Bis(phosphinimino)methanide rare earth amides: synthesis, structure, and catalysis of hydroamination/cyclization, hydrosilylation, and sequential hydroamination/hydrosilylation

A series of yttrium and lanthanide amido complexes [Ln{N(SiHMe(2))2}2{CH(PPh(2)NSiMe(3))2}] (Ln=Y, La, Sm, Ho, Lu) were synthesized by three different pathways. The title compounds can be obtained either from [Ln{N(SiHMe(2))2}3(thf)2] and [CH(2)(PPh(2)NSiMe(3))2] or from KN(SiHMe(2))2 and [Ln{CH(PPh(2)NSiMe(3))2}Cl(2)]2, while in a third approach the lanthanum compound was synthesized in a one-pot reaction starting from K{CH(PPh(2)NSiMe(3))2}, LaCl3, and KN(SiHMe(2))2. All the complexes have been characterized by single-crystal X-ray diffraction. The new complexes, [Ln{N(SiHMe(2))2}2{CH(PPh(2)NSiMe(3))2}], were used as catalysts for hydroamination/cyclization and hydrosilylation reactions. A clear dependence of the reaction rate on the ionic radius of the center metal was observed, showing the lanthanum compound to be the most active one in both reactions. Furthermore, a combination of both reactions--a sequential hydroamination/hydrosilylation reaction--was also investigated.     

A samarium cyclooctatetraene complex as catalyst for hydroamination/cyclisation catalysis

The cyclooctatetraene-bis(phosphinimino)methanide complex [[CH(PPh2NSiMe3)2]Sm(eta8-C8H8)] has been prepared; although this compound has no alkyl or amide ligand it shows moderate activity as a catalyst for the hydroamination/cyclisation reaction.     

Three-coordinate bis(phosphinimino)methanide derivatives of ‘open shell’ [M(II)] (M = Mn, Fe, Co) transition metals

An alternative two-step synthesis of the previously reported bis(diphenylphosphinimino)methane [CH₂(Ph₂P = NC₆H₃ⁱPr₂-2,6)₂] involving bromine oxidation of dppm and metathesis with 2,6-diisopropylaniline is described. [CH₂(Ph₂PNC₆H₃ⁱPr₂-2,6)₂] is readily deprotonated by the transition metal silylamides [M{N(SiMe₃)₂}₂] (M = Mn, Fe and Co) to provide a series of exclusively three-coordinate derivatives [{CH(Ph₂PNC₆H₃ⁱPr₂-2,6)₂M{N(SiMe₃)₂}] which have been characterised by elemental analysis, magnetic measurements and, in the case of the Fe derivative, X-ray structural analysis. Reactivity studies have shown that even such sterically demanding bis(phosphinimino)methanide ligands are prone to protonolysis and reductive [P(V) to P(III)] degradation which limits their utility as stable platforms for further M(II) derivitisation.     

Oxide surface-promoted Pd-complex catalysis for intramolecular O-activated alkene hydroamination: catalyst preparation, characterization, and performance

Supported Pd-P and Pd-N complexes prepared by a selective reaction of Pd-monomer precursors with SiO2, Al2O3 and TiO2 surfaces and characterized by EXAFS, XPS, XRF and gas analysis exhibited oxide surface-promoted catalysis for the catalytic intrahydroamination of 3-amino propanol vinyl ether to produce a cyclic amine.     

Bis(phosphinimino)methanides as ligands in divalent lanthanide and alkaline earth chemistry - synthesis, structure, and catalysis

Divalent bis(phosphinimino)methanide lanthanide complexes of composition [{(Me₃SiNPPh₂)₂CH}EuI(THF)]₂ and [{(Me₃SiNPPh₂)₂CH}YbI(THF)₂] have been prepared by a salt metathesis reactions of K{CH(PPh₂NSiMe₃)₂} and LnI₂. Further reactions of these complexes with [K(THF)_nN(PPh₂)₂] led selectively to the heteroleptic amido complexes [{(Me₃SiNPPh₂)₂CH}Ln{(Ph₂P)₂N}(THF)] (Ln = Eu, Yb). The ytterbium complex can also be obtained by reduction of [{CH(PPh₂NSiMe₃)₂}Yb{(Ph₂P)₂N}Cl] with elemental potassium. The single crystals of [{(Me₃SiNPPh₂)₂CH}Ln{(Ph₂P)₂N}(THF)] contain enantiomerically pure complexes. As a result of the similar ionic radii of the divalent lanthanides and the heavier alkaline earth metals some similarities in coordination chemistry of the bis(phosphinimino)methanide ligand were anticipated. Therefore, MI₂ (M = Ca, Sr, Ba) was reacted with K{CH(PPh₂NSiMe₃)₂} to give [{(Me₃SiNPPh₂)₂CH}CaI(THF)₂], [{(Me₃SiNPPh₂)₂CH}SrI(THF)]₂, and [{(Me₃SiNPPh₂)₂CH}BaI(THF)₂]₂, respectively. As expected the Sr and Eu complexes and the Ca and Yb complexes are very similar, whereas for the Ba compound, as a result of the large ion radius, a different coordination sphere is observed. For all new complexes the solid-state structures were established by single crystal X-ray diffraction. In the solid-state the {CH(PPh₂NSiMe₃)₂}⁻ ligand acts as tridentate donor forming a long methanide carbon metal bond. Thus, all complexes presented can be considered as organometallic compounds. [{(Me₃SiNPPh₂)₂CH}YbI(THF)₂] was also used as precatalyst for the intramolecular hydroamination/cyclization reaction of different aminoalkynes and aminoolefines. Good yields but moderate activities were observed.     

A chiral phenoxyamine magnesium catalyst for the enantioselective hydroamination/cyclization of aminoalkenes and intermolecular hydroamination of vinyl arenes

If Grignard had only known! A chiral magnesium complex catalyzes the intramolecular hydroamination/cyclization of aminoalkenes with high efficiency at temperatures as low as ?20?°C and enantioselectivities as high as 93?%?ee. The high activity of this system also allows the catalytic intermolecular anti-Markovnikov addition of pyrrolidine and benzylamine to vinyl arenes.     

C2-symmetric bis(oxazolinato)lanthanide catalysts for enantioselective intramolecular hydroamination/cyclization

C(2)-symmetric bis(oxazolinato)lanthanide complexes of the type [(4R,5S)-Ph(2)Box]La[N(TMS)(2)](2), [(4S,5R)-Ar(2)Box]La[N(TMS)(2)](2), and [(4S)-Ph-5,5-Me(2)Box]La[N(TMS)(2)](2) (Box = 2,2'-bis(2-oxazoline)methylenyl; Ar = 4-tert-butylphenyl, 1-naphthyl; TMS = SiMe(3)) serve as precatalysts for the efficient enantioselective intramolecular hydroamination/cyclization of aminoalkenes and aminodienes. These new catalyst systems are conveniently generated in situ from the known metal precursors Ln[N(TMS)(2)](3) or Ln[CH(TMS)(2)](3) (Ln = La, Nd, Sm, Y, Lu) and 1.2 equiv of commercially available or readily prepared bis(oxazoline) ligands such as (4R,5S)-Ph(2)BoxH, (4S,5R)-Ar(2)BoxH, and (4S)-Ph-5,5-Me(2)BoxH. The X-ray crystal structure of [(4S)-(t)BuBox]Lu[CH(TMS)(2)](2) provides insight into the structure of the in situ generated precatalyst species. Lanthanides having the largest ionic radii exhibit the highest turnover frequencies as well as enantioselectivities. Reaction rates maximize near 1:1 BoxH:Ln ratio (ligand acceleration); however, increasing the ratio to 2:1 BoxH:Ln decreases the reaction rate, while affording enantiomeric excesses similar to the 1:1 BoxH:Ln case. A screening study of bis(oxazoline) ligands reveals that aryl stereodirecting groups at the oxazoline ring 4 position and additional substitution (geminal dimethyl or aryl) at the 5 position are crucial for high turnover frequencies and good enantioselectivities. The optimized precatalyst, in situ generated [(4R,5S)-Ph(2)Box]La[N(TMS)(2)](2), exhibits good rates and enantioselectivities, comparable to or greater than those achieved with chiral C(1)-symmetric organolanthanocene catalysts, even for poorly responsive substrates (up to 67% ee at 23 degrees C). Kinetic studies reveal that hydroamination rates are zero order in [amine substrate] and first order in [catalyst], implicating the same general mechanism for organolanthanide-catalyzed hydroamination/cyclizations (intramolecular turnover-limiting olefin insertion followed by the rapid protonolysis of an Ln-C bond by amine substrate) and implying that the active catalytic species is monomeric.     

Catalysis of hydrosilylation. XV. A poly(phosphino-organosiloxanyl)silicate-supported rhodium(I) catalyst for gas-phase hydrosilylation of acetylene

Wilkinson's complex [RhCl(PPh₃)₃], anchored to phosphino-organosiloxane macromolecules grafted onto chrysotile asbestos, appeared to be an unusually effective and selective catalyst for the synthesis of vinylsilanes via gas-phase hydrosilylation of acetylene, particularly by methyldichlorosilane in a continuous-flow microreactor as well as in a laboratory reactor. Catalytic and kinetic parameters show an advantage for the catalyst based on the chrysotile-polyorganosiloxane support (catalyst CHR–Rh) over the phosphinated silica (catalyst A).     

A new uninegative ligand, tris-(diphenylthiophosphinyl)methanide

The reaction of tris-(diphenylthiophosphinyl)methane, [(C₆H₅)₂P(S)]₃CH, with mercury(II) halides produces complexes of the type [(C₆H₅)₂P(S)]₃CHgX, where X is Cl, Br and I.     

Cobalt bis(2‐ethylhexanoate) and terpyridine derivatives as catalysts for the hydrosilylation of olefins

A simple method for the hydrosilylation of olefins by using air‐stable cobalt catalysts is developed. The catalyst system is composed of simple, cheap, and readily available cobalt(II) salts and well‐defined terpyridine derivatives as cocatalysts or ligands, and the hydrosilylation processes can be processed smoothly under mild conditions without either Grignard reagents or NaHBEt₃ as activator.     

Biimidazole and bis(amide)bipyridine molybdenum carbonyl complexes as anions receptors

Compounds [Mo(CO)4(N-N)] (N-N = 4,4'-bis((4-methylphenyl)carbamoyl)-2,2'-bipyridine, bipy', 1; or 2,2'-biimidazole, H2biim, 2), [MoCl(eta3-methallyl)(CO)2(N-N)] (N-N = bipy', 3; H2biim, 4), and [Mo(eta3-methallyl)(CNtBu)(CO2)(N-N)]BAr'4 (Ar' = 3,5-bis(trifluoromethyl)phenyl; N-N= bipy', 5; H2biim, 6) were synthesized and characterized, and their behavior toward anions was investigated in solution (IR and 1H NMR) and in solid state (X-ray diffraction).     

Rare earth metal bis(amide) complexes bearing amidinate ancillary ligands: synthesis, characterization, and performance as catalyst precursors for cis-1,4 selective polymerization of isoprene

A family of rare earth metal bis(amide) complexes bearing monoanionic amidinate [RC(N-2,6-Me(2)C(6)H(3))(2)](-) (R = cyclohexyl (Cy), phenyl (Ph)) as ancillary ligands were synthesized and characterized. One-pot salt metathesis reaction of anhydrous LnCl(3) with one equivalent of amidinate lithium [RC(N-2,6-Me(2)C(6)H(3))(2)]Li, following the introduction of two equivalents of NaN(SiMe(3))(2) in THF at room temperature afforded the neutral and unsolvated mono(amidinate) rare earth metal bis(amide) complexes [RC(N-2,6-Me(2)C(6)H(3))(2)]Y[N(SiMe(3))(2)](2) (R = Cy (1); R = Ph (2)), and the "ate" mono(amidinate) rare earth metal bis(amide) complex [CyC(N-2,6-Me(2)C(6)H(3))(2)]Lu[N(SiMe(3))(2)](2)(μ-Cl)Li(THF)(3) (3) in 61-72% isolated yields. These complexes were characterized by elemental analysis, NMR spectroscopy, FT-IR spectroscopy, and X-ray single crystal diffraction. Single crystal structural determination revealed that the central metal in complexes 1 and 2 adopts a distorted tetrahedral geometry, and in complex 3 forms a distorted trigonal bipyramidal geometry. In the presence of AlMe(3), and in combination with one equimolar amount of [Ph(3)C][B(C(6)F(5))(4)], complexes 1 and 2 showed high activity towards isoprene polymerization to give high molecular weight polyisoprene (M(n) > 10(4)) with good cis-1,4 selectivity (>90%).     

Tin(IV) bis(perfluoroalkanesulfonyl)amide complex as a highly selective Lewis acid catalyst for Baeyer-Villiger oxidation using hydrogen peroxide in a fluorous recyclable phase

Sn[N(SO₂C₈F₁₇)₂]₄ catalyst was shown to give an excellent yield and selectivity in a fluorous biphasic catalytic system for Baeyer-Villiger oxidation of cyclic ketones by 35% aqueous hydrogen peroxide, a green, safe and cheap oxidant. Furthermore, the catalyst was completely recovered and reused in the fluorous immobilized phase without loss of activity.     

Diruthenium(II,III) bis(tetramethyl-1,3-benzenedipropionate) as a novel catalyst for tert-butyl hydroperoxide oxygenation

The reaction of Ru2(OAc)4Cl with 2.2 equiv of H2esp (esp = alpha,alpha,alpha',alpha'-tetramethyl-1,3-benzenedipropionate) resulted in a new compound, Ru2(esp)2Cl (1), that is soluble in organic media. 1 is an active catalyst for the oxygenation of organic sulfides by tert-butyl hydroperoxide (TBHP) in both an acetonitrile solution or neat (solvent-free) conditions. Solvent-free reactions display the quantitative utility of TBHP and hence excellent chemical selectivity for sulfoxide formation.     

Triethylammonium bis(tetrafluoromethylsulfonyl)amide protic ionic liquid as an electrolyte for electrical double-layer capacitors

This study describes the preparation, characterization and application of [Et(3)NH][TFSA], either neat or mixed with acetonitrile, as an electrolyte for supercapacitors. Thermal and transport properties were evaluated for the neat [Et(3)NH][TFSA], and the temperature dependence of viscosity and conductivity can be described by the VTF equation. The evolution of conductivity with the addition of acetonitrile rendered it possible to determine the optimal mixture at 25 °C, with a weight fraction of acetonitrile of 0.5. This mixture was also evaluated for transport properties, and showed a Newtonian behavior, as the neat PIL. An electrochemical study demonstrated, at first, a passivation on Al after the second cyclic voltammogram. Subsequently, the electrochemical window was estimated using a three-electrode cell to 4 V on a platinum electrode, and to 2.5 V on activated carbon. Finally, the neat PIL was found to exhibit good performances as promising electrolyte for supercapacitor applications.     

Iron(II) cage complexes of N-heterocyclic amide and bis(trimethylsilyl)amide ligands: synthesis, structure, and magnetic properties

Metallation of hexahydropyrimidopyrimidine (hppH) by [Fe{N(SiMe(3))(2)}(2)] (1) produces the trimetallic iron(II) amide cage complex [{(Me(3)Si)(2)NFe}(2)(hpp)(4)Fe] (2), which contains three iron(II) centers, each of which resides in a distorted tetrahedral environment. An alternative, one-pot route that avoids use of the highly air-sensitive complex 1 is described for the synthesis of the iron(II)-lithium complex [{(Me(3)Si)(2)N}(2)Fe{Li(bta)}](2) (3) (where btaH = benzotriazole), in which both iron(II) centers reside in 3-coordinated pyramidal environments. The structure of 3 is also interpreted in terms of the ring laddering principle developed for alkali metal amides. Magnetic susceptibility measurements reveal that both compounds display very weak antiferromagnetic exchange between the iron(II) centers, and that the iron(II) centers in 2 and 3 possess large negative axial zero-field splittings.     

(Dicyclopentadiene) platinum(II) dichloride: An efficient catalyst for the hydrosilylation reaction between alkenes and triethoxysilane

(Dicyclopentadiene) platinum(II) dichloride was found to be an efficient hydrosilylation catalyst (homogeneous) upon a wide variety of functionalized alkenes and alkenes terminated with chemical moieties (diphenyl amino-, N-carbazol- and N-isoindoline-1,3-dione-). It is noteworthy that the hydrosilylation of aminated alkenes with triethoxysilane exhibited the yield of over 70% and the selectivity (γ-isomer/β-isomer) of more than 3/1. Due to steric hindrance lowering Markovnikov probability, the alkenes with big terminal moieties (diphenyl amino-, N-carbazol- and N-isoindoline-1,3-dione-) presented the high ratio of anti-Markovnikov isomers. The strategy of the hydrosilylation of the protected diamino chelating alkene was developed.     

Anti-Markovnikov intermolecular hydroamination: a bis(amidate) titanium precatalyst for the preparation of reactive aldimines

[reaction: see text] A bulky bis(N-2',6'-diisopropylphenyl(phenyl)-amidate)titanium-bis(diethylamido) complex was identified as a highly active and regioselective precatalyst for the anti-Markovnikov hydroamination of a wide range of terminal alkyl alkynes with alkylamines. This titanium complex was fully characterized, including its X-ray crystal structure. The reactive aldimine products generated have been further elaborated using one-pot procedures to give substituted amines, aldehydes, and the isoquinoline framework.