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• 212786-67-9 bis(2,2,6,6-tetramethylpiperidino)methylaluminium 
• 1109-15-5 tris(pentafluorophenyl)borate 
• 544-97-8 dimethyl zinc(II) 
• 426827-42-1 (Cp₂ZrMe)(Me₂B(C₆F₅)2) 
• 852447-88-2 (C₅(CH₃)5)Ti(CH₃)2(OSi(CH₂CH₂Si(C₆H₅)2CH₃)3) 
• 67108-80-9 bis(pentamethylcyclopentadienyl)zirconium dimethyl 
• 1008098-66-5 [(2,3-dihydoxy-1,1,1,4,4,4-hexamethyl-2,3-bis(trimethylsilyl)tetrasilane(-2H))2Zn₃Me₂] 
• 412914-70-6 [In(CH₃)(N,N'-diisopropylaminotroponiminate)][B(CH₃)(C₆F₅)3] 

Relevant academic research and scientific papers

Structure, dynamics, and polymerization activity of zirconocenium ion pairs generated with boron-C6F5 compounds and Al 2R6

Figure Persented: The activation reaction of the olefin polymerization precatalyst Cp*2ZrMe2 with a boron-C 6F5 compound (B(C6F5)3, [Ph3C][B(C6F5)4]) and an aluminum alkyl species (Al2Me6, Al2iBu 6) is studied by NMR spectroscopy in order to determine the nature of the ion pairs that are formed preferentially. We show that a mixture of ion pairs with general formula Cp*2Zr(Me)-μ-Me-E(C 6F5)3-xRx (E = Al, B; x = 0, 1; R = Me, iBu) (1, 2a/b, 4) is generated due to a rapid transfer of pentafluorophenyl groups from boron to aluminum. Therefore, the molecular ratio of the activators determines the final composition of the ion pairs present in solution. When the pentafluorophenyl group transfer is suppressed, the ion pair Cp*2Zr-(μ-Me)2-AlMe2 (5) forms irrespective of the reagent ratio. The high dynamics of these solutions is demonstrated by DNMR studies. Gibbs free energies of activation were determined of 13.6(12) kcal mol-1 at 298 K for the cocatalyst exchange of ion pair Cp*2Zr(Me)-μ-Me-Al(C6F5) 2Me (2a) and 13(2) kcal mol-1 at 298 K for the methyl exchange in Al2(C6F5)xMe 6-x (x = 0, 1). Due to the stability of the ion pairs generated from the Cp*2ZrMe2 precatalyst at temperatures relevant for polymerization, correlations between activities in ethylene polymerization and the nature of the ion pairs can be established. All solutions containing the various ion pairs were found to be catalytically active in ethylene polymerization except that containing the ion pair 2a, which was attributed to the reduced Lewis acidity of the abstractor, as supported by DFT calculations.

Aluminium complexes of a phenoxyimine ligand with a pendant imidazolium moiety: Synthesis, characterisation and evidence for hydrogen bonding in solution

Novel alkylaluminium complexes (phim)AlMe2 (1) and (phimid)AlR2+Br- [R = Me (2), R = iBu (3)] bearing the Schiff base ligands 3,5-tBu2-2-(OH)C6H 2CH=NiPr (phim-H) and 3,5-tBu2-2-(OH)C6H 2CH=NCH2CH2[CH(NCHCHNiPr)]Br (phimid-H·Br) have been prepared and fully characterised. Complexes 1-3 each have a tetrahedral structure, with the aluminium atom surrounded by the oxygen and nitrogen atoms of the chelating ligand and two alkyl groups. The structures of phimid-H·Br and of complex 1 have been determined by X-ray diffraction studies. Investigation of the solution structures of 1-3 by 1H NMR spectroscopy revealed that the coordinated phimid ligand is involved in hydrogen bonding with bromide anion. Treatment of 1 with B(C 6F5)3 led smoothly to (phim)Al(C 6F5)Me (4) by transfer of a C6F5 group from MeB(C6F5)3- to the initially formed coordinatively unsaturated cationic intermediate. In contrast, treatment of 2 with one equiv. of B(C6F5)3 afforded the cationic monomethyl species (phimid)AlMeBr+MeB(C 6F5)3- (5), stabilised by the coordination of the bromide anion acting as a Lewis base. Wiley-VCH Verlag GmbH & Co. KGaA, 2009.

Synthesis and structure of cyclic trinuclear zinc disiloxides

The synthesis and structure of the new disilane-1,2-diol [(Me 3Si)2SiOH]2 (2b) and the trinuclear zinc disiloxides of the formula [Me2Si{(Me3Si)2SiO} 2]2Zn3Me2 (3a), [{(Me 3Si)2Si-O)2]2Zn3Me 2 (3b) and [E-{Me(Me3Si)3SiSiO} 2]2Zn3Me2 (3c) are reported. Compounds 3a-c were prepared by reactions of the corresponding silanedioles 2a-c with ZnMe2. The results of an X-ray structure analysis of 3b reveal an almost perfectly planar spirocyclic Zn3Q4 core with a square-planar geometry of the inner Zn2+ ion, whereas in 3a,c the inner zinc ions are distorted tetrahedral. Upon treatment with B(C 6F5)3, compounds 3b,c have been converted quantitatively into the complexes [{(Me3Si)2SiO} 2]2Zn3(C6F5)2 (4b) and [E-{Me(Me3Si)3SiSiO}2] 2Zn3(C6F5)2 (4c). Wiley-VCH Verlag GmbH & Co. KGaA, 2007.

Trisilane-1,3-diolato complexes of Ti and Zr: Syntheses and X-ray crystal structures

The syntheses and structures of zirconium and titanium complexes containing the novel chelating trisilane-1,3-diolate ligand [Me2Si(R 2SiO)2]2- (R = SiMe3) (5)-H 2 are reported. The chloride complexes [Me2Si(R 2SiO)2]TiCl2 (7a) and [Me2Si(R 2SiO)2]ZrCl2·2THF (7b) were prepared by the reaction of MCl4 (M = Ti, Zr) with [Me2Si(R 2-SiO)2]2Ti (6a) and [Me2Si(R 2SiO)2]2Zr (6b), which are derived from the reaction of 5 with M(NEt2)4, respectively. In the presence of TiCl4, complexes 6a and 7a undergo a ring-opening reaction to produce the dinuclear complex [Me2Si(R2SiO) 2][TiCl3]2 (9). [Me2Si(R 2SiO)2]TiMe2 (10) and [Me2Si(R 2SiO)2]TiBnZ2 (11) were prepared in moderate yields from reactions of 7a with 2 equiv of MeMgBr and BnzMgCl, respectively. According to NMR spectroscopic investigations, the reaction of the dimethyltitanium complex 10 with B(C6F5)3 led to full exchange of both methyl groups by C6F5 groups under quantitative formation of [Me2Si(R2SiO) 2]Ti(C6F5)2 (12) and a mixture of B(C6F5)3-nMen, where n = 1-3. The structure of 12 is further evidenced by the preparation of an identical sample from the reaction of 7a with 2 equiv of C6F5MgBr. Refluxing an ether solution of 12 surprisingly gave [Me2Si(R 2SiO)2]2TiC6F5] 2O (13) as a result of ether cleavage. The structures of the complexes 7a, 7b, 9, 10, and 13 were determined by X-ray crystallography, and structural discussion of the bond parameters will be given.

Neutral and cationic aluminum and titanium complexes incorporating sterically demanding organosilicon ligands

New complexes of aluminum and titanium containing sterically demanding ligands and their reaction with B(C6F5)3 are reported. Treatment of [(Ph2MeSiCH2CH2) 3Si]NCN[Si(CH2CH2SiMePh2) 3] (1) or Si(CH2CH2SiMePh2) 3OH (2) with 1 equiv of AlMe3 results in the formation of the neutral dimethylaluminum complexes {MeC[NSi(CH2CH 2SiMePh2)3]2}AlMe2 (3) and [(Ph2MeSiCH2CH2)3SiOAlMe 2]2 (4). Reaction of 3 with 1 equiv of B(C 6F5)3 forms the neutral complex {MeC[NSi(CH2CH2SiMePh2)3] 2}AlMe(C6F5) (5) and BMe(C6F 5)2. In the case of 4, the analogous reaction produced the dimer [(Ph2MeSiCH2CH2)3SiOAl] 2Me3(C6F5) (6). Treatment of 1 with Ti(C5Me5)Me3 fails to afford the corresponding amidinate complex. However, reaction of 2 with the same titanium half-sandwich complex cleanly gives Ti(C5Me5)[OSi(CH2CH 2SiMePh2)3]Me2 (7). Reaction of 7 with 1 equiv of B(C6F5)3 leads to the formation of the ion pair {Ti(C5Me5)[OSi(CH2CH 2SiMePh2)3]Me}[BMe(C6F 5)3] (8), which is relatively stable at room temperature, slowly decomposing (t1/2 ≈ 48 h) to give a mixture of two neutral titanium complexes, Ti(C5Me5)[OSi(CH2CH 2SiMePh2)3][CH2B(C6F 5)2](C6F5) (9) and TiC 5Me5)[OSi(CH2CH2SiMePh 2)3]Me(C6F5) (10). However, when this reaction is carried out in a 1:0.5 stoichiometry, the decomposition process occurs over the course of 22 h, giving complex 10 selectively. The implications of these results with related Ziegler-Natta catalyst systems are discussed.

A contribution to the chemistry of 2,2,6,6-tetramethylpiperidino aluminium compounds

tmpAlBr2 (tmp = 2,2,6,6-tetramethylpiperidino) was prepared from AlBr3 and tmp2AlBr at 90°C in the absence of a solvent, but could not be crystallised from toluene or hexane because it reacted with the solvents to form tmpH·AlBr3 in high yield. tmpH·AlMeCl2, obtained from the components, decomposes at elevated temperatures but no tmpAlCl2 could be isolated. Attempts to generate the cation [tmp-Al-tmp]+ from tmp2AlBr or tmp2AlCl by halide abstraction with B(C6F 5)3, Ph3C(SnCl5) or SbCl5 or from tmp2AlR (R = Me, Ph) and B(C6F5) 3 have failed. An unexpected reaction occurred on treatment of tmp-B=P(tBu)AlBr3 with BH3 in THF which led to the formation of [AlBr2(thf)4][AlBr4]. The attempted synthesis of tBu2Al(tmp) from tBu2AlBr and Li(tmp) gave a product which, on exposure to CO2 at dry ice temperature, yielded the salt [(tBuAl)2(O2C(tmp)) 3][tBu3 Al-Br-AltBu3] in low yield. All isolated products were characterized by NMR spectroscopy and by X-ray determination of their molecular structures.

Organoborane-modified silica supports for olefin polymerization: Soluble models for metallocene catalyst deactivation

Treatment of silsesquioxane 1 with 3.3 equiv of the reactive organoboranes 2 [(C6F5)2BX; X = H or Cl] provides the novel, trifunctional organoborane 3, which was characterized by spectroscopic means and single-crystal X-ray crystallography. Compound 3 is an effective cocatalyst for ethylene polymerization in combination with Cp2ZrMe2 but only when these two compounds are combined in situ, in the presence of monomer, suggesting limited stability of the putative ion-pair derived from these compounds. Reaction of 3 with Cp2ZrMe2 in toluene solution leads to formation of MeB(C6F5)2- and Cp2Zr-functionalized silsesquioxane 5 at room temperature. Monitoring of this reaction by NMR spectroscopy at low temperatures indicates that the only ion-pair present is [Cp2ZrMe] [Me2B(C6F5)2] (4), which results from reaction of Cp2ZrMe2 with the byproduct MeB(C6F5)2. Formation of 4 is reversible under these conditions, while production of 5 (from 3 and Cp2ZrMe2) is not; the latter process occurs at a rate that exceeds that observed for independent decomposition of 4 to form Me2B(C6F5) and Cp2Zr(C6F5)Me. These studies suggest that the active polymerization catalyst generated in situ from 3 and Cp2ZrMe2 is probably ion-pair 4.

Cationic indium alkyl complexes incorporating aminotroponiminate ligands

The synthesis and structures of indium complexes incorporating the bidentate monoanionic ligand N,N′-diisopropylaminotroponiminate (iPr2-ATI) are described. The reaction of InCl3 with Li[iPr2-ATI] yields (iPr2-ATI)InCl2 (3), which is converted to (iPr2-ATI)InMe2 (4) by reaction with MeLi; 4 is also formed by the reaction of InMe3 with (iPr2-ATI)H. The reaction of 4 with [Ph3C] [B(C6F5)4] at 23 °C yields the diimine complex [{1,2-(NiPr)2-5-CPh3-cyclohepta-3,6-diene}InMe 2] [B(C6F5)4] (5) via addition of Ph3C- to the C5 carbon of 4. Thermolysis of 5 (75 °C) yields [(iPr2-ATI)InMe] [B(C6F5)4] (6) and Ph3CMe. 6 was isolated as the chlorobenzene solvate 6·PhCl. An X-ray diffraction study shows that there are two independent cations in the asymmetric unit of 6·PhCl. One cation (In(1)) is ion-paired with two B(C6F5)4- anions, while the second cation is complexed with two PhCl molecules and is disordered between two equally occupied positions (In(2) and In(3)). Dative In-ClPh bonding and PhCl/ATI π-stacking interactions contribute to the PhCl coordination in 6·PhCl. The reaction of 4 with B(C6F5)3 yields [(iPr2-ATI)InMe] [MeB(C6F5)3] (7), which decomposes slowly at 23 °C by C6F5- transfer reactions. The reaction of 4 with [HNMe2Ph] [B(C6F5)4] yields the labile amine adduct [(iPr2-ATI)In(Me)(NMe2Ph)] [B(C6F5)4] (10).

Reactions of zinc dialkyls with (perfluorophenyl)boron compounds: Alkylzinc cation formation vs C6F5 transfer

Reaction between ZnR2 and [H(OEt2)2] [B(C6F5)4] in ether leads to the salts [RZn(OEt2)3]-[B(C6F5)4], while mixtures of ZnR2 (R = Me, Et) and B(C6F5)3 in toluene-d8 undergo facile alkyl/C6F5 group exchange to give Zn(C6F5)2·(toluene). Mixtures of ZnR2 and B(C6F5)3 in hydrocarbon/diethyl ether solvent mixtures react with alkyl transfer to afford the ion pairs [RZn(OEt2)3][RB(C6 F5)3], whereas the reaction of ZnEt2 with [Ph3C][B(C6F5)4] in toluene-d8 proceeds with β-H abstraction to give ethene and Ph3CH, with the subsequent rapid formation of Zn(C6F5)2.