Kinetics of propylene polymerization initiated by rac‐Me2Si(1‐C5H2‐2‐Me‐4‐tBu)2Zr(NME2)2/MAO catalyst

The kinetics of propylene polymerization initiated by ansa‐metallocene diamide compound rac‐Me₂Si(CMB)₂Zr(NMe₂)₂ (rac‐1, CMB = 1‐C₅H₂‐2‐Me‐4‐^tBu)/methylaluminoxane (MAO) catalyst were investigated. The formation of cationic active species has been studied by the sequential NMR‐scale reactions of rac‐1 with MAO. The rac‐1 is first transformed to rac‐Me₂Si(CMB)₂ZrMe₂ (rac‐2) through the alkylation mainly by free AlMe₃ contained in MAO. The methylzirconium cations are then formed by the reaction of rac‐2 and MAO. Small amount of MAO ([Al]/[Zr] = 40) is enough to completely activate rac‐1 to afford methylzirconium cations that can polymerize propylene. In the lab‐scale polymerizations carried out at 30°C in toluene, the rate of polymerization (R_p) shows maximum at [Al]/[Zr] = 6,250. The R_p increases as the polymerization temperature (T_p) increases in the range of T_p between 10 and 70°C and as the catalyst concentration increases in the range between 21.9 and 109.6 μM. The activation energies evaluated by simple kinetic scheme are 4.7 kcal/mol during the acceleration period of polymerization and 12.2 kcal/mol for an overall reaction. The introduction of additional free AlMe₃ before activating rac‐1 with MAO during polymerization deeply influences the polymerization behavior. The iPPs obtained at various conditions are characterized by high melting point (approximately 155°C), high stereoregularity (almost 100% [mmmm] pentad), low molecular weight (MW), and narrow molecular weight distribution (below 2.0). The fractionation results by various solvents show that iPPs produced at T_p below 30°C are compositionally homogeneous, but those obtained at T_p above 40°C are separated into many fractions. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 737–750, 1999     

The effect of AlR3 on propylene polymerization by rac‐(EBI)Zr(NMe2)2/AlR3/[CPh3][B(C6F5)4] catalyst

Ansa‐zirconocene diamide complex rac‐(EBI)Zr(NMe₂)₂ [rac‐1, EBI = ethylene‐1,2‐bis(1‐indenyl)] reacted with AlR₃ (R = Me, Et, iBu) or Al(iBu₂)H and then with [CPh₃][B(C₆F₅)₄] (2) in toluene in order to perform propylene polymerization by cationic alkylzirconium species, which are in situ generated during polymerization. Through the sequential NMR‐scale reactions of rac‐1 with AlR₃ or Al(iBu₂)H and then with 2, rac‐1 was demonstrated to be transformed to the active alkyzirconium cations via alkylated intermediates of rac‐1. The cationic species generated by using AlMe₃, AlEt₃, and Al(iBu₂)H as alkylating reagents tend to become heterodinuclear complex; however, those by using bulky Al(iBu)₃ become base‐free [rac‐(EBI)Zr(iBu)]⁺ cations. The activity of propylene polymerization by rac‐1/AlR₃/2 catalyst was deeply influenced by various parameters such as the amount and the type of AlR₃, metallocene concentration, [Al]/[2] ratio, and polymerization temperature. Generally the catalytic systems using bulky alkylaluminum like Al(iBu)₃ and Al(iBu)₂H show higher activity but lower stereoregularity than those using less bulky AlMe₃ and AlEt₃. The alkylating reagent Al(iBu)₃ is not a transfer agent as good as AlMe₃ or AlEt₃. The polymerization activities show maximum around [Al]/[2] ratio of 1.0 and increase monotonously with polymerization temperature. The overall activation energy of both rac‐1/Al(iBu)₃/2 and rac‐1/Al(iBu)₂H catalysts is 6.0 kcal/mol. As the polymerization temperature increases, the stereoregularity of the resulting polymer decreases markedly, which is demonstrated by the decrease of [mmmm] pentad value and by the increase of the amount of polymer soluble in low boiling solvent. The physical properties of polymers produced in this study were investigated by using ¹³C‐NMR, differential scanning calorimetry (DSC), viscometry, and gel permeation chromatography (GPC). © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1523–1539, 1999     

Higher α‐olefin polymerizations catalyzed by rac‐Me2Si(1‐C5H2‐2‐CH3‐4‐tBu)2Zr(NMe2)2/Al(iBu)3/[Ph3C][B(C6F5)4]

Polymerizations of higher α‐olefins, 1‐pentene, 1‐hexene, 1‐octene, and 1‐decene were carried out at 30 °C in toluene by using highly isospecific rac‐Me₂Si(1‐C₅H₂‐2‐CH₃‐4‐^t Bu)₂Zr(NMe₂)₂ (rac‐1) compound in the presence of Al(iBu)₃/[CPh₃][B(C₆F₅)₄] as a cocatalyst formulation. Both the bulkiness of monomer and the lateral size of polymer influenced the activity of polymerization. The larger lateral of polymer chain opens the π‐ligand of active site wide and favors the insertion of monomer, while the large size of monomer inserts itself into polymer chain more difficultly due to the steric hindrance. Highly isotactic poly(α‐olefin)s of high molecular weight (MW) were produced. The MW decreased from polypropylene to poly(1‐hexene), and then increased from poly(1‐hexene) to poly(1‐decene). The isotacticity (as [mm] triad) of the polymer decreased with the increased lateral size in the order: poly(1‐pentene) > poly(1‐hexene) > poly(1‐octene) > poly(1‐decene). The similar dependence of the lateral size on the melting point of polymer was recorded by differential scanning calorimetry (DSC). ¹H NMR analysis showed that vinylidene group resulting from β‐H elimination and saturated methyl groups resulting from chain transfer to cocatalyst are the main end groups of polymer chain. The vinylidene and internal double bonds are also identified by Raman spectroscopy. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1687–1697, 2000     

Rare‐Earth‐Metal Methyl,Amide, and Imide Complexes Supported by a Superbulky Scorpionate Ligand

The reaction of monomeric [(Tp^tBu,Me)LuMe₂] (Tp^tBu,Me=tris(3‐Me‐5‐tBu‐pyrazolyl)borate) with primary aliphatic amines H₂NR (R=tBu, Ad=adamantyl) led to lutetium methyl primary amide complexes [(Tp^tBu,Me)LuMe(NHR)], the solid‐state structures of which were determined by XRD analyses. The mixed methyl/tetramethylaluminate compounds [(Tp^tBu,Me)LnMe({μ₂‐Me}AlMe₃)] (Ln=Y, Ho) reacted selectively and in high yield with H₂NR, according to methane elimination, to afford heterobimetallic complexes: [(Tp^tBu,Me)Ln({μ₂‐Me}AlMe₂)(μ₂‐NR)] (Ln=Y, Ho). X‐ray structure analyses revealed that the monomeric alkylaluminum‐supported imide complexes were isostructural, featuring bridging methyl and imido ligands. Deeper insight into the fluxional behavior in solution was gained by ¹H and ¹³C NMR spectroscopic studies at variable temperatures and ¹H–⁸⁹Y HSQC NMR spectroscopy. Treatment of [(Tp^tBu,Me)LnMe(AlMe₄)] with H₂NtBu gave dimethyl compounds [(Tp^tBu,Me)LnMe₂] as minor side products for the mid‐sized metals yttrium and holmium and in high yield for the smaller lutetium. Preparative‐scale amounts of complexes [(Tp^tBu,Me)LnMe₂] (Ln=Y, Ho, Lu) were made accessible through aluminate cleavage of [(Tp^tBu,Me)LnMe(AlMe₄)] with N,N,N′,N′‐tetramethylethylenediamine (tmeda). The solid‐state structures of [(Tp^tBu,Me)HoMe(AlMe₄)] and [(Tp^tBu,Me)HoMe₂] were analyzed by XRD.     

Functionalization of [Ge9] with Small Silanes:[Ge9(SiR3)3]– (R = iBu,iPr, Et) and the Structures of (CuNHCDipp)[Ge9{Si(iBu)3}3], (K‐18c6)Au[Ge9{Si(iBu)3}3]2, and (K‐18c6)2[Ge9{Si(iBu)3}2]

Novel silylation reactions at [Ge₉] Zintl clusters starting from the chlorosilanes SiR₃Cl (R = iBu, iPr, Et) and the Zintl phase K₄Ge₉ are reported. The formation of the tris‐silylated anions [Ge₉(SiR₃)₃]^– [R = iBu ( 1a ), iPr ( 1b ), Et ( 1c )] by heterogeneous reactions in acetonitrile was monitored by ESI‐MS measurements. For R = iBu ¹H, ¹³C and ²⁹Si NMR experiments confirmed the exclusive formation of 1a . Subsequent reactions of 1a with CuNHC^DippCl and Au(PPh₃)Cl result in formation of the neutral metal complex (CuNHC^Dipp)[Ge₉{Si(iBu)₃}₃]·0.5 tol ( 2 ·0.5 tol) and the metal bridged dimeric unit {Au[Ge₉{Si(iBu)₃}₃]₂}^– ( 3a ), isolated as a (K‐18c6)⁺ salt in (K‐18c6)Au[Ge₉{Si(iBu)₃}₃]₂·tol ( 3 ·tol), respectively. Finally, from a toluene/hexane solution of 1a in presence of 18‐crown‐6, crystals of the compound (K‐18c6)₂[Ge₉{Si(iBu)₃}₂]·tol ( 4 ·tol), containing the bis‐silylated cluster anion [Ge₉(Si(iBu)₃)₂]^2– ( 4a ), were obtained. The compounds 2 ·0.5 tol, 3 ·tol and 4 ·tol were characterized by single‐crystal structure determination.     

Studien zur Reaktion von [Me2AlP(SiMe3)2]2 mit basenstabilisierten Organogalliumchloriden und ‐hydriden

Investigations on the Reactivity of [Me₂AlP(SiMe₃)₂]₂ with Base‐stabilized Organogalliumhalides and ‐hydrides [Me₂AlP(SiMe₃)₂]₂ ( 1 ) reacts with dmap?Ga(Cl)Me₂, dmap?Ga(Me)Cl₂, dmap?GaCl₃ and dmap?Ga(H)Me₂ with Al‐P bond cleavage and subsequent formation of heterocyclic [Me₂GaP(SiMe₃)₂]₂ ( 2 ) as well as dmap?AlMe_xCl_3?x (x = 3 8 ; 2 3 ; 1 4 ; 0 5 ). The reaction between equimolar amounts of dmap?Al(Me₂)P(SiMe₃)₂ and dmap?Ga(t‐Bu₂)Cl yield dmap?Ga(t‐Bu₂)P(SiMe₃)₂ ( 6 ) and dmap?AlMe₂Cl ( 3 ). 2 – 8 were characterized by NMR spectroscopy, 2 and 6 also by single crystal X‐ray diffraction.     

Imino‐Bridged Bisphosphaalkenes (2,4‐Diphospha‐3‐azapentadienes)

Deprotonation of aminophosphaalkenes (RMe₂Si)₂C?PN(H)(R′) (R=Me, iPr; R′=tBu, 1‐adamantyl (1‐Ada), 2,4,6‐tBu₃C₆H₂ (Mes*)) followed by reactions of the corresponding Li salts Li[(RMe₂Si)₂C?P(M)(R′)] with one equivalent of the corresponding P‐chlorophosphaalkenes (RMe₂Si)₂C?PCl provides bisphosphaalkenes (2,4‐diphospha‐3‐azapentadienes) [(RMe₂Si)₂C?P]₂NR′. The thermally unstable tert‐butyliminobisphosphaalkene [(Me₃Si)₂C?P]₂NtBu ( 4 a ) undergoes isomerisation reactions by Me₃Si‐group migration that lead to mixtures of four‐membered heterocyles, but in the presence of an excess amount of (Me₃Si)₂C?PCl, 4 a furnishes an azatriphosphabicyclohexene C₃(SiMe₃)₅P₃NtBu ( 5 ) that gave red single crystals. Compound 5 contains a diphosphirane ring condensed with an azatriphospholene system that exhibits an endocylic P?C double bond and an exocyclic ylidic P⁽⁺⁾? C^(?)(SiMe₃)₂ unit. Using the bulkier iPrMe₂Si substituents at three‐coordinated carbon leads to slightly enhanced thermal stability of 2,4‐diphospha‐3‐azapentadienes [(iPrMe₂Si)₂C?P]₂NR′ (R′=tBu: 4 b ; R′=1‐Ada: 8 ). According to a low‐temperature crystal‐structure determination, 8 adopts a non‐planar structure with two distinctly differently oriented P?C sites, but ³¹P NMR spectra in solution exhibit singlet signals. ³¹P NMR spectra also reveal that bulky Mes* groups (Mes*=2,4,6‐tBu₃C₆H₂) at the central imino function lead to mixtures of symmetric and unsymmetric rotamers, thus implying hindered rotation around the P? N bonds in persistent compounds [(RMe₂Si)₂C?P]₂NMes* ( 11 a , 11 b ). DFT calculations for the parent molecule [(H₃Si)₂C?P]₂NCH₃ suggest that the non‐planar distortion of compound 8 will have steric grounds.     

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     

Copolymerization of propylene and 1,5‐hexadiene with stereospecific metallocene/Al(i‐Bu)3/[Ph3C][B(C6F5)4]

Copolymerizations of propylene (P) with 1,5‐hexadiene (1,5‐HD) were carried out with isospecific rac‐1,2‐ethylenebis(1‐indenyl)Zr(NMe₂)₂ [rac‐(EBI)Zr(NMe₂)₂, 1] and syndiospecific isopropylidene(cyclopentadienyl)(9‐fluorenyl)ZrMe₂ [i‐Pr(Cp)(Flu)ZrMe₂, 2] compounds combined with Al(i‐Bu)₃/[Ph₃C][B(C₆F₅)₄] as a cocatalyst system. Microstructures of poly(propylene‐co‐1,5‐HD) were determined by ¹H NMR, ¹³C NMR, Raman spectroscopies and X‐ray powder diffraction. The isospecific 1/Al(i‐Bu)₃/[Ph₃C][B(C₆F₆)₄] catalyst showed much higher polymerization rate than 2/Al(i‐Bu)₃/[Ph₃C][B(C₆F₆)₄] system, however, the latter system showed higher incorporation of 1,5‐HD (r_P = 8.85, r_1,5‐HD = 0.274) than the former system (r_P = 16.25, r_1,5‐HD = 0.34). The high value of r_P × r_1,5‐HD far above 1 demonstrated that the copolymers obtained by both catalysts are somewhat blocky. The insertion of 1,5‐HD proceeded by enantiomorphic site control; however, the diastereoselectivity of the intramolecular cyclization reaction of 1,2‐inserted 1,5‐HD was independent of the stereospecificity of metallocene compounds, but dependent on the concentration of 1,5‐HD in the feed. The insertion of the monomers by enantiomorphic site control could also be realized by Raman spectroscopy and X‐ray powder diffraction of the polymers. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1590–1598, 2000     

Using Me3Si–F–Al(ORF)3 and Me3Si–Cl as Methylating Agents – Synthesis and Characterization of SeMeCl2[F{Al(ORF)3}2]

Upon reacting SeCl₄ with Me₃Si–F–Al(OR^F)₃, the selenonium salt SeMeCl₂[al‐f‐al] ( 1 ) {[al‐f‐al]^– = [F[Al(OC(CF₃)₃)₃]₂]^–} was obtained and characterized by NMR, IR, and Raman spectroscopy as well as single crystal XRD experiments. Despite the [SeX₃]⁺ (X = F, Cl, Br, I) and [SeR₃]⁺ salts (R = aliphatic organic residue) being well known and thoroughly studied, the mixed cations are scarce. The only previous example of a salt with the [SeMeCl₂]⁺ cation is SeMeCl₂[SbCl₆], which was never structurally characterized and is unstable in solution over hours. Only ¹H‐NMR studies and IR spectra of this compound are known. The unexpected use of Me₃Si–F–Al(OR^F)₃ as a methylating agent was investigated via DFT calculations and NMR experiments of the reaction solution. The reaction of SeCl₃[al‐f‐al] with Me₃Si‐Cl at room temperature in CH₂Cl₂ proved to yield the same product with Me₃Si–Cl acting as a methylating agent.     

Heterobi‐ and ‐trimetallic Ion Pairs of Zirconocene‐Based Isoselective Olefin Polymerization Catalysts with AlMe3

The reactivity towards AlMe₃ of discrete cationic ansa‐zirconocenes 2 a,b that are ubiquitously used in isoselective propylene polymerization and based on [{Ph(H)C(3,6‐tBu₂‐Flu)(3‐tBu‐5‐Et‐Cp)}ZrMe₂)] {Cp‐Flu} and rac‐[{Me₂Si‐(2‐Me‐4‐Ph‐Ind)₂}ZrMe₂] {SBI} was scrutinized. The first example of a structurally characterized Group 4 metallocene AlMe₃ adduct ( 3 b ) is reported. In the presence of excess AlMe₃, the {SBI}‐based AlMe₃ adduct 3 b undergoes a slow decomposition via C? H activation in a bridging methyl unit to yield a new species ( 4 b ) with a trimetallic {Zr(μ‐CH₂)(μ‐Me)AlMe(μ‐Me)AlMe₂} core. EXSY NMR data for the process 2 b ? 3 b → 4 b suggest very rapid and reversible binding of an additional AlMe₃ molecule onto AlMe₃ adduct 3 b . The resulting heterotrimetallic species intermediates exchange of methyl groups between different metal centers and slowly undergoes the C? H activation reaction towards 4 b .     

Komplexchemie P‐reicher Phosphane und Silylphosphane. XXII. Die Bildung von [η2‐{tBu–P=P–SiMe3}Pt(PR3)2]aus (Me3Si)tBuP–P=P(Me)tBu2 und [η2‐{C2H4}Pt(PR3)2]

Coordination Chemistry of P‐rich Phosphanes and Silylphosphanes. XXII. The Formation of [η²‐{^tBu–P=P–SiMe₃}Pt(PR₃)₂] from (Me₃Si)^tBuP–P=P(Me)^tBu₂ and [η²‐{C₂H₄}Pt(PR₃)₂] (Me₃Si)^tBuP–P = P(Me)^tBu₂ reacts with [η²‐{C₂H₄}Pt(PR₃)₂] yielding [η²‐{^tBu–P=P–SiMe₃}Pt(PR₃)₂]. However, there is no indication for an isomer which would be the analogue to the well known [η²‐{^tBu₂P–P}Pt(PPh₃)₂]. The syntheses and NMR data of [η²‐{^tBu–P=P–SiMe₃}Pt(PPh₃)₂] and [η²‐{^tBu–P=P–SiMe₃}Pt(PMe₃)₂] as well as the results of the single crystal structure determination of [η²‐{^tBu–P=P–SiMe₃}Pt(PPh₃)₂] are reported.     

ɛ‐caprolactone and lactide polymerization promoted by an ionic titanium(IV)/iron(III) polynuclear halo‐alkoxide

The ionic [Ti₃(µ₃‐OPrⁱ)₂(µ‐OPrⁱ)₃(OPrⁱ)₆][FeCl₄] halo‐alkoxide ( A ) was investigated for its activity towards the bulk polymerization of rac‐lactide (rac‐LA) and ?‐caprolactone (?‐CL) in various temperatures, monomer/ A molar proportions, and reaction times. The reactivity of A in the ring‐opening polymerization (ROP) of both monomers is mainly due to the cationic [Ti₃(OPrⁱ)₁₁]⁺ unity and proceeds through the coordination–insertion mechanism. Molecular weights ranging from 6,379 to 13,950 g mol^?1 and PDI values varying from 1.22 to 1.52 were obtained. Results of ROP kinetic studies for both ?‐CL and rac‐LA confirm that the reaction rates are first‐order with respect to monomers. The production of poly(?‐caprolactone) shows a higher sensitivity of the reaction rate to temperature, while the polymerization of rac‐LA is slower and more dependent on the thermal stability of the active species during the propagation step. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2509–2517     

8‐Amidoquinoline, 8‐(Trialkylsilylamido)quinoline, 2‐Pyridylmethylamide,and (2‐Pyridylmethyl)(trialkylsilyl)amide Complexes of Gallium

Lithium 8‐amidoquinoline ( 1 ) and lithium 8‐(trialkylsilylamido)quinoline [SiMe₂tBu ( 2 ), SiiPr₃ ( 3 )] react with dimethylgallium chloride to the metathesis products dimethylgallium 8‐amidoquinoline ( 4 ) as well as dimethylgallium 8‐(trialkylsilylamido)quinoline [SiMe₂tBu ( 5 ), SiiPr₃ ( 6 )]. The gallium atoms are in distorted tetrahedral environments. During the synthesis of 5 , orange dimethylgallium 2‐butyl‐8‐(tert‐butyldimethylsilylamido)quinoline ( 7 ) was found as by‐product. The metathesis reactions of Me₂GaCl with LiN(R)CH₂Py (Py = 2‐pyridyl) yield the corresponding 2‐pyridylmethylamides Me₂Ga‐N(H)CH₂Py ( 8 ), Me₂Ga‐N(SiMe₂tBu)CH₂Py ( 9 ) and Me₂Ga‐N(SiiPr₃)CH₂Py ( 10 ). In these complexes the gallium atoms show a distorted tetrahedral coordination sphere. However, derivative 8 crystallizes dimeric with bridging amido units whereas in 9 and 10 the 2‐pyridylmethylamido moieties act as bidentate ligands leading to monomeric molecules.     

Synthese und Charakterisierung neuer intramolekular stickstoffstabilisierter Organoaluminium‐ und Organogalliumalkoxide

Synthesis and Characterization of New Intramolecularly Nitrogen‐stabilized Organoaluminium‐ and Organogallium Alkoxides The intramolecularly nitrogen stabilized organoaluminium alkoxides [Me₂Al{μ‐O(CH₂)₃NMe₂}]₂ ( 1a ), Me₂AlOC₆H₂(CH₂NMe₂)₃‐2,4,6 ( 2a ), [(S)‐Me₂Al{μ‐OCH₂CH(i‐Pr)NH‐i‐Pr}]₂ ( 3a ) and [(S)‐Me₂Al{μ‐OCH₂CH(i‐Pr)NHCH₂Ph}]₂ ( 4 ) are formed by reacting equimolar amounts of AlMe₃ and Me₂N(CH₂)₃OH, C₆H₂[(CH₂NMe₂)₃‐2,4,6]OH, (S)‐i‐PrNHCH(i‐Pr)CH₂OH, or (S)‐PhCH₂NHCH(i‐Pr)CH₂OH, respectively. An excess of AlMe₃ reacts with Me₂N(CH₂)₂OH, Me₂N(CH₂)₃OH, C₆H₂[(CH₂NMe₂)₃‐2,4,6]OH, and (S)‐i‐PrNHCH(i‐Pr)CH₂OH producing the “pick‐a‐back” complexes [Me₂AlO(CH₂)₂NMe₂](AlMe₃) ( 5 ), [Me₂AlO(CH₂)₃NMe₂](AlMe₃) ( 1b ), [Me₂AlOC₆H₂(CH₂NMe₂)₃‐2,4,6](AlMe₃)₂ ( 2b ), and [(S)‐Me₂AlOCH₂CH(i‐Pr)NH‐i‐Pr](AlMe₃) ( 3b ), respectively. The mixed alkyl‐ or alkenylchloroaluminium alkoxides [Me(Cl)Al{μ‐O(CH₂)₂NMe₂}]₂ ( 6 ) and [{CH₂=C(CH₃)}(Cl)Al{μ‐O(CH₂)₂NMe₂}]₂ ( 8 ) are to obtain from Me₂AlCl and Me₂N(CH₂)₂OH and from [Cl₂Al{μ‐O(CH₂)₂NMe₂}]₂ ( 7 ) and CH₂=C(CH₃)MgBr, respectively. The analogous dimethylgallium alkoxides [Me₂Ga{μ‐O(CH₂)₃NMe₂}]₂ ( 9 ), [(S)‐Me₂Ga{μ‐OCH₂CH(i‐Pr)NH‐i‐Pr}]_n ( 10 ), [(S)‐Me₂Ga{μ‐OCH₂CH(i‐Pr)NHCH₂Ph}]_n ( 11 ), [(S)‐Me₂Ga{μ‐OCH₂CH(i‐Pr)N(Me)CH₂Ph}]_n ( 12 ) and [(S)‐Me₂Ga{μ‐OCH₂(C₄H₇NHCH₂Ph)}]_n ( 13 ) result from the equimolar reactions of GaMe₃ with the corresponding alcohols. The new compounds were characterized by elemental analyses, ¹H‐, ¹³C‐ and ²⁷Al‐NMR spectroscopy, and mass spectrometry. Additionally, the structures of 1a , 1b , 2a , 2b , 3a , 5 , 6 and 8 were determined by single crystal X‐ray diffraction.     

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.     

Sterically Tuned P‐Phosphanylamino Phosphaalkenes (Me3Si)2C=PN(R)PPh2 and (iPrMe2Si)2C=PN(R)PPh2

Deprotonation of the aminophosphanes Ph₂PN(H)R 1a – 1h [R = tBu ( 1a ), 1‐adamantyl ( 1b ), iPr ( 1c ), CPh₃ ( 1d ), Ph ( 1e ), 2,4,6‐Me₃C₆H₂ (Mes) ( 1f ), 2,4,6‐tBu₃C₆H₂ (Mes*) ( 1g ), 2,6‐iPr₂C₆H₃ (DIPP) ( 1h )], followed by reactions of the phosphanylamide salts Li[Ph₂PNR] 2a , 2b , 2g , and 2h with the P‐chlorophosphaalkene (Me₃Si)₂C=PCl, and of 2a – 2g with (iPrMe₂Si)₂C=PCl, gave the isolable P‐phosphanylamino phosphaalkenes (Me₃Si)₂C=PN(R)PPh₂ 3a , 3b , 3g , and (iPrMe₂Si)₂C=PN(R)PPh₂ 4a – 4g . ³¹P NMR spectra, supported by X‐ray structure determinations, reveal that in compounds 2a , 2b , 3a , and 3b , with bulky N‐alkyl groups the Si₂C=P–N–P skeleton is non‐planar (orthogonal conformation), whereas 3g , 3h , and 4g with bulky N‐aryl groups exhibit planar conformations of the Si₂C=P–N–P skeleton. Solid 3g and 4g exhibit cisoid orientation of the planar C=P–N–C units (planar I) but in solid 3h the transoid rotamer is present (planar II). From 3g , 4d , and 4g mixtures of rotamers were detected in solution by pairs of ³¹P NMR patterns ( 3h : line broadening).     

Synthese und Kristallstruktur von iso‐Butylimidogalliummethyl, [CH3Ga–NCH2CH(CH3)2]6

Synthesis and X‐Ray Structure Determination of iso ‐Butylimido Galliummethyl, [CH₃Ga–NCH₂CH(CH₃)₂]₆ The thermal decomposition of [Me₂Ga–N(ⁱBu)SnMe₃]₂ (prepared by the reaction of [Me₂SnNⁱBu]₃ with GaMe₃ in a 1:3 molar ratio) in an evacuated, sealed tube at 160°C forms [MeGaNⁱBu]₆ in high yield and SnMe₄. Mass, ¹H and ¹³C NMR as well as some IR and Raman spectroscopic data are given and the crystal structure of this cage molecule with a hexagonal prismatic Ga₆N₆ skeleton has been determined.     

An N‐Heterocyclic Silylene‐Stabilized Digermanium(0) Complex

The synthesis of an N‐heterocyclic silylene‐stabilized digermanium(0) complex is described. The reaction of the amidinate‐stabilized silicon(II) amide [LSiN(SiMe₃)₂] ( 1 ; L=PhC(NtBu)₂) with GeCl₂?dioxane in toluene afforded the Si^II–Ge^II adduct [L{(Me₃Si)₂N}Si→GeCl₂] ( 2 ). Reaction of the adduct with two equivalents of KC₈ in toluene at room temperature afforded the N‐heterocyclic carbene silylene‐stabilized digermanium(0) complex [L{(Me₃Si)₂N}Si→ Ge?Ge←Si{N(SiMe₃)₂}L] ( 3 ). X‐ray crystallography and theoretical studies show conclusively that the N‐heterocyclic silylenes stabilize the singlet digermanium(0) moiety by a weak synergic donor–acceptor interaction.     

Synthesis and Reactivity towards DIBAL‐H of Cyclo‐Siloxanes cyclo‐[R2SiOSi(Ot‐Bu)2O]2, cyclo‐(t‐BuO)2Si(OSiR2)2O,and cyclo‐R2Si[OSi(Ot‐Bu)2]2O (R = Me,Ph)

The six‐, eight‐ and twelve‐membered cyclo‐siloxanes, cyclo‐[R₂SiOSi(Ot‐Bu)₂O]₂ (R = Me ( 1 ), Ph ( 2 )), cyclo‐(t‐BuO)₂Si(OSiR₂)₂O (R = Me ( 3 ), Ph ( 4 )), cyclo‐R₂Si[OSi(Ot‐Bu)₂]₂O (R = Me ( 5 ), Ph ( 6 )) and cyclo‐[(t‐BuO)₂Si(OSiMe₂)₂O]₂ ( 3a ) were synthesized in high yields by the reaction of (t‐BuO)₂Si(OH)₂ and [(t‐BuO)₂SiOH]₂O with R₂SiCl₂ and (R₂SiCl)₂O (R = Me, Ph). Compounds 1 — 6 were characterized by solution and solid‐state ²⁹Si NMR spectroscopy, electrospray mass spectrometry and osmometric molecular weight determination. The molecular structure of 4 has been determined by single crystal X‐ray diffraction and features a six‐membered cyclo‐siloxane ring that is essentially planar. The reduction of 1 — 6 with i‐Bu₂AlH (DIBAL‐H) led to the formation of the metastable aluminosiloxane (t‐BuO)₂Si(OAli‐Bu₂)₂ ( 7 ) along with Me₂SiH₂ and Ph₂SiH₂.