Neuartige Silane mit sterisch anspruchsvollen Aryl‐Substituenten

Novel Silanes with Sterically Demanding Aryl Substituents A series of novel m‐terphenylsilanes was synthesized and fully characterized. Halogenation of Si(C₆H₃‐2,6‐Trip₂)H₃ ( 1 , Trip = C₆H₂‐2,4,6‐iPr₃) with ICl and BI₃ afforded the m‐terphenylmonochlorosilane Si(C₆H₃‐2,6‐Trip₂)H₂Cl ( 2 ) and the m‐terphenyldiiodosilane Si(C₆H₃‐2,6‐Trip₂)HI₂ ( 3 ), respectively. The chiral phosphanylmethylsilane Si(C₆H₃‐2,6‐Trip₂)HCl(CH₂PMe₂) ( 6 ) was obtained by metathetical exchange of Si(C₆H₃‐2,6‐Trip₂)HCl₂ ( 4 ) with the Grignard reagent Me₂PCH₂MgCl ( 5 ). Similarly, metathetical exchange of SiBr₄ with 0.5 equiv. of {Li(C₆H₃‐2,6‐Mes)}₂ ( 7 ) yielded the m‐terphenyltribromsilane Si(C₆H₃‐2,6‐Mes₂)Br₃ ( 8 ). A Pd(II) catalyzed reaction of MesSiH₃ ( 10 ) with 2‐iodopropane afforded the triiodosilane MesSiI₃ ( 11 ) bearing the sterically less demanding mesityl substituent. The silanes were fully characterized and the molecular structures of compounds 2 and 11 were determined by single‐crystal X‐ray diffraction.     

Synthesis and Utility of Neptunium(III) Hydrocarbyl Complex

To extend organoactinide chemistry beyond uranium, reported here is the first structurally characterized transuranic hydrocarbyl complex, Np[η⁴‐Me₂NC(H)C₆H₅]₃ ( 1 ), from reaction of NpCl₄(DME)₂ with four equivalents of K[Me₂NC(H)C₆H₅]. Unlike the U^III species, the neptunium analogue can be used to access other Np^III complexes. The reaction of 1 with three equivalents of HE₂C(2,6‐Mes₂‐C₆H₃) (E=O, S) yields [(2,6‐Mes₂‐C₆H₃)CE₂]₃Np(THF)₂, maintaining the trivalent oxidation state.     

Rhenium–Germanium Triple Bonds: Syntheses and Reactions of the Germylidyne Complexes mer‐[X2(PMe3)3ReGe?R] (X=Cl,I, H; R=m‐terphenyl)

A general approach to the first compounds that contain rhenium–germanium triple and double bonds is reported. Heating [ReCl(PMe₃)₅] ( 1 ) with the arylgermanium(II) chloride GeCl(C₆H₃‐2,6‐Trip₂) ( 2 ; Trip=2,4,6‐triisopropylphenyl) results in the germylidyne complex mer‐[Cl₂(PMe₃)₃Re?Ge? C₆H₃‐2,6‐Trip₂] ( 4 ) upon PMe₃ elimination. An equilibrium that is dependent on the PMe₃ concentration exists between complexes 1 and 4 . Removal of the volatile PMe₃ shifts the equilibrium towards complex 4 , whereas treatment of 4 with an excess of PMe₃ gives a 1:1 mixture of 1 and the PMe₃ adduct of 2 , GeCl(C₆H₃‐2,6‐Trip₂)(PMe₃) ( 2 ‐PMe₃). Adduct 2 ‐PMe₃ can be selectively obtained by addition of PMe₃ to chlorogermylidene 2 . The NMR spectroscopic data for 2 ‐PMe₃ indicate an equilibrium between 2 ‐PMe₃ and its dissociation products, 2 and PMe₃, which is shifted far towards the adduct site at ambient temperature. NMR spectroscopic monitoring of the reaction of complex 1 with 2 and the reaction of complex 4 with PMe₃ revealed the formation of two key intermediates, which were identified to be the chlorogermylidene complexes cis/trans‐[Cl(PMe₃)₄Re?Ge(Cl)C₆H₃‐2,6‐Trip₂] (cis/trans‐ 3 ) by using NMR spectroscopy. Labile chlorogermylidene complexes cis/trans‐ 3 can be also generated from trans‐[Cl(PMe₃)₄Re?Ge? C₆H₃‐2,6‐Trip₂]BPh₄ ( 9 ) and (nBu₄N)Cl at low temperature, and decompose at ambient temperature to give a mixture of complexes 1 and 4 . Complex 4 reacts with LiI to give the diiodido derivative mer‐[I₂(PMe₃)₃Re?Ge? C₆H₃‐2,6‐Trip₂] ( 5 ), which undergoes a metathetical iodide/hydride exchange with Na(BEt₃H) to give the dihydrido germylidyne complex mer‐[H₂(PMe₃)₃Re?Ge? C₆H₃‐2,6‐Trip₂] ( 6 ). Carbonylation of 4 induces a chloride migration from rhenium to the germanium atom to afford the chlorogermylidene complex mer‐[Cl(CO)(PMe₃)₃Re?Ge(Cl)C₆H₃‐2,6‐Trip₂] ( 7 ). Similarly, MeNC converts complex 4 into the methylisocyanide analogue mer‐[Cl(MeNC)(PMe₃)₃Re?Ge(Cl)C₆H₃‐2,6‐Trip₂] ( 8 ). Chloride abstraction from 4 by NaBPh₄ in the presence of PMe₃ gives the cationic germylidyne complex trans‐[Cl(PMe₃)₄Re?Ge? C₆H₃‐2,6‐Trip₂]BPh₄ ( 9 ). Heating complex 4 with cis‐[Mo(PMe₃)₄(N₂)₂] induces a germylidyne ligand transfer from rhenium to molybdenum to afford the germylidyne complex trans‐[Cl(PMe₃)₄Mo?Ge? C₆H₃‐2,6‐Trip₂] ( 10 ). All new compounds were fully characterized and their molecular structures studied by X‐ray crystallography, which led to the first experimentally determined Re? Ge triple‐ and double‐bond lengths.     

Heavy Carbene Analogues: Donor‐Free Bismuthenium and Stibenium Ions

Kinetically stabilized congeners of carbenes, R₂C, possessing six valence electrons (four bonding electrons and two non‐bonding electrons) have been restricted to Group 14 elements, R₂E (E=Si, Ge, Sn, Pb; R=alkyl or aryl) whereas isoelectronic Group 15 cations, divalent species of type [R₂E]⁺ (E=P, As, Sb, Bi; R=alkyl or aryl), were unknown. Herein, we report the first two examples, namely the bismuthenium ion [(2,6‐Mes₂C₆H₃)₂Bi][BAr^F₄] ( 1 ; Mes=2,4,6‐Me₃C₆H₂, Ar^F=3,5‐(CF₃)₂C₆H₃) and the stibenium ion [(2,6‐Mes₂C₆H₃)₂Sb][B(C₆F₅)₄] ( 2 ), which were obtained by using a combination of bulky meta‐terphenyl substituents and weakly coordinating anions.     

Sterically Crowded Terphenylselenium Compounds

Extremely bulky terphenyltriselanes RSeSeSeR with R = 2,6‐(2,4,6‐Me₃C₆H₂)₂C₆H₃ and 2,6‐(2,4,6‐iPr₃C₆H₂)₂C₆H₃ were prepared. The chlorination with sulfuryl chloride resulted in the formation of the corresponding selenenyl chlorides RSeCl. In the case of the methyl substituted derivative, also a chlorination of the mesityl groups was observed and the derivative could be isolated. The molecular structure of the isopropyl substituted triselane [2,6‐(2,4,6‐iPr₃C₆H₂)₂C₆H₃Se]₂Se and that of 2,6‐(2,4,6‐Me₃C₆Cl₂)₂C₆H₃SeCl, have been determined by X‐Ray diffraction.     

A Sterically Hindered Phosphonic Acid with a Hydrogen‐Bonded Cage Structure: [4‐tert‐Bu‐2,6‐Mes2‐C6H2P(O)(OH)2·H2O]4

The synthesis and molecular structure of the novel phosphonic acid 4‐tert‐Bu‐2,6‐Mes₂‐C₆H₂P(O)(OH)₂ ( 1 ) is reported. Compound 1 crystallizes in form of its monohydrate as a hydrogen‐bonded cluster ( 1·H₂O )₄ comprizing four phosphonic acid molecules (O···O 2.383(3)‐3.006(4) Å). Additionally, sterically hindered terphenyl‐substituted phosphorus compounds of the type 4‐tert‐Bu‐2,6‐Mes₂‐C₆H₂PR(O)(OH) ( 5 , R = H; 7 , R = O₂CC₆H₄‐3‐Cl; 9 , R = OEt) were prepared, which all show dimeric hydrogen‐bonded structures with O···O distances in the range 2.489(2)–2.519(3) Å. Attempts at oxidizing 5 using H₂O₂, KMnO₄, O₃, or Me₃NO in order to give 1 failed. Crystallization of 5 in the presence of Me₃NO gave the novel hydrogen bonded aggregate 4‐tert‐Bu‐2,6‐Mes₂‐C₆H₂PH(O)(OH)·ONMe₃ ( 6 ) showing an O–H···O distance of 2.560(4) Å.     

A Diazabutadiene stabilized Nickel(0) Cyclooctadiene Complex: Synthesis,Characterization and the Reaction with Diphenylacetylene

The reaction of [Ni(COD)₂] with one equivalent of DAB^Mes (DAB^Mes = (2,4,6‐Me₃C₆H₂)N=C(Me)‐C(Me)=N(2,4,6‐Me₃C₆H₂)) affords a mixture of the compound [Ni(DAB^Mes)₂] ( 2 ) and starting material [Ni(COD)₂]. The crystallographically characterized, diamagnetic complex 2 can be obtained in a stoichiometric reaction of [Ni(COD)₂] and two equivalents of DAB^Mes. This reaction can be accelerated by addition of 1‐chloro‐fluorobenzene or methyl iodide. In the presence of 1‐chloro‐fluorobenzene, [Ni(DAB^Mes)(COD)] ( 3 ) is available via reaction of [Ni(COD)₂] and one equivalent of DAB^Mes. The crystallographically characterized complex 3 reacts with diphenylacetylene to afford [Ni(DAB^Mes)(Ph‐C≡C‐Ph)] ( 4 ). A long‐wavelength absorption band in the UV‐Vis spectrum of this compound has to be assigned to a mixed MLCT/LL′CT transition, as quantum chemical calculations reveal.     

A New Method of Synthesis of Monomeric Aryloxide Complexes of Manganese(II): Structures of Manganese Phenoxides

Monomeric manganese(II) complexes of bulky alkyl/ aryl‐substituted phenoxides, [Mn{C₆H_nR_mO}₂(DME)] [ 1 : R = C₆H₅, n = 3, m = 2 (2,6); 2 : R = Me₃C, n = 3, m = 2 (2,6); 3 : R = Me₃C, n = 2, m = 3 (2,4,6)] were prepared in yields of 37, 44 and 72 %, respectively, from the reaction of manganese powder, Hg(C₆F₅)₂ and the corresponding phenol in the presence of a little mercury in dimethoxyethane (DME). The compounds were characterized spectroscopically and by magnetic measurements. The single crystal structures of 1 and 3 and also of the mixed phenoxide complex [Mn{(C₆H₃(C₆H₅)₂‐2,6‐O}{C₆H₃(Me₃C)₂‐2,6‐O}(DME)] 4 are reported.     

Palladium(II) complexes of Y,C,Y‐chelated phosphines: synthesis,structure, and catalytic activity in Suzuki–Miyaura reaction

The phosphines L¹PPh₂ (1) and L²PPh₂ (2) containing different Y,C,Y‐chelating ligands, L¹ = 2,6‐(^tBuOCH₂)₂C₆H₃^? and L² = 2,6‐(Me₂NCH₂)₂C₆H₃^?, were treated with PdCl₂ and di‐µ‐chloro‐bis[2‐[(N,N‐dimethylamino)methyl]phenyl‐C,N]‐dipalladium(II) and yielded complexes trans‐{[2,6‐(^tBuOCH₂)₂C₆H₃]PPh₂}₂PdCl₂ (3), {[2,6‐(Me₂NCH₂)₂C₆H₃]PPh₂} PdCl₂ (4), {[2,6‐(^tBuOCH₂)₂C₆H₃]PPh₂}Pd(Cl)[2‐(Me₂NCH₂)C₆H₄] (5) and {[2,6‐(Me₂NCH₂)₂C₆H₃]PPh₂}Pd(Cl)[2‐(Me₂NCH₂)C₆H₄] (6) as the result of different ability of starting phosphines 1 and 2 to complex PdCl₂. Compounds 3–6 were characterized by ¹H, ¹³C, ³¹P NMR spectroscopy and ESI‐MS. The molecular structures of 3,4 and 6 were also determined by X‐ray diffraction analysis. The catalytic activity of complexes 3–6 was evaluated in the Suzuki‐Miyaura cross‐coupling reaction. Copyright © 2010 John Wiley & Sons, Ltd.     

Bis(β‐diketiminato) lanthanide amides: synthesis,structure and catalysis for the polymerization of l‐lactide and ε‐caprolactone

Treatment of the chlorides (L^2,6‐iPr2_Ph)₂LnCl (L^2,6‐iPr2_Ph = [(2,6‐ⁱPr₂C₆H₃)NC(Me)CHC(Me)N(C₆H₅)]^?) with 1 equiv. of NaNH(2,6‐ⁱPr₂C₆H₃) afforded the monoamides (L^2,6‐iPr2_Ph)₂LnNH(2,6‐ⁱPr₂C₆H₃) (Ln = Y ( 1 ), Yb ( 2 )) in good yields. Anhydrous LnCl₃ reacted with 2 equiv. of NaL^2,6‐iPr2_Ph in THF, followed by treatment with 1 equiv. of NaNH(2,6‐ⁱPr₂C₆H₃), giving the analogues (L^2,6‐iPr2_Ph)₂LnNH(2,6‐ⁱPr₂C₆H₃) (Ln = Sm ( 3 ), Nd ( 4 )). Two monoamido complexes stabilized by two L^2‐Me ligands, (L^2‐Me)₂LnNH(2,6‐ⁱPr₂C₆H₃) (L^2‐Me = [N(2‐MeC₆H₄)C(Me)]₂CH)^?; Ln = Y ( 5 ), Yb ( 6 )), were also synthesized by the latter route. Complexes 1 , 2 , 3 , 4 , 5 , 6 were fully characterized, including X‐ray crystal structure analyses. Complexes 1 , 2 , 3 , 4 , 5 , 6 are isostructural. The central metal in each complex is ligated by two β‐diketiminato ligands and one amido group in a distorted trigonal bipyramid. All the complexes were found to be highly active in the ring‐opening polymerization of L‐lactide (L‐LA) and ε‐caprolactone (ε‐CL) to give polymers with relatively narrow molar mass distributions. The activity depends on both the central metal and the ligand (Yb < Y < Sm ≈ Nd and L^2‐Me < L^2,6‐iPr2_Ph). Remarkably, the binary 3/benzyl alcohol (BnOH) system exhibited a striking ‘immortal’ nature and proved able to quantitatively convert 5000 equiv. of L‐LA with up to 100 equiv. of BnOH per metal initiator. All the resulting PLAs showed monomodal, narrow distributions (M_w/M_n = 1.06 ? 1.08), with molar mass (M_n) decreasing proportionally with an increasing amount of BnOH. The binary 4/BnOH system also exhibited an ‘immortal’ nature in the polymerization of ε‐CL in toluene. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthetic,Mechanistic, and Theoretical Studies on the Generation of Iridium Hydride Alkylidene and Iridium Hydride Alkene Isomers

Experimental and theoretical studies on equilibria between iridium hydride alkylidene structures, [(Tp^Me2)Ir(H){?C(CH₂R)ArO }] (Tp^Me2=hydrotris(3,5‐dimethylpyrazolyl)borate; R=H, Me; Ar=substituted C₆H₄ group), and their corresponding hydride olefin isomers, [(Tp^Me2)Ir(H){R(H)C? C(H)OAr}], have been carried out. Compounds of these types are obtained either by reaction of the unsaturated fragment [(Tp^Me2)Ir(C₆H₅)₂] with o‐C₆H₄(OH)CH₂R, or with the substituted anisoles 2,6‐Me₂C₆H₃OMe, 2,4,6‐Me₃C₆H₂OMe, and 4‐Br‐2,6‐Me₂C₆H₂OMe. The reactions with the substituted anisoles require not only multiple C? H bond activation but also cleavage of the Me? OAr bond and the reversible formation of a C? C bond (as revealed by ¹³C labeling studies). Equilibria between the two tautomeric structures of these complexes were achieved by prolonged heating at temperatures between 100 and 140 °C, with interconversion of isomeric complexes requiring inversion of the metal configuration, as well as the expected migratory insertion and hydrogen‐elimination reactions. This proposal is supported by a detailed computational exploration of the mechanism at the quantum mechanics (QM) level in the real system. For all compounds investigated, the equilibria favor the alkylidene structure over the olefinic isomer by a factor of between approximately 1 and 25. Calculations demonstrate that the main reason for this preference is the strong Ir–carbene interactions in the carbene isomers, rather than steric destabilization of the olefinic tautomers.     

A Systematic Study of Structure and E−H Bond Activation Chemistry by Sterically Encumbered Germylene Complexes

A series of new germylene compounds has been synthesized offering systematic variation in the σ‐ and π‐capabilities of the α‐substituent and differing levels of reactivity towards E?H bond activation (E=H, B, C, N, Si, Ge). Chloride metathesis utilizing [(terphenyl)GeCl] proves to be an effective synthetic route to complexes of the type [(terphenyl)Ge(ER_n)] ( 1 – 6 : ER_n=NHDipp, CH(SiMe₃)₂, P(SiMe₃)₂, Si(SiMe₃)₃ or B(NDippCH)₂; terphenyl=C₆H₃Mes₂‐2,6=Ar^Mes or C₆H₃Dipp₂‐2,6=Ar^Dipp; Dipp=C₆H₃iPr₂‐2,6, Mes=C₆H₂Me₃‐2,4,6), while the related complex [{(Me₃Si)₂N}Ge{B(NDippCH)₂}] ( 8 ) can be accessed by an amide/boryl exchange route. Metrical parameters have been probed by X‐ray crystallography, and are consistent with widening angles at the metal centre as more bulky and/or more electropositive substituents are employed. Thus, the widest germylene units (θ>110°) are found to be associated with strongly σ‐donating boryl or silyl ancillary donors. HOMO–LUMO gaps for the new germylene complexes have been appraised by DFT calculations. The aryl(boryl)‐germylene system [Ar^MesGe{B(NDippCH)₂}] ( 6 ‐Mes), which features a wide C‐Ge‐B angle (110.4(1)°) and (albeit relatively weak) ancillary π‐acceptor capabilities, has the smallest HOMO–LUMO gap (119 kJ mol^?1). These features result in 6 ‐Mes being remarkably reactive, undergoing facile intramolecular C?H activation involving one of the mesityl ortho‐methyl groups. The related aryl(silyl)‐germylene system, [Ar^MesGe{Si(SiMe₃)₃}] ( 5 ‐Mes) has a marginally wider HOMO–LUMO gap (134 kJ mol^?1), rendering it less labile towards decomposition, yet reactive enough to oxidatively cleave H₂ and NH₃ to give the corresponding dihydride and (amido)hydride. Mixed aryl/alkyl, aryl/amido and aryl/phosphido complexes are unreactive, but amido/boryl complex 8 is competent for the activation of E?H bonds (E=H, B, Si) to give hydrido, boryl and silyl products. The results of these reactivity studies imply that the use of the very strongly σ‐donating boryl or silyl substituents is an effective strategy for rendering metallylene complexes competent for E?H bond activation.     

Synthesis,Characterization, and Reactivity of a Uranium(VI) Carbene Imido Oxo Complex

We report the uranium(VI) carbene imido oxo complex [U(BIPM^TMS)(NMes)(O)(DMAP)₂] ( 5 , BIPM^TMS=C(PPh₂NSiMe₃)₂; Mes=2,4,6‐Me₃C₆H₂; DMAP=4‐(dimethylamino)pyridine) which exhibits the unprecedented arrangement of three formal multiply bonded ligands to one metal center where the coordinated heteroatoms derive from different element groups. This complex was prepared by incorporation of carbene, imido, and then oxo groups at the uranium center by salt elimination, protonolysis, and two‐electron oxidation, respectively. The oxo and imido groups adopt axial positions in a T‐shaped motif with respect to the carbene, which is consistent with an inverse trans‐influence. Complex 5 reacts with tert‐butylisocyanate at the imido rather than carbene group to afford the uranyl(VI) carbene complex [U(BIPM^TMS)(O)₂(DMAP)₂] ( 6 ).     

Reversible Oxidative Addition at Carbon

The reactivity of N‐heterocyclic carbenes (NHCs) and cyclic alkyl amino carbenes (cAACs) with arylboronate esters is reported. The reaction with NHCs leads to the reversible formation of thermally stable Lewis acid/base adducts Ar‐B(OR)₂⋅NHC ( Add1 – Add6 ). Addition of cAAC^Me to the catecholboronate esters 4‐R‐C₆H₄‐Bcat (R=Me, OMe) also afforded the adducts 4‐R‐C₆H₄Bcat⋅cAAC^Me ( Add7 , R=Me and Add8 , R=OMe), which react further at room temperature to give the cAAC^Me ring‐expanded products RER1 and RER2 . The boronate esters Ar‐B(OR)₂ of pinacol, neopentylglycol, and ethyleneglycol react with cAAC at RT via reversible B−C oxidative addition to the carbene carbon atom to afford cAAC^Me(B{OR}₂)(Ar) ( BCA1 – BCA6 ). NMR studies of cAAC^Me(Bneop)(4‐Me‐C₆H₄) ( BCA4 ) demonstrate the reversible nature of this oxidative addition process.     

New Insights into the Formation and Reactivity of Molecular Organostannonic Acids

The controlled base hydrolysis of 2,6‐Mes₂C₆H₃SnCl₃ ( 1 ; Mes=mesityl) provided 2,6‐Mes₂C₆H₃Sn(OH)Cl₂?H₂O ( 2 ) and the trinuclear organostannonic acid trans‐[2,6‐Mes₂C₆H₃Sn(O)OH]₃ ( 3 ), respectively. In moist C₆D₆, 3 reversibly reacts with water to give the monomeric organostannonic acid 2,6‐Mes₂C₆H₃Sn(OH)₃ ( 3a ). The reaction of 3 with (tBu₂SnO)₃, Ph₂PO₂H, and NaH, gives rise to the multinuclear hypercoordinated organostannoxane clusters [tBu₂Sn(OH)OSnR(OH)₂OC(OSntBu₂OH)₂(O)SnR(OH)(H₂O)]₂ ( 5 ), [RSn(OH)₂(O₂PPh₂)]₂ ( 6 ), and Na₃(RSn)₄O₆(OH)₃ ( 7 ), respectively (R=2,6‐Mes₂C₆H₃). The characterization of the new compounds is achieved by multinuclear NMR spectroscopy and electrospray mass spectrometry in solution and ¹¹⁹Sn MAS NMR spectroscopy, IR spectroscopy, and X‐ray crystallography in the solid‐state.     

Synthesis and cytostatic activity of Pt(II) complexes of intramolecularly coordinated phosphine and stibine ligands

The intramolecularly coordinated phosphine and stibine ligands L¹PPh₂ ( 1 ), L²PPh₂ ( 2 ) and L²SbPh₂ ( 3 ) containing Y,C,Y‐chelating ligands, L¹ = 2,6‐(^tBuOCH₂)₂C₆H₄^? and L² = 2,6‐(Me₂NCH₂)₂C₆H₄^?, were prepared and characterized. The treatment of these ligands 1 , 2 , 3 with PtCl₂ yielded complexes trans‐{[2,6‐(^tBuOCH₂)₂C₆H₃]PPh₂}₂PtCl₂ (4), cis‐{[2,6‐(Me₂NCH₂)₂C₆H₃]PPh₂}PtCl₂ (5), and cis‐{[2,6‐(Me₂NCH₂)₂C₆H₃]SbPh₂}PtCl₂ (6) as the result of different ability of the starting compounds 1 , 2 , 3 to complex platinum centre. Compounds 1 , 2 , 3 , 4 , 5 , 6 were characterized by ¹H, ¹³C and ³¹P NMR spectroscopy and electrospray ionization mass spectrometry, and molecular structures of 3 , 4 , 5 , 6 were determined by X‐ray diffraction analysis. The substitution reactions of complexes 4 , 5 , 6 were also studied. The reaction of 5 and 6 with NaI yielded complexes {[2,6‐(Me₂NCH₂)₂C₆H₃]PPh₂}PtI₂ ( 7 ) and {[2,6‐(Me₂NCH₂)₂C₆H₃]SbPh₂}PtI₂ ( 8 ), while the same reaction of 4 with NaI did not proceed. As the compounds 7 and 8 structurally resemble cisplatin, complex {{[2‐(Me₂NCH₂)‐6‐(Me₂NHCH₂)C₆H₃]PPh₂}PtCl₂}⁺Cl^? ( 9 ) was prepared as water‐soluble platinum complex. The cytotoxic effect of complex 9 was evaluated on human T‐lymphocytic leukemia cells MOLT‐4 (IC₅₀ = 27.6 ± 1.8 µmol l^?1) and human promyelocytic leukemia HL‐60 (IC₅₀ = 55.9 ± 4.9 µmol l^?1). Copyright © 2012 John Wiley & Sons, Ltd.     

Olefin polymerization and copolymerization with soluble transition‐metal complex catalysts

Olefin polymerizations catalyzed by Cp′TiCl₂(O‐2,6‐ⁱPr₂C₆H₃) ( 1 – 5 ; Cp′ = cyclopentadienyl group), RuCl₂(ethylene)(pybox) { 7 ; pybox = 2,6‐bis[(4S)‐4‐isopropyl‐2‐oxazolin‐2‐yl]pyridine}, and FeCl₂(pybox) ( 8 ) were investigated in the presence of a cocatalyst. The Cp*TiCl₂(O‐2,6‐ⁱPr₂C₆H₃) ( 5 )–methylaluminoxane (MAO) catalyst exhibited remarkable catalytic activity for both ethylene and 1‐hexene polymerizations, and the effect of the substituents on the cyclopentadienyl group was an important factor for the catalytic activity. A high level of 1‐hexene incorporation and a lower r_E · r_H value with 5 than with [Me₂Si(C₅Me₄)(N^tBu)]TiCl₂ ( 6 ) were obtained, despite the rather wide bond angle of Cp Ti O (120.5°) of 5 compared with the bond angle of Cp Ti N of 6 (107.6°). The 7 –MAO catalyst exhibited moderate catalytic activity for ethylene homopolymerization and ethylene/1‐hexene copolymerization, and the resultant copolymer incorporated 1‐hexene. The 8 –MAO catalyst also exhibited activity for ethylene polymerization, and an attempted ethylene/1‐hexene copolymerization gave linear polyethylene. The efficient polymerization of a norbornene macromonomer bearing a ring‐opened poly(norbornene) substituent was accomplished by ringopening metathesis polymerization with the well‐defined Mo(CHCMe₂Ph)(N‐2,6‐ⁱPr₂C₆H₃)[OCMe(CF₃)₂]₂ ( 10 ). The key step for the macromonomer synthesis was the exclusive end‐capping of the ring‐opened poly(norbornene) with p‐Me₃SiOC₆H₄CHO, and the use of 10 was effective for this polymerization proceeding with complete conversion. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4613–4626, 2000     

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.     

Synthesis and Characterization of m‐Terphenyl (1,3‐Diphenylbenzene) Compounds Containing Trifluoromethyl Groups

The bis(silyl)triazene compound 2,6‐(Me₃Si)₂‐4‐Me‐1‐(N?N? NC₄H₈)C₆H₂ ( 4 ) was synthesized by double lithiation/silylation of 2,6‐Br₂‐4‐Me‐1‐(N?N? NC₄H₈)C₆H₂ ( 1 ). Furthermore, 2,6‐bis[3,5‐(CF₃)₂‐C₆H₃]‐4‐Me‐C₆H₂‐1‐(N?N? NC₄H₈)C₆H₂ derivative 6 can be easily synthesized by a C,C‐bond formation reaction of 1 with the corresponding aryl‐Grignard reagent, i.e., 3,5‐bis[(trifluoromethyl)phenyl]magnesium bromide. Reactions of compound 4 with KI and 6 with I₂ afforded in good yields novel phenyl derivatives, 2,6‐(Me₃Si)₂‐4‐MeC₆H₂? I and 2,6‐bis[3,5‐(CF₃)₂? C₆H₃]‐4‐MeC₆H₂? I ( 5 and 7 , resp.). On the other hand, the analogous m‐terphenyl 1,3‐diphenylbenzene compound 2,6‐bis[3,5‐(CF₃)₂? C₆H₃]C₆H₃? I ( 8 ) could be obtained in moderate yield from the reaction of (2,6‐dichlorophenyl)lithium and 2 equiv. of aryl‐Grignard reagent, followed by the reaction with I₂. Different attempts to introduce the ^tBu (Me₃C) or neophyl (PhC(Me)₂CH₂) substituents in the central ring were unsuccessful. All the compounds were fully characterized by elemental analysis, melting point, IR and NMR spectroscopy. The structure of compound 6 was corroborated by single‐crystal X‐ray diffraction measurements.     

Protonation and methylation of η-2,3,5,6-tetramethyl-1,4-benzoquinone(η-pentamethylcyclopentadienyl)cobalt

The preparation of the η⁴-4-2,3,5,6-tetramethyl-1,4-benzoquinonecomplex [CO(C₅Me₅)(C₁₀H₁₂O₂)] (I) is reported. Complex I undergoesreversible protonation to yield the 2-6-η-4-hydroxy-1-oxo-2,3,5,6-tetramethylcyclohexadienyl complex [Co(C₅Me₅)(C₁₀H₁₃O₂)BF₄ (II) and diprotonation to yield the η⁶-6-1,4-dihydroxy-2,3,5,6-tetramethylbenzene complex [Co(C₅Me₅)(C₁₀H₁₄O₂)] (BF₄)₂ (III). Methylation of complex I with MeI/AgPF₆ gives the 2---6-η-4-methoxy-1-oxo-2,3,5,6-tetramethylcyclohexadienyl complex [Co(C₅Me₅)(C₁₁H₁₅O₂])PF₆ (IV). In trifluoroacetic acid solution complex IV is protonated to form the η⁶-1-hydroxy-4-methoxy-2,3,5,6-tetramethylbenzene cation [Co(C₅Me₅)-(C₁₁H₁₆O₂)]²⁺