Alkali metal additions to unsaturated systems

Treatment of tetrakis(dimethoxyboryl)methane, C[B(OMe)₂]₄, with lithium methoxide or butyllithium followed by triphenyltin chloride yields (triphenylstannyl)tris(dimethoxyboryl)methane, Ph₃SnC[B(OMe)₂]₃, which on further treatment with butyllithium disproportionates to form bis(triphenylstannyl)bis(dimethoxyboryl)methane, (Ph₃Sn)₂C[B(OMe)₂]₂. The analogous monolead compound proved too base-sensitive to isolate, and only bis(triphenylplumbyl)bis(dimethoxyboryl)methane, (Ph₃Pb)₂C[B(OMe)₂]₂, was obtained from C[B(OMe)₂]₄, BuLi, and Ph₃PbCl. A brief study of protodeboronation and other reactions of these compounds has been carried out.     

Catalyst‐Controlled Regiodivergent CH Borylation of Multifunctionalized Heteroarenes by Using Iridium Complexes

The regiodivergent C?H borylation of 2,5‐disubstituted heteroarenes with bis(pinacolato)diboron was achieved by using iridium catalysts formed in situ from [Ir(OMe)(cod)]₂/dtbpy (cod=1,5‐cyclooctadiene, dtbpy: 4,4′‐di‐tert‐butyl‐2,2′‐bipyridine) or [Ir(OMe)(cod)]₂/2 AsPh₃. When [Ir(OMe)(cod)]₂/dtbpy was used as the catalyst, borylation at the 4‐position proceeded selectively to afford 4‐borylated products in high yields (dtbpy system A). The regioselectivity changed when the [Ir(OMe)(cod)]₂/2 AsPh₃ catalyst was used; 3‐borylated products were obtained in high yields with high regioselectivity (AsPh₃ system B). The regioselectivity of borylation was easily controlled by changing the ligands. This reaction was used in the syntheses of two different bioactive compound analogues by using the same starting material.     

Synthesis and reactivity of naphthalene sandwich complexes of molybdenum. X-ray structure of [Mo(η6-naphthalene) {P(OMe)3}3] and [Mo(H)(η6-naphthalene){P(OMe)3}3][BF4]

The sandwich complexes bis(η⁶-naphthalene)molybdenum(0) ( 1 ), bis(η⁶-1-methylnaphthalene)molybdenum(0) ( 2 ), and bis(η⁶-1,4-dimethylnaphthalene)molybdenum(0) ( 3 ) are synthesized by cocondensation of Mo-atoms with the naphthalene ligands. Complexes 1–3 are also obtained by reduction of MoCl₅ or MoCl₄. 2THF with highly activated Mg in the presence of the naphthalene ligands. Mg was activated by sublimation of the metal in a simple rotating solution reactor. Complex 2 exists as a mixture of regio- and stereoisomers. Three regioisomers, 3a–c , are formed in reactions of Mo-atoms with 1,4-dimethylnaphthalene, whereas 3a , the isomer with the Mo-atom coordinated to the unsubstituted rings, is formed selectively via the reductive method. The ligands in 1–3 are highly labile. CO displaces both naphthalene rings in 2 and 3 to give [Mo(CO)₆], while PF₃, P(OMe)₃, and PMe₃ displace only one coordinated naphthalene in 1 to yield the [Mo(η⁶-naphthalene)L₃] complexes 4–6 . In toluene, arene exchange is a competitive process in reactions of 1 with PF₃. Complexes 5 (L = P(OMe)₃) and 6 (L = PMe₃) react with HBF₄ to give the cationic metal hydride complexes 8 and 9 . The X-ray crystal structures of [Mo(η⁶-naphthalene) {P(OMe)₃}₃] ( 5 ) and [Mo(H)(η⁶-naphthalene) {P(OMe)₃}₃][BF₄] ( 8 ) are reported.     

Tuning the energy level of TAPC: crystal structure and photophysical and electrochemical properties of 4,4′‐(cyclohexane‐1,1‐diyl)bis[N,N‐bis(4‐methoxyphenyl)aniline]

The energy level of a hole‐transporting material (HTM) in organic electronics, such as organic light‐emitting diodes (OLEDs) and perovskite solar cells (PSCs), is important for device efficiency. In this regard, we prepared 4,4′‐(cyclohexane‐1,1‐diyl)bis[N,N‐bis(4‐methoxyphenyl)aniline] ( TAPC‐OMe ), C₄₆H₄₆N₂O₄, to tune the energy level of 4,4′‐(cyclohexane‐1,1‐diyl)bis[N,N‐bis(4‐methylphenyl)aniline] ( TAPC ), which is a well‐known HTM commonly used in OLED applications. A systematic characterization of TAPC‐OMe , including ¹H and ¹³C NMR, elemental analysis, UV–Vis absorption, fluorescence emission, density functional theory (DFT) calculations and single‐crystal X‐ray diffraction, was performed. TAPC‐OMe crystallized in the triclinic space group P, with two molecules in the asymmetric unit. The dihedral angles between the central amine triangular planes and those of the phenyl groups varied from 26.56 (9) to 60.34 (8)° due to the steric hindrance of the central cyclohexyl ring. This arrangement might be induced by weak hydrogen bonds and C—H…π(Ph) interactions in the extended structure. The emission maxima of TAPC‐OMe showed a significant bathochomic shift compared to that of TAPC . A strong dependency of the oxidation potentials on the nature of the electron‐donating ability of substituents was confirmed by comparing oxidation potentials with known Hammett parameters (σ).     

Synthesis and characterization of polysiloxane–polyamide block and graft copolymers

The synthesis of copolymers constituted of a central polydimethylsiloxane (PDMS) block flanked by two polyamide (PA) sequences is described. α, ω-diacyllactam PDMS, when used as macroinitiator of lactam polymerization, gives rise to the expected triblock copolymer. Likewise, PDMS-g-PA graft copolymers are obtained from acyllactam containing polysiloxanes. NaAlH₂(OCH₂CH₂OMe)₂ turns out to be the best suited activating agent for the polymerization of ?-caprolactam, in the experimental conditions required for the synthesis of polysiloxane–polyamide copolymers. The nucleophilic species formed by reaction of NaAlH₂(OCH₂CH₂OMe)₂ with ?-caprolactam—2-[bis(methoxyethoxy) aluminumoxy]-1-azacycloheptane sodium—is indeed nucleophilic enough to bring about the growth of PA chains and mild enough to stay inert towards PDMS. © 1993 John Wiley & Sons, Inc.     

A convenient method to reduce hydroxyl-substituted aromatic carboxylic acid with NaBH4/Me2SO4/B(OMe)3

The reduction of hydroxyl-substituted aromatic carboxylic acid with NaBH₄/Me₂SO₄/B(OMe)₃ is described. Borane is generated by the reaction of NaBH₄ with Me₂SO₄ in THF, which is as efficient as the commercial one. B(OMe)₃ has been successfully applied to increase the reactivity and selectivity of this reaction. The optimum ratio of borane/B(OMe)₃/acid is studied, and a variety of hydroxyl-substituted aromatic acids are reduced in good yields.     

Design and Synthesis of Novel Amino Acid‐Bearing Macrocyclic Calix[4]Arenes

Abstract

A new family of macrocyclic calix[4]arenes (4a–d) potentially capable of chiral recognition were synthesized by incorporating the chirality inducing moieties, bis α‐amino acylated polyethylene glycols, or tripeptide bis‐Phe Cystine(OMe)₂ to the lower rim.     

Single-Crystal to Single-Crystal Transformations: Stepwise CO2 Insertions into Bridging Hydrides of [(NHC)CuH]2 Complexes

Mechanistic studies of substrate insertion into dimeric [(NHC)CuH]₂ (NHC=N-heterocyclic carbene) complexes with two bridging hydrides have been shown to require dimer dissociation to generate transient, highly reactive (NHC)Cu−H monomers in solution. Using single-crystal to single-crystal (SC-SC) transformations, we discovered a new pathway of stepwise insertion of CO₂ into [(NHC)CuH]₂ without complete dissociation of the dimer. The first CO₂ insertion into dimeric [(IPr*OMe)CuH]₂ (IPr*OMe=N,N′-bis(2,6-bis(diphenylmethyl)-4-methoxy-phenyl)imidazole-2-ylidene) produced a dicopper formate hydride [(IPr*OMe)Cu]₂(μ-1,3-O₂CH)(μ-H). A second CO₂ insertion produced a dicopper bis(formate), [(IPr*OMe)Cu]₂(μ-1,3-O₂CH)(μ-1,1-O₂CH), containing two different bonding modes of the bridging formate. These dicopper formate complexes are inaccessible from solution reactions since the dicopper core cleanly ruptures to monomeric complexes when dissolved in a solvent.     

Preparation of organoalkoxysiloxanes by partial acidolysis of organoalkoxysilanes

Partial polycondensation of RSi(OMe)₃ (R = C₆H₅, CH₃) by the reaction with AcOH in the presence of HCl is studied. Oligoorganomethoxysiloxanes are obtained of the average composition [RSi(OMe)O]₄, [RSi (OMe)_4/6O_7/6]₆, RSi(OMe)_0.5O_1.25]₈, and [RSi(OMe)_0.4O_1.3]₁₀. Using the method of ²⁹Si NMR spectroscopy they were shown to contain three types of structural fragments: RSi(OMe)₂O-, RSiOMe(O-)₂, RSi(O-)₃. Based on the kinetic data, on the composition, properties, and the ²⁹Si NMR spectroscopy data of the products the conclusion is made that the obtained compounds have polycyclic structure with branched fragments. Using the GLC method the reaction was shown to have an induction period, whose duration can be substantially shortened by addition of HCl or methanol.     

Synthesis and antibacterial evaluation of new pyrido[3',2':4,5]thieno[3,2-d ]pyrimidin-4(3H)-one hybrids linked to different heteroarene units

A three-component protocol involving the reaction of 3-aminothieno[2,3-b]pyridine-2-carboxylate, Me₂NCH(OMe)₂ and heteroaryl (bis)amines in dioxane under microwave irradiation yielded a new series of pyrimidinones. The target hybrids were formed by an initial formamidine formation,Pyrazole-linked pyrimidinones displayed the best antibacterial activity against all the gram-positive and negative strains tested.     

Elaboration and characterization of hybrid organic-inorganic gels obtained by reaction of 1,4-butanediol on tetramethoxysilane

New hybrid organic-inorganic gels have been obtained by reaction of 1,4-butanediol, on tetramethoxysilane Si(OMe)₄ dissolved in CCl₄. This reaction does not require water and leads to the formation of polymeric transparent materials.Infrared, ²⁹Si and ¹³C NMR spectroscopy shows that interchange reactions between OMe groups of alkoxide and -O-(CH₂)₄-O of 1,4-butanediol occurred, leading to the monolithic transparent gels in which both organic (Si-O-(CH₂)₄-O-Si) and inorganic (Si-O-Si) bridges are formed.     

N-Aryl and N-Alkyl Carbamates from 1 Atmosphere of CO2

We have successfully isolated and characterized the zinc carbamate complex (phen)Zn(OAc)(OC(=O)NHPh) ( 1 ; phen=1,10-phenanthroline), formed as an intermediate during the Zn(OAc)₂/phen-catalyzed synthesis of organic carbamates from CO₂, amines, and the reusable reactant Si(OMe)₄. Density functional theory calculations revealed that the direct reaction of 1 with Si(OMe)₄ proceeds via a five-coordinate silicon intermediate, forming organic carbamates. Based on these results, the catalytic system was improved by using Si(OMe)₄ as the reaction solvent and additives like KOMe and KF, which promote the formation of the five-coordinated silicon species. This sustainable and effective method can be used to synthesize various N-aryl and N-alkyl carbamates, including industrially important polyurethane raw materials, starting from CO₂ under atmospheric pressure.     

Übergangsmetall—methylen-komplexe : XXXIV. Aufbau alicyclischer methylen-brucken nach einem modifizierten diazoalkan-verfahren

The mixed dinitrogen-isocyanide complexes mer-[ReCl(N₂)(CNMe)-{P(OMe)₃}₃] (I) and [ReCl(N₂)(CNMe)(PPh₃) {P(OEt)₃}₂] (II) are obtained by a novel route through reactions of CNMe with the organodiazenido species [ReCl₂(NNCOPh) {P(OMe)₃ }₃] and [ReCl₂(NNCOPh)(PPh₃){P(OEt)₃ }₂] (III, newly synthesized), whereas mer-[ReCl(N₂)(PPh₃) {P(OMe)₃ }₃] (IV) (which gives I by reaction with CNMe) is formed in the reaction of [$\text{ReCl}{}_2\text{(NNC}$OPh)(PPh₃)₂] with P(OMe)₃; the structure of complex I is authenticated by X-ray analysis.     

Complexation of methylparathion and bis(2‐hydroxyethyl)sulfide by the tridentate lewis acid [(o‐C6F4Hg)3]

The interaction of trimeric perflu‐ oro‐ortho‐phenylene mercury ( 1 ) with bis(2‐hydroxy‐ ethyl)sulfide (S((CH₂)₂OH)₂) in dichloromethane and methylparathion (SP(OMe)₂(p‐C₆H₄NO₂)) in 1,2‐dichloroethane leads to the crystallization of [ 1 ⋅ (S((CH₂)₂OH)₂)] and [ 1 ⋅ (μ₃‐SP(OMe)₂(p‐C₆H₄‐ NO₂))₂], respectively. These two adducts have been characterized by elemental analysis and single crystal X‐ray diffraction. The structure of [ 1 ⋅ S((CH₂)₂OH)₂] shows that the bis(2‐hydroxyethyl)sulfide molecule interacts with the mercury centers of 1 by formation of a Hg–S interaction of 3.138(4) Å. Association of the two components is further strengthened by the coordination of one of the oxygen atoms of the bis(2‐hydroxyethyl)sulfide molecule. This oxygen atom interacts simultaneously with three mercury centers of 1 with Hg–O distances ranging from 2.889(8) to 3.142(9) Å. In the lattice, molecules of [ 1 ⋅ (S((CH₂)₂OH)₂)] associate with compact cofacial dimers with Hg–Hg metallophilic contacts of 3.794 Å and 4.076 Å. The structure of [ 1 ⋅ (μ₃‐SP(OMe)₂(p‐C₆H₄NO₂))₂] is that of a 2:1 complex in which two molecules of methylparathion are triply coordinated via their sulfur atom to the mercury centers of 1 on either side of the molecular plane. The Hg–S contacts fall within the range of 3.278 and 3.651 Å. © 2005 Wiley Periodicals, Inc. 16:292–297, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20125     

Addition and migration of ligands on a metal atom pair: The oxidative addition of hexafluoro-2-butyne to dinuclear dihydridoiridium(II) complexes [Ir(H)(μ-SBu-t)(CO)(PR3)]2(IrIr) (R = OMe or Me), and its dehydrogenation reaction when R = OMe

Dissymmetric dinuclear complexes (PR₃)(CO)(H)₂Ir(μ-SBu-t)₂Ir(C₄F₆(CO)-(PR₃) (III, R = OMe or Me), which can be described as the juxtaposition of dihydrido and alkyne adducts of Vaska's complex associated through thiolato bridges, were obtained by the reaction of hexafluoro-2-butyne with symmetric dinuclear dihydridoiridium(II) complexes, [Ir(H)(μ-SBu-t)(CO)(PR₃)]₂(]IrIr) (II). When R = OMe, after the loss of H₂, a molecular rearrangement leads to the symmetric dinuclear iridium(II) complex [Ir(μ-SBu-t)(CO)(P(OMe)₃)]₂(C₄F₆) (IV). A correlation between the presence of an intense absorption near 230 nm in the UV-visible spectra and the existence of a metal—metal bond is established. A sequence of formation, splitting and re-formation of the metal—metal bond is observed along the series of derivatives obtained from [Ir(μ-SBu-t)(CO)P(OMe)₃]₂ (I) to IV, via II and III.     

Preparations and structures of titanium(IV) complexes containing 8-hydroxyquinolinate and a Schiff-base N-(2-oxyphenyl)salicylideneiminate

In methanol, the reaction of Ti(OⁱPr)₄, N-(2-hydroxyphenyl)salicylideneimine (H₂Sap) and 8-hydroxyquinoline (HQ) in stoichiometric ratio 1:1:x yielded Ti(Sap)₂ precipitate as initial product even when x was as high as 10. However, when the reaction mixture with x = 2 was left standing for 12 h or more, a small amount of red crystalline Ti(Sap)Q(OMe) was isolated. Addition of wet acetonitrile to the reaction mixture with x = 10, small amount of another red crystalline [Ti(Sap)Q]₂(μ-O) was obtained after standing for 2 days. The reaction between TiQ₂(OⁱPr)₂ and H₂Sap in methanol with stoichiometric ratio of y:1 also yielded Ti(Sap)₂ as initial product even for y as large as 10. ¹H NMR investigation of the reaction of TiQ₂(OMe)₂ with H₂Sap revealed that Ti(Sap)Q(OMe) was not detected initially. These experimental results can be explained based on a mechanism that includes: (i) rapid reaction of H₂Sap with Ti(IV) centers to form Ti(Sap)₂; (ii) equilibrium between TiQ₂(OMe)₂ and Ti(Sap)Q(OMe); (iii) equilibrium between Ti(Sap)Q(OR) and Ti(Sap)₂; and (iv) limited solubilities of Ti(Sap)Q(OR) and Ti(Sap)₂. The equilibrium constants and solubilities in the mechanism were determined by the ¹H NMR spectral method. The structures of Ti(Sap)Q(OMe) and [Ti(Sap)Q]₂(μ-O), consisting octahedrally coordinated Ti(IV), were determined by X-ray diffraction method.     

Influence of the nature of organic groups on the properties of organically modified silica aerogels

Organically modified aerogels were prepared by NH₄OH-catalyzed hydrolysis and condensation of RSi(OMe)₃ (R = Me, Pr ⁿ , Ph, Bu ⁱ )/Si(OMe)₄ or (MeO)₃Si-Y-Si(OMe)₃/Si(OMe)₄ (Y = C₂H₄, p-C₆H₄, C₆H₁₂) mixtures, followed by supercritical drying of the alcogels with methanol. Starting from 1:4 mixtures of RSi(OMe)₃ and Si(OMe)₄, hydrophobic aerogels with nearly no residual Si-OH or Si-OMe groups were obtained. These aerogels were therefore insensitive towards moisture. Their elastic constant was distinctly lower than that of unmodified silica aerogels. Aerogels similarly prepared from 1:8 mixtures of (MeO)₃Si-Y-Si(OMe)₃ and Si(OMe)₄ had a rather high concentration of residual Si-OMe groups, and therefore they were hydrophilic. Their elasticity was about the same as that of unmodified silica aerogels. The difference between the two types of aerogels suggests different microstructures, depending on the nature of the organic groups.     

Pseudochalkogenverbindungen. XIV. Die Synthese von Trimethylcyanamidophosphaten,ein Beitrag zur Ambivalenz der Cyanamidophosphat-lonen, [PO4−n(NCN)n]3−

Possible dochalcogeno Compounds. XIV. Synthesis of Trimethylcyanamidophosphates, a Contribution to the Ambivalency of Cyanamidophosphate Ions, [PO_4?n(NCN)_n]^3? Possible synthetic routes for isomeric trimethylcyanamidophosphates of the types P(O)(OMe)₂(N(CN)Me), P(O)(OMe)₂(NCNMe), P(NCN)(OMe)₃ as well as further compounds of the general formula P(O)(OMe)_3?n{N(CN)Me}_n are described. Influences of reaction media and counterion on the reaction site of the ambivalent monocyanamidophosphate ion, [PO₃NCN]^3? are discussed. The structures of the different trimethylcyanamidophosphates and of related compounds are discussed on the basis of their i.r. and n.m.r. spectra.     

Transition-Metal Complexes with Bidentate Ligands Spanning trans-Positions. Part XVII. Some platinum(II) complexes with anionic ligands such as methoxide,formate, carboxylate,hydride, and borohydride,and the X-ray crystal structure of [PtHCl( )] (PP = 2,11-bis(diphenylphosphinomethyl)benzo[c]phenanthrene)

The complexes trans-[PtXY( 2 ] (X = H or Me; Y = OMe, OCHO, CO₂H, and BH₄; 2 = 2,11-bis{bis[3-(trifluoromethyl)phenyl]phosphinomethyl}benzo[c]phenanthrene) were prepared, and their decompositions to trans[PtHX( 2 )] were studied. Some binuclear hydrido-bridged complexes, e.g.[( 2 )HPt(μ-H)PtH( 2 )]⁺, were also obtained. The preparation of complexes trans-[PtHX( 28 )₂] (X = H or Me, 28 = bis[3-(trifluoromethyl)phenyl]benzylphosphine) is also reported. The X-ray crystal structure of trans-[PtHCl 1 )] ( 1 = 2,11-bis(diphenylphosphinomethyl)benzo[c]phenanthrene) was carried out.     

Heterometallic Alkoxide Complexes of Variable Composition—A New Way to Ultrafine Powders of Metal Alloys

The anodic oxidation of Re metal in MeOH (Me = CH₃) provides a mixture of Re₂O₃(OMe)₆ and Re(V) oxoalkoxides that on storage or on heating give insoluble and air stable Re₄O_6–y (OMe)_12+y (I). I can be also obtained by reaction of Re₂O₇ with MeOH. In the presence of MoO(OMe)₄, a heterometallic complex ReMoO₂(OMe)₇(II) is formed as intermediate, the final product being Re_4–x Mo _x O_6–y (OMe)_12+y (III). The electrosynthesis in the presence of WO(OMe)₄ gives Re_4–x W _x O_6–y (OMe)_12+y (IV) only at very high Re : W ratios in solutions and the W content varies in one and the same sample. The dissolution of Re₂O₇ in the solutions of MO(OMe)₄, M = Mo,W in toluen on reflux yields Re_4–x M _x O_6–y (OMe)_12+y with uniform Re : M distribution. The cocrystallization of MoO(OMe)₄ and WO(OMe)₄ yields (Mo,W)O(OMe)₄ (V) with almost uniform Mo : W distribution. The thermal decomposition of II and III in inert atmosphere gives fine powder of the (Re,Mo)O₂ phase. The reduction with hydrogen gas converts II and III into an ultrafine powder of Re–Mo alloy at temperatures below 400°C. The latter can be sintered into compact metal at 800–900°C.