Crystalline Radicals Derived from Classical N‐Heterocyclic Carbenes

One‐electron reduction of C2‐arylated 1,3‐imidazoli(ni)um salts (IPr^Ar)Br (Ar=Ph, 3 a ; 4‐DMP, 3 b ; 4‐DMP=4‐Me₂NC₆H₄) and (SIPr^Ar)I (Ar=Ph, 4 a ; 4‐Tol, 4 b ) derived from classical NHCs (IPr=:C{N(2,6‐iPr₂C₆H₃)}₂CHCH, 1 ; SIPr=:C{N(2,6‐iPr₂C₆H₃)}₂CH₂CH₂, 2 ) gave radicals [(IPr^Ar)]^. (Ar=Ph, 5 a ; 4‐DMP, 5 b ) and [(SIPr^Ar)]^. (Ar=Ph, 6 a ; 4‐Tol, 6 b ). Each of 5 a , b and 6 a , b exhibited a doublet EPR signal, a characteristic of monoradical species. The first solid‐state characterization of NHC‐derived carbon‐centered radicals 6 a , b by single‐crystal X‐ray diffraction is reported. DFT calculations indicate that the unpaired electron is mainly located at the original carbene carbon atom and stabilized by partial delocalization over the adjacent aryl group.     

Ring-opening reaction of tetrahydrofuran on the penta(organo)[60]fullerenes: synthesis of hydroxybutyl, methacrylate, and norbornene derivatives

Ring-opening reaction of tetrahydrofuran takes place on penta(methyl)- and penta(n-butylphenyl)[60]fullerenes in the presence of chlorotrimethylsilane giving penta(organo)fullerene hydroxybutyl derivatives, C₆₀R₅(C₄H₈OH) (R = Me, ⁿBuC₆H₄). The hydroxyl groups were further transformed into methacrylate and norbornylcarbonyloxy groups via esterification with the corresponding acid chlorides. The methacrylate derivative, penta(methyl)[60]fullerenylbutyl methacrylates was crystallographically characterized.     

Hoop‐Shaped Condensed Aromatic Systems: Synthesis and Structure of Iron– and Ruthenium–Hepta(organo)[60]fullerene Complexes

Potassium reduction of iron– and ruthenium–penta(organo)[60]fullerene complexes, [M(η⁵‐C₆₀R₅)(η⁵‐Cp)] ( 1 a : M=Fe, R=Ph; 1 b : M=Fe, R=Me; 1 c : M=Ru, R=Ph; 1 d : M=Ru, R=Me; Cp=C₅H₅) gave mono‐ and dianions of these complexes. Treatment of the dianion 1 a with α‐bromodiphenylmethane gave three different iron–hepta(organo)[60]fullerenes, [Fe{η⁵‐C₆₀Ph₅(CHPh₂)₂}(η⁵‐Cp)], as a mixture of regioisomers. All three compounds were fully characterized by physical methods, including X‐ray crystallography and electrochemical measurements. One of the three compounds contains a new hoop‐shaped condensed aromatic system.     

Elusive Terminal Copper Arylnitrene Intermediates

We report herein three new modes of reactivity between arylazides N₃Ar with a bulky copper(I) β-diketiminate. Addition of N₃Ar^X3 (Ar^X3=2,4,6-X₃C₆H₂; X=Cl or Me) to [ⁱPr₂NN]Cu(NCMe) results in triazenido complexes from azide attack on the β-diketiminato backbone. Reaction of [ⁱPr₂NN]Cu(NCMe) with bulkier azides N₃Ar leads to terminal nitrenes [ⁱPr₂NN]Cu]=NAr that dimerize via formation of a C−C bond at the arylnitrene p-position to give the dicopper(II) diketimide 4 (Ar=2,6-ⁱPr₂C₆H₃) or undergo nitrile insertion to give diazametallocyclobutene 8 (Ar=4-Ph-2,6-iPr₂C₆H₂). Importantly, reactivity studies reveal both 4 and 8 to be “masked” forms of the terminal nitrenes [ⁱPr₂NN]Cu=NAr that undergo nitrene group transfer to PMe₃, ^tBuNC, and even into a benzylic sp³ C−H bond of ethylbenzene.     

Regioselective synthesis of tetra(aryl)-mono(silylmethyl)[60]fullerenes and derivatization to methanofullerene compound

A method for the facile synthesis of tetraaryl-trimethylsilylmethyl-hydro[60]fullerenes, C₆₀Ar₄(CH₂SiMeR)H, has been developed in which readily prepared anionic mono(silylmethyl) fullerene is subjected to reaction conditions for organocopper-mediated multiple addition. Penta(organo)fullerene derivatives bearing different substituents and diverse functionality were synthesized in moderate to good yield under simple and mild reaction conditions. Further organic and organometallic transformations of these fullerenes allowed us to synthesize transition-metal complexes and a new methanofullerene derivative, 1,9-methano-6,12,15,18-tetraphenyl[60]fullerene, C₆₀Ph₄(CH₂).     

Liquid‐Crystalline Mixed [5 : 1]Hexa‐adducts of [60]Fullerene. Preliminary Communication

A liquid‐crystalline mixed [5 : 1]hexa‐adduct of [60]fullerene was synthesized by addition of two different malonate derivatives onto C₆₀. The hexa‐adduct derivative 2 was prepared by a stepwise synthetic procedure (fullerene→mono‐adduct of C₆₀→hexa‐adduct of C₆₀). Cyanobiphenyl and octyloxybiphenyl derivatives were selected as mesogens. The malonate derivatives showed either a monotropic nematic phase or a monotropic smectic A phase, and the hexa‐adduct derivative gave rise to an enantiotropic smectic A phase.     

Activation of Open‐Cage Fullerenes with Ruthenium Carbonyl Clusters

Reactions of the open‐cage fullerene C₆₃NO₂(Py)(Ph)₂ ( 1 ) with [Ru₃(CO)₁₂] produce [Ru₃(CO)₈(μ,η⁵‐C₆₃NO₂(Py)(Ph)₂)] ( 2 ), [Ru₂H(CO)₃(μ,η⁷‐C₆₃N(Py)(Ph)(C₆H₄))] ( 3 ), and [Ru(CO)(Py)₂₍η³‐C₆₃NO₂(Py)(Ph)₂)] ( 4 ), in which the orifice sizes are modified from 12 to 8, 11, and 15‐membered ring, through ruthenium‐mediated C?O and C?C bond activation and formation.     

A Comparative 19F NMR study of electronic effects in some fluoroaryl compounds of antimony and bismuth and in their carbon and nitrogen analogues

A number of m- and p-fluorophenyl compounds of type Ar₂QC₆H₄F (Q = Sb, Bi, N and CH; Ar = C₆H₅, C₆H₄F) have been prepared. The ^l0F chemical shifts relative to fluorobenzene have been measured in cyclohexane, chloroform and pyridine for all these compounds. On the basis of the data obtained, the electronic nature of the Ar₂Sb and Ar₂Bi substituents has been studied and compared with that of the corresponding (C₆H₅)₂N and (C₆H₅)₂CH groups. The electronic effect of the Ar₂Sb and Ar₂Bi substituents has been shown to be mainly inductive, its solvent susceptibility being in most cases close to zero relative to both electron- and proton- donating solvents.     

Preparation of linear α‐olefins to high‐molecular weight polyethylenes using cationic α‐diimine nickel(II) complexes containing chloro‐substituted ligands

A series of α‐diimine nickel(II) complexes containing chloro‐substituted ligands, [(Ar)N?C(C₁₀H₆)C?N(Ar)]NiBr₂ ( 4a , Ar = 2,3‐C₆H₃Cl₂; 4b , Ar = 2,4‐C₆H₃Cl₂; 4c , Ar = 2,5‐C₆H₃Cl₂; 4d , Ar = 2,6‐C₆H₃Cl₂; 4e , Ar = 2,4,6‐C₆H₂Cl₃) and [(Ar)N?C(C₁₀H₆)C?N(Ar)]₂NiBr₂ ( 5a , Ar = 2,3‐C₆H₃Cl₂; 5b , Ar = 2,4‐C₆H₃Cl₂; 5c , Ar = 2,5‐C₆H₃Cl₂), have been synthesized and investigated as precatalysts for ethylene polymerization. In the presence of modified methylaluminoxane (MMAO) as a cocatalyst, these complexes are highly effective catalysts for the oligomerization or polymerization of ethylene under mild conditions. The catalyst activity and the properties of the products were strongly affected by the aryl‐substituents of the ligands used. Depending on the catalyst structure, it is possible to obtain the products ranging from linear α‐olefins to high‐molecular weight polyethylenes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1964–1974, 2006     

New Dinuclear Ru2(CO)4 Sawhorse‐Type Complexes Containing Bridging Carboxylato Ligands

The thermal reaction of Ru₃(CO)₁₂ with ethacrynic acid, 4‐[bis(2‐chlorethyl)amino]benzenebutanoic acid (chlorambucil), or 4‐phenylbutyric acid in refluxing solvents, followed by addition of two‐electron donor ligands (L), gives the diruthenium complexes Ru₂(CO)₄(O₂CR)₂L₂ ( 1 : R = CH₂O‐C₆H₂Cl₂‐COC(CH₂)C₂H₅, L = C₅H₅N; 2 : R = CH₂O‐C₆H₂Cl₂‐COC(CH₂)C₂H₅, L = PPh₃; 3 : R = C₃H₆‐C₆H₄‐N(C₂H₄‐Cl)₂, L = C₅H₅N; 4 : R = C₃H₆‐C₆H₄‐N(C₂H₄‐Cl)₂, L = PPh₃; 5 : R = C₃H₆‐C₆H₅, L = C₅H₅N; 6 : R = C₃H₆‐C₆H₅, L = PPh₃). The single‐crystal structure analyses of 2 , 3 , 5 and 6 reveal a dinuclear Ru₂(CO)₄ sawhorse structure, the diruthenium backbone being bridged by the carboxylato ligands, while the two L ligands occupy the axial positions of the diruthenium unit.     

Nine compounds containing high‐nuclearity [CunX2n+2]2− (n = 4, 5 or 7; X = Cl or Br) quasi‐planar oligomers

The structures of seven A₂Cu₄X₁₀ compounds containing quasi‐planar oligomers are reported: bis(1,2,4‐trimethylpyridinium) hexa‐μ‐chlorido‐tetrachloridotetracuprate(II), (C₈H₁₂N)₂[Cu₄Cl₁₀], (I), and the hexa‐μ‐bromido‐tetrabromidotetracuprate(II) salts of 1,2,4‐trimethylpyridinium, (C₈H₁₂N)₂[Cu₄Br₁₀], (II), 3,4‐dimethylpyridinium, (C₇H₁₀N)₂[Cu₄Br₁₀], (III), 2,3‐dimethylpyridinium, (C₇H₁₀N)₂[Cu₄Br₁₀], (IV), 1‐methylpyridinium, (C₆H₈N)₂[Cu₄Br₁₀], (V), trimethylphenylammonium, (C₉H₁₄N)₂[Cu₄Br₁₀], (VI), and 2,4‐dimethylpyridinium, (C₇H₁₀N)₂[Cu₄Br₁₀], (VII). The first four are isomorphous and contain stacks of tetracopper oligomers aggregated through semicoordinate Cu...X bond formation in a 4(,) stacking pattern. The 1‐methylpyridinium salt also contains oligomers stacked in a 4(,) pattern, but is isomorphous with the known chloride analog instead. The trimethylphenylammonium salt contains stacks of oligomers arranged in a 4(,) stacking pattern similar to the tetramethylphosphonium analog. These six structures feature inversion‐related organic cation pairs and hybrid oligomer/organic cation layers derived from the parent CuX₂ structure. The 2,4‐dimethylpyridinium salt is isomorphous with the known (2‐amino‐4‐methylpyridinium)₂Cu₄Cl₁₀ structure, in which isolated stacks of organic cations and of oligomers in a 4(,) pattern are found. In bis(3‐chloro‐1‐methylpyridinium) octa‐μ‐bromido‐tetrabromidopentacuprate(II), (C₆H₇ClN)[Cu₅Br₁₂], (VIII), containing the first reported fully halogenated quasi‐planar pentacopper oligomer, the oligomers stack in a 5(,) stacking pattern as the highest nuclearity [Cu_nX_2n+2]²⁻ oligomer compound known with isolated stacking. Bis(2‐chloro‐1‐methylpyridinium) dodeca‐μ‐bromido‐tetrabromidoheptacuprate(II), (C₆H₇ClN)₂[Cu₇Br₁₆], (IX), contains the second heptacopper oligomer reported and consists of layers of interleaved oligomer stacks with a 7[(,)][(−,−)] pattern isomorphous with that of the known 1,2‐dimethylpyridinium analog. All the oligomers reported here are inversion symmetric.     

Synthesis,Characterization, Luminescence,and Electrochemistry of the Tetranuclear Gold(I) Amidinate Clusters,Precursors to CO Oxidation Catalysts: Au4[(ArNC(H)NAr)]4, Au4[(PhNC(Ph)NPh)]4 and Au4[PhNC(CH3)NPh)4]

A summary of the chemistry of the tetranuclear Au(I) amidinate complexes is presented. Tetranuclear Au(I) amidinate clusters are produced by the reaction of the sodium salt of a amidine ligand with the gold precursor Au(THT)Cl in a (1:1) stoichiometry. The structures of the tetranuclear Au₄[ArNC(H)NAr]₄, Ar = C₆H₄‐4‐OMe, C₆H₃‐3,5‐Cl, C₆H₄‐4‐Me, C₆H₄‐3‐CF₃, C₆F₅, C₁₀H₇ and the tetranuclear Au₄[(PhNC(Ph)NPh]₄ and Au₄[PhNC(CH₃)NPh]₄ have been characterized by X‐ray crystallography. The average Au···Au distance between adjacent Au(I) atoms is ?3.0 Å, typical of compounds having an aurophilic interaction. The four gold atoms are located at the corner of a rhomboid with the amidinate ligands bridged above and below the near plane of the four Au(I) atoms. The angles at Au···Au···Au in the cyclic units are between 70° and 116°. The tetranuclear gold(I) amidinate clusters each show different luminescence behavior. The tetranuclear clusters Au₄[(ArNC(H)NAr]₄, Ar = C₆H₄‐4‐OMe, Ar = C₆H₄‐3‐CF₃, Ar = C₆H₄‐4‐Me and Ar = C₆H₄‐3,5‐Cl are the first tetranuclear gold(I) cluster species from group 11 elements that show fluorescence at room temperature. The tetranuclear naphthyl derivative Ar = C₁₀H₇ is luminescent only at 77 K. The pentafluorophenyl derivative Ar = C₆F₅ does not show any photoluminescence in the solid state nor in the solution. The lifetimes of the naphthyl and trifluoromethylphenyl complexes are in the millisecond range indicating phosphorescent processes. Electrochemical and chemical oxidation studies of the tetranuclear Au(I) amidinate clusters are presented. The tetranuclear complexes Au₄[ArNC(H)NAr]₄, Ar = C₆H₄‐4‐OMe, Ar = C₆H₄‐4‐Me, and Ar = C₆H₃‐3,5‐Cl, show three reversible waves at 0.75, 0.95, 1.09 V vs. Ag/AgCl at a scan rate of 500 mV/s in 0.1 M Bu₄NPF₆/CH₂Cl₂ at a Pt working electrode in CH₂Cl₂. Three reversible waves at 0.87, 1.19, 1.42 V vs. Ag/AgCl at a scan rate of 100 mV/s are also observed for the tetranuclear complex Au₄[PhNC(Ph)NPh]₄ in CH₂Cl₂. The pentafluorophenyl amidinate derivative, Au₄[ArNC(H)NAr]₄, Ar = C₆F₅ shows no oxidation wave below 1.8 V. Recently it has been shown that Au₄[ArNC(H)NAr]₄ is a very effective catalyst precursor for room temperature CO oxidation.     

Formation,Dynamic Behavior,and Chemical Transformation of Pt Complexes with a Rotaxane‐like Structure

The reaction of [Pt(CH₂COMe)(Ph)(cod)] (cod=1,5‐cyclooctadiene) with (ArCH₂NH₂CH₂‐C₆H₄COOH)⁺(PF₆)^? (Ar=4‐tBuC₆H₄ or 9‐anthryl) in the presence of cyclic oligoethers such as dibenzo[24]crown‐8 (DB24C8) and dicyclohexano[24]crown‐8 (DC24C8) produces {(ce)[ArCH₂NH₂CH₂C₆H₄COOPt(Ph)(cod)]}⁺(PF₆)^? (ce=DB24C8 or DC24C8, Ar=4‐tBuC₆H₄ or 9‐anthryl) with interlocked structures. FABMS and NMR spectra of a solution of these compounds indicate that the Pt complexes with a secondary ammonium group and DB24C8 (or DC24C8) make up the axis and cyclic components, respectively. Temperature‐dependent ¹H NMR spectra of a solution of {(DB24C8)[4‐tBuC₆H₄CH₂NH₂CH₂‐C₆H₄COOPt(Ph)(cod)]}⁺(PF₆)^? ({(DB24C8)[ 4 ‐H]}⁺(PF₆)^?) show equilibration with free DB24C8 and the axis component. The addition of DB24C8 to a solution of {(DC24C8)[ 4 ‐H]}⁺(PF₆)^? causes partial exchange of the macrocyclic component of the interlocked molecules, giving a mixture of {(DC24C8)[ 4 ‐H]}⁺(PF₆)^?, {(DB24C8)[ 4 ‐H]}⁺(PF₆)^?, and free macrocyclic compounds. The reaction of 3,5‐Me₂C₆H₃COCl with {(DB24C8)[ 4 ‐H]}⁺(PF₆)^? affords the organic rotaxane {(DB24C8)(4‐tBuC₆H₄CH₂NH₂CH₂‐C₆H₄COOCOC₆H₃Me₂‐3,5)}⁺(PF₆)^? through C? O bond formation between the aroyl group and the carboxylate ligand of the axis component. The addition of 2,2′‐bipyridine (bpy) to a solution of {(DB24C8)[ 4 ‐H]}⁺(PF₆)^? induces the degradation of the interlocked structure to form a complex with trigonal bipyramidal coordination, [Pt(Ph)(bpy)(cod)]⁺(PF₆)^?, whereas the reaction of bpy with [Pt(OCOC₆H₄Me‐4)(Ph)(cod)] produces the square‐planar complex [Pt(OCOC₆H₄Me‐4)(Ph)(bpy)].     

Super‐Bulky Penta‐arylcyclopentadienyl Ligands: Isolation of the Full Range of Half‐Sandwich Heavy Alkaline‐Earth Metal Hydrides

Hydrogenolysis of the half‐sandwich penta‐arylcyclopentadienyl‐supported heavy alkaline‐earth‐metal alkyl complexes (Cp^Ar)Ae[CH(SiMe₃)₂](S) (Cp^Ar=C₅Ar₅, Ar=3,5‐ⁱPr₂‐C₆H_3; S=THF or DABCO) in hexane afforded the calcium, strontium, and barium metal–hydride complexes as the same dimers [(Cp^Ar)Ae(μ‐H)(S)]₂ (Ae=Ca, S=THF, 2‐Ca ; Ae=Sr, Ba, S=DABCO, 4‐Ae ), which were characterized by NMR spectroscopy and single‐crystal X‐ray analysis. 2‐Ca , 4‐Sr , and 4‐Ba catalyzed alkene hydrogenation under mild conditions (30 °C, 6 atm, 5 mol % cat.), with the activity increasing with the metal size. A variety of activated alkenes including tri‐ and tetra‐substituted olefins, semi‐activated alkene (Me₃SiCH=CH₂), and unactivated terminal alkene (1‐hexene) were evaluated.     

Y,Lu, and Gd Complexes of NCO/NCS Pincer Ligands: Synthesis,Characterization, and Catalysis in the cis‐1,4‐Selective Polymerization of Isoprene

A series of NCO/NCS pincer precursors, 3‐(Ar²OCH₂)‐2‐Br‐(Ar¹N?CH)C₆H₃ ((^Ar1NCO^Ar2)Br, 3a , 3b , 3c , 3d ) and 3‐(2,6‐Me₂C₆H₃SCH₂)‐2‐Br‐(Ar¹N?CH)C₆H₃ ((^Ar1NCS^Me)Br, 4a and 4b ) were synthesized and characterized. The reactions of [^Ar1NCO^Ar2]Br/ [^Ar1NCS^Me]Br with nBuLi and the subsequent addition of the rare‐earth‐metal chlorides afforded their corresponding rare‐earth‐metal–pincer complexes, that is, [(^Ar1NCO^Ar2)YCl₂(thf)₂] ( 5a , 5b , 5c , 5d ), [(^Ar1NCO^Ar2)LuCl₂(thf)₂] ( 6a , 6d ), [(^Ar1NCO^Ar2)GdCl₂(thf)₂] ( 7 ), [{(^Ar1NCS^Me)Y(μ‐Cl)}₂{(μ‐Cl)Li(thf)₂(μ‐Cl)}₂] ( 8 , 9 ), and [{(^Ar1NCS^Me)Gd(μ‐Cl)}₂{(μ‐Cl)Li(thf)₂(μ‐Cl)}₂] ( 10 , 11 ). These diamagnetic complexes were characterized by ¹H and ¹³C NMR spectroscopy and the molecular structures of compounds 5a , 6a , 7 , and 10 were well‐established by X‐ray diffraction analysis. In compounds 5a , 6a , and 7 , all of the metal centers adopted distorted pentagonal bipyramidal geometries with the NCO donors and two oxygen atoms from the coordinated THF molecules in equatorial positions and the two chlorine atoms in apical positions. Complex 10 is a dimer in which the two equal moieties are linked by two chlorine atoms and two Cl? Li? Cl bridges. In each part, the gadolinium atom adopts a distorted pentagonal bipyramidal geometry. Activated with alkylaluminum and borate, the gadolinium and yttrium complexes showed various activities towards the polymerization of isoprene, thereby affording highly cis‐1,4‐selective polyisoprene, whilst the NCO? lutetium complexes were inert under the same conditions.     

Quantum Chemical Insight of the Dimetallic Sulfide Endohedral Fullerene Sc2S@C70: Does It Possess the Conventional D5h Cage?

Like C₆₀, C₇₀ is one of the most representative fullerenes in fullerene science. Even though there are 8149 C₇₀ isomers, only two of them have been found before: the conventional D_5h and an isolated pentagon rule (IPR)‐violating C_2v(7854). Through the use of quantum chemical methods, we report a new unconventional C₇₀ isomer, C₂(7892), which survives in the form of dimetallic sulfide endohedral fullerene Sc₂S@C₇₀. Compared with the IPR‐obeying C₇₀ and the C_2v(7854) fullerene with three pairs of pentagon adjacencies, the C₂(7892) cage violates the isolated pentagon rule and has two pairs of pentagon adjacencies. In Sc₂S@C₂(7892)‐C₇₀, two scandium atoms coordinate with two pentalene motifs, respectively, presenting two equivalent Sc? S bonds. The strong coordination interaction, along with the electron transfer from the Sc₂S cluster to the fullerene cage, results in the stabilization of the non‐IPR endohedral fullerene. The electronic structure of Sc₂S@C₇₀ can be formally described as [Sc₂S]⁴⁺@[C₇₀]^4?; however, a substantial overlap between the metallic orbitals and cage orbitals has also been found. Electrochemical properties and electronic absorption, infrared, and ¹³C NMR spectra of Sc₂S@C₇₀ have been calculated theoretically.     

Functionalization of Pentaphosphorus Cations by Complexation

The chemistry of polyphosphorus cations has rapidly developed in recent years, but their coordination behavior has remained mostly unexplored. Herein, we describe the reactivity of [P₅R₂]⁺ cations with cyclopentadienyl metal complexes. The reaction of [Cp^ArFe(μ‐Br)]₂ (Cp^Ar=C₅(C₆H₄‐4‐Et)₅) with [P₅R₂][GaCl₄] (R=iPr and 2,4,6‐Me₃C₆H₂ (Mes)) afforded bicyclo[1.1.0]pentaphosphanes ( 1‐R , R=iPr and Mes), showing an unsymmetric “butterfly” structure. The same products 1‐R were formed from K[Cp^Ar] and [P₅R₂][GaCl₄]. The cationic complexes [Cp^ArCo(η⁴‐P₅R₂)][GaCl₄] ( 2‐R [GaCl₄], R=iPr and Cy) and [(Cp^ArNi)₂(η^3:3‐P₅R₂)][GaCl₄] ( 3‐R [GaCl₄]) were obtained from [P₅R₂][GaCl₄] and [Cp^ArM(μ‐Br)]₂ (M=Co and Ni) as well as by using low‐valent “Cp^ArM^I” sources. Anion metathesis of 2‐R [GaCl₄] and 3‐R [GaCl₄] was achieved with Na[BArF₂₄]. The P₅ framework of the resulting salts 2‐R [BArF₂₄] can be further functionalized with nucleophiles. Thus reactions with [Et₄N]X (X=CN and Cl) give unprecedented cyano‐ and chloro‐functionalized complexes, while organo‐functionalization was achieved with CyMgCl.     

Experimental and Computational Studies of the Molybdenum‐Flanking Arene Interaction in Quadruply Bonded Dimolybdenum Complexes with Terphenyl Ligands

To clarify the nature of the Mo?C_arene interaction in terphenyl complexes with quadruple Mo?Mo bonds, ether adducts of composition [Mo₂(Ar′)(I)(O₂CR)₂(OEt₂)] have been prepared and characterized (Ar′=Ar^Xyl₂, R=Me; Ar′=ArMes₂, R=Me; Ar′=Ar^Xyl2, R=CF₃) (Mes=mesityl; Xyl=2,6‐Me₂C₆H₃, from now on xylyl) and their reactivity toward different neutral Lewis bases investigated. PMe₃, P(OMe)₃ and PiPr₃ were chosen as P‐donors and the reactivity studies complemented with the use of the C‐donors CNXyl and CN₂C₂Me₄ (1,3,4,5‐tetramethylimidazol‐2‐ylidene). New compounds of general formula [Mo₂(Ar′)(I)(O₂CR)₂( L )] were obtained, except for the imidazol‐2‐ylidene ligand that yielded a salt‐like compound of composition [Mo₂(Ar^Xyl2)(O₂CMe)₂(CN₂C₂Me₄)₂]I. The Mo?C_arene interaction in these complexes has been analyzed with the aid of X‐ray data and computational studies. This interaction compensates the coordinative and electronic unsaturation of one of the Mo atoms in the above complexes, but it seems to be weak in terms of sharing of electron density between the Mo and C_arene atoms and appears to have no appreciable effect in the length of the Mo?Mo, Mo?X, and Mo? L bonds present in these molecules.     

Micron‐granula polyolefin with self‐immobilized nickel and iron diimine catalysts bearing one or two allyl groups

Self‐immobilized nickel and iron diimine catalysts bearing one or two allyl groups of [ArN?C]₂(C₁₀H₆)NiBr₂ [Ar = 4‐allyl‐2,6‐(i‐Pr)₂C₆H₂] ( 1 ), [ArN?C(Me)][Ar′N? C(Me)]C₅H₃NFeCl₂ [Ar = Ar′ = 4‐allyl‐2,6‐(i‐Pr)₂C₆H₃, Ar = 2,6‐(i‐Pr)₂C₆H₃, and Ar′ = 4‐allyl‐2,6‐(i‐Pr)₂C₆H₃] were synthesized and characterized. All three catalysts were investigated for olefin polymerization. As a result, these catalysts not only showed high activities as the catalyst free from the allyl group, such as [ArN?C]₂C₁₀H₆NiBr₂ (Ar = 2,6‐(i‐Pr)₂C₆H₂)], but also greatly improved the morphology of polymer particles to afford micron‐granula polyolefin. The self‐immobilization of catalysts, the formation mechanism of microspherical polymer, and the influence on the size of the particles are discussed. The molecular structure of self‐immobilized nickel catalyst 1 was also characterized by crystallographic analysis. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1018–1024, 2004     

From Disilene (SiSi) to Phosphasilene (SiP) and Phosphacumulene (PCN)

The generation of heavier double‐bond systems without by‐ or side‐product formation is of considerable importance for their application in synthesis. Peripheral functional groups in such alkene homologues are promising in this regard owing to their inherent mobility. Depending on the steric demand of the N‐alkyl substituent R, the reaction of disilenide Ar₂Si?Si(Ar)Li (Ar=2,4,6‐iPr₃C₆H₂) with ClP(NR₂)₂ either affords the phosphinodisilene Ar₂Si?Si(Ar)P(NR₂)₂ (for R=iPr) or P‐amino functionalized phosphasilenes Ar₂(R₂N)Si? Si(Ar)?P(NR₂) (for R=Et, Me) by 1,3‐migration of one of the amino groups. In case of R=Me, upon addition of one equivalent of tert‐butylisonitrile a second amino group shift occurs to yield the 1‐aza‐3‐phosphaallene Ar₂(R₂N)Si? Si(NR₂)(Ar)? P?C?NtBu with pronounced ylidic character. All new compounds were fully characterized by multinuclear NMR spectroscopy as well as single‐crystal X‐ray diffraction and DFT calculations in selected cases.