Adamantane-like aluminum amide-phosphate from alumazene

A dealkylsilylation reaction between alumazene [2,6-(i-Pr)(2)C(6)H(3)NAlMe](3) (1) and tris(trimethylsilyl) ester of phosphoric acid (2) in a 1:3 molar ratio provides the heteroadamantane molecule (MeAl)[2,6-(i-Pr)(2)C(6)H(3)N](3)[Al[OP(OSiMe(3))(3)]](2)(O(3)POSiMe(3)) (3). Compound 3 was characterized by analytical and spectroscopic methods, and its molecular structure was established by a single-crystal X-ray diffraction experiment. Moreover, trialkyl and triaryl phosphates and dialkyl phosphonates react with 1 at elevated temperature to afford an intractable mixture of products. The reaction of phosphonic acids with 1 proceeds under decomposition to yield 2,6-diisopropylaniline and aluminophosphonates.     

Metal versus ligand alkylation in the reactivity of the (bis-iminopyridinato)Fe catalyst

The alkylation of the Brookhart-Gibson {2,6-[2,6-(i-Pr)2PhN=C(CH3)]2(C5H3N)} FeCl2 precatalyst with 2 equiv of LiCH2Si(CH3)3 led to the isolation of several catalytically very active products depending on the reaction conditions. The expected dialkylated species {2,6-[2,6-(i-Pr)2PhN=C(CH3)]2}(C5H3N)Fe(CH2SiMe3)2 (2) was indeed the major component of the reaction mixture. However, other species in which alkylation occurred at the pyridine ring ortho position, {2,6-[2,6-(i-Pr)2PhN=C(CH3)]2-2-CH2SiMe3}(C5H3N)Fe(CH2SiMe3) (1), and at the imine C atom, {2-[2,6-(i-Pr)2PhN=C(CH3)]-6-[2,6-(i-Pr)2PhNC(CH3)(CH2 SiMe3)](C5H3N)}Fe(CH2SiMe3) (3), have also been isolated and fully characterized. In addition, deprotonation of the methyl-imino functions and formation of a new divalent Fe catalyst {[2,6-[2,6-(i-Pr)2PhN-C=(CH2)]2(C5H3N)}Fe(mu-Cl)Li(THF)3 (4) also occurred depending on the reaction conditions. In turn, the formation of 4 might trigger the reductive coupling of two units through the methyl-carbon wings. This process resulted in the one-electron reduction of the metal center, affording a dinuclear Fe(I) alkyl catalyst {[{[2,6-(i-Pr)2C6H5]N=C(CH3)}(C5H3N){[2,6-(i-Pr)26H5]N=CCH2}Fe(CH2SiMe3)]}2 (5). Different from other metal derivatives, complex 5 could not be prepared from the monodeprotonated version of the ligand. Its reaction with a mixture of FeCl2 and RLi afforded instead [{2,6-[2,6-(i-Pr)2PhN-C=(CH2)]2(C5H3N)}FeCH2Si(CH3)3][Li(THF)4] (6) which is also catalytically active. All of these high-spin species have been shown to have high catalytic activity for olefin polymerization, producing polymers of two distinct natures, depending on the formal oxidation state of the metal center.     

Dinitrogen partial reduction by formally zero- and divalent vanadium complexes supported by the bis-iminopyridine system

Reduction of the two trivalent 2,6-{[2,6-(i-Pr)2C6H5]N=C(CH3)}2(C5H3N)VCl3 and {[2,6-{[2,6-(i-Pr)2C6H3]N-C=(CH2)}2(C5H3N)]VCl(THF) complexes with excess NaH afforded two corresponding end-on dinitrogen-bridged complexes [2,6-{[2,6-(i-Pr)2C6H5]N=C(CH3)}2(C5H3N)V]2(m-N2).(hexane) (1) and [{[2,6-{[2,6-(i-Pr)2C6H3]N-C=(CH2)}2(C5H3N)]V]2(m-N2).(hexane) (3). Despite their very close structural similarity, the two species have completely different natures. The first is paramagnetic and may be regarded as generated by the two-electron attack of two formally zerovalent vanadium moieties on the same N2 unit. In the nearly diamagnetic 3 instead, the N2 unit has been reduced by two vanadium atoms, formally divalent. Structural analysis and DFT calculations have indicated that partial reduction of the bridging nitrogen occurred for both complexes while, in the case of 1, substantial metal-to-ligand electron transfer also occurs.     

Dinitrogen activation, partial reduction, and formation of coordinated imide promoted by a chromium diiminepyridine complex

Reduction of {2,6-[2,6-(i-Pr)2PhN=C(CH3)]2(C5H3N)}CrCl (3) with NaH afforded the dinuclear dinitrogen complex {[{2,6-[2,6-(i-Pr)2PhN=C(CH3)]2(C5H3N)}Cr(THF)]2(mu-N2)}.THF (5). Reaction carried in exclusion of dinitrogen afforded instead deprotonation of the ligand with the formation of {2-[2,6-(i-Pr)2PhN=C(CH3)]-6-[2,6-(i-Pr)2PhNC=CH2](C5H3N)}Cr(THF) (4). Further reduction of 5 with NaH yielded a curious dinuclear compound formulated as [{2,6-[2,6-(i-Pr)2PhN=C(CH3)]2(C5H3N)}Cr(THF)][{2-[2,6-(i-Pr)2PhN=C(CH3)]-6-[2,6-(i-Pr)2PhNC=CH2](C5H3N)}Cr(THF)](mu-N2 H)(mu-Na)2 (6) containing two sodium atoms only bound to the dinitrogen unit and the pi systems of the two diiminepyridine ligands. Subsequent reduction with NaH triggered a complex series of events, leading to the formation of a species formulated as {2-[2,6-(i-Pr)2PhN=C(CH3)]-6-[2,6-(i-Pr)2PhNC=CH2](C5H3N)}Cr(mu-NH)][Na(THF)] (7) on the basis of crystallographic, spectroscopic, isotopic labeling, and chemical degradation experiments.     

Alumazene adducts with pyridines: synthesis, structure, and stability studies

Lewis acid-base adducts of the alumazene [2,6-(i-Pr)2C6H3NAlMe]3 (1) with pyridine (py) and 4-dimethylaminopyridine (dmap) were synthesized and structurally characterized: 1(py)2 (2), 1(py)3 (3), 1(dmap)2 (4), and 1(py)(dmap) (5). The bisadducts 2, 4, and 5 form the trans isomers. The trisadduct 3 exhibits an unexpected cis-cis isomer and can be prepared only in the presence of excess py. The planarity of the alumazene ring is lost upon coordination of the Lewis base molecules. A comparison of the Al-N(base) bond distances and pyramidality at Al suggests the higher basicity of dmap. NMR spectroscopy confirms stability to dissociation of the bisadducts in solution while the trisadduct 3 is labile and converts to 2. The thermodynamics of the adduct formation has been investigated experimentally and theoretically. Thermodynamic characteristics of the 1(py)n (n=2, 3) dissociation reactions in the temperature range 25-200 degrees C have been derived from the vapor pressure-temperature dependence measurements by the static tensimetric method. In all experiments, excess py was employed. Quantum chemical computations at the B3LYP/6-31G* level of theory have been performed for the 1(py)n and model complexes [HAlNH]3(py)n (n=1-3). Obtained results indicate that for the gas phase adducts upon increasing the number of py ligands the donor-acceptor Al-N(py) distance increases in accord with decreasing donor-acceptor bond dissociation energies.     

Preparation, characterization, and magnetic behavior of the ln derivatives (ln = nd, la) of a 2,6-diiminepyridine ligand and corresponding dianion

An unprecedented Nd[2,6-[[2,6-(i-Pr)(2)C(6)H(5)]N=C(CH(3))](2)(C(5)H(3)N)]NdI(2)(THF) (1) complex was prepared by oxidizing metallic Nd with I(2) in THF and in the presence of 2,6-[[2,6-(i-Pr)(2)C(6)H(5)]N=C(CH(3))](2)(C(5)H(3)N). The magnetic behavior at variable T clearly indicated that the complex should be regarded as a trivalent Nd atom antiferromagnetically coupled to a radical anion. By using the doubly deprotonated form of the diimino pyridine ligand [[2,6-[[2,6-(i-Pr)(2)C(6)H(5)]N-C=CH(2)](2)(C(5)H(3)N)](2-) (2) the corresponding trivalent complexes [[2,6-[[2,6-(i-Pr)(2)C(6)H(5)]N-C=CH(2)](2)(C(5)H(3)N)]Ln (THF)](mu-Cl)(2)[Li(THF)(2)].0.5 (hexane) [Ln = Nd (3), La (4)] were obtained and characterized. Reduction of these species afforded electron transfer to the ligand system which gave ligand dimerization via C-C bond formation through one of the two ene-amido functions of each molecule. The resulting dinuclear [[([2,6-(i-Pr)(2)C(6)H(5)]N-C=(CH(2)))(C(5)H(3)N)([2,6-(i-Pr)(2)C(6)H(5)]N=CCH(2))]Ln(THF)(2)(mu-Cl)[Li(THF)(3)])(2).2(THF) [Ln = Nd (5), La (6)] were isolated and characterized.     

Cationic Rh complexes with novel spiro tetraarylpentaborate anions prepared from arylboronic acids and aryloxorhodium complexes

Ar-B(OH)2 (1a: Ar = C6H4OMe-4, 1b: Ar = C6H3Me2-2,6) react immediately with Rh(OC6H4Me-4)(PMe3)3 (2) in 5 : 1 molar ratio at room temperature to generate [Rh(PMe3)4]+[B5O6Ar4]- (3a: Ar = C6H4OMe-4, 3b: Ar = C6H3Me2-2,6). p-Cresol (92%/Rh), anisole (80%/Rh) and H2O (364%/Rh) are formed from 1a and 2. The reaction of 1a with 2 for 24 h produces [Rh(PMe3)4]+[B5O6(OH)4]- (4) as a yellow solid. This is attributed to hydrolytic dearylation of once formed 3a because the direct reaction of 3a with excess H2O forms 4. An equimolar reaction of 2 with phenylboroxine (PhBO)3 causes transfer of the 4-methylphenoxo ligand from rhodium to boron to produce [Rh(PMe3)4]+[B3O3Ph3(OC6H4Me-4)]- (5). Arylboronic acids 1a and 1b react with Rh(OC6H4Me-4)(PR3)3 (6: R = Et, 8: R = Ph) and with Rh(OC6H4Me-4)(cod)(PR3) (11: R = iPr, 12: R = Ph) to form [Rh(PR3)4]+[B5O6Ar4]- (7a: R = Et, Ar = C6H4OMe-4, 7b: R = Et, Ar = C6H3Me2-2,6, 9a: R = Ph, Ar = C6H3Me2-2,6) and [Rh(cod)(PR3)(L)]+[B5O6Ar4]- (13b: R = iPr, L = acetone, Ar = C6H3Me2-2,6, 14a: R = Ph, L = PPh3, Ar = C6H4OMe-4, 14b: R = Ph, L = PPh3, Ar = C6H3Me2-2,6), respectively. Hydrolysis of 14a yields [Rh(cod)(PPh3)2]+[B5O6(OH)4]- (15) quantitatively.     

Neodymium monochloride and monoallyl complexes {2-[Ph2P(O)]C6H4NC(But)N(2,6-Me2C6H3)}2NdR (R = Cl,CH2CH=CH2) with the tridentate amidinate ligand in the catalysis of ring-opening polymerization of cyclic esters

Russian Chemical Bulletin - The reaction of tridentate amidine 2-[Ph2P(O)]C6H4NHC(But)=N(2,6-Me2C6H3) (1) containing the side-chain donor group Ph2P=O with NdCl[N(SiMe3)2]2 (2) in a molar ratio...     

Molybdenum-phosphorus triple bond stabilization by ancillary alkoxide ligation: synthesis and structure of a terminal phosphide tris-1-methylcyclohexanoxide complex

Using alcoholysis, we converted terminal phosphide PMo(N[i-Pr]Ar)3 into a new, monomeric terminal phosphide PMo(OR)3, where R = 1-methylcyclohexyl or 1-adamantyl. Dimerization of the PMo unit was observed upon alcoholysis with 2,6-dimethylphenol, and the dimer [PMo(N[i-Pr]Ar)(O-2,6-C6H3Me2)2]2 was isolated and characterized by X-ray crystallography.     

Syntheses and structures of quinuclidine-stabilized amido- and azidogallanes

Quinuclidine-stabilized amido- and azidogallanes, HGa[N(TMS)2]2(quin) (1), H2Ga[N(TMS)2](quin) (2), HGa-[N(H)(2,6-iPr2C6H3)]2(quin) (3), and H2GaN3(quin) (4), were synthesized from the quinuclidine adducts of mono- and dichlorogallane. Structural determinations revealed that all compounds were monomeric with four-coordinate gallium centers. Reactions of the five-coordinate compound, HGaCl2(quin)2, with 2 equiv of Li[N(TMS)2] or Li[N(H)(2,6-iPr2C6H3)] resulted in the isolation of compound 1 or 3. A ligand redistribution during the reaction of H2GaCl(quin) with Li[N(H)(2,6-iPr2C6H3)] produced compound 3 and H3Ga(quin) in a 1:1 molar ratio.     

Neutral and cationic aluminium complexes of a sterically demanding N-imidoylamidine ligand

The N-imidoylamidine ligand i-Pr2C6H3N(C(Me)NC6H3i-Pr2)2 2 was prepared. Direct reactions with AlI3 or AlMe3 afforded [(i-Pr2C6H3N(C(Me)NC6H3i-Pr2)2)AlI2][AlI4] 3 and [i-Pr2C6H3N(C(Me)NC6H3i-Pr2)2)AlMe2][AlMe4].AlMe3, 4 respectively. Thermolysis of 4 gave (i-Pr2C6H3NC(=CH2)(NC6H3i-Pr2)(C(Me)NC6H3i-Pr2)AlMe2 6. Subsequent reaction with B(C6F5)3 gave the zwitterionic species [(i-Pr2C6H3)N(C(=CH2)NC6H3i-Pr2)(C(Me)NC6H3i-Pr2)AlMe(mu-MeB(C6F5)3)] 7. In a related reactions of 2, [Ph3C][B(C6F5)4] and AlMe3, AlH3.NEtMe2 or AlD3.NMe3, the complexes [(i-Pr2C6H3N(C(Me)NC6H3i-Pr2)2)AlR2][B(C6F5)4] (R = Me 5, H 8, D 9) and [(i-Pr2C6H3)N(C(=CH2)NC6H3i-Pr2)(C(Me)NC6H3i-Pr2)AlH][B(C6F5)4] 10 are formed. Single-crystal X-ray data for 2, 3, 5 and 10 are reported.     

Imidomolybdenum(IV) porphyrin complexes: synthesis, characterization, and intermetal imido transfer reactivity

The imido(meso-tetra-p-tolylporphyrinato)molybdenum(IV) complexes, (TTP)Mo=NR, where R = C6H5 (1a), p-CH3C6H4 (1b), 2,4,6-(CH3)3C6H2 (1c), and 2,6-(i-Pr)2C6H4 (1d), can be prepared by the reaction of (TTP)MoCl2 with 2 equiv of LiNHR in toluene. Upon treatment of the imido complexes with pyridine derivatives, NC5H4-p-X (X = CH3, CH(CH3)2, C[triple bond]N), new six-coordinate complexes, (TTP)Mo=NR.NC5H4-p-X, were observed. The reaction between the molybdenum imido complexes, (TTP)Mo=NC6H5 or (TTP)Mo=NC6H4CH3, and (TTP)Ti(eta2-PhC[triple bond]CPh) resulted in complete imido group transfer and two-electron redox of the metal centers to give (TTP)Mo(eta2-PhC[triple bond]CPh) and (TTP)Ti=NC6H5 or (TTP)Ti=NC6H4CH3.     

Dinuclear palladium-azido complexes containing thiophene derivatives: reactivity toward organic isocyanides and isothiocyanates

Cyclopalladated tetranuclear Pd(II) complexes, [Pd2(micro-Cl)2(Y)]2 (Y = L1 or L2; H2L1 = di(2-pyridyl)-2,2'-bithiophene; H2L2 = 5,5'-di(2-pyridyl)-2,2':5',2'-terthiophene), containing two pyridyl-alpha, alpha'-disubstituted derivatives of thiophene were prepared. Treating these products with PR3 and subsequently with NaN3 produced the dinuclear Pd-azido complexes [(PR3)2(N3)Pd-Y-Pd(N3)(PR3)2] (Y = L1 or L2) or a cyclometallated complex [(PR3)(N3)Pd-Y'-Pd(N3)(PR3)] (Y' = C,N-L2). Reactions of these Pd-azido complexes with CN-Ar (Ar = 2,6-Me(2)C(6)H(3), 2,6-i-Pr(2)C(6)H(3)) or R-NCS (R = i-Pr, Et, allyl) led to the complexes containing end-on carbodiimido groups [(PMe3)2(N[double bond]C[double bond]N-Ar)Pd-Y-Pd(N[double bond]C[double bond]N-Ar)(PMe3)2] or S-coordinated tetrazole-thiolato groups {(PMe3)2[CN4(R)]S-Pd-Y-Pd-S[CN4)(R)](PMe3)2}. Interestingly, when treated with elemental sulfur, the carbodiimido complexes transformed into the cyclometallated derivatives, [(PMe3)(N[double bond]C[double bond]N-Ar)Pd-Y'-Pd(N[double bond]C[double bond]N-Ar)(PMe3)] (Y' = C,N-L1, C,N-L2). We also report the preparation of linear, thienylene-bridged dinuclear Pd complexes [L2(N3)Pd-X(or X')-Pd(N3)L2] (L = PMe3 or PMe2Ph; H2X = 2,2'-bithiophene or H2X' = 2,2':5',2'-terthiophene) and their reactivity toward organic isocyanide and isothiocyanates.     

Substituent effects on Ni-S bond dissociation energies and kinetic stability of nickel arylthiolate complexes supported by a bis(phosphinite)-based pincer ligand

Pincer complexes of the type [2,6-(R(2)PO)(2)C(6)H(3)]NiSC(6)H(4)Z (R = Ph and i-Pr; Z = p-OCH(3), p-CH(3), H, p-Cl, and p-CF(3)) have been synthesized from [2,6-(R(2)PO)(2)C(6)H(3)]NiCl and sodium arylthiolate. X-ray structure determinations of these thiolate complexes have shown a somewhat constant Ni-S bond length (approx. 2.20 ?) but an almost unpredictable orientation of the thiolate ligand. Equilibrium constants for various thiolate exchange (between a nickel thiolate complex and a free thiol, or between two different nickel thiolate complexes) reactions have been measured. Evidently, the thiolate ligand with an electron-withdrawing substituent prefers to bond with "[2,6-(Ph(2)PO)(2)C(6)H(3)]Ni" rather than "[2,6-(i-Pr(2)PO)(2)C(6)H(3)]Ni", and bonds least favourably with hydrogen. The reactions of the thiolate complexes with halogenated compounds such as PhCH(2)Br, CH(3)I, CCl(4), and Ph(3)CCl have been examined and several mechanistic pathways have been explored.     

Pyridine N-alkylation by lithium, magnesium, and zinc alkyl reagents: synthetic, structural, and mechanistic studies on the bis(imino)pyridine system

The 2,6-bis(alpha-iminoalkyl)pyridines 2,6-[ArNC(CR(3))](2)C(5)H(3)N [R = H, D; Ar = 2,6-i-Pr(2)C(6)H(3) (DIPP), 2,6-Me(2)C(6)H(3) (DMP)] react with MeLi in Et(2)O to give a binary mixture of products: the pyridine N-methylated species 2,6-[ArNC(CR(3))](2)C(5)H(3)N(Me)Li(OEt(2)) and the deprotonated/dedeuterated species 2-[ArNC(CR(3))],6-[ArNC(=CR(2))]C(5)H(3)NLi(OEt(2)). For R = D, the product ratio is 2:1 in favor of the N-methylated product, while, for R = H, the deprotonated product is favored by 5:1, increasing to 8:1 in toluene solvent. Warming solutions of the N-methylated species leads to clean conversion to the thermodynamically preferred deprotonated species. Crossover experiments show that MeLi is re-formed and dissociates from the terdentate ligand before deprotonating the ketimine methyl unit. For MgR(2) (R = Et, i-Pr) and ZnR(2) (R = Et) reagents, N-alkylation products are formed exclusively, but derivatives containing bulky aryl substituents are found to undergo further rearrangement to 2-alkylated species, arising by migration of the alkyl group of the N-alkyl moiety to the adjacent ring carbon atom. The reversibility of the N-alkylation process has been probed using deuterio-labeled Mg alkyl reagents and mixed alkyl zinc species. A cationic zinc derivative is shown to undergo "reverse" alkyl migration, from the heterocycle nitrogen atom to the zinc center. EPR spectroscopy reveals a paramagnetic intermediate in which the unpaired electron is delocalized over the heterocycle and di-imine moieties of the ligand, indicating that the N-alkylation reactions proceed via single electron-transfer processes.     

Bis(isothiocyanato)bis(phosphine) complexes of group 10 metals: reactivity toward organic isocyanides

Treatment of Ni(NCS)2(PMe2Ph)2 with organic isocyanides CN-R gave five-coordinate isocyanide Ni(II) complexes, Ni(CN-R)(NCS)2(PMe2Ph)2 (R = C6H3-2,6-Me2 (1), t-Bu (2)). Interestingly, the corresponding reaction of Ni(NCS)2(P(n-Pr)3)2 with 2 equiv. of CN-t-Bu gave an unusual compound, which exists as an ion pair of the trigonal bipyramidal cation [Ni(P(n-Pr)3)2(CN-t-Bu)3]2+ (3) and the dinuclear NCS-bridged anion [Ni(1,3-micro-NCS)(NCS)3]2(2-) (4). In contrast, Pd(NCS)2(P(n-Pr)3)2 underwent substitution with 2 equiv. of CN-t-Bu to give the four-coordinate mono(isocyanide) Pd(II) complex Pd(NCS)(SCN)(CN-t-Bu)(P(n-Pr)3) (5) via phosphine dissociation. Reactions of M(NCS)2L2 (M = Pd, Pt; L = PMe3, PEt3, PMePh2, P(n-Pr)3) with two equiv. of CN-R (R = t-Bu, i-Pr, C6H3-2,6-Me2) gave the corresponding bis(isocyanide) complexes [M(CN-R)2(PR3)2](SCN)2 (7-13), except for Pd(NCS)2(PEt3)2 that reacted with CN-R' (R' = i-Pr, C6H3-2,6-Me2) and produced the mono(isocyanide) Pd(II) complexes [Pd(CN-R')(SCN)(PEt3)2](SCN) (14 and 15). Finally, treatment of M(NCS)2(PMe3)2 (M = Ni, Pd, Pt) with sterically bulky isocyanide CN-C6H3-2,6-i-Pr2 gave various products, (16-18) depending on the identity of the metal.     

Al and Zn complexes bearing N,N,N-tridentate quinolinyl anilido-imine ligands: synthesis, characterization and catalysis in l-lactide polymerization

Reactions of N,N,N-tridentate quinolinyl anilido-imine ligands with AlMe(3) afford mononuclear aluminum complexes {κ(3)-[{2-[ArN[double bond, length as m-dash]C(H)]C(6)H(4)}N(8-C(9)H(6)N)]}AlMe(2) (Ar = 2,6-Me(2)C(6)H(3) (1a), 2,6-Et(2)C(6)H(3) (1b), 2,6-(i)Pr(2)C(6)H(3) (1c)) or dinuclear complexes AlMe(3){κ(1)-[{2-[ArN[double bond, length as m-dash]C(H)C(6)H(4)]N(8-C(9)H(6)N)}-κ(2)]AlMe(2) (R = 2,6-Me(2)C(6)H(3) (2a), 2,6-Et(2)C(6)H(3) (2b), 2,6-(i)Pr(2)C(6)H(3) (2c)) depending on the ratios of reactants used. Similar reactions of ZnEt(2) with these ligands give the monoligated ethyl zinc complexes {κ(3)-[{2-[ArN[double bond, length as m-dash]C(H)]C(6)H(4)}N(8-C(9)H(6)N)]}ZnEt (Ar = 2,6-Me(2)C(6)H(3) (3a), 2,6-Et(2)C(6)H(3) (3b), 2,6-(i)Pr(2)C(6)H(3) (3c)) or bisligated complexes {κ(3)-[{2-[ArN[double bond, length as m-dash]C(H)]C(6)H(4)}N(8-C(9)H(6)N)]}Zn{κ(2)-[{2-[ArN[double bond, length as m-dash]C(H)]C(6)H(4)}N(8-C(9)H(6)N)]} (Ar = 2,6-Me(2)C(6)H(3) (4a), 2,6-Et(2)C(6)H(3) (4b), 2,6-(i)Pr(2)C(6)H(3) (4c)). These complexes were well characterized by NMR and the structures of 1a, 2a, 2c, 3b and 4c were confirmed by X-ray diffraction analysis. The aluminum and zinc complexes were tested to initiate lactide polymerization in which the zinc complexes show moderate to high activities in the presence of benzyl alcohol.     

Stabilization of unsolvated europium and ytterbium pentafluorophenyls by pi-bonding encapsulation through a sterically crowded triazenido ligand

The one-pot transmetalation/deprotonation reaction of the bulky triazene Dmp(Tph)N3H with bis(pentafluorophenyl)mercury and europium or ytterbium affords the structurally characterized unsolvated metal(II) pentafluorophenyl triazenides [Dmp(Tph)N3MC6F5] (M = Eu, Yb; Dmp = 2,6-Mes2C6H3 with Mes = 2,4,6-Me3C6H2; Tph = 2-TripC6H4 with Trip = 2,4,6-(i)Pr3C6H2) or, depending on the molar ratio, the solvated complex [Dmp(Tph)N3YbC6F5(THF)].     

Synthesis, reactivity, and structural characterization of sodium and ytterbium complexes containing new imidazolidine-bridged bis(phenolato) ligands

A new imidazolidine-bridged bis(phenol) [ONNO]H2 ([ONNO]H2=1,4-bis(2-hydroxy-3,5-di-tert-butyl-benzyl)imidazolidine) was prepared in relatively high yield by Mannish reaction of 2,4-di-tert-butylphenol, formaldehyde, and ethylenediamine in a 2:3:1 molar ratio. Reaction of the bis(phenol) with NaH in THF, after workup, afforded the sodium bis(phenolate) {[ONNO]Na2(THF)2}2.2THF (1) as a dimeric tetranuclear complex in an almost quantitative yield. Reaction of YbCl3 with complex 1 in a 2:1 molar ratio in THF, in the presence of HMPA, produced the desired bis(phenolate) ytterbium dichloride as bimetallic complex [ONNO]{YbCl2(HMPA)}2.2.5C7H8 (2). Complex 2 can be used as a precursor for the synthesis of ytterbium derivatives by salt metathesis reactions. Reaction of complex 2 with NaOiPr in a 1:2 molar ratio in THF led to the formation of bimetallic alkoxide [ONNO]{Yb(mu-OiPr)Cl(HMPA)}2.THF (3). However, the residual chlorine atoms in complex 3 are inactive for the further substituted reaction. Further study revealed that the bulkiness of the reagent has profound effect on the outcome of the reaction. Complex 2 reacted with bulky NaOAr (ArO=2,6-di-tert-butyl-4-methylphenoxo) or NaNPh2 in a 1:2 molar ratio under the same reaction conditions, after workup, to give the ligand redistributed products, (ArO)2YbCl(HMPA)2 (4) and [ONNO]YbCl(HMPA)2 (5) for the former and complexes 5 and (Ph2N)2YbCl(HMPA)2 (6) for the latter. If the molar ratio of complex 2 to NaNPh2 decreased to 1:4, the expected ligand redistributed products [ONNO]YbNPh2(HMPA) (7) and (Ph2N)3Yb(HMPA)2.C7H8 (8) can be isolated in high yields. All of the complexes were well characterized, and the definitive molecular structures of complexes 1-4, 7, and 8 were provided by single-crystal X-ray analysis.