Generation of cationic [Zr-[tert-butyl enolate]] reactive species: methyl abstraction versus hydride abstraction

Treatment of the neutral methyl-Zr-enolate [Cp(2)Zr(Me)[O(tBuO)C=CMe(2)]] (1) with one equivalent of B(C(6)F(5))(3) or [HNMe(2)Ph][B(C(6)F(5))(4)] as a methyl abstractor in THF at 0 degrees C leads to the selective formation of the free ion pair complex [Cp(2)Zr(THF)[O(tBuO)C=CMe(2)]](+) [anion](-) (2) (anion=MeB(C(6)F(5))(3) (-), B(C(6)F(5))(4) (-)), which is relevant to the controlled polymerization of methacrylates. Cation 2 rapidly decomposes at 20 degrees C in THF with release of one equivalent of isobutene to form the cationic Zr-carboxylate species [Cp(2)Zr(THF)(O(2)CiPr)](+) (3), through a proposed intramolecular proton transfer process from the tert-butoxy group to the enolate. The reaction of 1 with one equivalent of B(C(6)F(5))(3) or [HNMe(2)Ph][B(C(6)F(5))(4)] in CH(2)Cl(2) leads to the direct, rapid formation of the dimeric micro-isobutyrato-Zr dicationic species [[Cp(2)Zr[micro-(O(2)CiPr)]](2)](2+) (4), which gives 3 upon dissolution in THF. Contrastingly, when [Ph(3)C][B(C(6)F(5))(4)] is used to generate the cationic Zr-enolate species from 1 in CD(2)Cl(2), a 15:85 mixture of dicationic complexes 4 and [[Cp(2)Zr[micro-(O(2)C-C(Me)=CH(2))]](2)](2+)[B(C(6)F(5))(4)]]2-(5-[B(C(6)F(5))(4)](2)) is obtained quantitatively. The formation of 5 is proposed to arise from initial hydride abstraction from a methyl enolate group by Ph(3)C(+), as supported by the parallel production of Ph(3)CH, and subsequent elimination of methane and isobutene. In addition to standard spectroscopic and analytical characterizations for the isolated complexes 2-5, complexes 4 and 5 have also been structurally characterized by X-ray diffraction studies.     

Chiral fluorous dialkoxy-diamino zirconium complexes: synthesis and use in stereospecific polymerization of 1-hexene

New catalysts for the isospecific polymerization of 1-hexene based on cationic zirconium complexes incorporating the tetradentate fluorous dialkoxy-diamino ligands [OC(CF(3))(2)CH(2)N(Me)(CH(2))(2)N(Me)CH(2)C(CF(3))(2)O](2-) [(ON(2)NO)(2-)] and [OC(CF(3))(2)CH(2)N(Me)(1R,2R-C(6)H(10))N(Me)CH(2)C(CF(3))(2)O](2-) [(ON(Cy)NO)(2-)] have been developed. The chiral fluorous diamino-diol [(ON(Cy)NO)H(2), 2] was prepared by ring-opening of the fluorinated oxirane (CF(3))(2)COCH(2) with (R,R)-N,N'-dimethyl-1,2-cyclohexanediamine. Proligand 2 reacts cleanly with [Zr(CH(2)Ph)(4)] and [Ti(OiPr)(4)] precursors to give the corresponding dialkoxy complexes [Zr(CH(2)Ph)(2)(ON(Cy)NO)] (3) and [Ti(OiPr)(2)(ON(Cy)NO)] (4), respectively. An X-ray diffraction study revealed that 3 crystallizes as a 1:1 mixture of two diastereomers (Lambda-3 and Delta-3), both of which adopt a distorted octahedral structure with trans-O, cis-N, and cis-CH(2)Ph ligands. The two diastereomers Lambda-3 and Delta-3 adopt a C(2)-symmetric structure in toluene solution, as established by NMR spectroscopy. Cationic complexes [Zr(CH(2)Ph)(ON(2)NO)(THF)(n)](+) (n=0, anion=[B(C(6)F(5))(4)](-), 5; n=1, anion=[PhCH(2)B(C(6)F(5))(3)](-), 6) and [Zr(CH(2)Ph)(ON(Cy)NO)(THF)](+)[PhCH(2)B(C(6)F(5))(3)](-) (7) were generated from the neutral parent precursors [Zr(CH(2)Ph)(2)(ON(2)NO)] (H) and [Zr(CH(2)Ph)(2)(ON(Cy)NO)] (3), and their possible structures were determined on the basis of (1)H, (19)F, and (13)C NMR spectroscopy and DFT methods. The neutral zirconium complexes H and 3 (Lambda-3/Delta-3 mixture), when activated with B(C(6)F(5))(3) or [Ph(3)C](+)[B(C(6)F(5))(4)](-), catalyze the polymerization of 1-hexene with overall activities of up to 4500 kg PH mol Zr(-1) h(-1), to yield isotactic-enriched (up to 74 % mmmm) polymers with low-to-moderate molecular weights (M(w)=4800-47 200) and monodisperse molecular-weight distributions (M(w)/M(n)=1.17-1.79).     

New titanium and zirconium complexes with M-NH2 bonds formed by facile deprotonation of H3N.B(C6F5)3

Facile deprotonation of H3N.B(C6F5)3 with [M(NMe2)4](M = Zr or Ti) yields the novel amidoborate complexes [Zr(NMe2)3{NH2B(C6F5)3}(HNMe2)] and [Ti(NMe2)3{NH2B(C6F5)3}].     

NOE and PGSE NMR spectroscopic studies of solution structure and aggregation in metallocenium ion-pairs

The solution structures of the metallocenium homogeneous polymerization catalyst ion-pairs [Cp(2)ZrMe](+)[MeB(C(6)F(5))(3)](-) (1), [(1,2-Me(2)Cp)(2)ZrMe](+)[MeB(C(6)F(5))(3)](-) (2), [(Me(2)SiCp(2))ZrMe](+)[MeB(C(6)F(5))(3)](-) (3), [Me(2)C(Fluorenyl)(Cp)ZrMe](+)[FPBA](-) (FPBA = tris(2,2',2' '-nonafluorobiphenyl)fluoroaluminate) (4), [rac-Et(Indenyl)(2)ZrMe](+)[FPBA](-) (5), [(Me(5)Cp)(2)ThMe](+)[B(C(6)F(5))(4)](-) (6), [(Me(2)SiCp(2))Zr(Me)(THF)](+)[MeB(C(6)F(5))(3)](-) (7), [(Me(2)SiCp(2))Zr(Me)(PPh(3))](+)[MeB(C(6)F(5))(3)](-) (8), [(Me(2)SiCp(2))Zr(Me)(THF)](+)[B(C(6)F(5))(4)](-) (9), [(Me(2)Si(Me(4)Cp)(t-BuN)Zr(Me)(solvent)](+)[B(C(6)F(5))(4)](-) (solvent = benzene, toluene) (10), [(Cp(2)ZrMe)(2)(mu-Me)](+)[MePBB](-) (PBB = tris(2,2',2"-nonafluorobiphenyl)borane) (11), and [(Cp(2)Zr)(2)(mu-CH(2))(mu-Me)](+)[MePBB](-) (12), having the counteranion in the inner (1, 3, 4, 5, and 6) or outer (7, 8, 9, 10, 11, and 12) coordination sphere, have been investigated for the first time in solvents with low relative permittivity such as benzene or toluene by (1)H NOESY and (1)H,(19)F HOESY NMR spectroscopy. It is found that the average interionic solution structures of the inner sphere contact ion-pairs are similar to those in the solid state with the anion B-Me (1, 3) or Al-F (5) vectors oriented toward the free zirconium coordination site. The HOESY spectrum of complex 6 is in agreement with the reported solid-state structure. In contrast, in outer sphere contact ion-pairs 7, 8, 9, and 10, the anion is located far from the Zr-Me(+) moiety and much nearer to the Me(2)Si bridge than in 3. The interionic structure of 8 is concentration-dependent, and for concentrations greater than 2 mM, a loss of structural localization is observed. PGSE NMR measurements as a function of concentration (0.1-5.0 mM) indicate that the tendency to form aggregates of nuclearity higher than simple ion-pairs is dependent on whether the anion is in the inner or outer coordination sphere of the metallocenium cation. Complexes 2, 3, 4, 5, and 6 show no evidence of aggregation up to 5 mM (well above concentrations typically used in catalysis) or at the limit of saturated solutions (complexes 3 and 6), while concentration-dependent behavior is observed for complexes 7, 8, 10, and 11. These outer sphere ion-pairs begin to exhibit significant evidence for ion-quadruples in solutions having concentrations greater than 0.5 mM with the tendency to aggregate being a function of metal ligation and anion structure. Above 2 mM, compound 8 exists as higher aggregates that are probably responsible for the loss of interionic structural specificity.     

Discrete cationic zinc and magnesium complexes for dual organic/organometallic-catalyzed ring-opening polymerization of trimethylene carbonate

We describe herein an original approach for the efficient immortal ring-opening polymerization (iROP) of trimethylene carbonate (TMC) under mild conditions using dual-catalyst systems combining a discrete cationic metal complex with a tertiary amine. A series of new zinc and magnesium cationic complexes of the type [{NNO}M](+) [anion](-) ({NNO}(-) = 2,4-di-tert-butyl-6-{[(2'-dimethylaminoethyl)methylamino]methyl}phenolate; M = Zn, [anion](-) = [B(C(6)F(5))(4)](-) (2), [H(2)N-{B(C(6)F(5))(3)}(2)](-) (3), and [EtB(C(6)F(5))(3)](-) (4); M = Mg, [anion](-) = [H(2)N{B(C(6)F(5))(3)}(2)](-) (7)) have been prepared from the corresponding neutral compounds [{NNO}ZnEt] (1) and [{NNO}-Mg(nBu)] (6). Compounds 2-4 and 7 exist as free ion pairs, as revealed by (1)H, (13)C, (19)F, and (11) B?NMR spectroscopy in THF solution, and an X-ray crystallographic analysis of the bis(THF) adduct of compound 7, 7?(THF)(2). The neutral complexes 1 and 6, in combination with one equivalent or an excess of benzyl alcohol (BnOH), initiate the rapid iROP of TMC, in bulk or in toluene solution, at 45-60?°C (turnover frequency, TOF, up to 25-30,000?mol(TMC)?mol(Zn)?h(-1) for 1 and 220-240,000?mol(TMC)?mol(Mg)?h(-1) for 6), to afford H-PTMC-OBn with controlled macromolecular features. ROP reactions mediated by the cationic systems 2/BnOH and 7/BnOH proceeded much more slowly (TOF up to 500 and 3000?mol(TMC)?mol(Zn or Mg)?h(-1) at 110?°C) than those based on the parent neutral compounds 1/BnOH and 6/BnOH, respectively. Use of original dual organic/organometallic catalyst systems, obtained by adding 0.2-5?equiv of a tertiary amine such as NEt(3) to zinc cationic complexes [{NNO}Zn](+) [anion](-) (2-4), promoted high activities (TOF up to 18,300?mol(TMC)?mol(Zn)?h(-1) at 45?°C) giving H-PTMC-OBn with good control over the M(n) and M(w)/M(n) values. Variation of the nature of the anion in 2-4 did not significantly affect the performance of these catalyst systems. On the other hand, the dual magnesium-based catalyst system 7/NEt(3) proved to be poorly effective.     

Unusual reactivity of tris(pyrazolyl)borate zirconium benzyl complexes

The synthesis and reactivity of [Tp*Zr(CH2Ph)2][B(C6F5)4] (2, Tp* = HB(3,5-Me2pz)3, pz = pyrazolyl) have been explored to probe the possible role of Tp'MR2+ species in group 4 metal Tp'MCl3/MAO olefin polymerization catalysts (Tp' = generic tris(pyrazolyl)borate). The reaction of Tp*Zr(CH2Ph)3 (1) with [Ph3C][B(C6F5)4] in CD2Cl2 at -60 degrees C yields 2. 2 rearranges rapidly to [{(PhCH2)(H)B(mu-Me2pz)2}Zr(eta2-Me2pz)(CH2Ph)][B(C6F5)4] (3) at 0 degrees C. Both 2 and 3 are highly active for ethylene polymerization and alkyne insertion. Reaction of 2 with excess 2-butyne yields the double insertion product [Tp*Zr(CH2Ph)(CMe=CMeCMe=CMeCH2Ph)][B(C6F5)4] (4). Reaction of 3 with excess 2-butyne yields [{(PhCH2)(H)B(mu-Me2pz)2}Zr(Cp*)(eta2-Me2pz)][B(C6F5)4] (6, Cp* = C5Me5) via three successive 2-butyne insertions, intramolecular insertion, chain walking, and beta-Cp* elimination.     

Synthesis, structures, and reactivity of weakly coordinating anions with delocalized borate structure: the assessment of anion effects in metallocene polymerization catalysts.

The formation of adducts of tris(pentafluorophenyl)borane with strongly coordinating anions such as CN(-) and [M(CN)(4)](2)(-) (M = Ni, Pd) is a synthetically facile route to the bulky, very weakly coordinating anions [CN[B(C(6)F(5))(3)](2)](-) and [M[CNB(C(6)F(5))(3)](4)](2-) which are isolated as stable NHMe(2)Ph(+) and CPh(3)(+) salts. The crystal structures of [CPh(3)][CN[B(C(6)F(5))(3)](2)] (1), [CPh(3)][ClB(C(6)F(5))(3)] (2), [NHMe(2)Ph](2)[Ni[CNB(C(6)F(5))(3)](4)].2Me(2)CO (4b.2Me(2)CO), [CPh(3)](2)[Ni[CNB(C(6)F(5))(3)](4)].2CH(2)Cl(2) (4c.2CH(2)Cl(2)), and [CPh(3)](2)[Pd[CNB(C(6)F(5))(3)](4)].2CH(2)Cl(2) (5c.2CH(2)Cl(2)) are reported. The CN stretching frequencies in 4 and 5 are shifted by approximately 110 cm(-1) to higher wavenumbers compared to the parent tetracyano complexes in aqueous solution, although the M-C and C-N distances show no significant change on B(C(6)F(5))(3) coordination. Zirconocene dimethyl complexes L(2)ZrMe(2) [L(2) = Cp(2), SBI = rac-Me(2)Si(Ind)(2)] react with 1, 4c or 5c in benzene solution at 20 degrees C to give the salts of binuclear methyl-bridged cations, [(L(2)ZrMe)(2)(mu-Me)][CN[B(C(6)F(5))(3)](2)] and [(L(2)ZrMe)(2)(mu-Me)](2)[M[CNB(C(6)F(5))(3)](4)]. The reactivity of these species in solution was studied in comparison with the known [[(SBI)ZrMe](2)(mu-Me)][B(C(6)F(5))(4)]. While the latter reacts with excess [CPh(3)][B(C(6)F(5))(4)] in benzene to give the mononuclear ion pair [(SBI)ZrMe(+).B(C(6)F(5))(4)(-)] in a pseudo-first-order reaction, k = 3 x 10(-4) s(-1), [(L(2)ZrMe)(2)(mu-Me)][CN[B(C(6)F(5))(3)](2)] reacts to give a mixture of L(2)ZrMe(mu-Me)B(C(6)F(5))(3) and L(2)ZrMe(mu-NC)B(C(6)F(5))(3). Recrystallization of [Cp' '(2)Zr(mu-Me)(2)AlMe(2)][CN[B(C(6)F(5))(3)](2)] affords Cp' '(2)ZrMe(mu-NC)B(C(6)F(5))(3) 6, the X-ray structure of which is reported. The stability of [(L(2)ZrMe)(2)(mu-Me)](+)X(-) decreases in the order X = [B(C(6)F(5))(4)] > [M[CNB(C(6)F(5))(3)](4)] > [CN[B(C(6)F(5))(3)](2)] and increases strongly with the steric bulk of L(2) = Cp(2) < SBI. Activation of (SBI)ZrMe(2) by 1 in the presence of AlBu(i)(3) gives extremely active ethene polymerization catalysts. Polymerization studies at 1-7 bar monomer pressure suggest that these, and by implication most other highly active ethene polymerization catalysts, are strongly mass-transport limited. By contrast, monitoring propene polymerization activities with the systems (SBI)ZrMe(2)/1/AlBu(i)(3) and CGCTiMe(2)/1/AlBu(i)(3) at 20 degrees C as a function of catalyst concentration demonstrates that in these cases mass-transport limitation is absent up to [metal] approximately 2 x 10(-5) mol L(-1). Propene polymerization activities decrease in the order [CN[B(C(6)F(5))(3)](2)](-) > [B(C(6)F(5))(4)](-) > [M[CNB(C(6)F(5))(3)](4)](2-) > [MeB(C(6)F(5))(3)](-), with differences in activation barriers relative to [CN[B(C(6)F(5))(3)](2)](-) of DeltaDeltaG = 1.1 (B(C(6)F(5))(4)(-)), 4.1 (Ni[CNB(C(6)F(5))(3)](4)(2-)) and 10.7-12.8 kJ mol(-)(1) (MeB(C(6)F(5))(3)(-)). The data suggest that even in the case of very bulky anions with delocalized negative charge the displacement of the anion by the monomer must be involved in the rate-limiting step.     

Bis(allyl)gallium cation, tris(allyl)gallium, and tetrakis(allyl)gallate: synthesis, characterization, and reactivity

A series of cationic, neutral, and anionic allylgallium complexes has been isolated and fully characterized. It includes neutral [Ga(η(1)-C(3)H(5))(3)(L)] (1, L = THF; 2, L = OPPh(3)), cationic [Ga(η(1)-C(3)H(5))(2)(THF)(2)](+)[A](-) (3, [A](-) = [B(C(6)F(5))(4)](-); 4, [A](-) = [B(C(6)H(3)Cl(2))(4)](-)), as well as anionic [Cat](+)[Ga(η(1)-C(3)H(5))(4)](-) (5, [Cat](+) = K(+); 6, [Cat](+) = [K(dibenzo-18-c-6](+); 7, [Cat](+) = [PPh(4)](+)). Binding modes of the allyl ligand in solution and in the solid state have been studied comparatively. Single crystal X-ray analyses revealed a four-coordinate neutral gallium center in 2, a five-coordinate cationic gallium center in 4 and [4·THF], and a four-coordinate anionic gallium center with a bridging μ(2)-η(1):η(2) coordination mode of the allyl ligand in 6. The reactivity of this series of allylgallium complexes toward benzophenone and N-heteroaromatics has been investigated. Counterion effects have also been studied. Reactions of 1 and 5 with isoquinoline revealed the first examples of organogallium complexes reacting under 1,2-insertion with pyridine derivatives.     

Oxygen-bridged borate anions from tris(pentafluorophenyl)borane: synthesis, NMR characterization, and reactivity

The previously known anion [(C6F5)3B(mu-OH)B(C6F5)3]- (2) has been prepared by a two-step procedure, involving deprotonation of (C6F5)3BOH2 to give [B(C6F5)3OH]- (1), followed by addition of B(C6F5)3. The solution structure and the dynamics of 2 have been investigated by 1H and 19F NMR spectroscopy. The reaction of [NHEt3]2 with NEt3 resulted in the formation of [NHEt3]+ [(C6F5)3BOH]-, [NHEt3]+ [(C6F5)3BH]-, and (C6F5)3B- (CH2CH=N+ Et2). This indicates that in the presence of a nucleophile anion 2 can dissociate to B(C6F5)3 and 1. The reaction of [HDMAN]2 with 1,8-bis(dimethylamino)naphthalene (DMAN) confirmed this trend. In the presence of water, 2 transformed into the adduct [(C6F5)3BO(H)H...O(H)B(C6F5)3]- (3), containing the borate 1 hydrogen-bonded to a water molecule coordinated to B(C6F5)3. The same compound is formed by treating (C6F5)3BOH2 with 0.5 equiv of a base. A competition study established that for 1 the Lewis acid-base interaction with B(C6F5)3 is about 5 times preferred over H-bonding to (C6F5)3BOH2. The X-ray single-crystal analysis of [2-methyl-3H-indolium]3 provided the first experimental observation of an asymmetric H-bond in the [H3O2]- moiety, the measured O-H and H...O bond distances being significantly different [1.14(2) vs 1.26(2) A]. The reaction of NEt3 with an equimolar mixture of B(C6F5)3 and bis(pentafluorophenyl)borinic acid, (C6F5)2BOH, afforded the novel borinatoborate salt [NHEt3]+ [(C6F5)3BOB(C6F5)2]- ([NHEt3]4). X-ray diffraction showed that the B-O bond distances are significantly shorter than in [(C6F5)3B(mu-OH)B(C6F5)3]-. Variable-temperature 19F NMR revealed high mobility of the five aryl rings, at variance with the more crowded anion 2. 2D NMR correlation experiments showed that in CD2Cl2 the two anions [(C6F5)3BOH]- and [(C6F5)3BH]- form tight ion pairs with [NHEt3]+, in which the NH proton establishes a conventional (BO...HN) or an unconventional (BH...HN), respectively, hydrogen bond with the anion. The diborate anions 2-4, on the contrary, gave loose ion pairs with the ammonium cation, due both to the delocalized anionic charge and to the more sterically encumbered position of the oxygen atoms that should act as H-bond acceptors.     

Two new borates containing the first examples of large isolated polyborate anions: chain [B7O9(OH)5]2- and ring [B14O20(OH)6]4-

Two novel hydrated borates were synthesized under mild solvothermal conditions. One is hydrated rubidium borate, Rb2B7O9(OH)5, which contains the first example of the isolated chain heptaborate anion, [B7O9(OH)5]2-. The other is hydrated diethylenetriamine borate, [(C4H15N3)]2[B14O20(OH)6], which contains the first example of the largest isolated ring tetradecaborate anion, [B14O20(OH)6]4-.     

(N-pyrrolyl)B(C6F5)2--a new organometallic Lewis acid for the generation of group 4 metallocene cation complexes

Treatment of the (C6F5)2BF x OEt2 (3) complex with N-pyrrolyl lithium gives bis(pentafluorophenyl)(N-pyrrolyl)borane (2), a strong organometallic Lewis acid, which was characterized by X-ray diffraction (B-N bond length: 1.401(5) A). It exhibits a columnar superstructure in the crystal and contains pi-stacks of pyrrolyl units. Compound 2 readily abstracts alkyl anions from a variety of alkyl Group 4 metallocene-type complexes and leads to the clean formation of the respective metallocene ions or ion pairs. For example, the treatment of Cp3ZrCH3 (9) with 2 transfers a methyl anion to yield the ion pair [Cp3Zr]+[(C4H4N)B(CH3)(C6F5)2]- (12). The X-ray crystal structure analysis of 12 shows a close contact between zirconium and the pyrrolyl-beta-carbon (2.641(2) A). The borane 2 adds to (butadiene)zirconocene (13) to yield the betaine system [Cp2Zr]+[(C4H6)B- (NC4H4)(C6F)2]- (15). Complex 15 contains a distorted eta3-allyl moiety inside the metallacyclic framework and it features an internal Zr+...(pyrrolyl)B- ion pair interaction with a Zr...pyrrolyl-alphacarbon separation of 2.723(3) A (determined by X-ray diffraction). From the dynamic NMR spectra of 15 the bond strength of the internal ion pair interaction was estimated to be deltaGdiss (223 K) approximately = to15 kcalmol(-1). Treatment of dimethylzirconocene (16) with 2 yields the metallocene borate salt [Cp2ZrCH3]+[(C4H4N)B(CH3)(C6F5)2]- (17), which is an active catalyst for the polymerization of ethene.     

Mass spectrometric investigation of gallium and zirconium complexes with octaethylporphyrin and tetraphenylporphyrin

Gallium and zirconium octaethylporphyrin (OEP) and tetraphenylporphyrin (TPP) were examined by electrospray ionization (ESI) mass spectrometry. All systems were prepared in dichloromethane with addition of a stabilizing lipophilic anionic agent, sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (NaTFPB). In the solutions examined both monomeric and dimeric metalloporphyrins were observed. In the gallium-OEP mass spectrum the ion registered at m/z 601 was attributed to monomeric [Ga(OEP)](+) and that at m/z 1219 to the dimeric form, [[Ga(OEP)](2)OH](+). Peaks appearing in the ESI mass spectra of zirconium systems were substantially less intense, probably owing to the relatively low stability of complexes of this metal caused by its different geometry preferences. The most abundant monomeric zirconium-OEP complexes were [[Zr(OEP)OH]](+) (m/z 639) and [Zr(OEP)Cl](+) (m/z 657), and dimeric [[Zr(OEP)OH](2)](2+) (m/z 639). Analogous species were observed in the Zr(TPP) system: monomeric [[Zr(OEP)OH]](+) (m/z 719) and [Zr(TPP)Cl](+) (m/z 737) and dimeric [[Zr(TPP)OH](2)](2+) (m/z 719). In both cases series of other dimers, e.g. [[Zr(OEP)](2)O(2)H](+) (m/z 1277), [[Zr(OEP)OH](2)Cl](+) (m/z 1313), [Zr(TPP)(2)O(2)H](+), (m/z 1437), [[Zr(TPP)OH](2)OH](+) (m/z 1455) and [[Zr(TPP)OH](2)Cl](+) (m/z 1473), appeared. The results obtained confirmed the hypothesis concerning the formation of dimeric metalloporphyrins in solutions containing stabilizing lipophilic anions. It also allowed us to explain the super-Nernstian slopes of the calibration curves towards primary anions of ion-selective electrodes with membranes containing the examined metalloporphyrins.     

[HN(C2H5)3][B5O6(OH)4]的合成、结构和热稳定性

利用水热法合成了五硼酸三乙胺[HN(C2H5)3][B5O6(OH)4], 并利用单晶X射线衍射技术解析了其结构, 同时利用傅立叶红外分析、元素分析及热分析技术加以佐证. 该化合物属于单斜晶系, 其空间群为P21/c, 相应的晶胞参数为a=1.0036(2) nm, b=1.1353(2) nm, c=1.4843(3) nm和β=106.54(3)°. 它由孤立的五硼酸阴离子[B5O6(OH)4]-和三乙胺阳离子[HN(C2H5)3]+构成. 五硼酸阴离子[B5O6(OH)4]-通过氢键构成三维网状结构, [HN(C2H5)3]+位于其中的孔道中.     

B(C6F5)3- vs Al(C6F5)3-derived metallocenium ion pairs. Structural, thermochemical, and structural dynamic divergences

The thermodynamic and structural characteristics of Al(C6F(5)3-derived vs B(C6F5)3-derived group 4 metallocenium ion pairs are quantified. Reaction of 1.0 equiv of B(C6F5)3 or 1.0 or 2.0 equiv of Al(C6F5)3 with rac-C2H4(eta5-Ind)2Zr(CH3)2 (rac-(EBI)Zr(CH3)2) yields rac-(EBI)Zr(CH3)(+)H3CB(C6)F5)(3)(-) (1a), rac-(EBI)Zr(CH3)+H3CAl(C6F5)(3)(-) (1b), and rac-(EBI)Zr2+[H3CAl(C6F5)3](-)(2) (1c), respectively. X-ray crystallographic analysis of 1b indicates the H3CAl(C6F5)(3)(-) anion coordinates to the metal center via a bridging methyl in a manner similar to B(C6F5)3-derived metallocenium ion pairs. However, the Zr-(CH3)(bridging) and Al-(CH3)(bridging) bond lengths of 1b (2.505(4) A and 2.026(4) A, respectively) indicate the methyl group is less completely abstracted in 1b than in typical B(C6F5)3-derived ion pairs. Ion pair formation enthalpies (DeltaH(ipf)) determined by isoperibol solution calorimetry in toluene from the neutral precursors are -21.9(6) kcal mol(-1) (1a), -14.0(15) kcal mol(-1) (1b), and -2.1(1) kcal mol(-1) (1b-->1c), indicating Al(C6F5)3 to have significantly less methide affinity than B(C6F5)3. Analogous experiments with Me2Si(eta5-Me4C5)(t-BuN)Ti(CH3)2 indicate a similar trend. Furthermore, kinetic parameters for ion pair epimerization by cocatalyst exchange (ce) and anion exchange (ae), determined by line-broadening in VT NMR spectra over the range 25-75 degrees C, are DeltaH++(ce) = 22(1) kcal mol(-1), DeltaS++(ce) = 8.2(4) eu, DeltaH++(ae) = 14(2) kcal mol(-1), and DeltaS++(ae) = -15(2) eu for 1a. Line broadening for 1b is not detectable until just below the temperature where decomposition becomes significant ( approximately 75-80 degrees C), but estimation of the activation parameters at 72 degrees C gives DeltaH++(ce) approximately 22 kcal mol(-1)and DeltaH++(ae) approximately 16 kcal mol(-1), consistent with the bridging methide being more strongly bound to the zirconocenium center than in 1a.     

Synthesis, characterization, and activity in ethylene polymerization of silica supported cationic cyclopentadienyl zirconium complexes

Cp*ZrMe3 reacts with silica pretreated at 800 degrees C, SiO(2-(800)) through two pathways: (a) protolysis of a Zr-Me group by surface silanols and (b) transfer of a methyl group to the surface by opening of strained siloxane bridges, in a relative proportion of ca. 9/1, respectively, affording a well-defined surface species [([triple bond]SiO)ZrCp*(Me)2], 3, but with two different local environments 3a, [([triple bond]SiO)ZrCp*(Me)2][[triple bond]Si-O-Si[triple bond]], and the other with 3b, [structure: see text]. The reaction of the species 3 with B(C6F5)3 is controlled by this local environment and gives three surface species [([triple bond]SiO)ZrCp*(Me)](+)[MeB(C6F5)3]- [[triple bond]Si-O-Si[triple bond]], 4a (20%), [([triple bond]SiO)ZrCp*(Me)](+)[(Me)B(C6F5)3]- [[triple bond]Si-Me], 4b (10%), and [([triple bond]SiO)2ZrCp*](+)[(Me)B(C6F5)(3)](-)[[triple bond]Si-O-Si[triple bond]], 5 (70%). On the contrary, the reaction of Cp*Zr(Me)3, Cp2Zr(Me)2 with [[triple bond]SiO-B(C6F5)3](-)[HNEt2Ph]+, 6, leads to a unique species [([triple bond]SiO)B(C6F5)3](-)[Cp*Zr(Me)2.NEt2Ph]+, 7, and [([triple bond]SiO)ZrCp2](+)[(Me)B(C6F5)3]-, 9 respectively. The complexes 4 and 7 are active catalysts in ethylene polymerization at room temperature, 93 and 67 kg PE mol Zr1- atm(-1) bar(-1), respectively, indicating that covalently bounded Zr catalyst 4 is slightly more active than the "floating" cationic catalyst 7.     

Synthesis and catalysis of di- and tetranuclear metal sandwich-type silicotungstates [(gamma-SiW10O36)2M2(mu-OH)2]10- and [(gamma-SiW10O36)2M4(mu4-O)(mu-OH)6]8- (M = Zr or Hf)

The di- and tetranuclear metal sandwich-type silicotungstates of Cs10[(gamma-SiW10O36)2{Zr(H2O)}2(mu-OH)2] x 18 H2O (Zr2, monoclinic, C2/c (No. 15), a = 25.3315(8) A, b = 22.6699(7) A, c = 18.5533(6) A, beta = 123.9000(12) degrees, V = 8843.3(5) A(3), Z = 4), Cs10[(gamma-SiW10O36)2{Hf(H2O)}2(mu-OH)2] x 17 H2O (Hf2, monoclinic, space group C2/c (No. 15), a = 25.3847(16) A, b = 22.6121(14) A, c = 18.8703(11) A, beta = 124.046(3) degrees, V = 8974.9(9) A(3), Z = 4), Cs8[(gamma-SiW10O36)2{Zr(H2O)}4(mu4-O)(mu-OH)6] x 26 H2O (Zr4, tetragonal, P4(1)2(1)2 (No. 92), a = 12.67370(10) A, c = 61.6213(8) A, V = 9897.78(17) A(3), Z = 4), and Cs8[(gamma-SiW10O36)2{Hf(H2O)}4(mu4-O)(mu-OH)6] x 23 H2O (Hf4, tetragonal, P4(1)2(1)2 (No. 92), a = 12.68130(10) A, c = 61.5483(9) A, V = 9897.91(18) A(3), Z = 4) were obtained as single crystals suitable for X-ray crystallographic analyses by the reaction of a dilacunary gamma-Keggin silicotungstate K8[gamma-SiW10O36] with ZrOCl2 x 8 H2O or HfOCl2 x 8 H2O. These dimeric polyoxometalates consisted of two [gamma-SiW10O36](8-) units sandwiching metal-oxygen clusters such as [M2(mu-OH)2](6+) and [M4(mu4-O)(mu-OH)6](8+) (M = Zr or Hf). The dinuclear zirconium and hafnium complexes Zr2 and Hf2 were isostructural. The equatorially placed two metal atoms in Zr2 and Hf2 were linked by two mu-OH ligands and each metal was bound to four oxygen atoms of two [gamma-SiW10O36](8-) units. The tertanuclear zirconium and hafnium complexes Zr4 and Hf4 were isostructural and consisted of the adamantanoid cages with a tetracoordinated oxygen atom in the middle, [M4(mu4-O)(mu-OH)6](8+) (M = Zr or Hf). Each metal atom in Zr4 and Hf4 was linked by three mu-OH ligands and bound to two oxygen atoms of the [gamma-SiW10O36](8-) unit. The tetra-nuclear zirconium and hafnium complexes showed catalytic activity for the intramolecular cyclization of (+)-citronellal to isopulegols without formation of byproducts resulting from etherification and dehydration. A lacunary silicotungstate [gamma-SiW10O34(H2O)2](4-) was inactive, and the isomer ratio of isopulegols in the presence of MOCl2 x 8 H2O (M = Zr or Hf) were much different from that in the presence of tetranuclear complexes, suggesting that the [M4(mu4-O)(mu-OH)6](8+) core incorporated into the POM frameworks acts as an active site for the present cyclization. On the other hand, the reaction hardly proceeded in the presence of dinuclear zirconium and hafnium complexes under the same conditions. The much less activity is possibly explained by the steric repulsion from the POM frameworks in the dinuclear complexes.     

Syntheses, structure, and luminescent properties of novel hydrated rare earth borates Ln2B6O10OH4•H2O (Ln = Pr, Nd, Sm, Eu, Gd, Dy, Ho, and Y)

Ln(2)B(6)O(10)(OH)(4)?H(2)O (Ln = Pr, Nd, Sm-Gd, Dy, Ho, and Y), a new series of hydrated rare earth borates, have been synthesized under hydrothermal conditions. A single crystal of Nd analogue was used for the structure determination by X-ray diffraction. It crystallizes in the monoclinic space group C2/c with lattice constants a = 21.756(4), b = 4.3671(9), c = 12.192(2) ?, and β = 108.29(3)°. The other compounds are isostructural to Nd(2)B(6)O(10)(OH)(4)?H(2)O. The fundamental building block (FBB) of the polyborate anion in this structure is a three-membered ring [B(3)O(6)(OH)(2)](5-). The FBBs are connected by sharing oxygen atoms forming an infinite [B(3)O(5)(OH)(2)](3-) chain, and the chains are linked by hydrogen bonds, establishing a two-dimensional (2-D) [B(6)O(10)(OH)(4)?H(2)O](6-) layer. The 2-D borate layers are thus interconnected by Ln(3+) ions to form the complex three-dimensional structure. Ln(2)B(6)O(10)(OH)(4)?H(2)O dehydrates stepwise, giving rise to two new intermediate compounds Ln(2)B(6)O(10)(OH)(4) and Ln(2)B(6)O(11)(OH)(2). The investigation on the luminescent properties of Gd(2-2x)Eu(2x)B(6)O(10)(OH)(4)?H(2)O (x = 0.01-1.00) shows a high efficiency of Eu(3+) f-f transitions and the existence of the energy transfer process from Gd(3+) to Eu(3+). Eu(2)B(6)O(10)(OH)(4)?H(2)O and its two dehydrated products, Eu(2)B(6)O(10)(OH)(4) and Eu(2)B(6)O(11)(OH)(2), present the strongest emission peak at 620 nm ((5)D(0) → (7)F(2) transition), which may be potential red phosphors.     

Discrete and infinite 1D, 2D/3D cage frameworks with inclusion of anionic species and anion-exchange reactions of Ag3L2 type receptor with tetrahedral and octahedral anions

Complexes [PF6 subset(Ag3(titmb)2](PF6)2 (8) and {SbF6 subset[Ag3(titmb)2](SbF6)2}.H2O.1.5 CH3OH (9) are obtained by reaction of titmb and Ag+ salts with different anions (PF6(-) and SbF6(-)), and crystal structures reveal that they are both M3L2 cage complexes with short Ag...F interactions between the silver atoms and the fluorine atoms of the anions. In complex 8, a novel cage dimer is formed by weak Ag...F contacts; an unique cage tetramer formed via Ag...pi interactions (Ag...eta5-imidazole) between dimers and an infinite 1D cage chain is presented. However, each of the external non-disordered SbF6(-) anions connect with six cage 9s via Ag...F contacts, and each cage 9 in turn connects with three SbF6(-) anions to form a 2D network cage layer; and the layers are connected by pi-pi interactions to form a 3D network. The anion-exchange reactions of four Ag3L2 type complexes ([BF4 subset(Ag3(titmb)2](BF4)2 (6), [ClO4 subset(Ag3(titmb)2](ClO4)2 (7b), [PF6 subset(Ag3(titmb)2](PF6)2 (8) and [SbF6 subset(Ag3(titmb)2](SbF6)2.1.5CH3OH (9)) with tetrahedral and octahedral anions (ClO4(-), BF4(-), PF6(-) and SbF6(-)) are also reported. The anion-exchange experiments demonstrate that the anion selective order is SbF6(-) > PF6(-) > BF4(-), ClO4(-), and this anion receptor is preferred to trap octahedral and tetrahedral anions rather than linear or triangle anions; SbF6(-) is the biggest and most preferable one, so far. The dimensions of cage complexes with or without internal anions, anion-exchange reactions, cage assembly and anion inclusions, silver(I) coordination environments, Ag-F and Ag-pi interactions of Ag3L2 complexes 1-9 are discussed.     

Synthesis of the new, weakly coordinating anions [RB(C6F5)3]- (R = CH2Me, CHMe2, CH2CMe3); utilization of [HNMe2Ph][Me3CCH2B(C6F5)3] to activate zirconocene catalysts for propylene polymerization

The compound [HNMe2Ph][NpB(C6F5)3](Np =(CH3)3CCH2) reacts with dimethylzirconocenes to give active propylene polymerization catalysts which are significantly more active and give higher molecular weight polypropylene than do the catalysts obtained using B(C6F5)3; the [NpB(C6F5)3]- anion is for steric reasons more weakly coordinating than is [MeB(C6F5)3]-.     

Coordinate covalent C --> B bonding in phenylborates and latent formation of phenyl anions from phenylboronic Acid

The results are reported of a theoretical study of the addition of small nucleophiles Nu(-) (HO(-), F(-)) to phenylboronic acid Ph-B(OH)(2) and of the stability of the resulting complexes [Ph-B(OH)(2)Nu](-) with regard to Ph-B heterolysis [Ph-B(OH)(2)Nu](-) --> Ph(-) + B(OH)(2)Nu as well as Nu(-)/Ph(-) substitution [Ph-B(OH)(2)Nu](-) + Nu(-) --> Ph(-) + [B(OH)(2)Nu(2)](-). These reactions are of fundamental importance for the Suzuki-Miyaura cross-coupling reaction and many other processes in chemistry and biology that involve phenylboronic acids. The species were characterized by potential energy surface analysis (B3LYP/6-31+G*), examined by electronic structure analysis (B3LYP/6-311++G**), and reaction energies (CCSD/6-311++G**) and solvation energies (PCM and IPCM, B3LYP/6-311++G*) were determined. It is shown that Ph-B bonding in [Ph-B(OH)(2)Nu](-) is coordinate covalent and rather weak (<50 kcal.mol(-1)). The coordinate covalent bonding is large enough to inhibit unimolecular dissociation and bimolecular nucleophile-assisted phenyl anion liberation is slowed greatly by the negative charge on the borate's periphery. The latter is the major reason for the extraordinary differences in the kinetic stabilities of diazonium ions and borates in nucleophilic substitution reactions despite their rather similar coordinate covalent bond strengths.