Synthesis of Heteroleptic Cerium(IV) Complexes Using a Heptadentate (N4O3) Tripodale Schiff‐base Ligand

The Cerium(IV) complexes [{N[CH₂CH₂N=CH(2‐O‐3,5‐^tBu₂C₆H₂)]₃}CeCl] ( 1 ) and [{N[CH₂CH₂N=CH(2‐O‐3,5‐^tBu₂C₆H₂)]₃}Ce(NO₃)] ( 2 ) were derived from the condensation of tris(2‐aminoethyl)amine and 3,5‐di‐tert‐butylsalicylaldehyde and the appropriate Ce starting material CeCl₃(H₂O)₆ and (NH₄)₂[Ce(NO₃)₆], respectively. Single crystal X‐ray diffraction studies reveal monomeric complexes.     

Synthesis and Structures of New Oxidation/ Cycloaddition Products of λ3‐Cyclodiphosphazanes

Reaction of the cyclodiphosphazane [(OC₄H₈N)P(μ‐N‐t‐Bu)₂P(HN‐t‐Bu)] ( 1 ) with an equimolar quantity of diisopropyl azodicarboxylate afforded the phosphinimine product [(OC₄H₈N)P(μ‐N‐t‐Bu)₂P=N‐t‐Bu)(N(CO₂ ‐i‐Pr)NHCO₂‐i‐Pr] ( 6 ) having a P^III‐N‐P^V skeleton. Similar products [(t‐BuNH)P(μ‐N‐t‐Bu)₂P=N‐t‐Bu)(N(CO₂Et)NHCO₂Et] ( 7 ) and [(CO₂‐i‐Pr)HNN(CO₂‐i‐Pr)](t‐BuN=P(μ‐N‐t‐Bu)₂POCH₂CMe₂CH₂O[P(μ‐N‐t‐Bu)₂P=N‐t‐Bu)(N(CO₂‐i‐Pr)NH(CO₂‐i‐Pr)] ( 8 ) were spectroscopically characterized in the reaction of [(t‐BuNH)P‐N‐t‐Bu]₂ ( 2 ) and [(t‐BuNH)P(μ‐N‐t‐Bu)₂POCH₂CMe₂CH₂OP(μ‐N‐t‐Bu)₂P(NH‐t‐Bu)] ( 3 ) with diethyl‐ and diisopropyl azodicarboxylate, respectively. By contrast, the reaction of [(μ‐t‐BuN)P]₂[O‐6‐t‐Bu‐4‐Me‐C₆H₂]₂CH₂ ( 4 ) and [(C₅H₁₀N)P‐μ‐N‐t‐Bu]₂ ( 5 ) with diisopropyl azodicarboxylate afforded the mono‐ and bis‐oxidized compounds [(O)P(μ‐N‐t‐Bu)₂P][O‐6‐t‐Bu‐4‐Me‐C₆H₂]₂CH₂ ( 9 ) and [(C₅H₁₀N)(O)P‐μ‐N‐t‐Bu]₂ ( 10 ), respectively. Oxidative addition of o‐chloranil to 7 and its DIAD analogue [(t‐BuNH)P(μ‐N‐t‐Bu)₂P=N‐t‐Bu)(N(CO₂‐i‐Pr)NHCO₂‐i‐Pr] ( 11 ) afforded [(C₆Cl₄‐1, 2‐O₂)(t‐BuNH)P(μ‐N‐t‐Bu)₂P=N‐t‐Bu)(N(CO₂R)NHCO₂R] [R = Et ( 12 ) and i‐Pr ( 13 )] containing tetra‐ and pentacoordinate P^V atoms in the cyclodiphosphazane ring. The structures of 6 , 9 , 12 and 13 have been confirmed by X‐ray structure determination. For comparison, the X‐ray structure of the double cycloaddition product [(C₆Cl₄‐1, 2‐O₂)(t‐BuNH)PN‐t‐Bu]₂ ( 14 ), obtained from the reaction of 2 with two mole equivalents of o‐chloranil is also reported.     

C‐O Bond Cleavage of Diethyl Ether and Tetrahydrofurane by [(dpp‐BIAN)AlI(Et2O)] [dpp‐BIAN = 1,2‐bis[(2,6‐di‐iso‐propylphenyl)‐imino]acenaphthene]

At elevated temperatures, the aluminum complex [(dpp‐BIAN)AlI(Et₂O)] ( 1 ) splits the C‐O bonds of diethyl ether and tetrahydrofurane yielding the dimeric alkoxides [(dpp‐BIAN)AlOEt]₂ ( 2 ) and [(dpp‐BIAN)AlO(CH₂)₄I]₂ ( 3 ), respectively. Already at ambient temperatures, a cleavage of the C‐O bond of THF is to observe in the reaction of 1 with CpNa in THF as confirmed by the formation of [(dpp‐BIAN)AlO(CH₂)₄C₅H₅]₂ ( 4a ) and [(dpp‐BIAN)Al{O(CH₂)₄C₅H₅}(THF)] ( 4b ) in a molar ratio of 1:2. The reaction of 1 with t‐BuOK affords the monomeric alkoxide [(dpp‐BIAN)AlO‐t‐Bu(Et₂O)] ( 5 ). Compounds 2 , 3 , and 4a/b were characterized by elemental analyses and IR spectra. Additionally, the structures of 2 and 3 were determined by single crystal X‐ray diffraction.     

1‐Azonia‐2‐boratanaphthalenes

The 1‐azonia‐2‐boratanaphthalenes (NH)(BX)C₈H₆ can be synthesized from 2‐aminostyrene and the dihaloboranes XBHal₂ ( 1 ‐ 4 : X = Cl, Br, iPr, tBu). Further derivatives (NH)(BX)C₈H₆ are obtained from 1 by replacing Cl by alkoxy or alkyl groups [ 5 ‐ 8 : X = OMe, OtBu, Me, (CH₂)₃NMe₂]. The hydrolysis of 1 gives a mixture of the bis(azoniaboratanaphthyl) oxide [(NH)BC₈H₆]₂O ( 9 ) and the hydroxy derivative (NH)[B(OH)]C₈H₆ ( 10 ). The diboryl oxide 9 crystallizes in the space group C2/c. The lithiation of 4 at the nitrogen atom gives [NLi(tmen)](BtBu)C₈H₆ ( 11 ), which upon reaction with the diborane(4) B₂Cl₂(NMe₂)₂ yields the 1, 2‐bis(azoniaboratanaphthyl)diborane B₂[N(BtBu)C₈H₆]₂(NMe₂)₂ ( 12 ). The 2‐chloro‐1‐methyl‐4‐phenyl derivative (NMe)(BCl)C₈H₅Ph ( 13 ) of the parent (NH)(BH)C₈H₆ can be synthesized from the aminoborane BCl₂(NMePh) and phenylethyne. Substitution of Cl in 13 gives the derivatives (NMe)(BX)C₈H₅Ph [ 14 ‐ 20 : X = N(SiMe₃)₂, Me, Et, iBu, tBu, CH₂SiMe₃, Ph] and the reaction of 13 with Li₂O affords the bis(azoniaboratanaphthyl) oxide [(NMe)BC₈H₅Ph]₂O ( 21 ). The reaction of 16 or 19 with [(MeCN)₃Cr(CO)₃] yields the complexes [{(NMe)(BX)C₈H₅Ph}Cr(CO)₃] ( 22 , 23 : X = Et, CH₂SiMe₃), in which the chromium atom is hexahapto bound to the homoarene part of 16 or 19 , respectively. The complex 23 crystallizes in the space group P2₁/c. Upon reaction of the phenols para‐C₆H₄R(OH) with the aryldichloroboranes ArBCl₂ and subsequent condensation of the products with phenylethyne, the 1‐oxonia‐2‐boratanaphthalenes O(BAr)C₈H₄RPh with R in position 6 and Ph in position 4 are formed ( 24 ‐ 26 : Ar = Ph, R = H, Me, OMe; 27 ‐ 29 : Ar = C₆F₅, R = H, Me, OMe). The azoniaboratanaphthalenes 1 ‐ 23 were characterized by NMR methods.     

A novel dinuclear MoVI complex with tris(3,5‐dimethyl‐1H‐pyrazol‐1‐yl)methane

Recrystallization of [MoO₂Cl{HC(3,5‐Me₂pz)₃}]Cl [where HC(3,5‐Me₂pz)₃ is tris(3,5‐dimethyl‐1H‐pyrazol‐1‐yl)methane] led to the isolation of large quantities of the dinuclear complex dichlorido‐2κ²Cl‐μ‐oxido‐κ²O:O‐tetraoxido‐1κ²O,2κ²O‐[tris(3,5‐dimethyl‐1H‐pyrazol‐1‐yl‐1κN²)methane]dimolybdenum(IV) acetonitrile monosolvate, [Mo₂Cl₂O₄(C₁₆H₂₂N₆)]·CH₃CN or [{MoO₂Cl₂}(μ₂‐O){MoO₂[HC(3,5‐Me₂pz)₃]}]·CH₃CN. At 150 K, this complex cocrystallizes in the orthorhombic space group Pbcm with an acetonitrile molecule. The complex has mirror symmetry: only half of the complex constitutes the asymmetric unit and all the heavy elements (namely Mo and Cl) are located on the mirror plane. The acetonitrile molecule also lies on a mirror plane. The two crystallographically independent Mo⁶⁺ centres have drastically different coordination environments: while one Mo atom is hexacoordinated and chelated to HC(3,5‐Me₂pz)₃ (which occupies one face of the octahedron), the other Mo atom is instead pentacoordinated, having two chloride anions in the apical positions of the distorted trigonal bipyramid. This latter coordination mode of Mo^VI was found to be unprecedented. Individual complexes and solvent molecules are close‐packed in the solid state, mediated by various supramolecular contacts.     

Polypropylene and poly(ethylene‐co‐1‐octene) effective synthesis with diamine‐bis(phenolate) complexes: Effect of complex structure on catalyst activity and product microstructure

A series of group 4 metal complexes bearing amine‐bis(phenolate) ligands with the amino side‐arm donor: (μ‐O)[Me₂N(CH₂)₂N(CH₂‐2‐O‐3,5‐tBu₂‐C₆H₂)₂ZrCl]₂ ( 1a ), R₂N(CH₂)₂N(CH₂‐2‐O‐3‐R¹‐5‐R²‐C₆H₂)₂TiCl₂ (R = Me, R¹, R² = tBu ( 2a ), R = iPr, R¹, R² = tBu ( 2b ), R = iPr, R¹ = tBu, R² = OMe ( 2c )), and Me₂N(CH₂)₂N(CH₂‐2‐O‐3,5‐tBu₂‐C₆H₂)(CH₂‐2‐O‐C₆H₄)TiCl₂ ( 2d ) are used in ethylene and propylene homopolymerization, and ethylene/1‐octene copolymerization. All complexes, upon their activation with Al(iBu)₃/Ph₃CB(C₆F₅)₄, exhibit reasonable catalytic activity for ethylene homo‐ and copolymerization giving linear polyethylene with high to ultra‐high molecular weight (600·× 10³–3600·× 10³ g/mol). The activity of 1a /Al(iBu)₃/Ph₃CB(C₆F₅)₄ shows a positive comonomer effect, leading to over 400% increase of the polymer yield, while the addition of 1‐octene causes a slight reduction of the activity of the complexes 2a‐2d . The complexes with the NMe₂ donor group ( 2a , 2d , 1a ) display a high ability to incorporate a comonomer (up to 9–22 mol%), and the use of a bulkier donor group, N(iPr)₂ ( 2b , 2c ), results in a lower 1‐octene incorporation. All the produced copolymers reveal a broad chemical composition distribution. In addition, the investigated complexes polymerized propylene with the moderate ( 1a , 2a ) to low ( 2b‐2d ) activity, giving polymers with different microstructures, from purely atactic to isotactically enriched (mmmm = 28%). © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2467–2476     

Homo‐ and Heterovalent Polynuclear Cerium and Cerium/Manganese Aggregates

Reactions of Ce^III(NO₃)₃?6 H₂O or (NH₄)₂[Ce^IV(NO₃)₆] with Mn‐containing starting materials result in seven novel polynuclear Ce or Ce/Mn complexes with pivalato (^tBuCO ) and, in most cases, auxiliary N,O‐ or N,O,O‐donor ligands. With nuclearities ranging from 6–14, the compounds present aesthetically pleasing structures. Complexes [Ce^IV₆(μ₃‐O)₄(μ₃‐OH)₄(μ‐O₂C^tBu)₁₂] ( 1 ), [Ce^IV₆Mn^III₄(μ₄‐O)₄(μ₃‐O)₄(O₂C^tBu)₁₂(ea)₄(OAc)₄]?4 H₂O?4 MeCN (ea^?=2‐aminoethanolato; 2 ), [Ce^IV₆Mn^III₈(μ₄‐O)₄(μ₃‐O)₈(pye)₄(O₂C^tBu)₁₈]₂[Ce^IV₆(μ₃‐O)₄(μ₃‐OH)₄(O₂C^tBu)₁₀(NO₃)₄] [Ce^III(NO₃)₅(H₂O)]?21 MeCN (pye^?=pyridine‐2‐ethanolato; 3 ), and [Ce^IV₆Ce^III₂Mn^III₂(μ₄‐O)₄(μ₃‐O)₄(^tbdea)₂(O₂C^tBu)₁₂(NO₃)₂(OAc)₂]?4 CH₂Cl₂ (^tbdea^2?=2,2′‐(tert‐butylimino]bis[ethanolato]; 4 ) all contain structures based on an octahedral {Ce^IV₆(μ₃‐O)₈} core, in which many of the O‐atoms are either protonated to give (μ₃‐OH)^? hydroxo ligands or coordinate to further metal centers (Mn^III or Ce^III) to give interstitial (μ₄‐O)^2? oxo bridges. The decanuclear complex [Ce^IV₈Ce^IIIMn^III(μ₄‐O)₃(μ₃‐O)₃(μ₃‐OH)₂(μ‐OH)(bdea)₄(O₂C^tBu)_9.5(NO₃)_3.5(OAc)₂]?1.5 MeCN (bdea^2?=2,2′‐(butylimino]bis[ethanolato]; 5 ) contains a rather compact Ce^IV₇ core with the Ce^III and Mn^III centers well‐separated from each other on the periphery. The aggregate in [Ce^IV₄Mn^IV₂(μ₃‐O)₄(bdea)₂(O₂C^tBu)₁₀(NO₃)₂]?4 MeCN ( 6 ) is based on a quasi‐planar {Mn^IV₂Ce^IV₄(μ₃‐O)₄} core made up of four edge‐sharing {Mn^IVCe^IV₂(μ₃‐O)} or {Ce^IV₃(μ₃‐O)} triangles. The structure of [Ce^IV₃Mn^IV₄Mn^III(μ₄‐O)₂(μ₃‐O)₇(O₂C^tBu)₁₂(NO₃)(furan)]?6 H₂O ( 7 ?6 H₂O) can be considered as {Mn^IV₂Ce^IV₂O₄} and distorted {Mn^IV₂Mn^IIICe^IVO₄} cubane units linked through a central (μ₄‐O) bridge. The Ce₆Mn₈ equals the highest nuclearity yet reported for a heterometallic Ce/Mn aggregate. In contrast to most of the previously reported heterometallic Ce/Mn systems, which contain only Ce^IV and either Mn^IV or Mn^III, some of the aggregates presented here show mixed valency, either Mn^IV/Mn^III (see 7 ) or Ce^IV/Ce^III (see 4 and 5 ). Interestingly, some of the compounds, including the heterovalent Ce^IV/Ce^III 4 , could be obtained from either Ce^III(NO₃)₃?6 H₂O or (NH₄)₂[Ce^IV(NO₃)₆] as starting material.     

A Cyclic Hydroxylaminato‐aminoxide Complex of Gallium

The reaction of HON(tBu)CH₂CH₂N(tBu)OH with tri‐tert‐butyl gallium affords a hydroxylaminato complex of the formula [tBu₂Ga{ON(tBu)CH₂CH₂N(H)(tBu)O}], which contains a monoanionic bishydroxylaminato ligand with one anionic and one neutral, but tautomeric aminoxide end, both linked to gallium by their oxygen atoms leading to a seven‐membered ring. The compound was characterised by elemental analysis, ¹H and ¹³C NMR and determination of its crystal structure.     

Chirale 1,3,2‐Oxazaborolidine aus chiralen 2,3‐Dihydro‐1H‐1,3,2‐diazaborolen und Diphenylketen

Chiral 1,3,2‐Oxazaborolidines from the Reaction of Chiral 2,3‐Dihydro‐1H‐1,3,2‐diazaboroles and Diphenylketene Reaction of equimolar amounts of diphenylketene with 1,3‐di‐tert‐butyl‐2‐isobutyl‐2,3‐dihydro‐1H‐1,3,2‐diazaborole ( 1 ) regioselectively afforded 1,3,2‐oxazaborolidine ( 2 ). The employment of a series of chiral diazaboroles ( 3a : X = nBu; b: iBu; c: CH₂SiMe₃; d: NHtBu) led to the formation of the diastereoisomeric oxazaborolidines ( 4a – d ) with diastereomeric excesses de, which increase with the steric demand of X from de = 55 % (X = nBu) to de ≥ 95 % (X = NHtBu). Under comparable conditions the treatment of the enantiomerically pure diazaborole ( 6 ) with the ketene yielded oxazaborolidine ( 7 ) with a de‐value of only 52 %. The new compounds, with exception of 2 and 4d , are thermolabile solids, which were characterized mainly by spectroscopy (¹H‐, ¹¹B{¹H}‐, ¹³C{¹H}‐NMR, MS). The X‐ray structure analysis of 2 revealed a slightly puckered five‐membered heterocycle with a long B–O bond.     

Surprisingly Different Reaction Behavior of Alkali and Alkaline Earth Metal Bis(trimethylsilyl)amides toward Bulky N‐(2‐Pyridylethyl)‐N′‐(2,6‐diisopropylphenyl)pivalamidine

N‐(2,6‐Diisopropylphenyl)‐N′‐(2‐pyridylethyl)pivalamidine (Dipp‐N=C(tBu)‐N(H)‐C₂H₄‐Py) ( 1 ), reacts with metalation reagents of lithium, magnesium, calcium, and strontium to give the corresponding pivalamidinates [(tmeda)Li{Dipp‐N=C(tBu)‐N‐C₂H₄‐Py}] ( 6 ), [Mg{Dipp‐N=C(tBu)‐N‐C₂H₄‐Py}₂] ( 3 ), and heteroleptic [{(Me₃Si)₂N}Ae{Dipp‐N=C(tBu)‐N‐C₂H₄‐Py}], with Ae being Ca ( 2 a ) and Sr ( 2 b ). In contrast to this straightforward deprotonation of the amidine units, the reaction of 1 with the bis(trimethylsilyl)amides of sodium or potassium unexpectedly leads to a β‐metalation and an immediate deamidation reaction yielding [(thf)₂Na{Dipp‐N=C(tBu)‐N(H)}] ( 4 a ) or [(thf)₂K{Dipp‐N=C(tBu)‐N(H)}] ( 4 b ), respectively, as well as 2‐vinylpyridine in both cases. The lithium derivative shows a similar reaction behavior to the alkaline earth metal congeners, underlining the diagonal relationship in the periodic table. Protonation of 4 a or the metathesis reaction of 4 b with CaI₂ in tetrahydrofuran yields N‐(2,6‐diisopropylphenyl)pivalamidine (Dipp‐N=C(tBu)‐NH₂) ( 5 ), or [(thf)₄Ca{Dipp‐N=C(tBu)‐N(H)}₂] ( 7 ), respectively. The reaction of AN(SiMe₃)₂ (A=Na, K) with less bulky formamidine Dipp‐N=C(H)‐N(H)‐C₂H₄‐Py ( 8 ) leads to deprotonation of the amidine functionality, and [(thf)Na{Dipp‐N=C(H)‐N‐C₂H₄‐Py}]₂ ( 9 a ) or [(thf)K{Dipp‐N=C(H)‐N‐C₂H₄‐Py}]₂ ( 9 b ), respectively, are isolated as dinuclear complexes. From these experiments it is obvious, that β‐metalation/deamidation of N‐(2‐pyridylethyl)amidines requires bases with soft metal ions and also steric pressure. The isomeric forms of all compounds are verified by single‐crystal X‐ray structure analysis and are maintained in solution.     

Zirconium Complexes of Two Different Iminopyrrolyl Ligands – Syntheses and Structures

The reaction involving N‐aryliminopyrrolyl ligand, 2‐((p‐Me‐C₆H₃N=CMe)–C₄H₃NH) ( 1a ) (Imp^Me‐H), and Zr(OtBu)₄ in a 2:1 molar ratio in toluene at 90 °C afforded the corresponding bis(iminopyrrolyl) complex of zirconium, [(Imp^Me)₂Zr(OtBu)₂] ( 2a ) having two bidentate iminopyrrole groups in the coordination sphere. In contrast, the bulkier 2‐((2,6‐iPr₂C₆H₃N=CH)–C₄H₃NH) ( 1b ) (Imp^Dipp‐H) and Zr(OtBu)₄ in a 1:1 molar ratio under the same condition yielded the corresponding mono(iminopyrrolyl) complex of zirconium, [(Imp^Dipp)Zr(OtBu)₃(THF)] ( 2b ), which contains only one bidentate iminopyrrole moiety in the coordination sphere. Both complexes were characterized by single‐crystal X‐ray diffraction analysis. The solid‐state structures reveal that the bulky iminopyrrole ligands cause a steric crowding around the zirconium ion along with three tert‐butoxide ligands attached to the central metal atom.     

Ein ungewöhnlicher ambivalenter Zinn(II)‐oxo‐Cluster

An Unusual Ambivalent Tin(II)‐oxo Cluster The reaction of the copper aryl CuDmp (Dmp = 2, 6‐Mes₂C₆H₃; Mes = 2, 4, 6‐Me₃C₆H₂) with the stannanediyl Sn{1, 2‐(tBuCH₂N)₂C₆H₄} followed by hydrolysis affords in the presence of lithium‐tert‐butoxide the tin(II)‐oxo cluster {(Et₂O)(LiOtBu)(SnO)(CuDmp)}₂ ( 5 ) in small yield. The solid state structure of the colorless compound shows a central Li₂Sn₂O₂(OtBu)₂ fragment with heterocubane structure. In addition, the Li‐acceptor and O(Sn)‐donor atoms are used for the coordination of one molecule diethylether and copper aryl CuDmp, respectively.     

The Counterion Effect on the Assembly of Coordination Networks of Cationic (η3‐Allyl)palladium Complexes Containing 3,5‐Dimethyl‐4‐nitro‐1H‐pyrazole

Two new (η³‐allyl)palladium complexes containing the ligand 3,5‐dimethyl‐4‐nitro‐1H‐pyrazole (Hdmnpz) were synthesized and characterized as [Pd(η³‐C₃H₅)(Hdmnpz)₂]BF₄ ( 1 ) and [Pd(η³‐C₃H₅)(Hdmnpz)₂]NO₃ ( 2 ). The structures of these compounds were determined by single‐crystal X‐ray diffraction to evaluate the intermolecular assembly. Each complex exhibits similar coordination behavior consistent with cationic entities comprised of two pyrazole ligands coordinated with the [Pd(η³‐C₃H₅)]⁺ fragment in an almost square‐planar coordination geometry. In 1 , the cationic entities are propagated through strong intermolecular H‐bonds formed between the pyrazole NH groups and BF ions in one‐dimensional polymer chains along the a axis. These chains are extended into two‐dimensional sheet networks via bifurcated H‐bonds. New intermolecular interactions established between NO₂ and Me substituents at the pyrazole ligand of neighboring sheets give rise to a three‐dimensional network. By contrast, compound 2 presents molecular cyclic dimers formed through N? H???O H‐bonds between two NO counterions and the pyrazole NH groups of two cationic entities. The dimers are also connected to each other through C? H???O H‐bonds between the remaining O‐atom of each NO ion and the allyl CH₂ H‐atom. Those interactions expand in a layer which lies parallel to the face (101).     

Neutral and Anionic Monomeric Zirconium Imides Prepared via Selective C=N Bond Cleavage of a Multidentate and Sterically Demanding β‐Diketiminato Ligand

A sterically encumbering multidentate β‐diketiminato ligand, ^tBuL2 (^tBuL2=[ArNC(tBu)CHC(tBu)NCH₂CH₂N(Me)CH₂CH₂NMe₂]^?, Ar=2,6‐iPr₂C₆H₃), is reported in this study along with its coordination chemistry to zirconium(IV). Using the lithio salt of this ligand, Li(^tBuL2) ( 4 ), the zirconium(IV) precursor (^tBuL2)ZrCl₃ ( 6 ) could be readily prepared in 85 % yield and structurally characterized. Reduction of 6 with 2 equiv of KC₈ resulted in formation of the terminal and mononuclear zirconium imide‐chloride [C(tBu)CHC(tBu)NCH₂CH₂N(Me)CH₂CH₂NMe₂]Zr(=NAr)(Cl) ( 7 ) as the result of reductive C=N cleavage of the imino fragment in the multidentate ligand ^tBuL2 by an elusive Zr^II species (^tBuL2)ZrCl ( A ). The azabutadienyl ligand in 7 can be further reduced by 2 e^? with KC₈ to afford the anionic imide [K(THF)₂]{[CH(tBu)CHC(tBu)NCH₂CH₂N(Me)CH₂CH₂N(Me)CH₂]Zr=NAr} ( 8‐2THF ) in 42 % isolated yield. Complex 8‐2THF results from the oxidative addition of an amine C?H bond followed by migration to the vinylic group of the formal [C(tBu)CHC(tBu)NCH₂CH₂N(Me)CH₂CH₂NMe₂]^? ligand in 7 . All halides in 6 can be replaced with azides to afford (^tBuL2)Zr(N₃)₃ ( 9 ) which was structurally characterized, and reduction with two equiv of KC₈ also results in C=N bond cleavage of ^tBuL2 to form [C(tBu)CHC(tBu)NCH₂CH₂N(Me)CH₂CH₂NMe₂]Zr(=NAr)(N₃) ( 10 ), instead of the expected azide disproportionation to N^3? and N₂. Solid‐state single crystal structural studies confirm the formation of mononuclear and terminal zirconium imido groups in 7 , 8‐Et₂O , and 10 with Zr=NAr distances being 1.8776(10), 1.9505(15), and 1.881(3) Å, respectively.     

Synthesis and Structural Characterization of Some Novel Trialkylsilyl‐substituted Lithium Benzyl Complexes [Li(tmeda)][CHRSiMe2R′] (R = Ph, 3,5‐Me2C6H3; R′ = Me,tBu, Ph)

The reactions of PhCH₂SiMe₃ ( 1 ), PhCH₂SiMe₂^tBu ( 2 ), PhCH₂SiMe₂Ph ( 3 ), 3,5‐Me₂C₆H₃CH₂SiMe₃ ( 4 ), and 3,5‐Me₂C₆H₃CH₂SiMe₂^tBu ( 5 ) with ⁿBuLi in tetramethylethylenediamine (tmeda) afford the corresponding lithium complexes [Li(tmeda)][CHRSiMe₂R′] (R, R′ = Ph, Me ( 6 ), Ph, ^tBu ( 7 ), Ph, Ph ( 8 ), 3,5‐Me₂C₆H₃, Me ( 9 ), and 3,5‐Me₂C₆H₃, ^tBu ( 10 )), respectively. The new compounds 5 , 7 , 8 , 9 and 10 have been characterized by ¹H and ¹³C NMR spectroscopy, compounds 7 , 8 and 9 also by X‐ray structure analysis.     

Organometallic Cerium Complexes from Tetravalent Coordination Complexes

The use of tetravalent cerium alkoxides, nitrates, and triflates was studied as a direct route to [Ce^IV(carbene)] complexes. Protonolysis reactions between 1H‐imidazolium‐ or imidazoline (=4,5‐dihydro‐1H‐imidazole)‐containing alkoxide proligands HL (L=OCMe₂CH₂[1‐C(NCHCHNⁱPr)]) and HL^S (L^S=OCMe₂CH₂[1‐C(NCH₂CH₂NⁱPr)]) and Ce^IV tert‐butoxide, triflate, and nitrate compounds were studied to target [Ce^IV(N‐heterocyclic carbene)] complexes (of unsaturated and saturated carbenes, resp.). Instead, tetravalent cerium imidazolium [(O^tBu)₃Ce(μ‐O^tBu)₂(μ‐HL)Ce(O^tBu)₃], or imidazolinium adducts [(O^tBu)₃Ce(μ‐O^tBu)₂(μ‐HL^S)Ce(O^tBu)₃] were isolated. However, the salt metathesis of cerium triflate with KL provided a simple route to [CeL₄], which was significantly improved if an external oxidant, benzoquinone, was included in the mixture to maintain oxidation‐state integrity. Likewise, the salt metathesis of cerium triiodide with KL and added benzoquinone provided a straightforward route to [CeL₄].     

ZnII and CuII complexes generated from 5‐(pyridin‐4‐yl)‐3‐[2‐(pyridin‐4‐yl)ethyl]‐1,3,4‐oxadiazole‐2(3H)‐thione

A new 1,3,4‐oxadiazole‐containing bispyridyl ligand, namely 5‐(pyridin‐4‐yl)‐3‐[2‐(pyridin‐4‐yl)ethyl]‐1,3,4‐oxadiazole‐2(3H)‐thione (L), has been used to create the novel complexes tetranitratobis{μ‐5‐(pyridin‐4‐yl)‐3‐[2‐(pyridin‐4‐yl)ethyl]‐1,3,4‐oxadiazole‐2(3H)‐thione}zinc(II), [Zn₂(NO₃)₄(C₁₄H₁₂N₄OS)₂], (I), and catena‐poly[[[dinitratocopper(II)]‐bis{μ‐5‐(pyridin‐4‐yl)‐3‐[2‐(pyridin‐4‐yl)ethyl]‐1,3,4‐oxadiazole‐2(3H)‐thione}] nitrate acetonitrile sesquisolvate dichloromethane sesquisolvate], {[Cu(NO₃)(C₁₄H₁₂N₄OS)₂]NO₃·1.5CH₃CN·1.5CH₂Cl₂}_n, (II). Compound (I) presents a distorted rectangular centrosymmetric Zn₂L₂ ring (dimensions 9.56 × 7.06 Å), where each Zn^II centre lies in a {ZnN₂O₄} coordination environment. These binuclear zinc metallocycles are linked into a two‐dimensional network through nonclassical C—H...O hydrogen bonds. The resulting sheets lie parallel to the ac plane. Compound (II), which crystallizes as a nonmerohedral twin, is a coordination polymer with double chains of Cu^II centres linked by bridging L ligands, propagating parallel to the crystallographic a axis. The Cu^II centres adopt a distorted square‐pyramidal CuN₄O coordination environment with apical O atoms. The chains in (II) are interlinked via two kinds of π–π stacking interactions along [01]. In addition, the structure of (II) contains channels parallel to the crystallographic a direction. The guest components in these channels consist of dichloromethane and acetonitrile solvent molecules and uncoordinated nitrate anions.     

Highly active copolymerization of ethylene with 10‐undecen‐1‐ol using phenoxy‐based zirconium/methylaluminoxane catalysts

Activated with methylaluminoxane (MAO), phenoxy‐based zirconium complexes bis[(3‐^tBu‐C₆H₃‐2‐O)‐CH?NC₆H₅]ZrCl₂, bis[(3,5‐di‐^tBu‐C₆H₂‐2‐O)‐PhC?NC₆H₅] ZrCl₂, and bis[(3,5‐di‐^tBu‐C₆H₂‐2‐O)‐PhC?N(2‐F‐C₆H₄)]ZrCl₂ for the first time have been used for the copolymerization of ethylene with 10‐undecen‐1‐ol. In comparison with the conventional metallocene, the phenoxy‐based zirconium complexes exhibit much higher catalytic activities [>10⁷ g of polymer (mol of catalyst)^?1 h^?1]. The incorporation of 10‐undecen‐1‐ol into the copolymers and the properties of the copolymers are strongly affected by the catalyst structure. Among the three catalysts, complex c is the most favorable for preparing higher molecular weight functionalized polyethylene containing a higher content of hydroxyl groups. Studies on the polymerization conditions indicate that the incorporated commoner content in the copolymers mainly depends on the comonomer concentration in the feed. The catalytic activity is slightly affected by the Al_(MAO)/Zr molar ratio but decreases greatly with an increase in the polymerization temperature. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5944–5952, 2005     

Diimido‐, Imido(oxo)‐, Dioxo‐ und Imido(alkyliden)‐Halbsandwich‐Verbindungen über selektive Hydrolyse und α—H‐Abstraktion an Organylkomplexen des sechswertigen Molybdäns und Wolframs

Diimido, Imido Oxo, Dioxo, and Imido Alkylidene Halfsandwich Compounds via Selective Hydrolysis and α—H Abstraction in Molybdenum(VI) and Tungsten(VI) Organyl Complexes Organometal imides [(η⁵‐C₅R₅)M(NR′)₂Ph] (M = Mo, W, R = H, Me, R′ = Mes, tBu) 4 — 8 can be prepared by reaction of halfsandwich complexes [(η⁵‐C₅R₅)M(NR′)₂Cl] with phenyl lithium in good yields. Starting from phenyl complexes 4 — 8 as well as from previously described methyl compounds [(η⁵‐C₅Me₅)M(NtBu)₂Me] (M = Mo, W), reactions with aqueous HCl lead to imido(oxo) methyl and phenyl complexes [(η⁵‐C₅Me₅)M(NtBu)(O)(R)] M = Mo, R = Me ( 9 ), Ph ( 10 ); M = W, R = Ph ( 11 ) and dioxo complexes [(η⁵‐C₅Me₅)M(O)₂(CH₃)] M = Mo ( 12 ), M = W ( 13 ). Hydrolysis of organometal imides with conservation of M‐C σ and π bonds is in fact an attractive synthetic alternative for the synthesis of organometal oxides with respect to known strategies based on the oxidative decarbonylation of low valent alkyl CO and NO complexes. In a similar manner, protolysis of [(η⁵‐C₅H₅)W(NtBu)₂(CH₃)] and [(η⁵‐C₅Me₅)Mo(NtBu)₂(CH₃)] by HCl gas leads to [(η⁵‐C₅H₅)W(NtBu)Cl₂(CH₃)] 14 und [(η⁵‐C₅Me₅)Mo(NtBu)Cl₂(CH₃)] 15 with conservation of the M‐C bonds. The inert character of the relatively non‐polar M‐C σ bonds with respect to protolysis offers a strategy for the synthesis of methyl chloro complexes not accessible by partial methylation of [(η⁵‐C₅R₅)M(NR′)Cl₃] with MeLi. As pure substances only trimethyl compounds [(η⁵‐C₅R₅)M(NtBu)(CH₃)₃] 16 ‐ 18 , M = Mo, W, R = H, Me, are isolated. Imido(benzylidene) complexes [(η⁵‐C₅Me₅)M(NtBu)(CHPh)(CH₂Ph)] M = Mo ( 19 ), W ( 20 ) are generated by alkylation of [(η⁵‐C₅Me₅)M(NtBu)Cl₃] with PhCH₂MgCl via α‐H abstraction. Based on nmr data a trend of decreasing donor capability of the ligands [NtBu]^2— > [O]^2— > [CHR]^2— ? 2 [CH₃]^— > 2 [Cl]^— emerges.     

Synthesis and Characterization of Metal Complexes (M = Al,Ti, W,Zn) Containing Pyrrole‐imine Ligands

A series of metal compounds (M = Al, Ti, W, and Zn) containing pyrrole‐imine ligands have been prepared and structurally characterized. The reactions of AlMe₃ with one and three equivs of pyrrole‐imine ligand [C₄H₃NH‐(2‐CH=N? CH₂Ph)] ( 1 ) generated aluminum compounds Al[C₄H₃N‐(2‐CH=N? CH₂Ph)]Me₂ ( 2 ) and Al[C₄H₃N‐(2‐CH=NCH₂Ph)]₃ ( 3 ), respectively, in relatively high yield. Reacting two equivs of 1 with Ti(OⁱPr)₄, W(NH^tBu)₂(=N^tBu)₂, or ZnMe₂ afforded Ti[C₄H₃N‐(2‐CH=NCH₂Ph)]₂(OⁱPr)₂ ( 4 ), W[C₄H₃N‐(2‐CH=NCH₂Ph)]₂(=N^tBu)₂ ( 5 ), and Zn[C₄H₃N‐(2‐CH=NCH₂Ph)]₂ ( 6 ), respectively. All the compounds have been characterized by ¹H and ¹³C NMR spectroscopy. Compounds 3 – 6 have also been characterized by single‐crystal X‐ray structural analysis. The biting angles of pyrrole‐imine ligand with metals decrease and their related M? N_pyrrole and M? N_imine bond lengths increase in the order of 6 , 3 , 4 , and 5 .