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The hydrophobic, low melting, 1-butyl-3-methylimidazolium (BMIm) salts [BMIm][BPh4] (1), [BMIm][B(C6H4Me-4)4] (2), [BMIm][B{C6H4(CF3)-4}4] (3), [BMIm][B{C6H3(CF3)2-3,5}4] (4), [BMIm][B{C6H4(C6F13)-4}4] (5), [BMIm][B{C6H4(SiMe3)-4}4] (6), [BMIm][B(C6H4{SiMe2(CH2CH2CF3)}-4)4] (7), [BMIm][B{C6H4(SiMe2C8H17}-4}4] (8) and [BMIm][B(C6H4{SiMe2(CH2CH2C6F13)}-4)4] (9) have been prepared. Systematic variation of the substituents on the tetraphenylborate anion allowed an assessment of their influence on the physical properties of the imidazolium salts. Structural investigations using NMR and IR spectroscopy, combined with single crystal X-ray structure determinations for 2, 3, 5 and 6, revealed hydrogen-bonding interactions between the imidazolium ring protons and the borate anion, both in the solid state and in solution. These interactions are weakened upon the introduction of electron-withdrawing substituents in the anion and follow the order 3,5-(CF3)2 < -C6F13 < -CF3 < -SiMe2CH2CH2C6F13 < -SiMe2CH2CH2CF3 < -H < -Me < -SiMe3. The melting points of the salts depend primarily on the bulk of the lipophilic substituents, and decrease with increasing size. Bulky lipophilic substituents dramatically enhance the solubility of the imidazolium borates 8 and 9 in hexane and reduce their relative polarity. These unique properties make imidazolium borates 8 and 9 interesting as amphiphilic ionic liquids with low polarity. Attempts to crystallise 7 resulted in decomposition. A single-crystal X-ray structure determination of the product, isolated in 6% yield, showed that a carbene-tris[4-{dimethyl(3,3,3-trifluoropropyl)silyl}phenyl]borane adduct was formed.

A series of cyclopalladated carbosilane dendrimers functionalized with monoanionic [C6H4(CH2NMe2)-4]- (= CN) C,N-chelating ligands via a multiple and selective C-H bond activation process have been prepared. The structure of the support, i.e., the branching degree as well as the nature of the alkanediyl linkers present in the carbosilane dendrimer, was varied to investigate its influence on the dimer formation of the peripheral [CN-PdCl] complexes and on the catalytic performance of these Pd(II)-functionalized dendrimers. Me2Si{(CH2)3SiMe2-CN-PdCl}2 (4) and Si{(CH2)2SiMe2-CN-PdCl}4 (7a) were characterized by a single X-ray crystal structure determination. In both cases a unique intramolecular halide-assisted macrocyclic ring structure was present. Variable-temperature NMR spectroscopic investigations indicated that in solutions of 4 and 7a the cis-bridging mode of the peripheral dimers is predominant. For the two asymmetrically branched [G1] palladodendrimers Si{(CH2)2Si(Me){(CH2)2SiMe2-CN-PdCl}2}4 (10a) and Si{(CH2)3Si(Me){(CH2)3SiMe2-CN-PdCl}2}4 (12a) isomeric forms of the [CN-PdCl] dimeric units were observed. In addition, for the [G2] dendrimer Si{(CH2)3Si{(CH2)3Si{(CH2)3SiMe2-CN-PdCl(pyr)}3}3}4, 15b, appended with a maximum of 36 [CN-PdCl(pyr)] complexes, a cis/trans isomerization of the peripheral [CN-PdCl(pyr)] groups is noted. The applicability of the cationic cyclopalladated carbosilane dendrimers, obtained by halide abstraction with AgBF4, as Lewis acid catalysts in a model aldol condensation reaction was demonstrated. Their catalytic performance was compared to that of the parent mononuclear derivative [Pd(C6H3{CH2NMe2}-2-(SiMe3)-5)(pyr)(H2O)]BF4 (16). The obtained catalytic data showed that up to generation [G2], the selectivity of the reaction is not affected. However, the rate of the reaction decreased with increasing steric congestion at the dendrimer periphery.

Trimethylsilyl- and dimethyl(1H,1H,2H,2H-perfluorooctyl)silyl substituents have been introduced in the para position of tetraphenylborate anions, resulting in enhanced solubility of their complexes n-Bu4N[B(C6H4SiMe2R-4)4] (R = Me, CH2CH2C6F13) and [Rh(dppe)2][B(C6H4SiMe2R-4)4] (dppe = 1,2-bis(diphenylphosphino)ethane, R = Me, CH2CH2C6F13) in apolar organic solvents.

Two different monoanionic O,N-chelating ligand systems, i.e., [OC6H2(CH2NMe2)-2-Me2-4,6]- (1) and [OCMe2([2]-Py)]- (2), have been applied in the synthesis of vanadium(V) complexes. The tertiary amine functionality in 1 caused reduction of the vanadium nucleus to the 4+ oxidation state with either [VOCl3], [V(=NR)Cl3], or [V(=NR)(NEt2)3] (R = Ph, (3a, 5a), R = p-Tol (3b, 5b)), and applying 1 as a reducing agent resulted in the synthesis of the vanadium(IV) complexes [VO(OC6H2(CH2NMe2)-2-Me2-4,6)2] (4) and [V(=NPh)(OC6H2(CH2NMe2)-2-Me2-4,6)2] (6). In the case of [V(=N-p-Tol)(NEt2)(OC6H2(CH2NMe2)-2-Me2-4,6)2] (7b), the reduction was sufficiently slow to allow its characterization by 1H NMR and variable-temperature studies showed it to be a five-coordinate species in solution. Although the reaction of 1 with [V(=N-p-Tol)(O-i-Pr)3] (9b) did not result in reduction of the vanadium nucleus, vanadium(V) compounds could not be isolated. Mixtures of the vanadium(V) (mono)phenolate, [V(=N-p-Tol)(O-i-Pr)2(OC6H2(CH2NMe2)-2-Me2-4,6)] (10), and the vanadium(V) (bis)phenolate, [V(=N-p-Tol)(O-i-Pr)(OC6H2(CH2NMe2)-2-Me2-4,6)2] (11), were obtained. With the pyridylalkoxide 2, no reduction was observed and the vanadium(V) compounds [VOCl2(OCMe2([2]-Py))] (12) and [V(=N-p-Tol)Cl2(OCMe2([2]-Py)] (13) were obtained. 51V NMR showed 7b and 12 to be five-coordinate in solution, whereas for 10, 11, and 13 a coordination number of 6 was found. Compounds 12 and 13 showed decreased activity compared to their nonchelated vanadium(V) analogues when applied as catalysts in ethene polymerization. Two polymorphic forms with a difference in the V-N-C angle of 12.5 have been found for 6. Crystal data: 6·Et2O, triclinic, P, a = 11.1557(6) Å, b = 12.5744(12) Å, c = 13.1051(14) Å, = 64.244(8), = 70.472(7), = 87.950(6), V = 1547(3) Å3, Z = 2; 6·C6H6, triclinic, P, a = 8.6034(3) Å, b = 13.3614(4) Å, c = 15.1044(5) Å, = 98.182(3), = 105.618(2), = 107.130(2), V = 1551.00(10) Å3, Z = 2; 12, orthorhombic, Pbca, a = 11.8576(12) Å, b = 12.6710(13) Å, c = 14.722(2) Å, V = 2211.9(4) Å3, Z = 8.

The configuration of the chiral ring atoms of the title compound, C26H26N2O, obtained in an enantioselective synthesis, has been established relative to the known R configuration of the ?-methylbenzyl moieties. The crystal packing involves a two-dimensional network of C-H...? interactions between the aromatic rings.

Reaction of 3, 5-bis[(dimethylamino)methyl]phenyl iodide with 3,5-bis[(dimethylamino)methyl]phenylacetylene in diethylamine in the presence of bis(triphenylphosphine)palladium(II) dichloride (3.6 mol%) and copper(I) iodide (3.0 mol%) gave 1,2-(bis(3,5-bis[(dimethylamino)methyl]phenyl)acetylene (1) in 82% yield. The palladium catalyst was recovered in 93% yield as trans-(3,5-bis[(dimethylamino)methyl]phenyl)bis(triphenylphosphine)palladium (II) iodide (2). The crystal structure of 2 shows that the coordination geometry of the palladium is distorted square-planar. No inter- or intramolecular interactions between the N-donor atoms and the Pd are observed.

New air-stable ruthenium(II) complexes that contain the aryldiamine ligand [C6H3(CH2NMe2)2-2,6]- (NCN) are described. These complexes are [RuCl{2-C,N-C6H3(CH2NMe2)2-2,6}(6-C10H14)] (2; C10H14 = p-cymene = C6H4Me-iPr-4), [Ru{2-C,N-C6H3(CH2NMe2)2-2,6}(5-C5H5)(PPh3)] (5), and their isomeric forms [RuCl{2-C,N-C6H3(CH2NMe2)2-2,4}(6-C10H14)] (3) and [Ru{2-C,N-C6H3(CH2NMe2)2-2,4}(5-C5H5)(PPh3)] (6), respectively. Complex 2 has been prepared from the reaction of [Li(NCN)]2 with [RuCl2(6-C10H14)]2, whereas complex 5 has been prepared by the treatment of [RuCl{3-N,C,N-C6H3(CH2NMe2)2-2,6}(PPh3)] (4) with [Na(C5H5)]n. Both 2 and 5 are formally 18-electron ruthenium(II) complexes in which the monoanionic potentially tridentate coordinating ligand NCN is 2-C,N-bonded. In solution (halocarbon solvent at room temperature or in aromatic solvents at elevated temperature), the intramolecular rearrangements of 2 and 5 afford complexes 3 and 6, respectively. This is a result of a shift of the metal-Caryl bond from position-1 to position-3 on the aromatic ring of the NCN ligand. The mechanism of the isomerization is proposed to involve a sequence of intramolecular oxidative addition and reductive elimination reactions of both aromatic and aliphatic C-H bonds. This is based on results from deuterium labeling, spectroscopic studies, and some kinetic experiments. The mechanism is proposed to contain fully reversible steps in the case of 5, but a nonreversible step involving oxidative addition of a methyl NCH2-H bond in the case of 2. The solid-state structures of complexes 2, 3, 5, and 6 have been determined by single-crystal X-ray diffraction. A new dinuclear 1,4-phenylene-bridged bisruthenium(II) complex, [1,4-{RuCl(6-C10H14)}2{C6(CH2NMe2)4-2,3,5,6-C,N,C',N'}] (9) has also been prepared from the dianionic ligand [C6(CH2NMe2)4-2,3,5,6]2- (C2N4). The C2N4 ligand is in an 2-C,N-2-C',N'-bis(bidentate) bonding mode. Compound 9 does not isomerize in solution (halocarbon solvent), presumably because of the absence of an accessible Caryl-H bond. Complex 9 could not be isolated in an analytically pure form, probably because of its high sensitivity to air and very low solubility, which precludes recrystallization.

The heteroatom assisted lithiation of 1, 3-bis[1-(dimethylamino)ethyl]benzene with n-BuLi afforded 2,6-bis[1-(dimethylamino)ethyl]phenyllithium. An X-ray crystal structure determination revealed a dimeric aggregate in which the four benzylic chiral centers are identical, pointing to stereoselective crystallization. In contrast, reaction of 1,3-bis[1-(dimethylamino)propyl]benzene with n-BuLi afforded a dimeric aggregate comprising the parent lithiated compound and n-BuLi in a 1:1 molar ratio. The four Li atoms and the four bridging carbon atoms are arranged in a unique ladder-type C-Li2-C2'-Li2-C framework.

Titanium(IV) derivatives of the chelating monoanionic aryldiamine ligand [C6H3(CH2NMe2)2-2,6]- (abbreviated as NCN) are prepared by treating [TiCl3(OR)] (R = i-Pr, C6H4OMe-4) with [Li(NCN)]2. [TiCl2(NCN)(O-i-Pr)] is smoothly methylated by methyllithium in toluene to give [TiClMe(NCN)(O-i-Pr)] and [TiMe2(NCN)(O-i-Pr)]. Enhancement of the Lewis acidity of the titanium center has been studied by substituting chloro ligands for triflato ligands to give [TiCl(NCN)(O-i-Pr)(OTf)] and [Ti(NCN)(O-i-Pr)(OTf)2]. X-ray studies of the dichloride and triflate complexes feature 3-pseudofacial and 3-meridional bonding modes for the NCN ligand, respectively. These different NCN bonding modes are explained in terms of the trans influence of the alkoxy and triflato ligands. A rare example of an organo titanium(IV) complex with a seven-coordinate titanium center is observed in the bis(triflate) complex as a result of bidentate O,O'-bonding mode of the triflato anion to one titanium center that is unprecedented in early transition metal chemistry. The triflato ligands exhibit a strong covalent bonding to titanium both in the solid state and in solution; the latter is demonstrated by the observation that cationic species are not formed upon addition of Lewis bases like THF, acetonitrile, and 1,2-bis(dimethylamino)ethane.

From the reactions of the unsubstituted tantalacyclobutane complex [Ta{(CH2)3-1,3}(CNN)(O-t-Bu)2] (CNN = [C6H4(CH2N(Me)CH2CH2NMe2)-2]-) (1) with propene and styrene have been isolated in good yields the substituted tantalacyclobutane complexes [Ta{CH2CH(Me)CH2-1,3}(CNN)(O-t-Bu)2] (2) and [Ta{CH2CH(Ph)CH2-1,3}(CNN)(O-t-Bu)2] (3), respectively. The X-ray molecular structures of 2 and 3 show them to be seven-coordinate pentagonal bipyramidal species in which the meridional ligation comprises C,N,N'-bonding of the aryldiamine ligand CNN and -bonding of two carbons of the metallacycle; the two alkoxide groups occupy the apical positions. The organyl substituent of the metallacycle is positioned on the -carbon. Complexes 2 and 3 can both be converted back into 1 by reacting them in Et2O with ethene. The reaction of 1 with carbon monoxide yields the oxytantalacyclopropane complex [Ta{C(O)((CH2)3-1,3)}(CNN)(O-t-Bu)2] (4), which has been isolated as an air-stable white solid in 59% yield. The X-ray molecular structure of 4 reveals that the carbon and oxygen atoms of the C=O function are ligated in the meridional plane with further 3-C,N,N'-ligation of CNN and the two alkoxides as found in 2 and 3. Reaction of the tantalacyclobutane complexes 2-4 with 1 equiv of t-BuNC affords the 1:1 insertion products [Ta{C(=N-t-Bu)CH2CH(R)CH2-1,4}(CNN)(O-t-Bu)2] (R = H (5), Me (6), and Ph (7), respectively). Complexes 5 and 7 have been isolated as yellow solids (yields: 5, 62%; 7, 50%), while 6 has been prepared and characterized in situ. 1H and 13C NMR spectroscopy of 6 and 7 indicate for each complex the presence of two isomers in solution. The X-ray molecular structure of 7 shows 2-C,N-bonding of the CNN ligand through the aryl Cipso atom and the N(Me) donor atom and, most importantly, the presence of two tantalacyclic rings of different sizes that have a common Ta-C bond. The smaller three-membered ring comprises the metal center with the nitrogen and the -carbon atom of the 2-bonded iminoacyl fragment, while the larger five-membered ring is a metallacylopentane system comprising the metal center and four carbon atoms.

Neutral compounds of the type [MX2(L)] and [MX(Me)(L)] and ionic complexes of the type [M(Me)(L)](O3SCF3), in which X = Cl, Br, I; M = Pd, Pt; L = 2-(diphenylphosphino)-benzylidene-S- − )--methyl-benzylamine, have been prepared and characterized. Single crystal X-ray determinations of [PdCl2(L)] (1a) and [PtI2(L)] (3b) showed, in both cases, a chelate coordination of the PN ligand thereby forming a six-membered ring. The square planar surrounding is completed by the two halide atoms. The single crystal X-ray determination of [PdCl(Me)Cl(L)] (4a) shows an analogous geometry with a chelating PN ligand, a chloride atom and a methyl group, which is positioned cis to the phosphorus atom, completes the square planar surrounding. The methylpalladium and -platinum complexes reacted with CO to give the corresponding acetyl complexes. The insertion rates increased in the order Cl

Reaction of aryllithium reagents LiR (R = C6H4((R)-CH(Me)NMe2)-2 (1a), C6H3(CH2NMe2)2-2,6 (1b), C6H4(CH2N(Me)CH2CH2OMe)-2 (1c)) with 1 equiv of sulfur (1/8 S8) results in the quantitative formation of the corresponding lithium arenethiolates [Li{SC6H4((R)-CH(Me)NMe2)-2}]6 (3), [Li{SC6H3(CH2NMe2)2-2,6}]6 (4), and [Li{SC6H4(CH2N(Me)CH2CH2OMe)-2}]2 (5). Alternatively, 3 can be prepared by reacting the corresponding arenethiol HSC6H4((R)-CH(Me)NMe2)-2 (2) with nBuLi. X-ray crystal structures of lithium arenethiolates 3 and 4, reported in abbreviated form, show them to have hexanuclear prismatic and hexanuclear planar structures, respectively, that are unprecedented in lithium thiolate chemistry. The lithium arenethiolate [Li{SC6H4(CH2N(Me)CH2CH2OMe)-2}]2 (5) is dimeric in the solid state and in solution, and crystals of 5 are monoclinic, space group P21/c, with a = 17.7963(9) Å, b = 8.1281(7) Å, c = 17.1340(10) Å, = 108.288(5), Z = 4, and final R = 0.047 for 4051 reflections with F > 4(F). Hexameric 4 reacts with 1 equiv of lithium iodide and 2 equiv of tetrahydrofuran to form the dinuclear adduct [Li2(SAr)(I)(THF)2] (6). Crystals of 6 are monoclinic, space group P21/c, with a = 13.0346(10) Å, b = 11.523(3) Å, c = 16.127(3) Å, = 94.682(10), Z = 4, and final R = 0.059 for 3190 reflections with F > 4(F).