Ether Adduct Research Articles

ChemInform Abstract: Organotin Triflate as Practical Catalyst for Michael Addition of Enol Silyl Ethers.

Abstract Dityltin bis(triflate) is a mild Lewis acid which catalyzes clean Michael addition of enol silyl ethers. The new catalyst allows to employ various labile acceptors such as methyl vinyl ketone and 2-cyclopentenone which do not undergo smooth reaction with conventional Lewis acids. A variety of enol silyl ethers are also employable and thus 2-(trimethylsiloxy)propene, the simplest one in this class of compounds, can be used. The adducts of enol silyl ethers of cycloalkanones with vinyl ketones are readily cyclized to give the desired annulated enones free from isomers. Consequently, a practical version of the Robinson annulation has been realized.

Synthesis and Structure of the Dimethyl Sulfide Adducts of Mono- and Bis(pentafluorophenyl)borane

The borane dimethyl sulfide adduct H3B·SMe2 and the diethyl ether adduct of tris(pentafluorophenyl)borane, (C6F5)3B·OEt2, undergo facile exchange of hydride and pentafluorophenyl ligands, yielding (C6F5)2HB·SMe2 (1) and (C6F5)H2B·SMe2 (2) depending upon the ratio of reagents used. In the presence of excess dimethyl sulfide, both compounds can be isolated as colorless crystals, which have been structurally characterized.

Bis[μ-N,N′-bis(2,6-diisopropylphenyl)ethene-1,2-diamido]-1,4(η2);1:2κ4N:N;3:4κ4N:N-bis(diethyl ether)-1κO,4κO-di-μ-hydrido-2:3κ4H:H-2,3-dichromium(II)-1,4-dilithium(I) pentane hemisolvate

The title compound, [Cr2Li2(C26H36N2)2(μ-H)2(C4H10O)2]·0.5C5H12, is a binuclear chromium complex bridged by two hydrogen atoms. Each chromium atom is coordinated in a distorted square-planar geometry by one chelating bis­(2,6-diisopropyl­phen­yl)ethene-1,2-diamido ligand via its two N atoms. Additionally, two diametrically opposed lithium ether adducts coordinate in an η4 mode on the backbone of the ligands. There is a crystallographic inversion center in the middle of the Cr2H2 ring. One of the isopropyl groups is disordered over two positions in a 0.567 (7):0.433 (7) ratio. Disorder is also observed in the pentane hemisolvate molecule.

Steric Control over Supramolecular Polymer Formation in trans-1,2-Bis(4-pyridyl)ethylene Adducts of Zinc Xanthates: Implications for Luminescence

Steric control over supramolecular aggregation is demonstrated for a series of adducts formed between Zn(S2COR)2 and trans-1,2-bis(4-pyridyl)ethylene, whereby supramolecular zigzag polymers are found when R is small, that is, Et (1) and n-Bu (2), but only bimetallic aggregates could be formed when R = Cy (3). This results in different coordination geometries: four-coordinate N2S2 zinc in 1 and 2, and five-coordinate NS4 zinc in 3, a feature which greatly influences photophysical responses in the solid state. When excited in the UV region, {Zn(S2COEt)2L}∞ (1) and {[Zn(S2COCy)2]2L} (3) produce broad luminescence in the visible region. Five-coordinate 3 produces more broad and intense luminescence than four-coordinate 1. The configuration interaction singles (CIS) and post-Hartree−Fock (HF) calculations for 1 and 3 indicate the A-band excited state is responsible for the observed luminescence which is strongly associated with charge transfer from S and Zn.

Condensation reaction through base assistance within (Ph 2SiO) 8[AlO(OH)] 4

When the polycyclic alumosiloxane (Ph 2SiO) 8[AlO(OH)] 4, which may be isolated as the diethyl ether adduct (Ph 2SiO) 8[AlO(OH)] 4·4OEt 2, is allowed to react with the double N-methylpiperidine (nmp) adduct of monochloroalane, AlH 2Cl·2nmp ( 1) (crystal structure analysis), the polycycle (Ph 2SiO) 8[AlO(O) 0.5] 4·2nmp ( 2) is obtained. Compared to the starting material and apart from the coordinating bases, the compound formally has lost two water molecules. The structure of (Ph 2SiO) 8[AlO(O) 0.5] 4·2nmp ( 2) can be derived from (Ph 2SiO) 8[AlO(OH)] 4 by substituting the central Al 4(OH) 4 motif through an Al 4O 2 entity which consists of a central Al 2O 2 ring coordinated to two further aluminum atoms through almost trigonal planar oxygen atoms. Using tris(ethylene)diamine (ted) as base and reacting it with (Ph 2SiO) 8[Al(OH)] 4, we have been able to isolate and completely characterize an intermediate on the way to these formally condensed alumosiloxane polycycles like in (Ph 2SiO) 8[AlO(O) 0.5] 4·2nmp ( 2). It has the composition (Ph 2SiO) 8[AlO(O) 0.25] 4·(OH·ted) 2·(OH 2·ted) ( 3) and has, compared to the starting material, the same number of hydrogen, oxygen, aluminum and silicon atoms within the inner molecular framework. Nevertheless, its structure is very different: whereas half of the molecule is structurally similar to (Ph 2SiO) 8[AlO(OH)] 4, with OH-groups forming hydrogen bridges to the nitrogen atoms of ted and connecting two aluminum atoms, the other half contains a unique oxygen atom which is in an almost planar trigonal bonding mode to three aluminum atoms. Furthermore, this part of the molecule has an aluminum atom to which a water molecule is coordinated, one of the hydrogen atoms being involved in hydrogen bonding to a further tris(ethylene)diamine (ted). This structure gives some important insights in the possible mechanism of the “condensation reaction” within (Ph 2SiO) 8[AlO(OH)] 4.

Ferrocenylhydridoborates: Synthesis, Structural Characterization, and Application to the Preparation of Ferrocenylborane Polymers

Mono- and ditopic lithium ferrocenylhydridoborates Li[FcBH(3)] (2) and Li(2)[H(3)B-fc-BH(3)] (4) have been synthesized from FcB(OMe)(2)/(MeO)(2)B-fc-B(OMe)(2) and Li[AlH(4)] (Fc = ferrocenyl; fc = 1,1'-ferrocenylene). X-ray quality crystals were grown from OEt(2). Depending on the amount of Li(+)-coordinated solvent molecules, dimeric (2(OEt(2))(2)) or tetrameric (2(OEt(2))) aggregates are observed in the solid state. The ditopic derivative 4 crystallizes as two different macrocyclic dimers (4(OEt(2))(5) and 4(OEt(2))(6)) in the unit cell. Each of the four aggregates is held together mainly by RBH(3)-eta(2)-Li bonds. Addition of Me(3)SiCl to 2 or 4 generates the corresponding boranes FcBH(2) (5) and H(2)B-fc-BH(2) (6), which can be trapped by adduct formation with NMe(2)Et or SMe(2). In contrast, when OEt(2) is present as the sole Lewis basic donor, no stable ether adducts are obtained, but condensation takes place leading to Fc(2)BH (10) and the novel borane polymer [-fcB(H)-](n) (9), respectively. In situ generation of FcBH(2) (5) in the presence of cyclohexene gives Fc(2)BCy and BCy(3) but no FcBCy(2), thereby indicating that 5 undergoes condensation to 10 more quickly than hydroboration of an internal olefin can occur (Cy = cyclohexyl). Fc(2)BH (10) was further studied as a model system for the optimization of modification reactions of polymer [-fcB(H)-](n) (9). Hydroboration of PhCCH or tBuCCH with 10 proceeds smoothly and quantitatively to give the corresponding vinylboranes Fc(2)B(CH horizontal lineCHR) (11(Ph), R = Ph; 11(tBu), R = tBu), which were fully characterized. In a similar manner, the polymeric borane 9 was successfully transformed into ferrocenylborane polymers [-fcB(CH horizontal lineCHR)-](n) (12(Ph), R = Ph; 12(tBu), R = tBu) that contain vinyl groups attached to boron. The structures of polymers 12 were confirmed by NMR and IR spectroscopy and mass spectrometry. The MALDI-TOF spectra of 12(Ph) and 12(tBu) showed patterns of equidistant peaks with peak separations that are consistent with the masses of the expected repeating units of each of the polymers. The absorption maxima in the UV-vis spectra of polymers 12 are significantly red-shifted in comparison to the dimeric model systems 11.

Transformations of Group 7 Carbonyl Complexes: Possible Intermediates in a Homogeneous Syngas Conversion Scheme

A variety of C−H and C−C bond forming reactions of group 7 carbonyl complexes have been studied as potential steps in a homogeneously catalyzed conversion of syngas to C_(2+) compounds. The metal formyl complexes M(CO)_3(PPh_3)_2(CHO) (M = Mn, Re) are substantially stabilized by coordination of boranes BX_3 (X = F, C_6F_5) in the form of novel boroxycarbene complexes M(CO)_3(PPh_3)_2(CHOBX_3), but these boron-stabilized carbenes do not react with hydride sources to undergo further reduction to metal alkyls. The related manganese methoxycarbene cations [Mn(CO)_(5−x)(PPh_3)_x(CHOMe)]+ (x = 1 or 2), obtained by methylation of the formyls, do react with hydrides to form methoxymethyl complexes, which undergo further migratory insertion under an atmosphere of CO. The resulting acyls, cis- and trans-Mn(PPh_3)(CO)_4(C(O)CH_2OMe), can be alkylated to form the cationic carbene complex [Mn(PPh_3)(CO)_4(C(OR)CH_2OMe)]^+, which undergoes a 1,2 hydride shift to form 1,2-dialkoxyethylene, which is displaced from the metal, releasing triflate or diethyl ether adducts of [Mn(PPh_3)(CO)_4]^+. The acyl can also be protonated with HOTf to form a hydroxycarbene complex, which rearranges to Mn(PPh_3)(CO)_4(CH_2COOMe) and is protonolyzed to yield methyl acetate and [Mn(PPh_3)(CO)_4]^+; addition of L (L = PPh_3, CO) to the manganese cation regenerates [Mn(PPh_3)(CO)_4(L)]^+. Since the original formyl complex can be obtained by the reaction of [Mn(PPh_3)(CO)_5]^+ with [PtH(dmpe)_2]^+, which in turn can be generated from H_2, this set of transformations amounts to a stoichiometric cycle for selectively converting H_2 and CO into a C_2 compound under mild conditions.

Kinetic Study of the Oxidation of Catechols in the Presence of Some Aza‐crown Ethers by Digital Simulation of Cyclic Voltammograms

AbstractThe electrochemical oxidation of catechols (1) have been studied in the presence of diaza‐18‐crown‐6 (DA18C6) (3a), diaza‐15‐crown‐5 (DA15C5) (3b), and aza‐15‐crown‐5 (A15C5) (3c) as nucleophiles in aqueous solution, by means of cyclic voltammetry and controlled‐potential coulometry. The results indicate the participation of electrochemically generated o‐benzoquinones (2) in Michael‐type reaction with aza‐crown ethers (3) to form the corresponding new o‐benzoquinone‐aza‐crown ether adducts (5). Based on ECE mechanism, the observed homogeneous rate constants (kobs) of the reaction of o‐bezoquinones (2) with aza‐crown ethers (3) were estimated by comparing the experimental cyclic voltammograms with the digital simulated results. The calculated observed homogeneous rate constants (kobs) was found to vary in the order DA18C6>DA15C5>A15C5.

Carbon monoxide and ethylene complexes of copper and silver supported by a highly fluorinated tris(triazolyl)borate

Copper and silver carbonyl and ethylene adducts supported by the highly fluorinated hydridotris(triazolyl)borate ligand [HB(3,5-(CF3)2Tz)3]- have been synthesized and characterized, and compared to the analogous complexes based on the hydridotris(pyrazolyl)borate ligand [HB(3,5-(CF3)2Pz)3]-. 1H and 13C NMR signals of the ethylene moiety of [HB(3,5-(CF3)2Tz)3]Cu(C2H4) and [HB(3,5-(CF3)2Tz)3]Ag(C2H4) appear at a relatively downfield position from the corresponding signals of the [HB(3,5-(CF3)2Pz)3]Cu(C2H4) and [HB(3,5-(CF3)2Pz)3]Ag(C2H4) complexes. This indicates the presence of relatively acidic metal sites in the [HB(3,5-(CF3)2Tz)3]- supported molecules. [HB(3,5-(CF3)2Tz)3]- is also a relatively weaker donor compared to the tris(pyrazolyl)borate version [HB(3,5-(CF3)2Pz)3]-. However, the CO stretching frequency values of [HB(3,5-(CF3)2Tz)3]CuCO (2138 cm(-1)) and [HB(3,5-(CF3)2Pz)3]CuCO (2137 cm(-1)) are essentially identical, and did not reflect the differences in the acidity of the metal sites. The analogous silver carbonyl adducts [HB(3,5-(CF3)2Tz)3]AgCO and [HB(3,5-(CF3)2Pz)3]AgCO also show similar nuCO values (2178 cm(-1)). These results illustrate the limitation of using the nu(CO) value of metal carbonyls as a sole indicator of the electronic structure of metal sites in some metal complexes, especially when the metal-->CO pi-back bonding is less important, and the nuCO values of two adducts are unexpectedly similar and appear at a region closer to that of the free CO (2143 cm(-1)).

Collision‐induced loss of AgH from Ag+ adducts of alkylamines, aminocarboxylic acids and alkyl benzyl ethers leads exclusively to thermodynamically favored product ions

The loss of AgH from [M+Ag]+ precursor ions of tertiary amines, aminocarboxylic acids and aryl alkyl ethers is examined by deuterium labeling combined with collision activation (CA) dissociation experiments. It was possible to demonstrate that the AgH loss process is highly selective toward the hydride abstraction. For tertiary amines and aminocarboxylic acids, hydrogen originates from the alpha-methylene group carrying the nitrogen function (formation of an immonium ion). In all cases examined, the most stable, i.e. the thermodynamically favored product ion is formed. In the AgH loss process, a large isotope effect operates discriminating against the loss of D. The [M+Ag]+ ion of benzyl methyl ether loses a hydride ion exclusively from the benzylic methylene group supporting the experimental finding that the AgH loss reaction selectively cleaves the weakest C-H bond available.

Hydride Reduction of NAD+ Analogues by Isopropyl Alcohol: Kinetics, Deuterium Isotope Effects and Mechanism

Observed pseudo-first-order rate constants (k(obs)) of the hydride-transfer reactions from isopropyl alcohol (i-PrOH) to two NAD(+) analogues, 9-phenylxanthylium ion (PhXn(+)) and 10-methylacridinium ion (MA(+)), were determined at temperatures ranging from 49 to 82 degrees C in i-PrOH containing various amounts of AN or water. Formations of the alcohol-cation ether adducts (ROPr-i) were observed as side equilibria. The equilibrium constants for the conversion of PhXn(+) to PhXnOPr-i in i-PrOH/AN (v/v = 1) were determined, and the equilibrium isotope effect (EIE = K(i-PrOH)/K(i-PrOD)) at 62 degrees C was calculated to be 2.67. The k(H) of the hydride-transfer step for both reactions were calculated on the basis of the k(obs) and K. The corresponding deuterium kinetic isotope effects (e.g., KIE(OD)(H) = k(H)(i-PrOH)/k(H)(i-PrOD) and KIE(beta-D6)(H) = k(obs)(i-PrOH)/k(obs)((CD3)2CHOH)), as well as the activation parameters, were derived. For the reaction of PhXn(+) (62 degrees C) and MA(+) (67 degrees C), primary KIE(alpha-D)(H) (4.4 and 2.1, respectively) as well as secondary KIE(OD)(H) (1.07 and 1.18) and KIE(beta-D6)(H) (1.1 and 1.5) were observed. The observed EIE and KIE(OD)(H) were explained in terms of the fractionation factors for deuterium between OH and OH(+)(OH(delta+)) sites. The observed inverse kinetic solvent isotope effect for the reaction of PhXn(+) (k(obs)(i-PrOH)/k(obs)(i-PrOD) = 0.39) is consistent with the intermolecular hydride-transfer mechanism. The dramatic reduction of the reaction rate for MA(+), when the water or i-PrOH cosolvent was replaced by AN, suggests that the hydride-transfer T.S. is stabilized by H-bonding between O of the solvent OH and the substrate alcohol OH(delta+). This result suggests an H-bonding stabilization effect on the T.S. of the alcohol dehydrogenase reactions.

Gold(I) Ethylene and Copper(I) Ethylene Complexes Supported by a Polyhalogenated Triazapentadienyl Ligand

A rare gold(I) ethylene complex and the closely related copper(I) ethylene adduct have been isolated using [N{(C3F7)C(2,6-Cl2C6H3)N}2]- as the supporting ligand. [N{(C3F7)C(2,6-Cl2C6H3)N}2]Au(C2H4) (1) is an air-stable solid. It features a U-shaped triazapentadienyl ligand backbone and a three-coordinate, trigonal-planar gold center. The copper(I) adduct [N{(C3F7)C(2,6-Cl2C6H3)N}2]Cu(C2H4) (2) also has a similar structure. The 13C NMR signal corresponding to the ethylene carbons of 1 appears at about 64 ppm upfield from the free ethylene, while the ethylene carbons of 2 show a relatively smaller (39 ppm) upfield shift. [N{(C3F7)C(2,6-Cl2C6H3)N}2]M(C2H4) (M=Cu, Au) mediate carbene-transfer reactions from ethyl diazoacetate to saturated and unsaturated hydrocarbons.

Fluorinated Diarylamido Complexes of Lithium, Zirconium, and Hafnium

Deprotonation of N-(2-fluorophenyl)-2,6-diisopropylaniline (H[ (i) PrAr-NF]) with 1 equiv of n-BuLi in toluene at -35 degrees C produced cleanly [ (i) PrAr-NF]Li. Subsequent recrystallization of [ (i) PrAr-NF]Li in diethyl ether generated the bis(ether) adduct [ (i) PrAr-NF]Li(OEt 2) 2. An X-ray study of [ (i) PrAr-NF]Li(OEt 2) 2 showed it to be a four-coordinate species with the coordination of the fluorine atom to the lithium center. The reactions of [ (i) PrAr-NF]Li with MCl 4(THF) 2 (M = Zr, Hf), regardless of the stoichiometry employed, afforded the corresponding dichloride complexes [ (i) PrAr-NF] 2MCl 2 (M = Zr, Hf). Alkylation of [ (i) PrAr-NF] 2MCl 2 with a variety of Grignard reagents generated [ (i) PrAr-NF] 2MR 2 (M = Zr, Hf; R = Me, i-Bu, CH 2Ph). The X-ray structures of [ (i) PrAr-NF] 2ZrCl 2, [ (i) PrAr-NF] 2HfCl 2, [ (i) PrAr-NF] 2ZrMe 2, [ (i) PrAr-NF] 2Zr( i-Bu) 2, and [ (i) PrAr-NF] 2Hf(CH 2Ph) 2 are all indicative of the coordination of the fluorine atoms to these group 4 metals, leading to a C 2-symmetric, distorted octahedral geometry for these molecules.

Structurally Characterized Coinage‐Metal–Ethylene Complexes

AbstractDespite the interest in them, easily isolable and thermally stable CuI, AgI, and AuIcomplexes of ethylene are stilllimited and get increasingly sparse as one descends the group 11 triad towards gold. Recently, there have been some notable developments in this field, including the isolation of gold–ethylene complexes and coinage‐metal adducts with more than one ethylene molecule on a metal center. This article focuses on the chemistry of coinage‐metal–ethylene adducts that have been synthesized and characterized by X‐ray crystallography. Thus far, bidentate and tridentate donors based on nitrogen appear to be the ligands of choice forstabilizing species with an M–C2H4(M = CuI, AgI, and AuI) moiety. Weakly donating ligands and anions are also commonly used, as they do not interfere with and displace the ethylene from the metal center. The ethylene13C NMR chemical shift provides useful information about the nature of the metal–ethylene interaction. In some adducts (especially those with relatively weak M–C2H4interactions), the change in the C=C bond length upon coordination to the metal site is difficult to discern because it falls within the errors associated with the crystallographically determined C=C bond length value. IR and Raman C=C stretching data would be useful but, probably due to the very weak nature of the IR band and the lack of convenient access to the Raman instruments, are often not reported. In this microreview, results from some computational and gas‐phase spectroscopic studies are also provided for comparison.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Structurally Characterized Coinage‐Metal–Ethylene Complexes (Eur. J. Inorg. Chem. 4/2008)

Abstractthe cover picture shows the formation of coinage metal (copper, silver, gold) complexes of ethylene supported by scorpionate ligands on an X‐ray diffraction background (because the article focuses on the structurally characterized molecules). Thermally stable molecules containing bonds between coinage metal atoms and ethylene are still rare but have grown in number significantly over the last few years. Tris(pyrazolyl)borate (commonly known as scorpionate) ligands have played a major role in this chemistry. Indeed, they have served as the supporting ligands in the isolation of the first ethylene adduct of all three coinage metal ions. Most of the resulting complexes feature κ3‐bonded scorpionate ligands, while a few others show rare κ2‐coordination (as depicted here, a gold atom held by a scorpion with the scorpion's tail up). Details are presented in the Microreview by H. V. R. Dias and J. Wu on p. 509 ff. H. V. R. D. gratefully acknowledges the Robert A. Welch Foundation (grant Y‐1289) for providing financial support for his research.

Bridged Dinuclear Tripodal Tris(amido)phosphane Complexes of Titanium and Zirconium as Diligating Building Blocks for Organometallic Polymers

AbstractAppropriate bridging ligands allow for the preparation of bimetallic titanium and zirconium precursors to transition‐metal‐containing polymers using the formally trianionic P(CH2NArR)3 ligand (where ArR = Ph, and 3,5‐Me2C6H3 for a and b, respectively). Lithiation of the known amidophosphane ligand precursors P(CH2NHArR)3 (1a,b) with 3 equiv. of nBuLi cleanly provided the diethyl ether adducts P(CH2NArR)3Li3(OEt2)1.5 (2a,b). The THF adduct P(CH2NPh)3Li3(THF)5 (2a‐THF) was characterized by X‐ray crystallography. Protonolysis reactions were used to prepare the mononuclear titanium complexes P(CH2NArR)3TiOC6H4tBu (4a,b) and dinuclear species [P(CH2NPh)3TiNMe2]2‐μ‐4,4′{O[3,3′,5,5′‐(C6H2Me2)2]O} (5a), [P(CH2NPh)3Ti]2(μ‐O) (6a), and P(CH2N‐3,5‐Me2C6H3)3Ti‐μ‐O‐Ti(NMe2)3 (7b), from P(CH2NArR)3TiNMe2. The reactions of 1a,b with Zr(NEt2)4 afforded metal complexes of the type P(CH2NArR)3ZrNEt2 (8a,b). The chloride complexes P(CH2NArR)3ZrCl(THF) (9a,b) were prepared by treatment of HNEt3Cl with 1 or 2. The complexes 9a,b reacted with cyclopentadienyllithium (C5H5Li) to produce P(CH2NArR)3ZrCp (10a,b), which were also prepared by the reactions of the lithium salts 2a,b with CpZrCl3. The dilithium salt of the fulvalene dianion (Li2C10H8) reacts with 9a,b to produce the dinuclear complexes trans‐[P(CH2NArR)3Zr]2(μ‐η5:η5‐C10H8) (10a,b), respectively. The facile preparation of transition‐metal‐containing polymers from the bridged dinuclear complexes was illustrated by the reaction of 6a with half an equivalent of [Rh(CO)2(μ‐Cl)]2, which precipitated polymeric Cl(CO)Rh[P(CH2NPh)3Ti]2(μ‐O). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Mechanism of Ethylene Oligomerization by a Cationic Palladium(II) Alkyl Complex that Contains a (3,5-Me2-pyrazolyl)2CHSi(p-tolyl)3) Ligand

The reactivity of the ethylene oligomerization catalyst (N^N)Pd(Me)(ethylene)+ (5), which contains a silyl-capped bis-pyrazolyl methane ligand (N^N = (3,5-Me2-pyrazolyl)2CHSi(p-tolyl)3 (1)) was investigated. The reaction of (N^N)PdMeCl (3) with Li[B(C6F5)4] and ethylene in CH2Cl2 generates 5. Complex 5 undergoes ethylene insertion at −10 °C with a rate constant of kinsert,Me = 3.3(3) × 10−3 s−1. Complex 5 catalytically oligomerizes ethylene to branched C6–C20 internal olefins (−10 to 20 °C; 2.7–30 atm ethylene). NMR studies show that an equilibrium mixture of base-free β-agostic secondary alkyl (N^N)PdR+ species (8) and ethylene adducts (N^N)Pd(R)(ethylene)+ (9) is present under oligomerization conditions. Complex 9 decomposes to Pd0 at 20 °C, resulting in catalyst decomposition. (N^N)Pd(R)(L)+ species containing R groups that can function as internal donors (either η2-acyl or agostic β-H) undergo a dynamic process that exchanges the two pz* rings and are thermally unstable. It is proposed that catalyst d...

Thermally Stable Gold(I) Ethylene Adducts: [(HB{3,5‐(CF3)2Pz}3)Au(CH2CH2)] and [(HB{3‐(CF3),5‐(Ph)Pz}3)Au(CH2CH2)

Captured by scorpionates: Using fluorinated scorpionates, remarkably stable gold(I) complexes containing ethylene are isolated and structurally characterized (see structure of molecule core: yellow Au, blue N, red B, light gray C). These adducts feature κ2-bonded tris(pyrazolyl)borate ligands, and show in the 1H and 13C NMR spectra considerably upfield-shifted ethylene signals.

Thermally Stable Gold(I) Ethylene Adducts: [(HB{3,5‐(CF3)2Pz}3)Au(CH2CH2)] and [(HB{3‐(CF3),5‐(Ph)Pz}3)Au(CH2CH2)

In den Scheren des Skorpionats: Durch die Verwendung fluorierter Skorpionat-Liganden konnten stabile Gold(I)-Ethen-Komplexe isoliert und strukturanalytisch charakterisiert werden (siehe Bild der zentralen Einheit: Au gelb, N blau, B rot, C hellgrau). In den Addukten liegen die Tris(pyrazolyl)borat-Liganden κ2-gebunden vor, und die Ethensignale in den 1H- und 13C-NMR-Spektren sind stark hochfeldverschoben.

Volatile Magnesium Octahydrotriborate Complexes as Potential CVD Precursors to MgB2. Synthesis and Characterization of Mg(B3H8)2 and Its Etherates

The solid-state reaction of MgBr2 and NaB3H8 at 20 degrees C, followed by sublimation at 80 degrees C and 0.05 Torr, affords Mg(B3H8)2 as a white solid. Similar reactions with MgBr2(Et2O) and MgBr2(Me2O)1.5 afford the crystalline ether adducts Mg(B3H8)2(Et2O)2 and Mg(B3H8)2(Me2O)2, respectively. In contrast, reactions of MgBr2 with NaB3H8, the presence of excess solvent result in the formation of nonvolatile, probably ionic, magnesium compounds of the type [MgLx][B3H8]2. The adducts Mg(B3H8)2(Et2O)2 and Mg(B3H8)2(Me2O)2 are the first crystallographically characterized magnesium complexes of the B3H8- ligand; in both structures, the magnesium center adopts a distorted cis-octahedral geometry with two bidentate B3H8 groups and two Et2O ligands. Owing to their volatility, Mg(B3H8)2(Et2O)2 and Mg(B3H8)2(Me2O)2 are potential precursors for the deposition of MgB2 thin films, although preliminary efforts to employ them as chemical vapor deposition sources produce boron-rich MgBx films instead, with x approximately 7. Finally, the synthesis and structure of Cp2Mg(thf) are described: this mono-thf adduct of Cp2Mg bears two eta5-Cp groups, unlike other Lewis base adducts of Cp2Mg, which contain one eta5-Cp group and one eta1- or eta2-Cp group.