199607-95-9

Upstream product

• 165612-94-2 bis(pentafluorophenyl)borohydride 
• 2720-03-8 bis(pentafluorophenyl)boron chloride 
• 199607-72-2 (Me₂Si(NCMe₃)2)Zr(benzyl)(benzyl-B(pentafluorophenyl)3) 
• 365215-43-6 (N,N'-diisopropylaminotroponiminate)Al(CH₂Ph)2 

Relevant academic research and scientific papers

Cationic aluminum alkyl complexes incorporating aminotroponiminate ligands

The synthesis, structures, and reactivity of cationic aluminum complexes containing the N,N'-diisopropylaminotroponiminate ligand (iPr2-ATI-) are described. The reaction of (iPr2-ATI)A1R2 (1a-e,g,h; R = H (a), Me (b), Et (c), Pr (d), iBu (e), Cy (g), CH2Ph (h)) with [Ph3C][B(C6F5)4] yields (iPr2-ATI)A1R+ species whose fate depends on the properties of the R ligand. 1a and 1b react with 0.5 equiv of [Ph3C]-[B(C6F5)4] to produce dinuclear monocationic complexes [{(iPr2-ATI)AIR}2(μ-R)][ (C6F5)4] (2a,b). The cation of 2b contains two (iPr2-ATI)AlMe+ units linked by an almost linear Al-Me-Al bridge; 2a is presumed to have an analogous structure. 2b does not react further with [Ph3C][B(C6F5)4]. However, 1a reacts with 1 equiv of [Ph3C][B(C6F5)4] to afford (iPr2-ATI)Al(C6F5) (μ-H)2B(C6F5)2 (3) and other products, presumably via C6F5- transfer and ligand redistribution of a [(iPr2-ATI)AlH] [(C6F5)4] intermediate. 1c-e react with 1 equiv of [Ph3C]-[B(C6F5)4] to yield stable base-free [(iPr2-ATI)AIR][B (C6F5)4] complexes (4c-e). 4c crystallizes from chlorobenzene as 4c(ClPh)·0.5PhCl, which has been characterized by X-ray crystallography. In the solid state the PhCl ligand of 4c(ClPh) is coordinated by a dative PhCl-Al bond and an ATI/Ph π-stacking interaction. 1g,h react with [Ph3C][B(C6F5)4] to yield (iPr2-ATI)Al(R)(C6F5)(5g,h) via C6F5- transfer of [(iPr2-ATI)A1R]-[ (BC6F5)4] intermediates. 1c,h react with B(C6F5)3 to yield [(iPr2-ATI)Al(R)](C6F5) (5c,h) via C6F5- transfer of [iPr2-ATI)A1R][RB (C6F5)3] intermediates. The reaction of 4c-e with MeCN or acetone yields [(iPr2-ATI)-Al(R)(L)][B (C6F5)4] adducts (L = MeCN (8c-e), acetone (9 c-e)), which undergo associative intermolecular L exchange. 9c-e undergo slow β-H transfer to afford the dinuclear dicationic alkoxide complex [{(iPr2 -ATI)Al(μ-OiPr)}2][B (C6F5)4]2 (10) and the corresponding olefin. 4c-e catalyze the head-to-tail dimerization of tert-butyl acetylene by an insertion/σ-bond metathesis mechanism involving [(iPr2-ATI)Al(C≡CtBu)]- [B(C6F5)4] (13) and [(iPr2-ATI)Al(CH =C(tBu)C≡Ct(Bu)] [B(C6F5)4] (14) intermediates. 13 crystallizes as the dinuclear dicationic complex [{(iPr2-ATI)Al (μ-C≡tBu)}2] [B(C6F5)4]2·5PhCl from chlorobenzene. 4e catalyzes the polymerization of propylene oxide and 2a catalyzes the polymerization of methyl methacrylate. 4c,e react with ethylene-d4 by β-H transfer to yield [(iPr2- ATI)AlCD2CD2H][B (C6F5)4 initially. Polyethylene is also produced in these reactions by an unidentified active species.

Reactions of bis(pentafluorophenyl)borane with titanocene dialkyls: Synthesis and structure of Cp2Ti[η2-H2B(C6F 5)2]

Clean reactions of Cp2TiR2 (R = CH3, CH2-Ph) with HB(C6F5)2 occur when 2.5 equiv of borane are used. The products of the reaction are the Ti(III) complex Cp2Ti[η2-H2B(C6F 5)2], which has been fully characterized, RH, and RB(C6F5)2. A plausible explanation for these observations, which contrast with other reactions of boranes with group 4 metallocenes, is presented.

Mechanistic aspects of the reactions of bis(pentafluorophenyl)borane with the dialkyl zirconocenes Cp2ZrR2 (R = CH3, CH2SiMe3, and CH2C6H5)

The reactions of bis(pentafluorophenyl)borane with simple dialkyl zirconocenes Cp2ZrR2 (R = CH3, CH2SiMe3, CH2Ph) proceed via initial alkyl/hydride exchange to yield Cp2Zr-(H)R and RB(C6F5)2. Two reaction paths are then followed depending on whether further equivalents of HB(C6F5)2 are present or not. If present, HB(C6F5)2 reacts with the newly formed Zr-H moiety to form dihydridoborate compounds, ultimately yielding Cp2Zr[(μ-H)2B-(C6F5) 2]2, 1, and 2 equiv of RB(C6F5)2. Compound 1 was characterized by X-ray crystallography. In the absence of more HB(C6F5)2, the products of alkyl/hydride exchange react to eliminate RH and produce the borane-stabilized alkylidene compounds Cp2Zr(μ-CH2)[(μ-H)B(C6F5) 2], 2, and Cp2Zr{η3-CH(C6H 5)[μ-H)B(C6F5)2]}, 4. The latter compound is formed cleanly in 92percent yield and was characterized by X-ray crystallography. Mechanistic studies on these reactions involving partially deuterated compounds reveal that the alkyl/hyride exchange process is reversible and takes place via a stepwise alkide-abstraction-hydridereplacement sequence rather than a concerted, four-centered σ-bond metathesis type mechanism. This is most convincingly demonstrated by the observed inversion of stereochemistry observed when erythro-Cp2Zr[CH(D)CH(D)-t-C4H9](Cl) (3JHH = 12.82 ± 0.05 Hz) is treated with excess HB(C6F5)2, producing threo-(C6F5)2B-CH(D)CH(D)-t-C4H 9 (3JHH = 5.00 ± 0.05 Hz). Further experiments reveal a H/D scrambling process involving the borane proton and the Cα-H positions of the zirconium alkyl groups (R = CH3, CH2Ph). For example, treatment of Cp2Zr(CD2C6D5)2 with 1 equiv of HB(C6F5)2 leads to a mixture of isotopomers of 4 and toluene, including C6D5CH3 and C6D5CH2D, suggesting a scrambling process in which the borane engages in multiple contacts with the metallocene reagent prior to alkane elimination. The HTD scrambling event is proposed to involve hydridoborate attack of the remaining alkyl group on the forming metallocene cation as HB(C6F5)2 abstracts the other alkide ligand. The implications of these mechanistic studies within the realms of metallocene activation and metallocene-catalyzed hydroborations are discussed.

Controlled alkene and alkyne insertion reactivity of a cationic zirconium complex stabilized by an open diamide ligand

The chemistry of electrophilic zirconium complexes stabilized by a sterically open diamide ligand has been studied. Treatment of Me2Si(NLiCMe3)2 with ZrCl4(THF)2 afforded {Me2Si(NCMe3)2}ZrCl2(THF) 2 (1), which, in solution, was in equilibrium with a dimeric zirconium dichloride species [{Me2Si(NCMe3)2}ZrCl2] 2(THF). Complex 1 was converted to dialkyl complexes {Me2Si(NCMe3)2}ZrR2 (R = CH2Ph, 4; CH2CMe3, 5) using MgBz2(dioxane)0.5 and LiCH2CMe3, respectively, but dimethylation was unsuccessful. Alkyl abstraction from 4 using B(C6F5)3 cleanly afforded {Me2Si(NCMe3)2}Zr(CH2Ph){η 6-PhCH2B(C6F5)3} (6), in which the anion strongly coordinates to the benzylzirconium cation via the aromatic ring. Protonolysis of 4 using [PhMe2NH][B(C6F5)4] afforded the Lewis-base adduct [{Me2Si(NCMe3)2}Zr{CH2Ph)(NMe 2Ph)]+ (7), whereas [Ph3C][B(C6F5)4] gave 1 equiv of Ph3CCH2Ph and a mixture of two cationic species, 9a/b, proposed to be monomeric and dimeric benzylzirconium cations. Reaction of 4 with 0.5 equiv of the trityl reagent afforded the dizirconium complex [{Me2Si(NCMe3)2}2Zr 2(CH2Ph)3]+. Cations 6, 7, and 9a/b cleanly and rapidly reacted with 2-butyne to afford the single insertion product, [{Me2Si(NCMe3)2}Zr{η1,η 6C(Me)=C(Me)CH2Ph]+, stabilized by a chelating π-coordination of the benzene ring of the hydrocarbyl ligand. Structurally similar insertion products were obtained from the reaction of 9a with a range of alkenes, [{Me2Si(NCMe3)2}Zr{η1,η 6-CH2CH(R)CH2Ph]+ (R = H, Me, n-Bu, CH2Ph). Benzylborate adduct 6 also underwent single alkene insertion giving {Me2Si(NCMe3)2}Zr{η1-CH 2CH(R)CH2Ph}{η6-PhCH2B(C 6F5)3} (R = H, Me), stabilized by anion coordination to zirconium. The dramatic effects of anion, Lewis base, solvent, and substrate variation on the rate of insertion have been rationalized in terms of the facility of anion or base dissociation from the benzylzirconium cation.