Branched and dendritic metallo-carbosiloxanes with OCH2PPh2MLn end-grafted units

A straightforward method for the preparation of metallo carbosiloxanes of type Si(OCH₂CH₂CH₂SiMe₂[OCH₂PPh₂M(CO)_n])₄ (n = 3, M = Ni, 7a; n = 4, M = Fe, 7b; n = 5: M = Mo, 7c; M = W, 7d), Si(OCH₂CH₂CH₂SiMe[OCH₂PPh₂Ni(CO)₃]₂)₄ (8) and Me₂Si(OCH₂CH₂CH₂SiMe[OCH₂PPh₂Ni(CO)₃]₂)₂ (11) is described. The reaction of Si(OCH₂CH₂CH₂SiMeXCl)₄ (1: X = Me, 2: X = Cl) or Me₂Si(OCH₂CH₂CH₂SiMeCl₂)₂ (9) with HOCH₂PPh₂ (3) produces Si(OCH₂CH₂CH₂SiMe₂(OCH₂PPh₂))₄ (4), Si(OCH₂CH₂CH₂SiMe(OCH₂PPh₂)₂)₄ (5) or Me₂Si(OCH₂CH₂CH₂SiMe(OCH₂PPh₂)₂)₂ (10) in presence of DABCO. Treatment of the latter molecules with Ni(CO)₄ (6a), Fe₂(CO)₉ (6b), M(CO)₅(Thf) (6c: M = Mo; 6d: M = W), respectively, gives the title compounds 7a-7d, 8 and 11 in which the PPh₂ groups are datively bound to a 16-valence-electron metal carbonyl fragment.The formation of analytical pure and uniform branched and dendritic metallo carbosiloxanes is based on elemental analysis, and IR, ¹H, ¹³C{¹H}, ²⁹Si{¹H} and ³¹P{¹H} NMR spectroscopic studies. In addition, ESI-TOF mass spectrometric studies were carried out.     

Carbosiloxandendrimere mit terminalen SiH-Bindungen

An efficient method for the preparation of carbosiloxane dendrimers with end-grafted SiH-bonds is given by using the alcohols HOCH(Me)(CH₂)₄SiMe_3 − nH_n (4a: n = 1, 4b: n = 2, 4c: n = 3), which themselves are accessible by the hydrosilylation of MeCOCH₂CH₂CHCH₂ (1) with the chlorosilanes HSiMe_3 − nCl_n (2a: n = 1, 2b: n = 2, 2c: n = 3) and hydrogenation of the latter species with Li[AlH₄]. Alcohols 4a-4c can be used as starting materials for the preparation of carbosiloxane dendrimers of the 1^st-3^rd generation. For the synthesis of the 1^st generation dendrimers, Me_4 − mSiCl_m (5a: m = 1, 5b: m = 2, 5c: m = 3, 5d: m = 4) is reacted with 4a-4c in presence of NEt₃ as base. The dendritic molecules Me_4 − mSi[OCH(Me)(CH₂)₄SiMe_3 − nH_n]_m (n = 1: 6a, m = 1; 6b, m = 2; 6c, m = 3; 6d, m = 4. n = 2: 7a, m = 1; 7b,m = 2; 7c, m = 3; 7d, m = 4. n = 3: 8a, m = 3; 8b, m = 4) are thereby obtained in excellent yield. Carbosiloxane dendrimers of the 2^nd and 3^rd generation with a MeSiO₃- or SiO₄-core can be isolated from the reaction of MeSi(OCH₂CH₂CH₂SiMe₂Cl)₃ (9), MeSi(OCH₂CH₂CH₂SiMeCl₂)₃ (11), Si(OCH₂CH₂CH₂SiMe₂Cl)₄ (13) and MeSi(OCH₂CH₂CH₂SiMe(OCH₂CH₂CH₂SiMe₂Cl)₂)₃ (15) with 4a or 4b, respectively, under similar reaction conditions. Thereby MeSi[OCH₂CH₂CH₂SiMe₂OCH(Me)(CH₂)₄SiMe₂H]₃ (10), MeSi[OCH₂CH₂CH₂SiMe[OCH(Me)(CH₂)₄SiMe_3 − nH_n]₂]₃ (12a, n = 1; 12b, n = 2), Si[OCH₂CH₂CH₂SiMe[OCH(Me)(CH₂)₄SiMe₂H]₂]₄ (14) and MeSi[OCH₂CH₂CH₂SiMe[OCH₂CH₂CH₂SiMe₂OCH(Me)(CH₂)₄SiMe_3 − nH_n]₂]₃ (16) are formed as colourless oils.Compounds 3, 4, 6-8, 10, 12, 14 and 16 were characterised by elemental analysis as well as spectroscopic (IR, NMR) and mass spectrometric (ESI-TOF) studies.     

Bicyclo[2.2.2]octanes HC(SiMe2E)3MR (E=S, Se; M=Si, Ge, Sn; R=Me, Ph, Vi)

The reactions of 1:1 mixtures of the trisilylmethane HC(SiMe₂Cl)₃ (1b) and organo Group 14 trichlorides (RMCl₃, R=Me, Ph, vinyl (Vi); M=Si, Ge, Sn) with Li₂E (E=S, Se) in THF yielded the new bicyclo[2.2.2]octanes HC(SiMe₂E)₃MR (2a-6b). The products were identified by GC-MS and multinuclear NMR spectroscopy. Trends of the NMR data are discussed. The molecular structures of HC(SiMe₂S)₃SiMe (2a), HC(SiMe₂S)₃SiPh (3a), HC(SiMe₂Se)₃SiVi (4b) and HC(SiMe₂Se)₃GeMe (5b) are reported.     

Introduction of a phosphorus ylide moiety into [η-(ω-hydroxy)alkenyl]chromium(0) carbene complexes with Ph3PCCO and consecutive Wittig alkenations with 2-alkynals. Part 12: the chemistry of metallacyclic alkenylcarbene complexes

Ketenylidenetriphenylphosphorane, Ph₃PCCO (2), reacts selectively with the ω-hydroxy group of the alkene-carbene complexes (OC)₄CrC(η²-NMeCH₂CHCHCH₂OH)R¹ (1) (R¹=Me: (1a); Ph: (1b)) to give the acyl ylide terminated complexes (OC)₄CrC[(4,5-η²)-NMeCH₂CHCHCH₂O(O)C-CHPPh₃]R¹ (3) (R¹=Me: (3a); Ph: (3b)). Complexes 3 undergo Wittig alkenation reactions with aldehydes such as 2-alkynals, R²-CC-CHO (R²=H, SiMe₃, Ph), to give the corresponding 4Z, 9E-dien-11-ynes (OC)₄CrC[(4,5-η²)-NMeCH₂CHCHCH₂O(O)C-CHCH-CC-R²]R¹ (4-6) (R¹=Me, R²=H, SiMe₃, Ph: (4a-6a); R¹=Ph, R²=H, SiMe₃, Ph: (4b-6b)). All complexes were characterized in solution by one- and two-dimensional NMR spectroscopy (¹H, ¹³C, ²⁹Si, ³¹P, ¹H/¹H COSY, ¹³C/¹H HETCOR, ³¹P/³¹P EXSY).     

Synthesis and characterization of new silicon-centred tin-dendrimers Si[CH2CH2SnR3]4. Single-crystal X-ray structure of the tetrahydrofuran adduct of tetrakis[2-(tribromostannyl)ethyl]silane

A series of novel first-generation silicon-centred tin dendrimers Si(CH₂CH₂SnR₃)₄ [R = CH₃ (3), ⁱBu (4), CCCH₃ (5), C₆H₄CH₃-4 (6), C₆H₄OCH₃-4 (7), (CH₂)₄OCH₂CH₂OCH₃ (8), CH₂SiMe₃ (9)] was prepared by the reaction of Si(CH₂CH₂SnBr₃)₄ (2) with the appropriate Grignard reagent or LiCH₂SiMe₃ in tetrahydrofuran. The new compounds were characterized by multinuclear NMR studies (¹H, ¹³C, ¹¹⁹Sn), mass spectrometry (MALDI-TOF, EI) and elemental analyses. The molecular structure of Si[CH₂CH₂SnBr₃(THF)₂]₂[CH₂-CH₂SnBr₃(THF)]₂ (2a) was determined by single-crystal X-ray diffraction.     

Formation and structural characterization of mercury complexes from Te(R)CH2SiMe3 (R = Ph, CH2SiMe3) and HgCl2

The reaction of HgCl₂ and Te(R)CH₂SiMe₃ [R = CH₂SiMe₃ (1), Ph (2)] in ethanol yielded a mononuclear complex [HgCl₂{Te(R)CH₂SiMe₃}₂] (R = Ph, 3a; R = CH₂SiMe₃, 3b). The recrystallization of 3a or 3b from CH₂Cl₂ produced a dinuclear complex [Hg₂Cl₂(μ-Cl)₂{Te(R)CH₂SiMe₃}₂] (R = Ph, 4a; R = CH₂SiMe₃, 4b). When 3a was dissolved in CH₂Cl₂, the solvent quickly removed, and the solid recrystallized from EtOH, a stable ionic [HgCl{Te(Ph)CH₂SiMe₃}₃]Cl·2EtOH (5a·2EtOH) was obtained. Crystals of [HgCl₂{Te(CH₂SiMe)₂}]·2HgCl₂·CH₂Cl₂ (6b·2HgCl₂·CH₂Cl₂) were obtained from the CH₂Cl₂ solution of 3b upon prolonged standing. The complex formation was monitored by ¹²⁵Te-, and ¹⁹⁹Hg NMR spectroscopy, and the crystal structures of the complexes were determined by single crystal X-ray crystallography.     

Activation of C-H and C-Br bonds in cyclopalladation reactions of Schiff base ligands: Influence of the benzylidene ring substituents

Reaction of Pd(AcO)₂ with the Schiff base ligands 2-Br-4,5-(OCH₂O)C₆H₂C(H)N(Cy) (a) and 4,5-(OCH₂CH₂)C₆H₃C(H)N(Cy) (b) leads to the cyclometallated compounds [Pd{2-Br-4,5-(OCH₂O)C₆HC(H)N(Cy)-C6,N}(μ-O₂CMe)]₂ (1a) and [Pd{4,5-(OCH₂CH₂)C₆H₂C(H)N(Cy)-C6,N}(μ-O₂CMe)]₂ (1b), respectively, via C-H activation. Treatment of a with Pd₂(dba)₃ gave [Pd{4,5-(OCH₂O)C₆H₂C(H)N(Cy)-C2,N}(μ-Br)]₂ (6a), via C-Br activation. The metathesis reaction of 1a and 1b with aqueous sodium chloride gave the corresponding cyclopalladated dimers with bridging chloride ligands, 2a and 2b, respectively. Treatment of the halogen-bridged compounds with tertiary tri- and diphosphines in the appropriate molar ratio gave the mono and dinuclear compounds 3a-5a, 7a-9a and 3b-5b. The structure of compounds 3a, 4a, 5a, 8a, 2b, 3b and 5b has been determined by X-ray diffraction analysis.     

Synthesis and selective silylation of ω-hydroxy functionalized (η-alkenyl)carbene complexes of chromium(0) and tungsten(0) Part 11. The chemistry of metallacyclic alkenylcarbene complexes

Tungsten(0) carbene complexes of the type (OC)₅WC(NMeCH₂CHCHCH₂OH)R 2 (R=Me: 2a; R=Ph: 2b) were generated by aminolysis of (OC)₅WC(OMe)R with cis-NHMeCH₂CHCHCH₂OH. Like their Cr-congeners 1, complexes 2 exist at room temperature as mixtures of Z- and E-isomers with regard to the C-N bond. The metallacyclic complexes (OC)₄WC(η²-NMeCH₂CHCHCH₂OH)R (4) were obtained in good yields upon photo-decarbonylation of 2. Deprotonation/silylation of the complexes (OC)₄MC(η²-NMeCH₂CHCHCH₂OH)Me (M=Cr: 3a; M=W: 4a) with one equivalent of ⁿBuLi/Me₃SiCl gave (OC)₄MC(η²-NMeCH₂CHCHCH₂OSiMe₃)CH₃ (M=Cr: 5; M=W: 6), whereas with two equivalents of ⁿBuLi/Me₃SiCl complexes (OC)₄MC(η²-NMeCH₂CHCHCH₂OSiMe₃)CH₂SiMe₃ (M=Cr: 7; M=W: 8) were formed. Hydrolysis of the latter yielded selectively (OC)₄MC(η²-NMeCH₂CHCHCH₂OH)CH₂SiMe₃ (M=Cr: 9; M=W: 10). The complexes 1-10 were analyzed in solution by one- and two-dimensional NMR spectroscopy (¹H, ¹³C, ²⁹Si, ¹H/¹H COSY, ¹H/¹H NOESY, ¹³C/¹H HETCOR).     

Ring-opening reactions of cyclic ethers with diiodo- and dibromodimethylsilane equivalents

Ring-opening halosilation of cyclic ethers with reagents of (Me₂N)₂SiMe₂/4MeI (1a) and (Me₂N)₂SiMe₂/4allylBr (1b) was studied. Tetrahydrofuran and cyclohexene oxide reacted with 1a and 1b to give ring-opened di(haloalkoxy)dimethylsilanes in good yield. With less strained tetrahydropyran, however, only reagent 1a gave the ring-opened product. Reactions of reagents 1a and 1b with propylene oxide also proceeded smoothly, although the regioselectivity was rather low. When similar reactions were carried out with (Me₂N)₂SiMe₂/2MeI (2a) and (Me₂N)₂SiMe₂/2allylBr (2b) in a ratio of cyclic ethers/2a or 2b = 1/1, the corresponding 1:1 adducts were obtained.     

Novel titana-2,4-cyclopentadienes by 1,1-alkylboration

Bis(trimethylsilyl)amino-(2,2,5,5-tetramethyl-1,2,5-azadisila-cyclopent-1-yl)-titanium dichloride (3) and bis(2,2,5,5-tetramethyl-1,2,5-azadisila-cyclopent-1-yl)-titanium dichloride (4) were prepared and converted into the di(1-alkynyl)titanium derivatives, (Me₃Si)₂N[(CH₂Me₂Si)₂N]Ti(CCR)₂ (5) and [(CH₂Me₂Si)₂N]₂Ti(CCR)₂ (6) [R=Me (a), Ph (b), SiMe₃ (c)]. The reaction of 5a and 5b with trialkylboranes such as Et₃B leads almost quantitatively to titana-2,4-cyclopentadienes 7a and 7b, in which a diethylboryl group functions as a substituent in 3-position. In the same manner, 6b reacts with Et₃B or Pr₃B to titana-2,4-cyclopentadienes 8b or 9b, respectively. It is proposed that these reactions proceed by 1,1-alkylboration. Compound 5c also reacts with Et₃B, however, a complex mixture was obtained. All products were characterised by ¹H-, ¹¹B-, ¹³C-, ¹⁵N- and ²⁹Si-NMR spectroscopy.     

Greener fluorous chemistry: Convenient preparation of new types of ‘CF3-rich’ secondary alkyl mesylates and their use for the synthesis of azides, amines, imidazoles and imidazolium salts

2,2,2-Trifluoroethanol, 1,1,1,3,3,3-hexafluoro-2-propanol, and nonafluoro-tert-butyl alcohol were used as precursors for the preparation of the appropriate bis(polyfluoroalkoxymethyl)carbinols [(R_FHOCH₂)₂CHOH, 1a-c, R_FH = (a) CF₃CH₂, (b) (CF₃)₂CH, and (c) (CF₃)₃C] and the corresponding mesylates [(R_FHOCH₂)₂CHOSO₂CH₃, 2a-c]. This novel design paradigm is introduced to eliminate the persistence and bioaccumulation problems of fluorous chemistry, which are associated with the use of longer linear perfluoroalkyl groups (e.g. R_fn ≥ n-C₈F₁₇, n-C₇F₁₅). Secondary mesylates 2a,b and the primary tosylate [(CF₃)₃COCH₂CH₂OTs, 2d] displayed acceptable reactivity towards azide and imidazole nucleophiles to allow the syntheses of novel fluorous azides, which on hydrogenolysis with H₂/Pd-C offered fluorous amines [(R_FHOCH₂)₂CHNH₂, 8a,b], and 1-(polyfluoroalkyl)imidazoles (5a,b,d), respectively, while 2c showed no reactivity due to steric hindrance. The reaction of 8a,b with formaline, glyoxal and hydrochloric acid gave symmetrical 1,3-dialkylated imidazolium chlorides (9a,b), while 5a,b,d were effectively alkylated using n-C₈F₁₇(CH₂)₃I, methyl iodide, 2-bromoethanol, and 2d to yield the corresponding 1,3-dialkylimidazolium iodides, bromides, and tosylates (7aa-ec). Some physical properties of new compounds including mp, bp and solubility patterns were also analyzed; and the fluorophilicity values of 1a-c, and 2a-c were experimentally determined by GC and/or ¹⁹F NMR spectroscopy.     

Metallo-Carbosiloxan-Dendrimere mit Titanocendichlorid-Endgruppen

The synthesis of titanocenedichloride end-grafted carbosiloxane dendrimers of the 1^st and 2^nd generation is reported. To find the optimal reaction conditions, Me₂ClSiH (1) was reacted with (η⁵-C₅H₄SiMe₂CHCH₂)(η⁵-C₅H₅)TiCl₂ (2). The best result could be obtained with the Karstedt catalyst, whereby exclusively the β-isomer ((η⁵-C₅H₄SiMe₂CH₂CH₂SiMe₂Cl)(η⁵-C₅H₅)TiCl₂, 3) is formed. Under similar conditions Me₃SiOCH(Me)(CH₂)₄SiMe₂H (4) reacts with 2 to give (η⁵-C₅H₄SiMe₂CH₂CH₂SiMe₂(CH₂)₄CH-(Me)OSiMe₃)(η⁵-C₅H₅)TiCl₂ (5). When using MeSi(OCH(Me)(CH₂)₄SiMe₂H)₃ (6), Si(OCH(Me)(CH₂)₄SiMe₂H)₄ (8) and MeSi[O(CH₂)₃SiMe(OCH(Me)(CH₂)₄SiMe₂H)₂]₃ (10) instead of 1 and 4, the respective metallo dendrimers MeSi[OCH(Me)(CH₂)₄-SiMe₂CH₂CH₂SiMe₂(η⁵-C₅H₄)(η⁵-C₅H₅)TiCl₂]₃ (7), Si[OCH(Me)(CH₂)₄SiMe₂CH₂CH₂SiMe₂(η⁵-C₅H₄)(η⁵-C₅H₅)TiCl₂]₄ (9) and MeSi{O(CH₂)₃SiMe[OCH(Me)(CH₂)₄SiMe₂CH₂CH₂SiMe₂(η⁵- C₅H₄)(η⁵-C₅H₅)TiCl₂]₂}₃ (11) can be isolated.Compounds 3, 5, 7, 9 and 11 were characterised by elemental analysis as well as IR and NMR spectroscopy (¹H, ¹³C{¹H}, ²⁹Si{¹H}).     

Sulfur and oxygen functionalized cyclopentadienyl half-sandwich cobalt complexes with 1,2-dicarba-closo-dodecaborane-1,2-dichalcogenolato ligands

Sulfur and oxygen functionalized cyclopentandienyl half-sandwich cobalt dicarbonyl complexes [η⁵-C₅H₄(CH₂)₂SCH₂CH₃]Co(CO)₂ (3) and [η⁵-C₅H₄(CH₂)₂OCH₃]Co(CO)₂ (7) were prepared. Oxidation of 3 or 7 with I₂ led to formation of 18-electron complexes [η⁵-C₅H₄(CH₂)₂SCH₂CH₃]CoI₂ (4) and [η⁵-C₅H₄(CH₂)₂OCH₃]Co(CO)I₂ (8). The reactions of diiodide complex (4) with dilithium 1,2-dicarba-closo-dodecaborane(12)-1,2-dichalcogenolates [(THF)₃LiE₂C₂B₁₀H₁₀Li(THF)]₂ [E=S (1a), Se (1b)] afforded 18-electron mononuclear complexes [η⁵-C₅H₄(CH₂)₂SCH₂CH₃]Co(E₂C₂B₁₀H₁₀) [E=S (5a), Se (5b)] in which sulfur atoms of side-chain were attached via an intramolecular coordination. Complex 7 reacted with 1a and 1b to give the binuclear complexes {[η⁵-C₅H₄(CH₂)₂OCH₃]Co(E₂C₂B₁₀H₁₀)}₂ [E=S (10a), Se (10b)]. The molecular structures of 5a and 10b were determined by X-ray crystallographic analysis. According to the X-ray structure analyses, 10b contains two o-carborane diselenolate bridges, and each Cp^′Co fragment is attached to one terminal and two bridging selenolato ligands. The central Co₂Se₂ four-membered ring is planar, and the direct metal-metal interaction is absent.     

From bis(silylamino)tin dichlorides via di(1-alkynyl)-bis(silylamino)tin to new heterocycles by 1,1-organoboration

Bis(silylamino)tin dichlorides 1 [X₂SnCl₂ with X=N(Me₃Si)₂ (a), N(9-BBN)SiMe₃ (b), N(^tBu)SiMe₃ (c), and N(SiMe₂CH₂)₂ (d)] were prepared from the reaction of two equivalents of the respective lithium amides (Li-a-d) with tin tetrachloride, SnCl₄, or from the 1:1 reaction of the respective bis(amino)stannylene with SnCl₄. The compounds 1 react with two equivalents of lithium alkynides LiCCR¹ to give the di(1-alkynyl)-bis(silylamino)tin compounds X₂Sn(CCR¹)₂, 2 (R¹=Me), 3 (R¹=^tBu), and 4 (R¹=SiMe₃). Problems were encountered, mainly with LiCC^tBu as well as with 1b, since side reactions also led to the formation of 1-alkynyl-bis(silylamino)tin chlorides 5-7 and tri(1-alkynyl)(silylamino)tin compounds 8 and 9. 1,1-Ethylboration of compounds 2-4 led to stannoles 10, 11, and in the case of propynides, also to 1,4-stannabora-2,5-cyclohexadiene derivatives 12. The molecular structure of the stannole 11b (R¹=SiMe₃) was determined by X-ray analysis. The reaction of 2a and d with triallylborane afforded novel heterocycles, the 1,3-stannabora-2-ethylidene-4-cyclopentenes 14. These reactions proceed via intermolecular 1,1-allylboration, followed by an intramolecular 1,2-allylboration to give 14, and a second intramolecular 1,2-allylboration leads to the bicyclic compounds 15.     

(Amidomethyl)dimethylsilanol hydrohalides: Synthesis, NMR and IR studies. Characteristic features of the electronic structure from high-resolution X-ray study and quantum chemical calculation

(C,O)-chelate silanol hydrohalides RC(O)NHCH₂SiMe₂OH · HHal (2a,b and 5b), and their precursors, (C,O)-chelate chlorosilanes RC(O)NHCH₂SiMe₂Cl (6a,b) and disiloxanes [RC(O)NHCH₂SiMe₂]₂O (8a,b) (R = Me (a), Ph (b); Hal = Cl (2), Br (5)), were obtained by several routes. The original scheme of hydrolysis of the above chlorides was discussed in detail. X-ray analysis has shown that the silanol hydrohalogenides PhC(O)NHCH₂SiMe₂OH · HX (2b and 5b) in the crystal exist in the form of cation-anion pairs [PhC(O)NHCH₂SiMe₂(OH₂)]⁺ · X⁻ (14b · Cl⁻ and 14b · Br⁻) assembled by H-bonds in a 3D framework. The Si atom in the cation has a trigonal bipyramidal configuration with the oxygen atom of the carbonyl group and protonated hydroxyl exo-substituent in axial positions. The endocyclic Si-O bonds are equal with an average of 1.905 Å while the exocyclic Si-O bonds are 1.979 and 2.009 Å, for Hal = Cl and Br, respectively.Quantum chemical calculations have shown that the cation [PhC(O)NHCH₂SiMe₂(OH₂)]⁺ (14b) is stable only in the crystal. Based on a high-resolution X-ray study and a quantum chemical calculation, it was found that the chemical bonding pattern in the OSiO axial fragment of the cation 14b corresponds to a three-centred four electron interaction. The cation 14b should be considered as a silylium cation stabilized by coordinated H₂O molecules rather than a silyloxonium ion.     

Self-immobilized metallocene catalysts bearing an allyl group for ethylene polymerization, X-ray crystal structure of [(CH2CHCH2)CH3Si(C13H8)2]ZrCl2

A series of ansa-metallocene complexes with an allyl substituted silane bridge [(CH₂CHCH₂)CH₃Si(C₅H₄)₂]TiCl₂ (1), [(CH₂CHCH₂)CH₃Si(C₉H₆)₂]MCl₂ [M=Ti (2), Zr (3), Hf (4)] and [(CH₂CHCH₂)CH₃Si(C₁₃H₈)₂]ZrCl₂ (6) have been synthesized and characterized. The molecular structure of 6 has been determined by X-ray crystallographic analysis. Complexes 1-4, 6 bearing allyl groups have been investigated as self-immobilized catalysts for ethylene polymerization in the presence of MMAO. The results showed that the self-immobilized catalysts 1-4, 6 kept high ethylene polymerization activities of ca. 10⁶ g PE mol⁻¹ M h⁻¹ and high molecular weight (M_w≈10⁵) of polyethylene.     

Heteroleptic tin (II) dialkoxides stabilized by intramolecular coordination Sn(OCH2CH2NMe2)(OR) (R = Me, Et, Pr, Bu, Ph). Synthesis, structure and catalytic activity in polyurethane synthesis

A straightforward method of synthesis of heteroleptic tin (II) alkoxides stabilized by one intramolecular coordination bond was developed. Addition of one equivalent of dimethylamino ethanol to diamide Sn(N(SiMe₃)₂)₂ (5) yields alkoxy-amido derivative Sn(OCH₂CH₂NMe₂)(N(SiMe₃)₂) (2). Further addition of alcohol leads to corresponding heteroleptic dialkoxides Sn(OCH₂CH₂NMe₂)(OR) (R = Me (6), Et (7), ⁱPr (8), ^tBu (9), Ph (10)). Catalytic activity of tin (II) compounds in polyurethane formation was tested.     

Synthesis, structure and dynamic stereochemistry of (O → Si)-chelate N-(trifluorosilylmethyl)-[N-(S)-(1-phenylethyl)]acetamide and 1-(trifluorosilylmethyl)-2-oxoperhydroazepine: Retention of the O → Si coordination in the adduct with KF and 18-crown-6

The novel compounds, N-(trifluorosilylmethyl)-[N-(S)-(1-phenylethyl)]-acetamide (1a) and 1-(trifluorosilylmethyl)-2-oxoperhydroazepine (1b) have been prepared from the corresponding NH-compounds using ClCH₂SiCl₃/Et₃N or ClCH₂SiCl₃/(Me₃Si)₂NH followed by methanolysis or hydrolysis of the reaction mixture in the presence of Lewis bases, and then BF₃ etherate. Potassium-(18-crown-6)-(2-oxoperhydroazepinomethyl)tetrafluorosilicate (2) was synthesized by reaction of the trifluoride (1b) with KF in the presence of 18-crown-6. Using ¹⁹F, ²⁹Si NMR and X-ray diffraction techniques it was established that the silicon atom is pentacoordinate in the trifluorides (1a, b) and hexacoordinate in the adduct 2. Thus the internal coordination of the O → Si bond present in the trifluoride (1b) is retained in the adduct 2.The stereochemical non-rigidity of the trifluorides (1a, b) and the N-(trifluorosilylmethyl)-N-methylacetamide (1c) was investigated using dynamic ¹⁹F NMR spectroscopy. The activation barriers for permutational isomerization are in the range 9.5-10 kcal mol⁻¹. Lower values of ΔG^# for permutation of trifluorides (1a-c) compared to the monofluorides with the coordination core OSiC₃F together with small negative values for the activation entropy implies a non-dissociative mechanism. Quantum-chemical analysis suggests a mechanism involving a turnstile rotation.     

Hydroxy- and boronic-acid-functionalized carbosilanes: Synthesis and solid state structure of Si(C6H4-4-SiMe2((CH2)3OH))4

Consecutive synthesis methodologies for the preparation of carbosilanes (Ph)(Me)Si((CH₂)₃B(OH)₂)₂ (2), Si(C₆H₄-4-SiMe₂((CH₂)₃B(OH)₂))₄ (5), (Ph)(Me)Si((CH₂)₃OH)₂ (3), and Si(C₆H₄-4-SiMe_3−n((CH₂)₃OH)_n)₄ (6a, n = 1; 6b, n = 2; 6c, n = 3) are reported. Boronic acids 2 and 5 are accessible by treatment of (Ph)(Me)Si(CH₂CHCH₂)₂ (1) or Si(C₆H₄-4-SiMe₂(CH₂CHCH₂))₄ (4a) with HBBr₂·SMe₂ followed by addition of water, while 3 and 6 are available by the hydroboration of 1 or Si(C₆H₄-4-SiMe_3−n(CH₂CHCH₂)_n)₄ (4a, n = 1; 4b, n = 2; 4c, n = 3) with H₃B·SMe₂ and subsequent oxidation with H₂O₂.The single molecular structure of 6a in the solid state is reported. Representative is that 6a crystallized in the chiral non-centrosymmetric space group P2₁2₁2₁ forming 2D layers due to intermolecular hydrogen bond formation of the HO functionalities along the crystallographic a and c axes.     

Synthesis and crystal structures of organometallic compounds containing the ligands C(SiMe3)2(SiMe2H) and C(SiMe2Ph)2(SiMe2H)

Metallation of (HMe₂Si)(Me₃Si)₂CH (1) by LiMe gave the organolithium compound Li(THF)₂C(SiMe₃)₂(SiMe₂H) (2a), which exists in toluene solution as a mixture of covalent species and ion pairs [Li(THF)₄][Li{C(SiMe₃)₂(SiMe₂H)}₂] (2b). Treatment of a mixture of 1 and LiMe with KOBu^t gave KC(SiMe₃)₂(SiMe₂H) (3). This reacted with AlMe₂Cl in hexane/THF to give Al(THF)Me₂{C(SiMe₃)₂(Si Me₂H)} (4). Treatment of (HMe₂Si)(PhMe₂Si)₂CH (5) with LiMe in Et₂O/THF gave the THF adduct [Li(THF)₂C(SiMe₂Ph)₂(SiMe₂H)] (6); in the presence of KOBu^t the solvent-free [K][C(SiMe₂Ph)₂(SiMe₂H)] (7) was obtained. Crystal structure determinations showed that 6 crystallizes in a molecular lattice and 7 in an ionic lattice in which the coordination sphere of the potassium comprises phenyl groups and hydrogen atoms attached to silicon, as well as the central carbon of the bulky carbanion. Compound 7 reacted with an excess of AlMe₂Cl to give [AlClMe{C(SiMe₂Ph)₂(SiMe₂H)}]₂ (8) and AlMe₃. A small amount of the methoxo derivative [Al(OMe)Me{C(SiMe₂Ph)₂(SiMe₂H)}]₂ (9) was obtained as a byproduct, presumably after the accidental admission of traces of air. X-ray structural determinations showed that 8 forms halogen-bridged dimers, with the bulky ligands in the anti-configuration, and 9 forms methoxo-bridged species in which the bulky ligands are syn.