Syntheses and Structures of Coordination Polymers Constructed by Semi‐Rigid Bicarboxylic Acid Ligands

The complexes [Co(L¹)(mpy)] ( 1 ), [Ni(L¹)(mpy)] ( 2 ), [Co(L¹)(tbpy)] · 2H₂O ( 3 ), [Ni₂(L¹)₂(tbpy)₂] · 5H₂O ( 4 ), [Mn₂(L¹)₂(tbpy)₂] · 3H₂O ( 5 ), [Mn(L¹)(biim‐3)] ( 6 ), [Ni₂(L¹)₂(btb)₂(H₂O)] · 2H₂O ( 7 ), [Cu(L²)(mpy)] · 7H₂O ( 8 ), [Co(L²)(tbpy)(H₂O)] ( 9 ), [Ni(L²)(tbpy)(H₂O)] · H₂O ( 10 ), [Cu(L²)(bib)] · 2H₂O ( 11 ), and [Cu(L²)(btb)] · 2H₂O ( 12 ) [H₂L¹ = (3‐carboxyl‐phenyl)‐(4‐(2′‐carboxyl‐phenyl)‐benzyl)ether, H₂L² = 3‐carboxy‐1‐(4′‐carboxybenzyl)‐2‐oxidopyridinium, mpy = 2‐(4‐(4′‐methylphenyl)‐6‐(pyrindin‐2‐yl)pyridin‐2‐yl)pyridine), tbpy = 2‐(4‐(4′‐tert‐butylphenyl)‐6‐(pyrindin‐2‐yl)pyridin‐2‐yl)pyridine), biim‐3 = 1,3‐bis(imidazol‐1′‐yl)propane, btb = 1,4‐bis(1,2,4‐triazol‐1‐ylmethyl)benzene, bib = 1,4‐bis(imidazol‐1′‐ylmethyl)benzene] were synthesized. Compounds 1 – 6 have similar 1D chain structures, which are further linked by π–π interactions to generate supramolecular double chains for 1 and 2 , and supramolecular layers for 3 – 6 . Compound 7 displays a 3D 6‐connected framework with (4⁴ · 6¹¹) topology. Compound 8 features a monomolecular structure, which is further linked by hydrogen bonds between the lattice water molecules and carboxylate oxygen atoms of L² anions to form a 2D supramolecular layer. The monomolecular structures of 9 and 10 are connected by hydrogen bonds and π–π interactions simultaneously to generate supramolecular layers. Compounds 11 and 12 show layer structures.     

Dilithium Hexaorganostannate(IV) Compounds

Hypercoordination of main‐group elements such as the heavier Group 14 elements (silicon, germanium, tin, and lead) usually requires strong electron‐withdrawing ligands and/or donating groups. Herein, we present the synthesis and characterization of two hexaaryltin(IV) dianions in form of their dilithium salts [Li₂(thf)₂{Sn(2‐py^Me)₆}] (py^Me=C₅H₃N‐5‐Me) ( 2 ) and [Li₂{Sn(2‐py^OtBu)₆}] (py^OtBu=C₅H₃N‐6‐OtBu) ( 3 ). Both complexes are stable in the solid state and solution under inert conditions. Theoretical investigations of compound 2 reveal a significant valence 5s‐orbital contribution of the tin atom forming six strongly polarized tin–carbon bonds.     

Synthesis of rhodium(III) complexes with tris/tetrakis‐benzimidazoles and benzothiazoles—quick identification of cyclometallation by nuclear magnetic resonance spectroscopy

Reactions of rhodium(III) halides with multidentate N,S‐heterocycles, (LH₃) 1,3,5‐tris(benzimidazolyl)benzene (L¹H₃; 1 ), 1,3,5‐tris(N‐methylbenzimidazolyl) benzene (L²H₃; 2 ) and 1,3,5‐tris(benzothiazolyl)benzene (L³H₃; 3 ), in the molar ratio 1:1 in methanol–chloroform produced mononuclear cyclometallated products of the composition [RhX₂(LH₂)(H₂O)] (X = Cl, Br, I; LH₂ = L¹H₂, L²H₂, L³H₂). When the metal to ligand ( 1–3 or 1,2,4,5‐tetrakis(benzothiazolyl)benzene [L⁴H₂; 4 ]) molar ratio was 2:1, the reactions yielded binuclear complexes of the compositions [Rh₂Cl₅(LH₂)(H₂O)₃] (LH₂ = L¹H₂, L²H₂, L³H₂) and [Rh₂X₄(L⁴)(H₂O)₂] (X = Cl, Br, I). Elemental analysis, IR and ¹H nuclear magnetic resonance (NMR) chemical shifts supported the binuclear nature of the complexes. Cyclometallation was detected by conventional ¹³C NMR spectra that showed a doublet around ～190 ppm. Cyclometallation was also detected by gradient‐enhanced heteronuclear multiple bond correlation (g‐HMBC) experiment that showed cross‐peaks between the cyclometallated carbon and the central benzene ring protons of 1–3 . Cyclometallation was substantiated by two‐dimensional ¹H? ¹H correlated experiments (gradiant‐correlation spectroscopy and rotating frame Overhauser effect spectroscopy) and ¹H? ¹³C single bond correlated two‐dimensional NMR experiments (gradient‐enhanced heteronuclear single quantum coherence). The ¹H? ¹⁵N g‐HMBC experiment suggested the coordination of the heterocycles to the metal ion via tertiary nitrogen. Copyright © 2009 John Wiley & Sons, Ltd.     

Lanthanide(II) Complexes of the Dihydrotriazinido Ligand [N{C(Ph)=N}2C(tBu)Ph]−

The potassium dihydrotriazinide K(L^Ph,tBu) ( 1 ) was obtained by a metal exchange route from [Li(L^Ph,tBu)(THF)₃] and KOtBu (L^Ph,tBu = [N{C(Ph)=N}₂C(tBu)Ph]). Reaction of 1 with 1 or 0.5 equivalents of SmI₂(thf)₂ yielded the monosubstituted Sm^II complex [Sm(L^Ph,tBu)I(THF)₄] ( 2 ) or the disubstituted [Sm(L^Ph,tBu)₂(THF)₂] ( 3 ), respectively. Attempted synthesis of a heteroleptic Sm^II amido‐alkyl complex by the reaction of 2 with KCH₂Ph produced compound 3 due to ligand redistribution. The Yb^II bis(dihydrotriazinide) [Yb(L^Ph,tBu)₂(THF)₂] ( 4 ) was isolated from the 1:1 reaction of YbI₂(THF)₂ and 1 . Molecular structures of the crystalline compounds 2 , 3· 2C₆H₆ and 4· PhMe were determined by X‐ray crystallography.     

Synthesis and spectroscopic characterization of aryloxide derivatives of titanium(IV) and zirconium(IV)

Homo- and heteroleptic aryloxides of the type MX_4–x(OAr)_x [M = Ti^IV, Zr^IV; X = OPrⁱ, Cl; x = 1,2,3,4; OAr = OC₆H₄Prⁱ-4(OAr¹), OC₆H₃Me-2-Prⁱ-5(OAr²), OC₆H₃Me-5-Prⁱ-2(OAr³), OC₆H₂Me₃-2,4,6(OAr⁴), OC₆H₃Bu^t₂-2,4(OAr⁵), OC₆H₃Bu^t₂-2,6(OAr⁶)] have been prepared either by alkoxo–aryloxo or chloro-aryloxo exchange reactions in benzene or tetrahydrofuran. All these new derivatives have been characterized by elemental analyses, spectroscopic (i.r., ¹H-, ¹³C-n.m.r.) studies and molecular weight measurements. The FAB mass spectral studies of four representative derivatives Support a dimeric nature for [Ti(OC₆H₃Me-5-Prⁱ-2)₄], [TiCl₂(OC₆H₃Me-5-Prⁱ-2)₂], and [Zr(OC₆H₃Bu^t₂-2,4)₄(thf)], whereas the derivative [ZrCl(OC₆H₃Bu^t₂-2,4)₃(thf)] is monomeric.     

Discrete Magnesium Hydride Aggregates: A Cationic Mg13H18 Cluster Stabilized by NNNN‐Type Macrocycles

Large magnesium hydride aggregates [Mg₁₃(Me₃TACD)₆(μ₂‐H₁₂)(μ₃‐H₆)][A]₂ ((Me₃TACD)H=1,4,7‐trimethyl‐1,4,7,10‐tetraazacyclododecane; A=AlEt₄, AlnBu₄, B{3,5‐(CF₃)₂C₆H₃}₄) were synthesized stepwise from alkyl complexes [Mg₂(Me₃TACD)R₃] (R=Et, nBu) and phenylsilane in the presence of additional Mg^II ions. The central magnesium atom is octahedrally coordinated by six hydrides as in solid α‐MgH₂ of the rutile type. Further coordination to six magnesium atoms leads to a substructure of seven edge‐sharing octahedra as found in the hexagonal layer of brucite (Mg(OH)₂). Upon protonolysis in the presence of 1,2‐dimethoxyethane (DME), this cluster was degraded into a tetranuclear dication [Mg₂(Me₃TACD)(μ‐H)₂(DME)]₂[A]₂.     

Synthesis and Crystal Structures of Lithium,Sodium, and ­Potassium Derivatives of 2‐(Methylthio)aniline and 2‐(Phenylthio)aniline

2‐(Methylthio)aniline (H₂L¹) and 2‐(phenylthio)aniline (H₂L²) were treated with n‐butyllithium to yield the corresponding anilides [LiHL¹] and [LiHL²]. Recrystallization from diethyl ether and THF afforded the solvates [LiHL¹(Et₂O)] and [LiHL²(THF)₂]. The X‐ray crystal structure determination revealed dimeric molecules which exhibit a centrosymmetric Li₂N₂ ring. In the case of [LiHL¹(Et₂O)] the SMe group is involved in Li coordination and in the case of [LiHL²(THF)₂] the SPh group is part of an intramolecular N–H ··· S hydrogen bridge. The sodium anilides [NaHL¹(DME)] and [NaHL²(DME)] were obtained from the reaction of H₂L¹ and H₂L² with sodium amide in DME as solvent. Like in the case of the lithium amides the sodium derivatives [NaHL¹(DME)] and [NaHL²(DME)] display centrosymmetric Na₂N₂ cores. The coordination sphere of the sodium atoms is completed by DME molecules, which act as chelating ligands. In the case of [NaHL¹(DME)] the DME molecules enable additionally a linkage of the dimeric subunits to give a chain structure. The potassium derivatives [KNHL¹] and [KNHL²(DME)] were obtained from H₂L¹ and H₂L² and potassium hydride in DME as solvent. [KNHL¹] displays a distinct structure based on [(KNHL¹)₂] dimers, which are linked by additional [KNHL¹] units to give a 3D coordination polymer with {4.8.16(3)} topology. [KNHL²(DME)] forms dimers linked by bridging DME molecules to give a chain‐like coordination polymer.     

Ein‐ und zweikernige Rhodiumkomplexe mit Arsino(phosphino)methanen in unterschiedlichen Koordinationsformen

Mono‐ and Dinuclear Rhodium Complexes with Arsino(phosphino)methanes in Different Coordination Modes The cyclooctadiene complex [Rh(η⁴‐C₈H₁₂)(κ²‐tBu₂AsCH₂PiPr₂)](PF₆) ( 1a ) reacts with CO and CNtBu to give the substitution products [Rh(L)₂(κ²‐tBu₂AsCH₂PiPr₂)](PF₆) ( 2 , 3 ). From 1a and Na(acac) in the presence of CO the neutral compound [Rh(κ²‐acac)(CO)(κ‐P‐tBu₂AsCH₂PiPr₂)] ( 4 ) is formed. The reactions of 1a , the corresponding B(Ar_F)₄‐salt 1b and [Rh(η⁴‐C₈H₁₂)(κ²‐iPr₂AsCH₂PiPr₂)](PF₆) ( 5 ) with acetonitrile under a H₂ atmosphere affords the complexes [Rh(CH₃CN)₂(κ²‐R₂AsCH₂PiPr₂)]X ( 6a , 6b , 7 ), of which 6a (R = tBu; X = PF₆) gives upon treatment with Na(acac‐f₆) the bis(chelate) compound [Rh(κ²‐acac‐f₆)(κ²‐tBu₂AsCH₂PiPr₂)] ( 8 ). From 8 and CH₃I a mixture of two stereoisomers of composition [Rh(CH₃)I(κ²‐acac‐f₆)(κ²‐tBu₂AsCH₂PiPr₂)] ( 9/10 ) is generated by oxidative addition, and the molecular structure of the racemate 9 has been determined. The reactions of 1a and 5 with CO in the presence of NaCl leads to the formation of the “A‐frame” complexes [Rh₂(CO)₂(μ‐Cl)(μ‐R₂AsCH₂PiPr₂)₂](PF₆) ( 11 , 12 ), which have been characterized crystallographically. From 11 and 12 the dinuclear substitution products [Rh₂(CO)₂(μ‐X)(μ‐R₂AsCH₂PiPr₂)₂](PF₆) ( 13 ‐ 16 ) are obtained by replacing the bridging chloride for bromide, hydride or hydroxide, respectively. While 12 (R = iPr) reacts with NaI to give the related “A‐frame” complex 18 , treatment of 11 (R = tBu) with NaI yields the mononuclear chelate compound [RhI(CO)(κ²‐tBu₂AsCH₂PiPr₂)] ( 20 ). The reaction of 20 with CH₃I affords the acetyl complex [RhI₂{C(O)CH₃}(κ²‐tBu₂AsCH₂PiPr₂)] ( 21 ) with five‐coordinate rhodium atom.     

Electrochemical Synthesis and Characterization of Tin(IV) Complexes of Dianionic Terdentate Schiff Base Ligands

Tin(IV) complexes of the series of dianionic terdentate Schiff bases N‐[(2‐pyrroyl)methylidene]‐N′‐tosylbenzene‐1,2‐diamine, (H₂L¹), N‐[(2‐hydroxyphenyl)methylidene]‐N′‐tosylbenzene‐1,2‐diamine (H₂L²) and some R substituted 2‐{[(2‐hydroxyphenyl)imino]methyl}phenols [R = H (H₂L³), 4,6‐(OCH₃)₂ (H₂L⁴), 3‐(OC₂H₅) (H₂L⁵) and 3,5‐Br₂ (H₂L⁶)] have been synthesized. The compounds were obtained by the electrochemical oxidation of a tin anode in a cell containing an acetonitrile solution of the corresponding ligand. The complex [SnL¹₂] was also obtained by reaction of SnCl₂·2H₂O and H₂L¹ in methanol in the presence of triethylamine. The crystal structure of the ligand [H₂L⁶] and the complexes [SnL¹₂] (1) , [SnL²₂] (2) , [SnL³₂] (3) and [SnL⁶₂] (6) were determined by X‐ray diffraction. In the complexes, the tin atom is in an octahedral environment coordinated by two dianionic terdentate ligands. Spectroscopic data for the complexes (IR, ¹H and ¹¹⁹Sn NMR and mass spectra) are discussed and related to structural information.     

Crystalline Diuranium Phosphinidiide and μ‐Phosphido Complexes with Symmetric and Asymmetric UPU Cores

Reaction of [U(Tren^TIPS)(PH₂)] ( 1 , Tren^TIPS=N(CH₂CH₂NSiPrⁱ₃)₃) with C₆H₅CH₂K and [U(Tren^TIPS)(THF)][BPh₄] ( 2 ) afforded a rare diuranium parent phosphinidiide complex [{U(Tren^TIPS)}₂(μ‐PH)] ( 3 ). Treatment of 3 with C₆H₅CH₂K and two equivalents of benzo‐15‐crown‐5 ether (B15C5) gave the diuranium μ‐phosphido complex [{U(Tren^TIPS)}₂(μ‐P)][K(B15C5)₂] ( 4 ). Alternatively, reaction of [U(Tren^TIPS)(PH)][Na(12C4)₂] ( 5 , 12C4=12‐crown‐4 ether) with [U{N(CH₂CH₂NSiMe₂Bu^t)₂CH₂CH₂NSi(Me)(CH₂)(Bu^t)}] ( 6 ) produced the diuranium μ‐phosphido complex [{U(Tren^TIPS)}(μ‐P){U(Tren^DMBS)}][Na(12C4)₂] [ 7 , Tren^DMBS=N(CH₂CH₂NSiMe₂Bu^t)₃]. Compounds 4 and 7 are unprecedented examples of uranium phosphido complexes outside of matrix isolation studies, and they rapidly decompose in solution underscoring the paucity of uranium phosphido complexes. Interestingly, 4 and 7 feature symmetric and asymmetric UPU cores, respectively, reflecting their differing steric profiles.     

The Simplest Amino‐borane H2B=NH2 Trapped on a Rhodium Dimer: Pre‐Catalysts for Amine–Borane Dehydropolymerization

The μ‐amino–borane complexes [Rh₂(L^R)₂(μ‐H)(μ‐H₂B=NHR′)][BAr^F₄] (L^R=R₂P(CH₂)₃PR₂; R=Ph, ⁱPr; R′=H, Me) form by addition of H₃B?NMeR′H₂ to [Rh(L^R)(η⁶‐C₆H₅F)][BAr^F₄]. DFT calculations demonstrate that the amino–borane interacts with the Rh centers through strong Rh‐H and Rh‐B interactions. Mechanistic investigations show that these dimers can form by a boronium‐mediated route, and are pre‐catalysts for amine‐borane dehydropolymerization, suggesting a possible role for bimetallic motifs in catalysis.     

Reactions of 1,2-catechol with Bu3M (M = Ga, In). Structures of intermediate products

Reactions of 1,2-catechol with ^tBu₃M (M = Ga, In) have been studied. Trinuclear compounds [^tBu₅M₃(OC₆H₄O)₂] [M = Ga (1), M = In (2)] were synthesised in the reaction of 2 equiv. of C₆H₄(OH)₂ with 3 equiv. of ^tBu₃M in refluxing solvents. At room temperature the reaction of 1,2-catechol with ^tBu₃In in Et₂O leads to the formation of a binuclear complex [^tBu₄In₂(OC₆H₄OH)₂ · 2Et₂O] (3) possessing a four-membered In₂O₂ core and two unreacted hydroxyl groups. The same reaction carried out in a non-coordinating solvent (CH₂Cl₂) results in formation a compound [^tBu₃In₂(OC₆H₄O)(OC₆H₄OH)] (4), which undergoes a reaction with ^tBu₃In to yield the product 2. Moreover two intermediate isomeric products 5 and 6 of formula [^tBu₃Ga₂(OC₆H₄O)(OC₆H₄OH)] were isolated from the post-reaction mixture of 1,2-catechol with ^tBu₃Ga. The compound 6 possessing a different coordination of gallium atoms than 5 is a result of the intramolecular rearrangement of the compound 5 to decrease the steric repultion between ligands. Compounds 3 and 6 were structurally characterised. According to the structure of intermediate products 3-6 a reaction pathway of 1,2-catechols with group 13 metal trialkyls was proposed.     

Synthesis of uranium complexes incorporating extended azo-imine ligands: Molecular and electronic structure

The new azo-imine ligands 2,4-di-tert-butyl-6-((2-((2-hydroxyphenyl)diazenyl) phenylimino)methyl)phenol, H₂L¹, 1a, and 2,4-di-tert-butyl-6-((2-((2-hydroxyphenyl) diazenyl)p-chlorophenylimino)phenol, H₂L², 1b, were prepared. Reaction of H₂L¹;1a, and H₂L²;1b, with uranyl nitrate hexahydrate afforded the mononuclear complexes of compositions [U(O)₂(L¹)(H₂O)]; 2a, and [U(O)₂(L²)(H₂O)]; 2b, complexes respectively. The newly synthesised ligands (1a and 1b) and the complexes (2a and 2b) were characterised unequivocally. The x-ray structure of 2a was determined. The tetradentate dianionic ligand (L¹)^2- coordinated the uranium ion equatorially with a water molecule in the same plane. Two axially coordinated oxo ligands completed the overall pentagonal bipyramid geometry around U(VI) ion. Structural pattern, electron transfer properties (oxidation near 1.32 ​V vs Ag/AgCl) and electronic transitions of [U(O)₂(L¹)(H₂O)]; 2a, and [U(O)₂(L²)(H₂O)]; 2b have been rationalized by DFT calculations.     

Structural diversity of polynuclear MgxOy cores in magnesium phenoxide complexes

The binuclear complex bis(2,6‐di‐tert‐butyl‐4‐methylphenolato)‐1κO ,2κO‐(1,2‐dimethoxyethane‐1κ²O ,O ′)bis(μ‐phenylmethanolato‐1:2κ²O :O )(tetrahydrofuran‐2κO )dimagnesium(II), [Mg₂(C₇H₇O)₂(C₁₅H₂₃O)₂(C₄H₈O)(C₄H₁₀O₂)] or [(BHT)(DME)Mg(μ‐OBn)₂Mg(THF)(BHT)], (I), was obtained from the complex [(BHT)Mg(μ‐OBn)(THF)]₂ by substitution of one tetrahydrofuran (THF) molecule with 1,2‐dimethoxyethane (DME) in toluene (BHT is O‐2,6‐^t Bu₂‐4‐MeC₆H₄ and Bn is benzyl). The trinuclear complex bis(2,6‐di‐tert‐butyl‐4‐methylphenolato)‐1κO ,3κO‐tetrakis(μ‐2‐methylphenolato)‐1:2κ⁴O :O ;2:3κ⁴O :O‐bis(tetrahydrofuran)‐1κO ,3κO‐trimagnesium(II), [Mg₃(C₇H₇O)₄(C₁₅H₂₃O)₂(C₄H₈O)₂] or [(BHT)₂(μ‐O‐2‐MeC₆H₄)₄(THF)₂Mg₃], (II), was formed from a mixture of Bu₂Mg, [(BHT)Mg(ⁿ Bu)(THF)₂] and 2‐methylphenol. An unusual tetranuclear complex, bis(μ₃‐2‐aminoethanolato‐κ⁴O :O :O ,N )tetrakis(μ₂‐2‐aminoethanolato‐κ³O :O ,N )bis(2,6‐di‐tert‐butyl‐4‐methylphenolato‐κO )tetramagnesium(II), [Mg₄(C₂H₆NO)₆(C₁₅H₂₃O)₂] or Mg₄(BHT)₂(OCH₂CH₂NH₂)₆, (III), resulted from the reaction between (BHT)₂Mg(THF)₂ and 2‐aminoethanol. A polymerization test demonstrated the ability of (III) to catalyse the ring‐opening polymerization of ϵ‐caprolactone without activation by alcohol. In all three complexes (I)–(III), the BHT ligand demonstrates the terminal κO‐coordination mode. Complexes (I), (II) and (III) have binuclear rhomboid Mg₂O₂, trinuclear chain‐like Mg₃O₄ and bicubic Mg₄O₆ cores, respectively. A survey of the literature on known polynuclear Mg_x O_y core types for ArO–Mg complexes is also presented.     

Die Reaktion von Ytterbium mit N‐Iod‐triphenylphosphanimin. Kristallstrukturen von [Yb2I(THF)2(NPPh3)4] · 2 THF, [YbI2(HNPPh3)(DME)2] und [{YbI2(DME)2}2(μ‐DME)]

The Reaction of Ytterbium with N‐iodo‐triphenylphosphaneimine. Crystal Structures of [Yb₂I(THF)₂(NPPh₃)₄] · 2 THF, [YbI₂(HNPPh₃)(DME)₂], and [{YbI₂(DME)₂}₂(μ‐DME)] When treated with ultrasound, the reaction of ytterbium powder with INPPh₃ in tetrahydrofuran leads to [YbI₂(THF)₄] and to the mixed‐valence phosphoraneiminato complex [Yb₂I(THF)₂(NPPh₃)₄] · 2 THF ( 1 ), which forms red single‐crystals. In the analogous reaction in 1,2‐dimethoxyethane (DME) only the ytterbium(II) iodide solvates [YbI₂(HNPPh₃)(DME)₂] ( 2 ) and [{YbI₂(DME)₂}₂ · (μ‐DME)] ( 3 ) can be isolated, which form yellow single crystals. All compounds were characterized by crystal structure analyses. 1 : Space group P1, Z = 2, lattice dimensions at –80 °C: a = 1337.6(5), b = 1389.6(5), c = 2244.2(17) pm; α = 86.11(7)°, β = 88.06(7)°, γ = 88.63(4)°; R = 0.0759. In 1 the two ytterbium atoms are connected via the N atoms of two phosphoraneiminato groups (NPPh₃^–) to form a planar Yb₂N₂ four‐membered ring. The structure can also be described as an ion pair consisting of [YbI(THF)₂]⁺ and [Yb(NPPh₃)₄]^–. 2 : Space group P2₁, Z = 2, lattice dimensions at –80 °C: a = 811.9(1), b = 1114.0(1), c = 1741.3(1) pm; β = 95.458(5)°; R = 0.0246. 2 forms molecules in which the ytterbium atom is coordinated in a pentagonal‐bipyramidal fashion with the iodine atoms in the axial positions. The O atoms of the two DME‐chelates and the N atom of the phosphaneimine ligand HNPPh₃ are in the equatorial positions. 3 : Space group P1, Z = 2, lattice dimensions at –70 °C: a = 817.5(1), b = 1047.7(1), c = 1115.5(2) pm; α = 90.179(10)°, β = 97.543(15)°, γ = 91.087(12)°; R = 0.0317. 3 has a dimeric molecular structure, in which the two fragments {YbI₂(DME)₂} are connected centrosymmetrically via a μ‐DME bridge. As in 2 , the ytterbium atoms are coordinated in a pentagonal‐bipyramidal fashion with the iodine atoms in the axial positions, as well as with the two DME chelates and with one O atom each of the μ‐DME ligand in the equatorial positions.     

Koordinativ ungesättigte Dieisenkomplexe: Synthese und Kristallstrukturen von [Fe2(CO)4(μ‐H)(μ‐PtBu2)(μ‐Ph2PCH2PPh2)] und [Fe2(CO)4(μ‐CH2)(μ‐H)(μ‐PtBu2)(μ‐Ph2PCH2PPh2)]

Coordinatively Unsaturated Diiron Complexes: Synthesis and Crystal Structures of [Fe₂(CO)₄(μ‐H)(μ‐P^tBu₂)(μ‐Ph₂PCH₂PPh₂)] and [Fe₂(CO)₄(μ‐CH₂)(μ‐H)(μ‐P^tBu₂)(μ‐Ph₂PCH₂PPh₂)] [Fe₂(μ‐CO)(CO)₆(μ‐H)(μ‐P^tBu₂)] ( 1 ) reacts spontaneously with dppm (dppm = Ph₂PCH₂PPh₂) to give [Fe₂(μ‐CO)(CO)₄(μ‐H)(μ‐P^tBu₂)(μ‐dppm)] ( 2 c ). By thermolysis or photolysis, 2 c loses very easily one carbonyl ligand and yields the corresponding electronically and coordinatively unsaturated complex [Fe₂(CO)₄(μ‐H)(μ‐P^tBu₂)(μ‐dppm)] ( 3 ). 3 exhibits a Fe–Fe double bond which could be confirmed by the addition of methylene to the corresponding dimetallacyclopropane [Fe₂(CO)₄(μ‐CH₂)(μ‐H)(μ‐P^tBu₂)(μ‐dppm)] ( 4 ). The reaction of 1 with dppe (Ph₂PC₂H₄PPh₂) affords [Fe₂(μ‐CO)(CO)₄(μ‐H)(μ‐P^tBu₂)(μ‐dppe)] ( 5 ). In contrast to the thermolysis of 2 c , yielding 3 , the heating of 5 in toluene leads rapidly to complete decomposition. The reaction of 1 with PPh₃ yields [Fe₂(CO)₆(H)(μ‐P^tBu₂)(PPh₃)] ( 6 a ), while with ^tBu₂PH the compound [Fe₂(μ‐CO)(CO)₅(μ‐H)(μ‐P^tBu₂)(^tBu₂PH)] ( 6 b ) is formed. The thermolysis of 6 b affords [Fe₂(CO)₅(μ‐P^tBu₂)₂] and the degradation products [Fe(CO)₃(^tBu₂PH)₂] and [Fe(CO)₄(^tBu₂PH)]. The molecular structures of 3 , 4 and 6 b were determined by X‐ray crystal structure analyses.     

Highly Active,Thermally Stable,Ethylene‐Polymerisation Pre‐Catalysts Based on Niobium/Tantalum?Imine Systems

The reactions of MCl₅ or MOCl₃ with imidazole‐based pro‐ligand L¹H, 3,5‐tBu₂‐2‐OH‐C₆H₂‐(4,5‐Ph₂‐1H‐)imidazole, or oxazole‐based ligand L²H, 3,5‐tBu₂‐2‐OH‐C₆H₂(1H‐phenanthro[9,10‐d])oxazole, following work‐up, afforded octahedral complexes [MX(L^{1, 2})], where MX=NbCl₄ (L¹, 1 a ; L², 2 a ), [NbOCl₂(NCMe)] (L¹, 1 b ; L², 2 b ), TaCl₄ (L¹, 1 c ; L², 2 c ), or [TaOCl₂(NCMe)] (L¹, 1 d ). The treatment of α‐diimine ligand L³, (2,6‐iPr₂C₆H₃N?CH)₂, with [MCl₄(thf)₂] (M=Nb, Ta) afforded [MCl₄(L³)] (M=Nb, 3 a ; Ta, 3 b ). The reaction of [MCl₃(dme)] (dme=1,2‐dimethoxyethane; M=Nb, Ta) with bis(imino)pyridine ligand L⁴, 2,6‐[2,6‐iPr₂C₆H₃N?(Me)C]₂C₅H₃N, afforded known complexes of the type [MCl₃(L⁴)] (M=Nb, 4 a ; Ta, 4 b ), whereas the reaction of 2‐acetyl‐6‐iminopyridine ligand L⁵, 2‐[2,6‐iPr₂C₆H₃N?(Me)C]‐6‐Ac‐C₅H₃N, with the niobium precursor afforded the coupled product [({2‐Ac‐6‐(2,6‐iPr₂C₆H₃N?(Me)C)C₅H₃N}NbOCl₂)₂] ( 5 ). The reaction of MCl₅ with Schiff‐base pro‐ligands L⁶H–L¹⁰H, 3,5‐(R¹)₂‐2‐OH‐C₆H₂CH?N(2‐OR²‐C₆H₄), (L⁶H: R¹=tBu, R²=Ph; L⁷H: R¹=tBu, R²=Me; L⁸H: R¹=Cl, R²=Ph; L⁹H: R¹=Cl, R²=Me; L¹⁰H: R¹=Cl, R²=CF₃) afforded [MCl₄(L^6–10)] complexes (M=Nb, 6 a – 10 a ; M=Ta, 6 b – 9 b ). In the case of compound 8 b , the corresponding zwitterion was also synthesised, namely [Ta^?Cl₅(L⁸H)⁺] ? MeCN ( 8 c ). Unexpectedly, the reaction of L⁷H with TaCl₅ at reflux in toluene led to the removal of the methyl group and the formation of trichloride 7 c [TaCl₃(L^7‐Me)]; conducting the reaction at room temperature led to the formation of the expected methoxy compound ( 7 b ). Upon activation with methylaluminoxane (MAO), these complexes displayed poor activities for the homogeneous polymerisation of ethylene. However, the use of chloroalkylaluminium reagents, such as dimethylaluminium chloride (DMAC) and methylaluminium dichloride (MADC), as co‐catalysts in the presence of the reactivator ethyl trichloroacetate (ETA) generated thermally stable catalysts with, in the case of niobium, catalytic activities that were two orders of magnitude higher than those previously observed. The effects of steric hindrance and electronic configuration on the polymerisation activity of these tantalum and niobium pre‐catalysts were investigated. Spectroscopic studies (¹H NMR, ¹³C NMR and ¹H? ¹H and ¹H? ¹³C correlations) on the reactions of compounds 4 a / 4 b with either MAO(50) or AlMe₃/[CPh₃]⁺[B(C₆F₅)₄]^? were consistent with the formation of a diamagnetic cation of the form [L⁴AlMe₂]⁺ (MAO(50) is the product of the vacuum distillation of commercial MAO at +50 °C and contains only 1 mol % of Al in the form of free AlMe₃). In the presence of MAO, this cationic aluminium complex was not capable of initiating the ROMP (ring opening metathesis polymerisation) of norbornene, whereas the 4 a / 4 b systems with MAO(50) were active. A parallel pressure reactor (PPR)‐based homogeneous polymerisation screening by using pre‐catalysts 1 b , 1 c , 2 a , 3 a and 6 a , in combination with MAO, revealed only moderate‐to‐good activities for the homo‐polymerisation of ethylene and the co‐polymerisation of ethylene/1‐hexene. The molecular structures are reported for complexes 1 a – 1 c , 2 b , 5 , 6 a , 6 b, 7 a, 8 a and 8 c .     

Catalytic activity of some organolanthanoid derivatives in styrene and propene polymerization

Organolanthanoids of several classes were examined as potential styrene and propene polymerization catalysts. They are: molecular hydrides of divalent lanthanoids (samarium, europium, ytterbium); naphthalene and stilbene complexes of neodymium(III), samarium(II), europium(II), ytterbium(II), lutetium(III); amides and alkoxides (including heterobifunctional derivatives) of praseodymium(III), neodymium(III), samarium(II), europium(II), thulium(III), ytterbium(II, III); thiolate of samarium(III); phenyl and phenylethinyl derivatives of europium(II), thulium(III), ytterbium(II); methylytterbium cluster Yb₈ (μ‐CH₃)₁₄(μ‐CH₂)(THF)₆; heterobimetallic samarium(II), ytterbium(II, III) complexes; diazabutadiene ytterbium(III) derivatives; metallic praseodymium and ytterbium, activated by iodine. The highest activity in styrene polymerization revealed hydrides, naphthalene and stilbene complexes of samarium(II), europium(II) and ytterbium(II). In the propene polymerization only [(η⁵‐C₅H₄)CH₂CH­(CH₂OBu)(η¹‐O)]YbMe(THF) displayed noticeable activity.Copyright © 2001 John Wiley & Sons, Ltd.     

Modulation of the unpaired spin localization in Pentavalent Uranyl Complexes

The electronic structure of various complexes of pentavalent uranyl species, namely UO₂⁺, is described, using DFT methods, with the aim of understanding how the structure of the ligands may influence the localisation of the unpaired 5f electron of uranium (V) and, finally, the stability of such complexes towards oxidation. Six complexes have been inspected: [UO₂py₅]⁺ (1), [(UO₂py₅)KI₂] (2), [UO₂(salan-^tBu₂)(py)K] (3), [UO₂(salophen-^tBu₂)(thf)K] (4), [UO₂(salen-^tBu₂)(py)K] (5), [and UO₂-cyclo[6]pyrrole]^1? (6), chosen to explore various ligands. In the five first complexes, the UO₂⁺ species is well identified with the unpaired electron localized on the 5f uranium orbital. Additionally, for the salan, salen and salophen ligands, some covalent interactions have been observed, resulting from the presence of both donor and acceptor binding sites. In contrast, the last complex is best described by a UO₂²⁺ uranyl (VI) coordinated by the anionic radical cyclopyrrole, the highly delocalized π orbitals set stabilizing the radical behaviour of this ligand.     

Binary and ternary oxorhenium(V) complexes: synthesis,characterization, and crystal structure

A series of anionic five-coordinate binary oxorhenium(V) complexes with dithiolato ligands, Bu₄N[ReO(L¹)₂] (1a), Bu₄N[ReO(L²)₂] (1b), and Bu₄N[ReO(L³)₂] (1c), and a series of neutral octahedral ternary oxorhenium(V) complexes of mixed dithiolato and bipyridine ligands, [ReO(L¹)(bpy)Cl] (2a), [ReO(L²)(bpy)Cl] (2b), and [ReO(L³)(bpy)Cl] (2c) (where L¹H₂ = ethane-1,2-dithiol, L²H₂ = propane-1,3-dithiol, L³H₂ = toluene-3,4-dithiol, and bpy = 2,2′-bipyridine), were isolated and characterized by physicochemical and spectroscopic methods. The solid state structure of 1c was established by X-ray crystallography. All the mononuclear oxorhenium(V) complexes are diamagnetic. The redox behavior of all the complexes has been studied voltammetrically.