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The neutral, mixed 2:2 aryl-alkynyl-cuprates [Cu2Li2(CCR)2Ar2] (Ar = [C6H4{CH2N(Me)CH2CH2NMe2}-2]-; R = C6H4Me-4 (3a) or C6H4SiMe3-4 (3b)) are the first examples of cuprates that contain two different organic homocuprate parts ([Ar-Cu-Ar]- and [(RCC)-Cu-(CCR)]-) in one assembled structure. Each part has a two-coordinate Cu atom in linear geometry. They are held together by Li-Cipso interactions to two Li atoms. Tetrahedral four-coordination at the Li centers is completed by N,N'-chelation of the ortho-diamine substituent of the Ar ligand. Compound 3 is formed as the only reaction product in almost quantitative yield when LiAr and Cu(CCR) aggregates are mixed together in equimolar amounts. This cuprate is an example of ion-pairing between two different homocuprate anions and two Li cations.

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.

The complex trans-PtCl(p-Tol)(SEt{2}){2} is obtained from the reaction of [Pt(p-Tol){2}(SEt{2})]{2} with PtCl{2}(SEt{2}){2} and SEt{2} in mole ratio 1:2:2. The mono(p-tolyl)platinum(II) and bis(p-tolyl)platinum(II) complexes of diethylsulfide react with 2, 2'-bipyridine to form the complexes PtX(p-Tol)(bpy) (X=p-Tol, Cl) and are useful reagents for organoplatinum chemistry. X-ray crystal structures are presented for square planar PtCl(p-Tol)(bpy) and the centrosymmetric dimer [Pt(p-Tol){2}(@m-SEt{2})]{2}.

The synthesis of enantiopure (oxo-functionalized) C{2}-symmetric NCN pincer ligands is described. A key step is the symmetric functionalization of the benzylic positions, which was achieved by enantioselective ketone reduction and subsequent stereoselective substitution protocols. The introduction of @a-alkyl substituents has a pronounced effect on the cavity for metal binding. For example, lithiation of the @a-ethyl-functionalized pincer ligand afforded mixed (alkyl)(aryl)lithium aggregates rather than dinuclear bis(aryl) lithium [Li(NCN)]{2} species as usually observed for NCN-lithium complexes. Similar effects were established for the (trans)-metalation reaction, which proceeded significantly slower when the steric demand of the @a-substituent is increased. The potential of the corresponding enantiopure palladium and ruthenium complexes as enantioselective catalyst has been probed in the asymmetric aldol condensation and hydrogen transfer reactions. The low enantiomeric excess of the products of both reactions indicated that face-discrimination of substrates is not induced by these catalysts and that the chiral information must be located in closer proximity to the metal center.

The reaction of cationic platinum aqua complexes 2 [Pt(C6H2{CH2NMe2}2-E-4)(OH2)](X') (X' = SO3CF3, BF4) with alkyl halides RX gave various air-stable arenium complexes 3-5 containing a new C-C bond (R = Me, 3; Et, 4; Bn, 5). Electron-releasing oxo-substituents on the aromatic ligand (E = e.g., OH, b; OMe, c) enhance the reactivity of the aqua complex 2 and were essential for arenium formation from alkyl halides different from MeX. This process is initiated by oxidative addition of alkyl halides to the platinum(II) center of 2, which affords (alkyl)(aryl) platinum(IV) complexes (e.g., 9, alkyl = benzyl) as intermediates. Spectroscopic analyses provided direct evidence for a subsequent reversible 1,2-sigmatropic shift of the alkyl group along the Pt-Caryl bond, which is identical to repetitive Carenium-Calkyl bond making and breaking and concerted metal reduction and oxidation. Temperature-dependent NMR spectroscopy revealed H = -1.3 (± 0.1) kJ mol-1, S = +3.8 (± 0.2) J mol-1 K-1, and G298 = -2.4 (± 0.1) kJ mol-1 for the formation of the arenium complex 5b from 9 involving the migration of a benzyl group. The arenium complexes were transformed to cyclohexadiene-type addition products 7 or to demetalated alkyl-substituted arenes, 8, thus completing the platinum-mediated formation of a sp2-sp3 C-C bond which is analogous to the aromatic substitution of a [PtX]+ unit by an alkyl cation R+. The formation of related trimethylsilyl arenium complexes 6 suggests arenium complexes as key intermediates, not only in (metal-mediated) sp2-sp3 C-C bond making and breaking but also in silyl-directed cyclometalation.

Dit onderzoek beschrijft een serie polykationische arylether-dendrimeren, die in kwantitatieve opbrengst zijn verkregen door reactie van dendritische benzyl bromides met organosilanen die vier aryl(di)amine substituenten bevatten. Deze dendrimeren zijn opgebouwd uit een polykationische kern en een polaire buitenlaag. Tevens wordt de synthese van het eerste gemengde, polykationische dendrimeer beschreven. Dit nieuwe type dendrimeer bestaat achtereenvolgens uit een [G1] carbosilaandendrimeer kern, een poly-ionische tussenlaag en een polaire buitenlaag opgebouwd uit [G1] Fréchet type dendrons. De bindingscapaciteiten van deze dendrimeren ten aanzien van anionische gast-molekulen zijn onderzocht. Spectroscopische metingen (UV/Vis, NMR en MALDI-TOF) wijzen erop dat alle kationische centra in de dendrimeren beschikbaar zijn voor de vorming van ionparen. Zo is het mogelijk om een maximum aantal van 24 anionische gasten te binden. De grote NMR spectroscopische verschuivingen gecombineerd met relaxatiemetingen van de groepen die aanwezig zijn in de kern van de dendrimeren, duiden op een duidelijke associatie van de anionen met de kationische centra van de dendrimeren. De kristalstructuur van de octakationische model-verbinding [Si(C6H3{CH2NMe3}2-3,5)4]8+8 I- laat zien dat de (jodide) anionen zich voornamelijk in de buurt van de kationische centra bevinden. De nieuwe polykationische dendrimeren zijn gebruikt in fase-transfer katalyse en voor het transport van organische substraten door nanofiltratiemembranen. The convergent synthesis of a series of polycationic aryl ether dendrimers has been accomplished by a convenient procedure involving quantitative quaternarization of aryl(poly)amine core molecules. The series has been expanded to the preparation of the first polycationic, mixed core-shell dendrimer. All these dendrimers consist of an apolar core with a peripheral ionic layer which is surrounded by a less polar layer of dendritic wedges. These cationic, macromolecular species have been investigated for their ability to form assemblies with (anionic) guest molecules. The results obtained from UV/Vis and NMR spectroscopies, and MALDI-TOF-MS demonstrate that all the cationic sites throughout the dendrimer core are involved in ion pair formation with anionic guests giving predefined guest/host ratios up to 24. The large NMR spectroscopic shifts of resonances correlated with the groupings located in the core of the dendrimers, together with the relaxation time data indicate that the anionic guests are associated with the cationic core of these dendrimers. The X-ray molecular structure of the octacationic, tetra-arylsilane model derivative [Si(C6H3{CH2NMe3}2-3,5)4]8+8 I- shows that the iodide counterions are primarily located near the polycationic sphere. The new polycationic dendrimers have been investigated for their catalytic phase-transfer behavior and substrate delivery over a nanofiltration membrane.

The preparation and structure of the rigid rod-like platinum monoacetylide {Pt}CC-4-C6H2I-1-(CH2NMe2)2-2,6) ({Pt} = [Pt(C6H3{Me2NCH2}2-2,6)]) are described. Its oxidative addition to Pd(dba)2 yields a heterobinuclear {Pt}CC{Pd}I complex ({Pd} = [Pd(-4-C6H2{Me2NCH2}2-2,6)]+); this provides a new strategy for the controlled and stepwise construction of rigid rod-like metallopolymers.

Novel strategies for the preparation of rigid cartwheel pincer metal complexes have been developed. The aromatic backbone of these materials ensures a high rigidity, which is expected to be important for a high retention when these multimetallic nanosize complexes are applied as homogeneous catalysts in a nanomembrane reactor. The ligand precursors C6[C6H3(CH2Y)2-3,5]6 (10, Y = NMe2; 11, Y = SPh; 12, Y = PPh2; 13, Y = pz = pyrazol-1-yl) have been prepared in high yields from the key intermediate C6[C6H3(CH2Br)2-3,5]6 (9). The hexakis(pincer) palladium(II) complexes C6[(PdX)-4-C6H2(CH2Y)2-3,5]6 (14, Y = SPh, L = Cl; 15, Y = PPh2, L = Cl; 16, Y = pyrazol-1-yl, L = OAc; 17, Y = pyrazol-1-yl, L = Cl) have been prepared via direct electrophilic palladation of the corresponding ligands. The (tris)pincer ligand C6H3[Br-4-C6H3(CH2NMe2)2-3,5]3-1,3,5 (20) was prepared via a triple-condensation reaction of 4-bromo-3,5-bis[(dimethylamino)methyl]acetophenone (19). Reaction of 20 with Pd(dba)2 yielded the tripalladium complex C6H3[(PdBr)-4-C6H3(CH2NMe2)2-3,5]3-1,3,5 (21). The crystal structure of 21 shows a propeller-like structure with D3 symmetry and a fixed bromine-bromine distance of 17.4573(4) Å, approximately forming a triangle with a height of 15.2 Å. These nanosize cartwheel pincer metal complexes based on tridentate Y,C,Y' pincer ligands have been used as homogeneous Lewis-acid catalysts. Moreover, the influence of the donor substituent Y on the catalytic activity of cationic mono-Y,C,Y' PdII complexes as Lewis-acid catalysts in the double Michael reaction between methyl vinyl ketone and ethyl -cyanoacetate, as a model reaction, has been investigated. It was found that cationic N,C,N'-type pincer complexes (1a, Y = NMe2; 1b, Y = pz; 1c, Y = pz* = 3,5-dimethylpyrazol-1-yl; 23) were superior to the P,C,P'- and S,C,S'-pincer complexes (1d, Y = PPh2; 1e, Y = SPh). The nanosize cationic tri-N,C,N' PdII complex 23 was found to have a catalytic activity per catalytic site in the double Michael reaction of the same order of magnitude as the monopincer analogue 1a (k = 279 × 10-6 s-1 for 1a vs k = 232 × 10-6 s-1 for 23). The combination of the nanosize dimensions, the catalytic activity, and the high thermal and air stability makes these complexes excellent candidates for application in a continuous process in a nanomembrane reactor.

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.

Monoanionic, potentially bi- or terdentate aminophenolates, ([OC6H3(CH2NMe2)-2-R-4)]-, R = H (a), Me (b), tBu (c), Cl (d), N=NPh (e), MeO (f) and [OC6H2(CH2NMe2)2-2,6-Me-4]- (g)), have been used in the synthesis of well-defined vanadium-based catalysts for the polymerization of -olefins. The reaction of [Cp2V] with the parent phenol of g resulted in oxidation of the vanadium(II) nucleus to obtain the vanadium(III) (tris)phenolate [V(OC6H2(CH2NMe2)2-2,6-Me-4)3] (1). Vanadium(III) aminophenolates could not be obtained by reaction of [VCl3(THF)3] with the sodium phenolates because of incorporation of NaCl. However, use of the corresponding silyl ether Me3SiOC6H3(CH2NMe2)-2-Me-4 (2) resulted in the formation of the chlorovanadium (bis)phenolate [VCl(OC6H3(CH2NMe2)-2-Me-4)2] (3). Attempts to oxidize 3 to the corresponding dichlorovanadium(IV) (bis)phenolate were not successful. No reaction was observed with CuCl, AgCl and PbCl2. A dark blue compound 4 was obtained with CuCl2, which was tentatively assigned as a VIII/CuII dinuclear species. Treatment of the vanadium(IV) oxo (bis)phenolates 5a-5f with SOCl2 in benzene at room temperature or in toluene at reflux temperature resulted in the formation of dark blue compounds 6a-6f, whose stoichiometries indicated excess chloride. Only when 5a and 5d were reacted with SOCl2 at -70 °C could the desired dichlorovanadium (bis)phenolates [VCl2(OC6H4(CH2NMe2)-2)2] (7a) and [VCl2(OC6H3(CH2NMe2)-2-Cl-4)2] (7d) be obtained. X-ray crystal structure determination of 1 and 3 showed that both compounds have a trigonal bipyramidal geometry with two aminophenolate ligands bound in a bidentate 2-O,N fashion to the vanadium center in similar ways. The compounds 1, 3, 6 and 7 were tested for ethene/propene copolymerization.

A series of cycloplatinated carbosilane dendrimers appended with the monoanionic C, N-bidentate ligand [C{6}H{4}{CH{2}NMe{2}}-2]}-{ (CN) was prepared via a multiple C@?H activation reaction. Ligand exchange in the parent model species [PtCl(C{6}H{3}{CH{2}NMe{2}}-2-SiMe{3}-5)(DMSO)] (1) in the presence of PPh{3} gave the phosphine complex [PtCl(C{6}H{3}{CH{2}NMe{2}}-2-SiMe{3}-5)(PPh{3})] (2). The crystal structure of 2 was also determined, showing a close proximity between one of the Ar@?H of the phosphine ligand and the Ar@?H{o}{r}{t}{h}{o} of the CN ligand.

The application of platinum(II) complexes based on the N,N-dimethylbenzylamine ligand (abbreviated as H-C,N) in macromolecular synthesis was demonstrated. Two cationic C,N-platinum moieties were linked with a 4,4'-bipyridine bridge, giving [{C6H4(CH2NMe2)-2-Pt(PPh3)}2(4,4'-bpy)](BF4)2 (2), the crystal structure of which was determined. To introduce C60 groups into this assembly, [1,2]-methanofullerene-substituted H-C,N ligands were prepared and platinated using cis-PtCl2(DMSO)2. Application of the methanofullerene C,N-platinum complexes in the preparation of macrostructures afforded insoluble compounds. Therefore, phosphine ligands containing perfluoroalkyl groups were introduced into the fullerene-based complexes via a ligand exchange reaction. These fluorous complexes showed enhanced solubility in organic and fluorinated solvents. A soluble bismethanofullerene C,N-platinum(II) structure with a 4,4'-bipyridine bridge was obtained using these fluorinated fullerenes.

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.

A series of homodinuclear Pt compounds containing the anionic, potentially terdentate NCN ligand (NCN=[C{6}H{3}(Me{2}NCH{2}){2}-2, 6]}-{) or its 4-ethynyl derivative were prepared. The two platinum centres are linked together in two different fashions: (i) directly linked by an ethynyl or diethynylphenyl group (head-to-head) and (ii) indirectly bonded by a ethynyl- or butadiynyl-linked bis-NCN ligand (tail-to-tail). The reaction of the head-to-head @s,@s'-ethynylide complex {Pt}C@8C{Pt} ({Pt}=[Pt(C{6}H{3}{CH{2}NMe{2}}{2}-2,6)]}+{) with [CuCl]{n} yields {Pt}Cl and [Cu{2}C{2}]{n}, while with [Cu(NCMe){4}][BF{4}] a Cu(I) bridged complex was formed: [(@h}2{-{Pt}C@8C{Pt}){2}Cu][BF{4}]. The results of cyclic voltammetry experiments reveal that both connection modes of the two platinum centres lead to electrochemically independent Pt-NCN units. The X-ray crystal structure analysis of the neutral, tail-to-tail bridging butadiyne bis-NCNH ligand [C{6}H{3}(CH{2}NMe{2})-1,3-(C@8C)-5]{2} is reported.

Square-planar platinum(II) complexes containing N,C,N terdentate coordinating, anionic 'pincer' ligands reversibly bind gaseous SO2 in the solid state by Pt-S bond formation and cleavage giving five-coordinate adducts. When the starting material is crystalline, exposure to this gas leads to quantitative adduct formation with the unique feature that the product is also crystalline, although the crystal structures of the adduct and the SO2 free complex are significantly different from each other and are both non-porous. Remarkably, the reverse reaction, i.e. the release of SO2 gas, modifies but does not destroy the crystalline ordering in the arylplatinum assemblies. These processes include repetitive expansion and reduction of the crystal lattice without any loss of crystallinity of the material. Variation of the ligand framework revealed that the presence of intermolecular interactions such as - or -type networks is not an essential prerequisite for these crystalline transformations. Consequently, this class of supermolecules provides access to sensitive crystalline switches with 'on' and 'off ' positions which are a direct response to the gaseous environment.

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.

series of square-planar platinum(II) complexes of the N,C,N-terdentate-coordinating monoanionic pincer ligand, [PtX(4-E-2,6-{CH2NRR}2-C6H2)] (X=Cl, Br, I, tolyl; R, R=Et, Me; E=H, OH, OSiMe2tBu) has been prepared. In the presence of sulfur dioxide, these complexes spontaneously adsorb this gas to form pentacoordinated adducts. Solid-state crystal-structure analyses of the SO2 adducts 8 c (X=I, R=R=Me, E=OSiMe2tBu) and 11 (X=Cl, R=R=Me, E=OH) show a square-pyramidal geometry around the metal center with SO2 in the apical position. Most interestingly, the adduct 11 forms similar Pt-ClH-O hydrogen-bonded -type networks as the corresponding SO2-free complex 5. The conservation of the supramolecular information (hydrogen-bonded self-assembly) throughout a reaction (SO2 adsorption) is unprecedented in crystal engineering. Adduct formation in the solid state or in solution is fast and reversible and is indicated by a characteristic color change of the material from colorless to bright orange. Since facile methods have been developed to remove SO2 from the adducts and to regenerate the square-planar starting complexes, these complexes fulfill several essential prerequisites of sensor materials for repeated diagnostic SO2 detection. The platinum sensors have been found to be highly selective for sulfur dioxide and particularly sensitive for submilimolar to molar gas quantities. Their response capacity is tuneable by electronic and steric modifications of the ligand array by introduction of, for example, different substituents on the nitrogen donors. The periphery of dendrimers is shown to be an appropriate macromolecular support for anchoring the detection-active sites, thus allowing full recovery of the sensor materials for repeated use. By using this concept, metallo-dendrimers 3 and 15 have been prepared. Owing to the dendritic connectivity, these sensors are suitable for repetitive qualitative and quantitative detection of small amounts of SO2.

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.

The binuclear Ru(II) N2-bridged complex [{RuCl2(NN'N)}2(-N2)] (1; NN'N = 2,6-bis[(dimethylamino)methyl]pyridine) promotes the atom transfer radical polymerization (ATRP) of methyl methacrylate under mild conditions. The intermediate paramagnetic Ru(III) species mer-[RuCl3(NN'N)] (2) has been isolated and characterized by X-ray diffraction methods. The reaction of 1 with CH2Cl2 gives the dichloromethyl Ru(II) complex [RuCl(CHCl2)(NN'N)] (3).

Two novel fluorous tris(arylphosphine)rhodium(I) chloride complexes RhCl[P{C6H4-p-SiMe2(CH2)2CnF2n+1}3]3 (3a: n = 6, 3b: n = 8) being fluorous analogues of Wilkinson's catalyst show high activity in hydrogenation of 1-alkenes under single phase fluorous conditions and can be effectively recycled using the new concept of fluorous biphasic separation. For comparison the p-(trimethylsilyl)-substituted derivative RhCl[P(C6H4-p-SiMe3)3]3 (3c) has also been synthesized and the X-ray structure of dimeric [Rh(-Cl){P(C6H4-p-SiMe3)3}2]2 (4c) was determined. A comparison of the catalytic activity of the fluorous catalysts and the nonfluorous derivatives under identical conditions revealed a decreasing activity in the order 3c > 3a > RhCl(PPh3)3 > 3b. The recycling efficiency of the new catalysts (> 98% for 3b) is much better than expected on the basis of the fluorous phase affinity of the free phosphine ligands themselves and is in fact the result of the much higher fluorous phase affinity of the phosphine-containing rhodium species that are present during and after catalysis. Hence it is demonstrated that assembling multiple fluorous ligands in a specific configuration at one metal center can drastically improve the fluorous phase affinity of the resulting complexes

Novel [2,6-bis((dimethylamino)methyl)phenyl]gold(I) dimer (4) was prepared in 60% yield from [AuCl(tht)] (tht = tetrahydrothiophene) and [2,6-bis((dimethylamino)methyl)phenyl]lithium. Compound 4 is a rare example of a dimeric organogold(I) species involving intermolecular gold(I)-N(sp3) coordination. Variable-temperature NMR points to the formation of a 10-membered ring and provides evidence for the occurrence of a boat-chair ring conformation equilibrium. Reaction of 4 with MeI affords the unexpected heteroaurate(I) [Au(C6H3{CH2NMe3}2-2,6)I]I (5) by Me transfer to the nitrogen atom of the ortho amino ligand. The molecular structure of 5 was elucidated by means of X-ray analysis. Conversely, the reaction of 4 with CH2I2 afforded the organogold(III) complex [Au(C6H3{CH2NMe2}-2-{CH2N(Me)2CH2}-6)I]I (6), containing a methylene fragment bridging a Au(III) center and a quaternary N center, as confirmed by a single-crystal X-ray diffraction study. A mechanistic pathway involving prior coordination of the alkyl halide to gold(I) followed by oxidative addition and alkyl transfer is proposed to account for the formation of both 5 and 6.

Two diphenylboron ortho-aminophenolate complexes, [BPh2(OC6H4(CH2NMe2)-2)] (2) and [BPh2(OC6H2(CH2NMe2)2-2,6-Me-4)] (6), have been prepared in a one-pot procedure approach starting from B(OMe)3. The starting material was reacted with two equivalents of phenylmagnesium bromide, followed by hydrolysis with HCl. The resulting borinic acid, BPh2(OH), was reacted with either HOC6H4(CH2NMe2)-2 or HOC6H2(CH2NMe2)2-2,6-Me-4 to give 2 or 6, respectively. An X-ray structure determination of 2 showed it to be a four-coordinate boron compound with a tetrahedral coordination geometry. The six-membered chelate ring in 2 is puckered. Variable temperature 1H-NMR analysis of 6 showed the existence of two dynamic processes in solution, i.e. one process involving flipping of the puckered chelate ring conformation (ÄG‡=41 kJ mol−1) and a second, higher energy, process (ÄG‡=65 kJ mol−1) in which exchange of coordinated and non-coordinated amine functions occurs. The exchange is (at least partly) assisted intermolecularly.

The bis(ortho-)chelated platinum complex [PtCl(NCN)], 1 (NCN = [C6H3(CH2NMe2)2-2,6]-), has been used as a novel metal precursor for C-H bond activation and subsequent cyclometalation of the potentially terdentate coordinating pincer ligand PCHP (PCP = [C6H3(CH2PPh2)2-2,6]-). Depending on the reaction temperature various intermediates, each with unique structural features, could be isolated and identified during the formation of the final, bis(ortho-)cyclometalated product [PtCl(PCP)], 2. These results provide valuable insight into the intimate steps of this reaction for which we like to introduce the term transcyclometalation process (see note). At room temperature, a sparingly soluble dimetallic complex is formed, which comprises a 1-monodentate C-bound NCN ligand and a bridging, P,P 2-2-coordinating PCHP ligand. Solution spectroscopy and X-ray analysis of this platinum dimer established a C-H bond which is interacting by intramolecular noncovalent H···Cl hydrogen bonding with the Pt-Cl motif. As a further intermediate, the formation of a trans-bis(phenyl) complex [Pt(3-PCP)(1-HNCN)]Cl, 5, has been identified, which is characterized by a bis(ortho-)cyclometalated PCP ligand which is 3-P,C,P' coordinated to the platinum center as well as an 1-monodentate C-bound NCN ligand. The equivalent HCl, which is formally released during the formation of 5, is intramolecularly trapped by one of the basic amine groups, as is apparent from the identification of precursors of 5, i.e., compounds in which either one ([3]Cl) or two ([4]X2) of the NMe2 groups have become protonated (see Scheme 5). Remarkably, the proton in [4]X2 is not only bound to the nitrogen lone pair but also interacts with the filled dz2 orbital of the nucleophilic platinum(II) center, thus disclosing complex 5 as an organometallic proton sponge that is able to sequester protons due to Pt,N-bidentate chelating properties. Prolonged exposure of the reaction mixture at 80 C or performing the reaction at 110 C afforded the transcyclometalated complex 2 and 1 equiv of the diaminoarene NCHN as the two ultimate products.

The binuclear Ru(II) 2-dinitrogen complex [{RuCl2(3-NN'N)}2(-N2)] (1, NN'N = 2,6-bis[(dimethylamino)methyl]pyridine) is an excellent starting material for the synthesis of mononuclear 2-alkene complexes: mer,trans-[RuCl2(3-NN'N)(2-H2C=CHR)] (R = H, CH=CH2, Ph, CH2Ph, CH2Br, CH2OH, CHO, CN, CO2Me; yields 73-93%). These new 2-alkene Ru(II) compounds are stable at room temperature even when the alkene carbon atoms are substituted with potentially reactive functional groups. Of particular note is the reaction of 1 with allyl bromide, which leads to a rare example of a stable 2-allyl bromide Ru(II) complex. Disubstituted alkenes are unreactive, but in contrast, maleic anhydride forms a stable 2-alkene complex. Also with a terminal alkyne such as phenylacetylene, the 2-N2 Ru(II) complex 1 reacts cleanly, leading to the formation of the neutral Ru(II) vinylidene complex mer,cis-[Ru(=C=CHPh)Cl2(NN'N)] (12, X-ray structure). The corresponding 2-alkyne complexes could not be detected. Via an alternative pathway, related mono- and dicationic vinylidene derivatives with phosphine ligands were synthesized using the neutral compound mer,trans-[RuCl2(NN'N)(PPh3)] (13) as starting material. Its treatment with silver salts in the presence of phenylacetylene yielded the complex mer-[Ru(=C=CHPh)(OTf)(NN'N)(PPh3)][OTf] (17, OTf = trifluoromethane sulfonate; X-ray). Both Ru(II) starting materials, 1 and 13, used in this study are unreactive toward internal alkynes such as diphenylacetylene, while the use of acetylene gas leads to the formation of complex product mixtures.

The synthesis and characterization of new, five-coordinate molybdenum bis(imido) chloride complexes [MoCl(NCN)(N-t-Bu)2] (2) and [MoCl(2-C,N-NCN)(NAr)2] (3) and the methylated derivative [Mo(2-C,N-NCN)(Me)(NAr)2] (5) (NCN = [C6H3(CH2NMe2)2-2,6]-, Ar = C6H3-i-Pr2-2,6) are reported. Compounds 3 and 5 react with HCl to yield the corresponding air-stable salts [MoCl2{C6H3(CH2NMe2)-2-(CH2NHMe2)-6}(NAr)2] (4) and [MoCl{C6H3(CH2NMe2)-2-(CH2NHMe2)-6}(Me)(NAr)2] (6), respectively, of which 3-5 have been characterized by X-ray analysis. X-ray structure determination of 4 shows an additional chloride anion bonded to the molybdenum metal center while one of the ortho-(dimethylamino)methyl substituents of the NCN ligand has been selectively protonated. This proton is hydrogen bonded to one of the chloride ligands (N-H···Cl 166.2; H···Cl 1.94 Å). Because the spectroscopic data (NMR, IR) of 6 are very similar to those found for 4, complex 6 is believed to have structural characteristics (both in solution and in the solid state) similar to 4. The proton on the ortho-(dimethylamino)methyl group of the NCN ligand in 4 and 6 reacts immediately with an alkyl-Grignard or lithium reagents with formation of the corresponding alkane, the magnesium or lithium salt, and 3 and 5, respectively. Further reactions of 2, 4, and 6 with an excess of HCl, aimed at cleaving one of the imido groups, yielded unidentifiable reaction mixtures instead.

A set of model compounds have been designed in order to develop useful synthetic routes to novel dendritic carbosilane molecules functionalized with organometallic complexes derived from the monoanionic [C6H3(CH2NMe2)2-2,6]- (=NCN) and [C6H4(CH2NMe2)-2]- (=CN) ligands. Selective electrophilic palladation of both [C6H2(CH2NMe2)2-2,6-(SiMe3)2-1,4] (1) and [C6H4(CH2NMe2)-4-SiMe3-1] (6) using Pd(OAc)2 afforded, after addition of LiCl, [PdCl(C6H2{CH2NMe2}2-2,6-SiMe3-4)] (2) and dimeric [PdCl(C6H3{CH2NMe2}-2-SiMe3-5)]2 (7), respectively, in 98% and 84% yield. Lithiation of [C6H3(CH2NMe2)2-3,5-SiMe3-1] followed by transmetalation using 1 equiv of PtCl2(SEt2)2 in THF at room temperature yielded the platinated complex [PtCl(C6H2{CH2NMe2}2-2,6-SiMe3-4)] (3). Reaction of the iodinated analogue of 1, [IC6H2(CH2NMe2)2-2,6-SiMe3-4] (4), with an excess of Ni(PPh3)4 in THF at room temperature afforded the nickel complex [NiI(C6H2{CH2NMe}2-2,6-SiMe3-4)] (5). Similar synthetic approaches have also been applied to the (N)CN-substituted carbosilane ligand systems [CH2Si(Me)2C6H3(CH2NMe2)2-3,5]2 and [CH2Si(Me)2C6H4(CH2NMe2)-4]2 to give the bismetalated species [CH2Si(Me)2C6H2(CH2NMe2)2-3,5-(MX)-4]2 (MX = PdCl (9), PtCl (10), PdI (12)) and [CH2Si(Me)2C6H3(CH2NMe2)-4-(PdCl)-3]2 (13) in good yields. The molecular structures of 5 and bispalladated 13 have been determined. The molecular structure of 13 shows this species to be a centrosymmetric dimeric aggregate in the solid state, with the two bis(amino)arylpalladium carbosilane molecules held together via two terminal-terminal chlorine bridging atoms, thus forming a 26-membered macrocyclic ring.

The reaction of I2 with platinum 'pincer' complexes of the general formula [PtI(NCN' ')] (NCN' ' = [C6H3(CH2NRR')2-2,6]-; R = R' = Me or Et; or R = Me, R' = t-Bu) is reported. All three complexes contain an end-on (1) I2 unit, and these compounds represent the only known isolable organometallic species which contain I2 in this bonding motif. These compounds can be envisioned as representing the initial stages of oxidative addition of dihalides to d8 transition metal complexes. The complexes [PtI{C6H3(CH2NMe2)2-2,6}(1-I2)] (1) and exo-meso-[PtI3{C6H3(CH2NMe[t-Bu])2-2,6}(1-I2)] (3b) have been structurally characterized by single-crystal X-ray diffraction methods. Mechanistic and spectroscopic (IR, Raman, NMR, UV/vis) investigations have led to the conclusion that complex 1 is formed via a 1,2-shift of the dihalide from the primary product [Pt(1-I3){C6H3(CH2NMe2)2-2,6}]. The role of the metal-bound halide anion as the point of initial attack of I2 is described. The results of these investigations are discussed in terms of the basic mechanism of oxidative addition and its implications for catalysis.

A useful synthetic procedure for the incorporation of the potentially multidentate monoanionic 1-[C6H2(CH2NMe2)2-3,5]- (=NCN) and 1-[C6H3(CH2NMe2)-4]- (=CN) ligands via the para-position on the periphery of carbosilane (CS) dendrimers has been developed. Lithiation of suitable brominated precursors [C6H3(CH2NMe2)2-3,5-Br-1], 1, and [C6H4(CH2NMe2)-4-Br-1], 2, in Et2O at -78 C with 2 equiv of t-BuLi gives the monolithiated aminoaryl compounds Li[C6H3(CH2NMe2)2-3,5], 1-Li, and Li[C6H4(CH2NMe2)-4], 2-Li, which can be subsequently treated in situ with the silicon chlorides ClSiMe2(CH2)nSiMe2Cl (n = 2 or 6) to yield the functionalized CS-ligand systems [CH2SiMe2C6H3(CH2NMe2)2-3,5]2, 3, and [(CH2)nSiMe2C6H4(CH2NMe2)-4]2 (for 4, n = 1; for 5, n = 3). The ligand systems 3-5 react with 2 equiv of t-BuLi to give the dilithiated derivatized carbosilane molecules [CH2SiMe2C6H2(CH2NMe2)2-3,5-Li-4]2 and [(CH2)nSiMe2C6H4(CH2NMe2)-4-Li-3]2 (7, n = 1) in good chemical yields. Quench reactions of the in situ prepared lithiated derivatives with either D2O, Me3SiCl/Me3SiOTf, or MeSSMe clearly showed that the CS-ligand systems have been quantitatively converted into their lithiated derivatives. In addition, the functionalized carbosilane dendrimers G0-SiMe2-(N)CN and G1-SiMe2-(N)CN (13-16), which can be prepared in high yield by using the same synthetic approach used for the model compounds, can also be quantitatively converted into highly aggregated, polylithium derivatives. An X-ray molecular structure determination of 7 revealed this compound to be a unique dimeric aggregate {[CH2SiMe2C6H3(CH2NMe2)-4-Li-3]2}2 with their respective 2-electron-4-center (4c-2e) anionic Cipso centers each bonded to a Li3 face. As a result the (Me)2SiCH2CH2Si(Me)2 CS backbone exhibits a nonideal trans conformation with a vicinal dihedral angle of -161.

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 new chiral arylplatinum(II) compounds [2, 6-bis(1-(dimethylamino)ethyl)phenyl]chloroplatinum(II) (4) and (-)-[(1R,1'R)-bis(1-(dimethylamino)propyl)phenyl]chloroplatinum(II) (5) have been synthesized. The transmetallation of the corresponding aryllithium compounds does not affect either stereogenic centres of the organic ligand while the rate of the transmetallation is shown to be influenced by the size of the benzylic substituents. The X-ray crystal structure of 5 is reported from which the absolute configuration of both stereogenic centres of the organic ligand was determined to be (R).

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.

A homologous series of mono- and dicationic, neutral, and mono- and dianionic zinc diazabutadiene complexes, Kx[Zn(t-BuNCHCHN-t-Bu)2], Zn(t-BuNCHCHN-t-Bu)2, and [Zn(t-BuNCHCHN-t-Bu)2](OTf)x (x = 1, 2), have been prepared and isolated in pure form. The crystal structures of the mono- and dicationic as well as of the monoanionic complexes are reported. In this series, the formal charge on the t-BuNCHCHN-t-Bu ligands ranges from -2 to +2, and the way in which the molecular geometry of the ligands varies with the charge is discussed. [Zn(t-BuNCHCHN-t-Bu)2](OTf)2 reacts with methanol to give 1,3-di-tert-butylimidazolium triflate. Crystal data: dicationic 2 ([Zn(t-BuNCHCHN-t-Bu)2](OTf)2, C22H40F6S2N4O6Zn), monoclinic, space group C2/c, with a = 18.015(6) Å, b = 9.257(6) Å, c = 20.012(5) Å, = 109.63(3), and Z = 4; monocationic 3·thf ([Zn(t-BuNCHCHN-t-Bu)2]OTf·thf, C25H48F3N4O3SZn), orthorhombic, space group P212121, with a = 10.3077(6) Å, b = 17.1974(6) Å, c = 17.8241(13) Å, and Z = 4; monoanionic 5·thf (K(thf)3[Zn(t-BuNCHCHN-t-Bu)2], C36H72KN4O3Zn), triclinic, space group P, with a = 10.8702(10) Å, b = 11.5175(9) Å, c = 18.2815(13) Å, = 73.795(6), = 74.227(6), = 75.736(7), and Z = 2; 7 (1,3-di-tert-butylimidazolium triflate, C12H21F3N2O3S), orthorhombic, space group Pbca, with a = 14.4086(8) Å, b = 12.0293(8) Å, c = 18.6985(12) Å, and Z = 8.

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.

The potentially C,N,N'-chelating anionic aryldiamine ligand [C6H4(CH2N(Me)CH2CH2NMe2)-2]- (CNN) has been employed in the preparation of six-coordinate Ta(V) alkylidene complexes. The new dichloro alkylidene complex [TaCl2(=CH-t-Bu)(CNN)], 2, prepared from [TaCl3(=CH-t-Bu)(THF)2] and [Li(CNN)]2, 1, has been obtained as a mixture of three diastereoisomers (2a-c) in 51% yield. The molecular structure of the major isomer 2a, determined by X-ray methods, shows this to be a tetragonal bipyramidal complex in which the metal coordination sphere is comprised of the C,N,N' facially bonded CNN, two cis-positioned chlorides in the equatorial plane, and a neopentylidene group and the NMe2 nitrogen donor mutually trans-positioned at the apices. The dialkoxide complexes [Ta(=CHR)(CNN)(O-t-Bu)2] (R = t-Bu (3a), CMe2Ph (3b)) have been obtained by transmetallation of [TaCl(=CHR)(O-t-Bu)2(PMe3)] with 1. The neopentylidene complex 3a was isolated as an analytically pure orange solid in 47% yield, whereas the neophylidene complex 3b was isolated as an orange oil of ±90% purity. Complex 3b reacts in pentane with ethene at room temperature to afford the tantalacyclobutane complex [Ta{(CH2)3-1,3}(CNN)(O-t-Bu)2], 4, which was isolated as a white solid in 81% yield. An X-ray diffraction study of 4 shows it to be a heptacoordinate pentagonal bipyramidal tantalum species in which two mutually trans alkoxide groups are in the apical positions; the meridional ligation is comprised of the C,N,N'-coordination of CNN and the -bonded carbon atoms of the metallacyle. Reaction of 3b in hexane at 69 C with ethene gives a mixture of the new tantalum alkene complex [Ta(CNN)(O-t-Bu)2(H2C=CH2)], 5, and 4 in a 5:2 ratio. Complex 5 can be isolated from this mixture as a yellow solid by recrystallization from diethyl ether at -30 C. The X-ray molecular structure of 5 shows it to be a pentagonal bipyramidal complex in which the array of atoms directly bonded to tantalum is like that in 4. However, in 5, the meridional ligation is comprised of the C,N,N'-coordination of CNN and the two C atoms of the ethene molecule. Complexes 3b and 4 initiate ring-opening metathesis polymerization with strained cyclic olefins; dicyclopentadiene produces cross-linked polymers, whereas norbornene produces polycyclopentamers with approximately 90% trans-vinylene bonds. In contrast, none of the isomers of alkylidene complex 2 show any reactivity toward either ethene or norbornene.

A carbosilane dendrimer with 12 peripheral iodoarene groups, Si{(CH2)3{Si(CH2)3O2C(C6H4I-4)}3}4 (G1-ArI, 5), and the corresponding G0 model compound, Si{(CH2)3O2CC6H4I-4}4 (G0-ArI, 4) have been prepared from polyol precursors. These compounds react with Pd(dba)2/tmeda (dba = dibenzylideneacetone, tmeda = N,N,N',N'-tetramethylethylenediamine) to yield periphery-palladated complexes, Si{(CH2)3O2C(C6H4-4)PdI(tmeda)}4 (G0-ArPdI(tmeda), 6) and Si{(CH2)3{Si(CH2)3O2C(C6H4-4)PdI(tmeda)}3}4 (G1-ArPdI(tmeda), 7). Dendrimer 7 represents the first example of an exclusively -bonded completely periphery-palladated dendrimer. Reactions of the model palladium(II) complexes PdI(EtO2C(C6H4)-4)(tmeda) (2) and PdI(EtO2C(C6H4)-4)(bpy) (3) (bpy = 2,2'-bipyridyl) with the transmetalation reagents LiMe and SnMe4 were not successful, while no reaction occurred with the related reagent Sn(C~N)Me3 [C~N = 8-(dimethylamino)-1-naphthyl]. The molecular structure of G0-ArI (5) has been determined by X-ray crystallography and has C2v symmetry in the solid state.

Reaction of [TiCl{3}(O-i-Pr)] with [Li(CNN)]{2} (CNN = monoanionic C{6}H{4}(CH{2}N(Me)CH{2}CH{2}NMe{2})-2) in 2:1 molar ratio in toluene at -78}o{C afforded [TiCl{2}(CNN)(O-i-Pr)] as a 3:2 molar mixture of two stereoisomers. The stereoisomers differ by the mutual position of the chloro and alkoxy ligands. Molecular modelling calculations and an X-ray analysis of one of the stereoisomers indicated that the alkoxy ligand exhibits a strong trans preference to the weakest @p-donating ligated atom, i.e., the N(Me{2}) atom of the CNN ligand. The molecular structure of this stereoisomer, as determined by X-ray analysis, involves an octahedral titanium center with an @h}3{-fac-C, N,N'-bonded CNN ligand. A strong M-O(alkoxy) interaction is illustrated by an almost linear M-O-C bond angle of 172.4(2)}o{. As a result of the pseudofacially bonded CNN ligand, the titanium center as well as the central N-donor center are stereogenic resulting in the formation of two enantiomers. A (CNN)titanium(IV) dimethyl complex is accessible via reaction of 1 with two equivalents of MeLi and contains likewise an @h}3{-fac-C,N,N'-bonded CNN ligand.

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.

The reaction of 2 equiv of LiO-t-Bu with [TaCl2(=CH-t-Bu){C6H3(CH2NMe2)2-2,6}] (1), in which there is an N,C,N-chelated 1,2,6-trisubstituted aryldiamine ligand, affords in a one-pot procedure at 80 C the new rearranged product [Ta(=CH-t-Bu){C6H3(CH2NMe2)2-2,4}(O-t-Bu)2] (2), in which there is a C,N-chelated 1,2,4-trisubstituted aryldiamine ligand. Complex 2 is a yellow solid that has been isolated in 69% yield. The reaction mechanism for the formation of 2 involves a crucial isomerization of the intermediate [TaCl(=CH-t-Bu){C6H3(CH2NMe2)2-2,6}(O-t-Bu)] (3) to the rearranged intermediate [TaCl(=CH-t-Bu){C6H3(CH2NMe2)2-2,4}(O-t-Bu)] (4). The intermediate complexes 3 and 4 have been independently prepared and characterized. The known complex 3 can be obtained by reaction of 1 with LiO-t-Bu at room temperature. Complex 4 is obtained exclusively, as revealed by 1H NMR spectroscopy, by heating a benzene solution of 3 to 80 C and has been isolated as a purple solid in 77% yield. In solution 4 exists as two rotational isomers for the Ta=C(H)-t-Bu moiety; G = 71 kJ mol-1. The X-ray molecular structure of 3 shows it to be a pentacoordinate Ta(V) species in which the aryl Cipso atom, the alkylidene functionality, and the alkoxide group define the meridional plane of a trigonal bipyramid, with one of the NMe2 nitrogen donors of the C,N-bidentate-bonded aryldiamine and the chloride occupying the axial positions. The lone pair of the N-donor atom of the second ortho amine substituent is oriented toward Ta (Ta···N = 2.629.4 Å), providing incipient 3(N,C,N) facial bonding of the aryldiamine ligand. The structure of 3 also shows a pseudo-parallel orientation of the alkylidene C-H bond and the Cipso-Ta bond that points to potential C-H activation via a four-membered metallacyclic ring that contains Ta, Cipso, C, and H. The involvement of the alkylidene functionality in the sequence of highly regiospecific C-H bond-making and -breaking processes necessary to produce complex 4 from 3 was confirmed by deuterium-labeling experiments. The mechanism probably involves an -H abstraction from the alkylidene moiety in 3 (assisted by the weakly coordinated dimethylamino group) that leads to an intermediate which has a geometry similar to that of a known aryltantalum(V) zinc alkylidene adduct.

The synthesis and characterization of the complexes [(5-C5H4SiMe3)2Ti(CCSiMe3)2]MX (M = Cu, X = OTf (2), SC6H5 (4), SC6H4NMe2-2 (5), SC6H4CH2NMe2-2 (6), S-1-C10H6NMe2-8 (7), Cl (8), (NCMe)PF6 (9); M = Ag, X = OTf (3)) are described. These complexes contain monomeric MX entities, which are 2-bonded by both alkyne functionalities of the organometallic bis(alkyne) ligand [(5-C5H4SiMe3)2Ti(CCSiMe3)2] (1). The reactions of 2 with the Lewis bases NCPh and NCC(H)=C(H)CN afford the cationic complexes {[(5-C5H4SiMe3)2Ti(CCSiMe3)2]Cu(NCPh)}OTf (10) and {[(5-C5H4SiMe3)2Ti(CCSiMe3)2]Cu}2(NCC(H)=C(H)CN)(OTf)2 (11), respectively. The X-ray structures of 2, 3, and 6 have been determined. Crystals of 2 are monoclinic, space group P21/c, with a = 12.8547(7) Å, b = 21.340(2) Å, c = 18.279(1) Å, = 133.623(5), V = 3629.7(5) Å3, Z = 4, and final R = 0.047 for 5531 reflections with I 2.5(I) and 400 variables. The silver triflate complex 3 is isostructural, but not isomorphous, with the corresponding copper complex 2, and crystals of 3 are monoclinic, space group P21/c, with a = 13.384(3) Å, b = 24.55(1) Å, c = 13.506(3) Å, = 119.21(2), V = 3873(2) Å3, Z = 4, and final R = 0.038 for 3578 reflections with F 4(F) and 403 variables. Crystals of the copper arenethiolate complex 6 are triclinic, space group P, with a = 11.277(3) Å, b = 12.991(6) Å, c = 15.390(6) Å, = 65.17(4), = 78.91(3), = 84.78(3), V = 2008(2) Å3, Z = 2, and final R = 0.079 for 6022 reflections and 388 variables. Complexes 2-11 all contain a monomeric bis(2-alkyne)M(1-X) unit (M = Cu, Ag) in which the group 11 metal atom is trigonally coordinated by the chelating bis(2-alkyne) entity Ti(CCSiMe3)2 and an 1-bonded monoanionic ligand X. The copper arenethiolate complexes 4-7 are fluxional in solution.