Aluminium complexes containing bidentate and symmetrical tridentate pincer type pyrrolyl ligands: synthesis, reactions and ring opening polymerization

A series of aluminium derivatives containing substituted bidentate and symmetrical tridentate pyrrolyl ligands, [C(4)H(3)NH(2-CH(2)NH(t)Bu)] and [C(4)H(2)NH(2,5-CH(2)NH(t)Bu)(2)], in toluene or diethyl ether were synthesized. Their reactivity and application for the ring opening polymerization of ε-caprolactone have been investigated. The reaction of AlMe(3) with one equiv. of [C(4)H(3)NH(2-CH(2)NH(t)Bu)] in toluene at room temperature affords [C(4)H(3)N(2-CH(2)NH(t)Bu)]AlMe(2) (1) in 70% yield by elimination of one equiv. of methane. Interestingly, while reacting AlMe(3) with one equiv. of [C(4)H(3)NH(2-CH(2)NH(t)Bu)] in toluene at 0 °C followed by refluxing at 100 °C, [{C(4)H(3)N(2-CH(2)N(t)Bu)}AlMe](2) (2) has been isolated via fractional recrystalliztion in 30% yield. Similarly, reacting AlMe(3) with two equiv. of C(4)H(3)NH(2-CH(2)NH(t)Bu) generates [C(4)H(3)N(2-CH(2)NH(t)Bu)](2)AlMe (3) in a moderate yield. Furthermore, complex 1 can be transformed to an aluminium alkoxide derivative, [C(4)H(3)N(2-CH(2)NH(t)Bu)][OC(6)H(2)(-2,6-(t)Bu(2)-4-Me)]AlMe (4) by reacting 1 with one equiv. of HOC(6)H(2)(-2,6-(t)Bu(2)-4-Me) in toluene via the elimination of one equiv. of methane. The reaction of AlR(3) with one equiv. of [C(4)H(2)NH(2,5-CH(2)NH(t)Bu)(2)] in toluene at room temperature affords [C(4)H(2)N(2,5-CH(2)NH(t)Bu)(2)]AlR(2) (5, R = Me; 6, R = Et) in moderate yield. Surprisingly, from the reaction of two equiv. of [C(4)H(2)NH(2,5-CH(2)NH(t)Bu)(2)] with LiAlH(4) in diethyl ether at 0 °C, a novel complex, [C(4)H(2)N(2-CH(2)N(t)Bu)(5-CH(2)NH(t)Bu)](2)AlLi (7) has been isolated after repeating re-crystallization. Furthermore, reacting one equiv. of C(4)H(2)NH(2,5-CH(2)NH(t)Bu)(2) with AlH(3)·NMe(3) in diethyl ether generates an aluminium dihydride complex, [C(4)H(2)N(2,5-CH(2)NH(t)Bu)(2)]AlH(2) (8), in high yield. Additionally, treating 8 with one equiv. of HOC(6)H(2)(-2,6-(t)Bu(2)-4-Me) in methylene chloride produces [C(4)H(2)N(2,5-CH(2)NH(t)Bu)(2)][OC(6)H(2)(-2,6-(t)Bu(2)-4-Me)]AlH (9) with the elimination of one equiv. of H(2). The aluminium alkoxide complex 4 shows moderate reactivity toward the ring opening polymerization of ε-caprolatone in toluene.     

Multiple C-H bond activation in group 3 chemistry: synthesis and structural characterization of an yttrium-aluminum-methine cluster

Complete donor-induced alkylaluminate cleavage of halfmetallocene complex Cp*Y(AlMe4)2, that is, treatment of Cp*Y(AlMe4)2 with 2 equiv of diethyl ether, produces [Cp*Y(mu2-Me)2]3 in high yield (95%). In contrast, the equimolar reaction of Cp*Y(AlMe4)2 with diethyl ether reproducibly formed complex [Cp*4Y4(mu2-CH3)2{(CH3)Al(mu2-CH3)2}4(mu4-CH)2] in low yield (10-30%) via a multiple C-H bond activation. The synthesis of the heterooctametallic yttrium-aluminum-methine cluster was also accomplished in moderate yield (47%) by the equimolar reaction of discrete Cp*Y(AlMe4)2 and [Cp*Y(mu2-Me)2]3 in the absence of any donor solvent and "free" AlMe3. This gives strong evidence that preformed heterometal-bridged Y-CH3-Al moieties are prone to multiple hydrogen abstraction in the presence of a highly basic reagent such as [Cp*Y(mu2-Me)2]3. The monocylopentadienyl complexes [Cp*Y(mu2-Me)2]3 and [Cp*4Y4(mu2-CH3)2{(CH3)Al(mu2-CH3)2}4(mu4-CH)2] were structurally characterized.     

Amino-functionalised diarylphosphide complexes of the alkali metals and lanthanum

The secondary phosphines Ar(C6H4-2-CH2NMe2)PH [Ar = mes (3), Tripp (4)] may be isolated in good yields from reactions between Li(C6H4-2-CH2NMe2) and the respective dichlorophosphine, followed by reduction with LiAlH4 [mes = 2,4,6-Me3C6H2, Tripp = 2,4,6-Pri3C6H2]. Metalation of either 3 or 4 with BunLi gives the corresponding lithium compound; the lithium derivative of 3 was isolated as the separated ion pair complex [Li(12-crown-4)2][(mes)(C6H4-2-CH2NMe2)P].THF (5). The lithium complexes Ar(C6H4-2-CH2NMe2)PLi undergo metathesis reactions with either NaOBut or KOBut to give the heavier alkali metal phosphides {Ar(C6H4-2-CH2NMe2)P}M.1/2OEt2 [Ar = mes, M = Na (8), K (9); Ar = Tripp, M = K (10)]. Metathesis reactions between 9 and LaI3(THF)4 give only intractable products; in contrast, a metathesis reaction between 10 and LaI3(THF)4 yields the heteroleptic complex {(Tripp)(C6H4-2-CH2NMe2)P}2LaI (11). Compound 11 reacts cleanly with K{N(SiMe3)2} to give {(Tripp)(C6H4-2-CH2NMe2)P}2La{N(SiMe3)2} (14). Compounds 3-5, 8-11 and 14 have been characterised by multi-element NMR spectroscopy; in addition, compounds 5, 11 and 14 have been studied by X-ray crystallography.     

Lewis acid stabilized methylidene and oxoscandium complexes

The methylidene scandium complex (PNP)Sc(mu3-CH2)(mu2-CH3)2[Al(CH3)2]2 (PNP = N[2-P(CHMe2)2-4-methylphenyl]2-) can be prepared from the reaction of (PNP)Sc(CH3)2 and 2 equiv of Al(CH3)3. The Lewis acid stabilized methylidenes candium complex has been crystallographically characterized, and its bonding scheme analyzed by DFT. In addition, we report preliminary reactivity studies of the Sc-CH2 ligand with substrates such as H2NAr and OCPh2. While the former results in an Br?nsted acid-base reaction, the latter reagent produces the olefin H2C CPh2 along with the novel oxoscandium complex (PNP)Sc(mu3-O)(mu2-CH3)2[Al(CH3)2]2, quantitatively.     

Guided-ion beam and theoretical study of the potential energy surface for activation of methane by W+

A guided-ion beam tandem mass spectrometer is used to study the reactions, W(+) + CH(4) (CD(4)) and [W,C,2H](+) + H(2) (D(2)), to probe the [W,C,4H](+) potential energy surface. The reaction W(+) + CH(4) produces [W,C,2H](+) in the only low-energy process. The analogous reaction in the CD(4) system exhibits a cross section with strong differences at the lowest energies caused by zero-point energy differences, demonstrating that this reaction is slightly exothermic for CH(4) and slightly endothermic for CD(4). The [W,C,2H](+) product ion reacts further at thermal energies with CH(4) to produce W(CH(2))(x)(+) (x = 2-4). At higher energies, the W(+) + CH(4) reaction forms WH(+) as the dominant ionic product with smaller amounts of WCH(3)(+), WCH(+), and WC(+) also formed. The energy dependent cross sections for endothermic formation of the various products are analyzed and allow the determination of D(0)(W(+)-CH(3)) approximately 2.31 +/- 0.10 eV, D(0)(W(+)-CH(2)) = 4.74 +/- 0.03 eV, D(0)(W(+)-CH) = 6.01 +/- 0.28 eV, and D(0)(W(+)-C) = 4.96 +/- 0.22 eV. We also examine the reverse reaction, [W,C,2H](+) + H(2) (D(2)) --> W(+) + CH(4) (CH(2)D(2)). Combining the cross sections for the forward and reverse processes yields an equilibrium constant from which D(0)(W(+)-CH(2)) = 4.72 +/- 0.04 eV is derived. Theoretical calculations performed at the B3LYP/HW+/6-311++G(3df,3p) level yield thermochemistry in reasonable agreement with experiment. These calculations help identify the structures and electronic states of the species involved and characterize the potential energy surface for the [W,C,4H](+) system.     

Imine-assisted C-F bond activation by electron-rich iron complexes supported by trimethylphosphine

C-F bond activation of ortho-fluorinated benzalimines 2,6-F(2)C(6)R1R2R3-CH=N-R (1-3) using the electron-rich complex Fe(PMe(3))(4) is reported. With the assistance of the imine group as the anchoring group, bis-chelated iron(II) complexes (C(6)FR1R2R3-CH=N-R)(2)Fe(PMe(3))(2) (4-6) were formed. The reaction of 2,6-difluorobenzylidenenaphthalen-1-amine 2,6-F(2)C(6)H(3)-CH=N-C(10)H(7) (9) with Fe(PMe(3))(4) affords [CNC]-pincer iron(II) complex (C(6)H(3)F-CH=N-C(10)H(6))Fe(PMe(3))(3) (10) through both C-F and C-H bond activation and π-(C=N) coordinate iron(0) complex (C(6)H(3)F-CH=N-C(10)H(7))(2)Fe(PMe(3))(2) (11) with C,C-coupling, while a similar reaction with perfluorobenzylidenenaphthalen-1-amine C(6)F(5)-CH=N-C(10)H(7) (14) gave rise to only [CNC]-pincer iron(II) complex (C(6)F(4)-CH=N-C(10)H(6))Fe(PMe(3))(3) (15). The proposed formation mechanisms of these complexes are discussed. The structures of complexes 5, 6, 10 and 11 were confirmed by X-ray single crystal diffraction.     

Cyanide-bridged Mn(III)-Fe(III) bimetallic complexes based on the pentacyano(1-methylimidazole)ferrate(III) building block: structure and magnetic characterizations

Seven cyanide-bridged bimetallic complexes have been synthesized by the reaction of [Fe(1-CH3im)(CN)5]2- with Mn(III) Schiff base complexes. Their crystal structure and magnetic properties have been characterized. Five complexes, [Mn2(5-Brsalen)2Fe(CN)5(1-CH3im)] x H2O (1), [Mn2(5-Clsalen)2(H2O)2Fe(CN)5(1-CH3im)] x H2O (2), [Mn2(5-Clsaltn)2(H2O)2Fe(CN)5(1-CH3im)] (3), [Mn2(5-Clsaltmen)2(H2O)2Fe(CN)5(1-CH3im)] x H2O (4), and [Mn2(5-Brsaltmen)2(H2O)2Fe(CN)5(1-CH3im)] x CH3OH (5), are neutral and trinuclear with two [Mn(SB)]+ (SB2- = Schiff base ligands) and one [Fe(1-CH3im)(CN)5]2-. Complex {[Et4N][Mn(acacen)Fe(CN)5(1-CH3im)]}n x 6nH2O (6) is one-dimensional with alternate [Mn(acacen)]+ and [Fe(CN)5(1-CH3im)]2- units. The two-dimensional complex {[Mn4(saltmen)4Fe(CN)5(1-CH3im)]}n[ClO4]2n x 9nH2O (7) consists of Mn4Fe units which are further connected by the phenoxo oxygen atoms. Magnetic studies show the presence of ferromagnetic Mn(III)-Fe(III) coupling in the trinuclear compounds with the magnetic coupling constant (J) ranging from 4.5 to 6.0 cm-1, based on the Hamiltonian H = -2JSFe(SMn(1) + SMn(2)). Antiferromagnetic interaction has been observed in complex 6, whereas ferromagnetic coupling occurs in complex 7. Complexes 6 and 7 exhibit long-range magnetic ordering with a TN value of 4.0 K for 6 and Tc of 4.8 K for 7. Complex 6 shows metamagnetic behavior at 2 K, and complex 7 possesses a hysteresis loop with a coercive field of 500 Oe, typical of a soft ferromagnet.     

希土取代苯基化合物的合成

1970年Hart等利用苯基锂的乙醚溶液与希土氯化物的四氢呋喃悬浮液反应,首次合成了希土苯基化合物(C_6H_5)_3Ln(Ln=Sc、Y),LiLn(C_6H_5)_4(Ln=La、Pr),但没有得到满意的碳氢分析数据,碳的实测值仅为计算值的三分之二左右。其他希土苯基化合物的合成也有报道。为了进一步探索希土芳基化合物的合成方法,希土和芳基之间成键的可能性,我们使用邻甲氧基苯基锂和对甲基苯基锂与希土氯化物反应,试图合成新的希土取代苯基化合物。     

Effect of peripheral donor substituents on the binding modes of phosphinomethanide ligands. Synthesis and crystal structures of alkali metal derivatives of an O-functionalised phosphinomethanide ligand

The O-functionalised tertiary phosphine {(Me3Si)2CH}P(C6H4-2-CH2OMe)2 (9) is accessible via the reaction of {(Me3Si)2CH}PCl2 with two equivalents of in situ generated 2-LiC6H4CH2OMe. Phosphine 9 is readily deprotonated by Bu(n)Li to give the lithium phosphinomethanide [[{(Me3Si)2C}P(C6H4-2-CH2OMe)2]Li] (13), which undergoes metathesis reactions with the alkoxides MOR [M = Na, K, R = Bu(t); M = Rb, R = 2-ethylhexyl] to give the heavier alkali metal phosphinomethanides [[{(Me3Si)2C}P(C6H4-2-CH2OMe)2]M]n in good yields [M = Na (14), n= 2; M = K (15), Rb (16), n=[infinity]]. Compounds 9, [{(Me3Si)2CH}P(C6H4-2-CH2OMe)2LiBr]2 (10), and 14-16 have been studied by X-ray crystallography; in the solid state 14 adopts a dimeric structure, whereas 15 and 16 crystallise as one-dimensional polymers.     

Enantioselective self-assembly of bimetallic [Mn(II) (delta)-Cr(III)(C2O4)3]- and [Mn(II) (lambda)-Cr(III)(C2O4)3]- layered anionic networks templated by the optically active (Rp)- and (Sp)-[1-CH2N(n-C3H7)3-2-CH3-C5H3Fe-C5H5]+ ions

The ferrocenic ammonium (Rp)- and (Sp)-[1-CH2NR(3-)-2-CH3-C5H3Fe-C5H5] iodide salts with R=CH3, C2H5, n-C3H7, n-C4H9, were synthesized starting from the (Rp)- and (Sp)-[1-CH2N(CH3)2-2-CH3-C5H3Fe-C5H5] amines obtained in their optically active forms through asymmetric cyclopalladation of [C5H5Fe-C5H4CH2N(CH3)2]. 1H NMR studies of these planar chiral 1,2-disubstituted ferrocenic ammonium iodide salts in the presence of the (Delta)-(tris(tetrachlorobenzenediolato)phosphate(V) anion), [(Delta)-Trisphat] support the formation of specific diastereomeric ion pairs. Such intermolecular interactions can be related to the self-assembly of the two-dimensional optically active compounds [[(Sp)-1-CH2N(n-C3H7)3-2-CH3-C5H3Fe-C5H5][Mn (Delta)-Cr(C2O4)3]] and [[(Rp)-1-CH2N(n-C3H7)3-2-CH3-C5H3Fe-C5H5][Mn (Lambda)-Cr(C2O4)3]] starting from the resolved (Rp)- and (Sp)-[1-CH2N(n-C3H7)3-2-CH3-C5H3Fe-C5H5]+ ion associated to the racemic anionic building block rac-[Cr(C2O4)3]3- and Mn2+. Both enantiomeric forms of the networks behave as ferromagnets with a Curie temperature of 5.7 K.     

Potential energy surface for activation of methane by Pt(+): a combined guided ion beam and DFT study

A guided-ion beam tandem mass spectrometer is used to study the reactions of Pt(+) with methane, PtCH(2)(+) with H(2) and D(2), and collision-induced dissociation of PtCH(4)(+) and PtCH(2)(+) with Xe. These studies experimentally probe the potential energy surface for the activation of methane by Pt(+). For the reaction of Pt(+) with methane, dehydrogenation to form PtCH(2)(+) + H(2) is exothermic, efficient, and the only process observed at low energies. PtH(+), formed in a simple C-H bond cleavage, dominates the product spectrum at high energies. The observation of a PtH(2)(+) product provides evidence that methane activation proceeds via a (H)(2)PtCH(2)(+) intermediate. Modeling of the endothermic reaction cross sections yields the 0 K bond dissociation energies in eV (kJ/mol) of D(0)(Pt(+)-H) = 2.81 +/- 0.05 (271 +/- 5), D(0)(Pt(+)-2H) = 6.00 +/- 0.12 (579 +/- 12), D(0)(Pt(+)-C) = 5.43 +/- 0.05 (524 +/- 5), D(0)(Pt(+)-CH) = 5.56 +/- 0.10 (536 +/- 10), and D(0)(Pt(+)-CH(3)) = 2.67 +/- 0.08 (258 +/- 8). D(0)(Pt(+)-CH(2)) = 4.80 +/- 0.03 eV (463 +/- 3 kJ/mol) is determined by measuring the forward and reverse reaction rates for Pt(+) + CH(4) right harpoon over left harpoon PtCH(2)(+) + H(2) at thermal energy. We find extensive hydrogen scrambling in the reaction of PtCH(2)(+) with D(2). Collision-induced dissociation (CID) of PtCH(4)(+), identified as the H-Pt(+)-CH(3) intermediate, with Xe reveals a bond energy of 1.77 +/- 0.08 eV (171 +/- 8 kJ/mol) relative to Pt(+) + CH(4). The experimental thermochemistry is favorably compared with density functional theory calculations (B3LYP using several basis sets), which also establish the electronic structures of these species and provide insight into the reaction mechanism. Results for the reaction of Pt(+) with methane are compared with those for the analogous palladium system and the differences in reactivity and mechanism are discussed.     

Asymmetric allylic amination in water catalyzed by an amphiphilic resin-supported chiral palladium complex

[reaction: see text] Catalytic asymmetric allylic amination of cycloalkenyl carbonates (methyl cyclohexen-2-yl carbonate, methyl cyclohepten-2-yl carbonate, methyl 5-methoxycarbonylcyclohexen-2-yl carbonate, methyl cyclohexenyl carbonate, tert-butyl 5-methoxycarbonyloxy-1,2,5,6-tetrahydropyridinedicarboxylate) with dibenzylamines ((C6H5CH2)2NH, (C6H5CH2)(4-CH3OC6H4CH2)NH, (4-CH3OC6H4CH2)2NH) was achieved in water under heterogeneous conditions by use of a palladium complex of (3R,9aS)-3-[2-(diphenylphosphino)phenyl]-2-phenyltetrahydro-1H-imidazo[1,5-a]indole-1-one anchored on polystyrene-poly(ethylene glycol) copolymer resin to give the corresponding cycloalkenylamines with high enantiomeric selectivity (90-98% ee).     

Aluminum compounds containing eta1- and/or eta5-bidentate dianionic pyrrolyl-methylamide ligands

A series of dialuminum compounds have been synthesized and their reactivity and application for lactide polymerization have been studied. The reaction of AlH3 x NMe3 with [C4H3NH(2-CH2NHtBu)] in diethyl ether generated a dimeric aluminum hydride compound, [[[C4H3N(2-CH2NtBu)]AlH]2] (1). The structure of 1 was confirmed by spectroscopy of a deuterated analogue of 1 with an Al--D function. Direct treatment of [C4H3NH(2-CH2NHtBu)] with LiAlH4 in diethyl ether resulted in colorless crystals of [[Li[micro-eta1:eta5-C4H3N(2-CH2NtBu)]2Al]2] (2) in 80 % yield after recrystallization from a toluene solution. The micro-eta1:eta5-pyrrolyl protons exhibit high-field shifts at delta=5.73, 6.15, and 6.72 comparable to a similar eta5-bonding mode in the literature. Treatment of 1 with 1 equiv acetone oxime or acetone in dichloromethane gave [[[C4H3N(2-CH2NtBu)]Al[varkappaO,varkappaN-(ON==CMe2)]]2] (3) and [[[C4H3N(2-CH2NtBu)]Al(O--CHMe2)]2] (4) in 67 % and 60 % yield, respectively. Compounds 1-4 have been characterized by X-ray diffractometry and were used as catalysts for epsilon-caprolactone polymerization.     

Unusual ligand transformations initiated by dppm deprotonation in methylene-bridged Rh/Os complexes

The reaction of [RhOs(CO)(3)(μ-CH(2))(dppm)(2)][CF(3)SO(3)] (dppm = μ-Ph(2)PCH(2)PPh(2)) with 1,3,4,5-tetramethylimidazol-2-ylidene (IMe(4)) results in competing substitution of the Rh-bound carbonyl by IMe(4) and dppm deprotonation by IMe(4) to give the two products [RhOs(IMe(4))(CO)(2)(μ-CH(2))(dppm)(2)][CF(3)SO(3)] and [RhOs(CO)(3)(μ-CH(2))(μ-κ(1):η(2)-dppm-H)(dppm)] [3; dppm-H = bis(diphenylphosphino)methanide], respectively. In the latter product, the dppm-H group is P-bound to Os while bound to Rh by the other PPh(2) group and the adjacent methanide C. The reaction of the tetracarbonyl species [RhOs(CO)(4)(μ-CH(2))(dppm)(2)][CF(3)SO(3)] with IMe(4) results in the exclusive deprotonation of a dppm ligand to give [RhOs(CO)(4)(μ-CH(2))(μ-κ(1):κ(1)-dppm-H)(dppm)] (4) in which dppm-H is P-bound to both metals. Both deprotonated products are cleanly prepared by the reaction of their respective precursors with potassium bis(trimethylsilyl)amide. Reversible conversion of the μ-κ(1):η(2)-dppm-H complex to the μ-κ(1):κ(1)-dppm-H complex is achieved by the addition or removal of CO, respectively. In the absence of CO, compound 3 slowly converts in solution to [RhOs(CO)(3)(μ-κ(1):κ(1):κ(1)-Ph(2)PCHPPh(2)CH(2))(dppm)] (5) as a result of dissociation of the Rh-bound PPh(2) moiety of the dppm-H group and its attack at the bridging CH(2) group. Compound 4 is also unstable, yielding the ketenyl- and ketenylidene/hydride tautomers [RhOs(CO)(3)(μ-κ(1):η(2)-CHCO)(dppm)(2)] (6a) and [RhOs(H)(CO)(3)(μ-κ(1):κ(1)-CCO)(dppm)(2)] (6b), initiated by proton transfer from μ-CH(2) to dppm-H. Slow conversion of these tautomers to a pair of isomers of [RhOs(H)(CO)(3)(μ-κ(1):κ(1):κ(1)-Ph(2)PCH(COCH)PPh(2))(dppm)] (7a and 7b) subsequently occurs in which proton transfer from a dppm group to the ketenylidene fragment gives rise to coupling of the resulting dppm-H methanide C and the ketenyl unit. Attempts to couple the ketenyl- or ketenylidene-bridged fragments in 6a/6b with dimethyl acetylenedicarboxylate (DMAD) yield [RhOs(κ(1)-CHCO)(CO)(3)(μ-DMAD)(dppm)(2)], in which the ketenyl group is terminally bound to Os.     

Synthetic and structural studies of monocyclopentadienyl cyclometalated aryl tantalum(V) compounds

Cyclometalated aryl tetra- or trichlorido cyclopentadienyl tantalum complexes [TaXCl(3){C(6)H(4)(2-CH(2)NMe(2))-κ(2)C,N}] (X = Cl 1, η(5)-C(5)H(5)2, η(5)-C(5)H(4)(SiMe(3)) 3, η(5)-C(5)Me(5)4) containing a five-membered TaC(3)N chelate ring were synthesized by reaction of the TaXCl(4) (X = Cl, η(5)-C(5)H(5), η(5)-C(5)H(4)(SiMe(3)), η(5)-C(5)Me(5)) with the appropriate lithium aryl reagent [Li{C(6)H(4)(2-CH(2)NMe(2))}]. The reported complexes were studied by IR and NMR spectroscopy and the X-ray molecular structures of compounds 2, 3 and 4 were determined by diffraction methods. These compounds were theoretically analyzed by the DFT method and their structures were rationalized. The preferential coordination of the 2-{(dimethylamino)methyl}phenyl ligand was justified by an analysis of the molecular orbitals of the Ta(η(5)-C(5)H(5))Cl(3) and C(6)H(4)(2-CH(2)NMe(2)) fragments. In addition, the exchange pathways that account for the NMR equivalency of the Me(2)N- methyl groups and -CH(2)- hydrogen atoms of the coordinated C(6)H(4)(2-CH(2)NMe(2))-κ(2)C,N ligand were theoretically studied.     

Synthesis of a chelating hexadentate ligand with a P3N3 donor set. Crystal and molecular structure of [OC-6-22]-[Co{(RP*,RP*,RP*)-CH3C(CH2PPhC6H4NH2-2)3}](PF6)3

The first structurally authenticated example of a hexadentate chelating tertiary phosphine in which all six donors are bound to a single metal centre is described. The multidentate ligand (RP*,RP*,RP*)- and (RP*,RP*,SP*)-CH3C(CH2PPhC6H4NH2-2)3 has been prepared in 80% yield via the reaction of five equivalents of sodium (2-aminophenyl)phenylphosphide (generated in situ from (2-aminophenyl)phenylphosphine and sodium in thf) with 1,1,1-tri(bromomethyl)ethane in thf. The diastereomeric mixture has been complexed to cobalt(III) and the resulting pair of complexes, viz. [Co{(RP*,RP*,RP*)-CH3C(CH2PPhC6H4NH2-2)3}]Cl3 and [CoCl{(RP*,RP*,SP*)-CH3C(CH2PPhC6H4NH2-2)3}]Cl2, separated by ion exchange chromatography. The structure of the former (as the corresponding hexafluorophosphate salt) has been confirmed by X-ray crystallography and clearly shows all six donors of the P3N3 ligand coordinated to a single cobalt(III) centre. The related hexadentate ligand with internal N donors and terminal diphenylphosphino groups, viz. CH3C(CH2NHC6H4PPh2-2)3, has also been synthesised, albeit in low yield, via the reaction of [Li(tmeda)][2-NHC6H4PPh2] (generated in situ from (2-aminophenyl)diphenylphosphine, n-butyllithium and tmeda in diethyl ether) with 1,1,1-tri(iodomethyl)ethane in thf. No formation of a P3N3 ligand has been observed when either Na[2-PPhC6H4NH2] or [Li(tmeda)][2-NHC6H4PPh2] is reacted with the related tripodal substrate 1,1,1-tris(tolyl-4-sulfonyloxymethyl)ethane in thf. Rather the P-methyloxetane (+/-)-[3-{(2-aminophenyl)phenylphosphinomethyl}]-3-methyloxetane and the sulfonamide 2-(4-CH3C6H4SO2)NHC6H4PPh2 and the corresponding N-methyloxetane [3-{(2-diphenylphosphinophenyl)aminomethyl}]-3-methyloxetane have been isolated from the respective reactions. The structure of the sulfonamide has been confirmed by an X-ray analysis of the platinum(II) complex trans-[PtCl(CH3){2-PPh2C6H4NH(SO2C6H4CH(3-4)}2].     

Cooperative metal-boron interactions in the reaction of nido-1,2-(Cp*RuH)2B3H7, Cp* = eta5-C5Me5, with HC(triple bond)CPh

Products of the reaction of nido-1,2-(CpRuH)(2)B(3)H(7), 1, and phenylacetylene demonstrate the ways in which cluster metal and main group fragments can combine with an alkyne. Observed at 22 degrees C are (a) reduction to mu-alkylidene Ru-B bridges (isomers nido-1,2-(CpRu)(2)(1,5-mu-C{Ph}Me)B(3)H(7), 2, and nido-1,2-(CpRu)(2)(1,5-mu-C{CH(2)Ph}H)B(3)H(7), 3), (b) reduction to exo-cluster alkyl substituents on boron (nido-1,2-(CpRuH)(2)-3-CH(2)CH(2)Ph-B(3)H(6), 4), (c) cluster insertion with extrusion of a BH(2) fragment into an exo-cluster bridge (nido-1,2-(CpRu)(2)(mu-H)(mu-BH(2))-4-or-5-Ph-4,5-C(2)B(2)H(5), 5), (d) combined insertion with BH(2) extrusion and reduction (nido-1,2-(CpRu)(2)(mu-H)(mu-BH(2))-3-CH(2)CH(2)Ph-5-Ph-4,5-C(2)B(2)H(4), 6), (e) insertion and loss of borane with and without reduction (nido-1,2-(CpRu)(2)-5-Ph-4,5-C(2)B(2)H(7), 7, and isomers nido-1,2-(CpRu)(2)-3-CH(2)CH(2)Ph-4-(and-5-)Ph-C(2)B(2)H(6), 8 and 9), and (f) insertion and borane loss plus reduction (nido-1,2-(CpRu)(2)-3-(trans-CH=CHPh)-5-Ph-4,5-C(2)B(2)H(6), 10). Along with 7, 8, and 10, the reaction at 90 degrees C generates products of insertion and nido- to closo-cluster closure (closo-4-Ph-1,2-(CpRuH)(2)-4,6-C(2)B(2)H(3), 11, closo-1,2-(CpRuH)(2)-3-CH(2)CH(2)Ph-5-Ph-7-CH(2)CH(2)Ph-4,5-C(2)B(3)H(2), 12, closo-1,2-(CpRuH)(2)-5-Ph-4,5-C(2)B(3)H(4), 13, and isomers closo-1,2-(CpRuH)(2)-3-and-7-CH(2)CH(2)Ph-5-Ph-4,5-C(2)B(3)H(3), 14 and 15). The clusters with an exo-cluster bridging BH(2) groups are shown to be intermediates by demonstrating that the major products 5 and 6 rearrange to 13 and convert to 14, respectively. 14 then isomerizes to 15, thus connecting low- and high-temperature products. Finally, all available information shows that the high reactivity of 1 with alkynes can be associated with the "extra" two Ru-H hydrides on the framework of 1 which are required to meet the nido-cluster electron count.     

Protonation of a lanthanum phosphide-alkyl occurs at the P-La not the C-La bond: isolation of a cationic lanthanum alkyl complex

Protonation of the heteroleptic, cyclometalated lanthanum phosphide complex [((Me3Si)2CH)(C6H4-2-CH2NMe2)P]La(THF)[P(C6H4-2-CH2NMe2)(CH(SiMe3)(SiMe2CH2))] with [Et3NH][BPh4] yields the cationic alkyllanthanum complex [(THF)4La[P(C6H4-2-CH2NMe2)(CH(SiMe3)(SiMe2CH2))]][BPh4].     

Solvent effects in thermodynamically controlled multicomponent nanocage syntheses

The solvent effects on the condensation reaction between tetraformylcavitand 2 and ethylene-1,2-diamine 3 are reported. Earlier, it was found that the trifluoroacetic acid-catalyzed condensation of 2 and 2 equiv of 3 in CHCl(3) provides in 82% yield an octahedral nanocage 1 composed of 6 cavitands that are linked together by 12 -CH=N-CH(2)CH(2)-N=CH- linker groups (Liu, X.; Liu, Y.; Li, G.; Warmuth, R. Angew. Chem., Int. Ed. 2006, 45, 901). In tetrahydrofuran, the same reactants yield a tetrameric nanocage 4 (35% yield), which resembles a distorted tetrahedron built up from four cavitands that occupy the apexes. Each cavitand is doubly linked to one other cavitand and singly linked to the other two cavitands via -CH=N-CH(2)CH(2)N=CH- connectors. In CH(2)Cl(2), the reaction between 8 2 and 16 3 yields a square antiprismatic nanocage 5 (65% yield), in which each cavitand occupies one of the eight corners and is connected to four neighboring cavitands via -CH=N-CH(2)CH(2)-N=CH- linkers. Nanocage 5 is also the main product in CH(2)ClCH(2)Cl (26% yield) and CHCl(2)CHCl(2) (33% yield). Reduction of all imine bonds in 4 and 5 yields polyaminonanocontainers 7 and 8, respectively, which were isolated as trifluoroacetate salts. Contrary to the formation of larger capsules composed of four, six, or eight cavitands in the reaction between 2 and 3, the acid-catalyzed reaction of 2 with 2 equiv of H(2)N-X-NH(2) (X = (CH(2))(n)(=3,4,5), 1,3-C(6)H(4), 1,4-(CH(2))(2)C(6)H(4), or 1,3-(CH(2))(2)C(6)H(4)) quantitatively yields octaiminohemicarcerands 9-14, in which two cavitands are connected with four -CH=N-X-N=CH- linkers. The outcomes of these condensation reactions are rationalized with the different diamine structures and the relative orientation of cavitands in 1, 4, 5, and 9-14.     

Energetics and mechanisms of C-H bond activation by a doubly charged metal ion: guided ion beam and theoretical studies of Ta2+ + CH4

A guided ion beam tandem mass spectrometer is used to study the kinetic-energy dependence of doubly charged atomic tantalum cations (Ta(2+)) reacting with CH4 and CD4. As for the analogous singly charged system, the dehydrogenation reaction to form TaCH2(2+) + H2 is exothermic. The charge-transfer reaction to form Ta(+) + CH4(+) and the charge-separation reaction to form TaH(+) + CH3(+) are also observed at low energies in exothermic processes, as is a secondary reaction of TaCH2(2+) to form TaCH3(+) + CH3(+). At higher energies, other doubly charged products, TaC(2+) and TaCH3(2+), are observed, although no formation of TaH(2+) was observed. Modeling of the endothermic cross sections provides 0 K bond dissociation energies (in electronvolts) of D0(Ta(2+)-C) = 5.42 +/- 0.19 and D0(Ta(2+)-CH3) = 3.40 +/- 0.16. These experimental bond energies are in poor agreement with density functional calculations at the B3LYP/HW+/6-311++G(3df,3p) level of theory. However, the Ta(2+)-C bond energy is in good agreement with calculations at the QCISD(T) level of theory, and the Ta(2+)-CH3 bond energy is in good agreement with density functional calculations at the BHLYP level of theory. Theoretical calculations reveal the geometric and electronic structures of all product ions and are used to map the potential energy surface, which describes the mechanism of the reaction and key intermediates. Both experimental and theoretical results suggest that TaH(+), TaCH2(2+), and TaCH3(2+) are formed through a H-Ta(2+)-CH3 intermediate.