculations have been carried out for complexes 3a and 6 and also for the model complexes [(eta(8)-C(8)H(8))Sc(NIm(Me))] (7), [(eta(8)-C(8)H(8))Ti(NIm(Me))](+) (8), and [(eta(8)-C(8)H(8))Ti(NXy)] (9), revealing a marked similarity of the bonding in imidazolin-2-iminato and conventional imido metal complexes.