956972-12-6Relevant articles and documents
Time-Resolved Ultraviolet-Infrared Experiments Suggest Fe-Cu Dinuclear Arene Borylation Catalyst Can Be Photoactivated
Davis, Jacob T.,Martinez, Erin E.,Clark, Kyle J.,Kwon, Doo-Hyun,Talley, Michael R.,Michaelis, David J.,Ess, Daniel H.,Asplund, Matthew C.
, p. 1859 - 1865 (2021)
Heterodinuclear complexes with a direct metal-metal bond offer the possibility of unique mechanisms and intermediates. The Cp(CO)2Fe-Cu(IPr) (IPr = N,N-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) heterodinuclear complex 1 was reported to photochemically catalyze arene borylation. To examine possible initial steps of photoinitiated catalysis, we synthesized a triethylsilyl-substituted Fe-Cu catalyst derivative 5 that provided cyclohexane solubility to conduct time-resolved UV-IR studies. Time-resolved vibrational spectroscopic measurements suggest that photolysis of 5 stimulates CO dissociation without Fe-Cu metal-metal bond cleavage. UV-IR measurements of 5 with added pinacolborane (HBPin) showed a very similar set of IR bleaches and a new monocarbonyl IR absorbance, and HBPin appears to stabilize the monocarbonyl species. This suggests that arene borylation catalysis may begin with a photochemical step rather than a relatively endothermic thermal-induced cleavage of the Fe-Cu bond, and therefore a new possible catalytic cycle is proposed.
Synthesis and reactivity of an anionic NHC-borane featuring a weakly coordinating silicate anion
Deis, Thomas,Fensterbank, Louis,Lemière, Gilles,Medici, Fabrizio,Poussard-Schulz, Antoine
supporting information, (2021/10/21)
We report herein the synthesis of a new NHC-stabilised borane complex featuring a weakly coordinating anion, namely a pentaorganosilicate, on the NHC backbone. The synthesis can be achieved from a zwitterionic abnormal silicate-imidazolium adduct by deprotonation with a strong base followed by quenching with a borane transfer agent. Alternatively, the IPr-BH3 complex can also be deprotonated and the resulting vinylanion is trapped by a tetravalent spirosilane. The first structural data on a lithium derivative of an anionic NHC-borane complex functionalized by a silicate have been obtained and reveal an interaction between the three hydrogens of the borane and the lithium cation. Assessment of the reactivity highlights the higher hydridicity of the anionic NHC-borane compared to the parent IPr-BH3. Finally, electronic properties of this new species have been evaluated by means of DFT calculations and the presence of the silicate on the NHC backbone raises the HOMO which can in part explain the high hydride-donor abilities. This is consistent with the smooth reduction of an aldehyde without Lewis acid additive.
Insight into the Decomposition Mechanism of Donor-Acceptor Complexes of EH2(E = Ge and Sn) and Access to Germanium Thin Films from Solution
Brown, Alex,Dai, Guoliang,Ferguson, Michael J.,Mcdonald, Robert,Rivard, Eric,Sinclair, Jocelyn
supporting information, (2020/08/12)
Electron-donating N-heterocyclic carbenes (Lewis bases, LB) and electron-accepting Lewis acids (LA) have been used in tandem to yield donor-acceptor complexes of inorganic tetrelenes LB·EH2·LA (E = Si, Ge, and Sn). Herein, we introduce the new germanium (II) dihydride adducts ImMe2·GeH2·BH3 (ImMe2 = (HCNMe)2C:) and ImiPr2Me2·GeH2·BH3 (ImiPr2Me2 = (MeCNiPr)2C:), with the former complex containing nearly 40 wt % germanium. The thermal release of bulk germanium from ImMe2·GeH2·BH3 (and its deuterated isotopologue ImMe2·GeD2·BD3) was examined in solution, and a combined kinetic and computational investigation was undertaken to probe the mechanism by which Ge is liberated. Moreover, the thermolysis of ImMe2·GeH2·BH3 in solution cleanly affords conformal nanodimensional layers of germanium as thin films of variable thicknesses (20-70 nm) on silicon wafers. We also conducted a computational investigation into potential decomposition pathways for the germanium(II)- and tin(II)-dihydride complexes NHC·EH2·BH3 (NHC = [(HCNR)2C:]; R = 2,6-iPr2C6H3 (Dipp), Me, and H; and E = Ge and Sn). Overall, this study introduces a mild and convenient solution-only protocol for the deposition of thin films of Ge, a widely used semiconductor in materials research and industry.
Preparation and structures of group 12 and 14 element halide-carbene complexes
Ibrahim Al-Rafia,Lummis, Paul A.,Swarnakar, Anindya K.,Deutsch, Kelsey C.,Ferguson, Michael J.,McDonald, Robert,Rivard, Eric
, p. 1235 - 1245 (2013/10/22)
The synthesis of a series of N-heterocyclic carbene (NHC) complexes involving zinc, cadmium, and the heavy Group 14 elements germanium, tin, and lead is reported. The direct reaction between the bulky carbene IPr (IPr≤(HCNDipp)2C:, Dipp≤2,6-iPr2C6H3) and the Group 14 halide reagents GeCl4 and SnCl4 afforded the 1:1 complexes IPr·ECl4 (E≤Ge and Sn) in high yield; similarly, ZnI2 interacted with IPr in THF to give the THF-bound complex IPr·ZnI2·THF. CdCl2 underwent divergent chemistry with IPr and the major product isolated was the imidazolium salt [IPrH] [IPr·CdCl3], which could be converted into IPr·CdCl2·THF upon treatment with Tl[OTf]. In addition, the stable PbII amide adduct, IPr·PbBr(NHDipp), was prepared. Each of the new carbene-element halide adducts was treated with the hydride sources Li[BH4] and Li[HBEt3] in order to potentially access new element hydride adducts and/or clusters. In most instances scission of the element-carbene bonds transpired, except in the case of IPr·ZnI2·THF, which reacted with two equivalents of Li[BH4] to yield the thermally stable bis(borohydride) zinc complex IPr·Zn(BH4)2.
Donor-acceptor complexation and dehydrogenation chemistry of aminoboranes
Malcolm, Adam C.,Sabourin, Kyle J.,McDonald, Robert,Ferguson, Michael J.,Rivard, Eric
, p. 12905 - 12916 (2013/02/22)
A series of formal donor-acceptor adducts of aminoborane (H 2BNH2) and its N-substituted analogues (H 2BNRR′) were prepared: LB-H2BNRR′2- BH3 (LB = DMAP, IPr, IPrCH2 and PCy3; R and R′ = H, Me or tBu; IPr = [(HCNDipp)2C:] and Dipp = 2,6-iPr 2C6H3). To potentially access complexes of molecular boron nitride, LB-BN-LA (LA = Lewis acid), preliminary dehydrogenation chemistry involving the parent aminoborane adducts LB-H2BNH 2-BH3 was investigated using [Rh(COD)Cl]2, CuBr, and NiBr2 as dehydrogenation catalysts. In place of isolating the intended dehydrogenated BN donor-acceptor complexes, the formation of borazine was noted as a major product. Attempts to prepare the fluoroarylborane-capped aminoborane complexes, LB-H2BNH 2-B(C6F5)3, are also described.
The parent borylene: Betwixt and between
Curran, Dennis P.,Boussonniere, Anne,Geib, Steven J.,Lacote, Emmanuel
, p. 1602 - 1605 (2012/05/05)
Still elusive: The reduction of dimethylimidazol-2-ylidene dichloroborane by sodium naphthalenide has been suggested to provide a borylene that cycloadds to naphthalene to make a borirane. Evidence has been provided that this borirane instead arises from
Lithium complex of an abnormal carbene
Jana, Anukul,Azhakar, Ramachandran,Tavcar, Gasper,Roesky, Herbert W.,Objartel, Ina,Stalke, Dietmar
scheme or table, p. 3686 - 3689 (2011/11/07)
A lithium complex of an abnormal carbene with the composition [H 3BC{{N(2,6-iPr2C6H3)} 2CHCLi(THF)3}] was synthesized by the lithiation reaction of the N-heterocyclic carbene borane adduct
Substitution reactions at tetracoordinate boron: Synthesis of N-heterocyclic carbene boranes with boron-heteroatom bonds
Solovyev, Andrey,Chu, Qianli,Geib, Steven J.,Fensterbank, Louis,Malacria, Max,Lacote, Emmanuel,Curran, Dennis P.
supporting information; experimental part, p. 15072 - 15080 (2011/01/10)
Boryl halide, carboxylate and sulfonate complexes of 1,3-bis(2,6- diisopropylphenyl)imidazol-2-ylidene (dipp-Imd-BH2X, X = halide or sulfonate) have been prepared from the parent borane dipp-Imd-BH3 by (1) substitution reactions with R-X (X = halide or sulfonate), (2) reactions with electrophiles (like I2 or NIS), or (3) acid/base reactions with HX (provided that HX has a pKa of about 2 or less). Dipp-Imd-BH 2I is most conveniently prepared by reaction with diiodine while dipp-Imd-BH2OTf is best prepared by reaction with triflic acid. These and other less reactive complexes behave as electrophiles and can be substituted by a wide range of heteroatom nucleophiles including halides, thiolates and other sulfur-based nucleophiles, isocyanate, azide, nitrite, and cyanide. The resulting products are remarkably stable, and many have been characterized by X-ray crystallography. Several are members of very rare classes of functionalized boron compounds (boron azide, nitro compound, nitrous ester, etc.).
Preparation of NHC borane complexes by lewis base exchange with amine- and phosphine-boranes
Brahmi, Malika Makhlouf,Monot, Julien,Desage-El Murr, Marine,Curran, Dennis P.,Fensterbank, Louis,Lacote, Emmanuel,Malacria, Max
supporting information; experimental part, p. 6983 - 6985 (2010/11/24)
A versatile new method for the preparation of NHC boranes starting from two stable, readily available reactants-an heterocyclic salt and an amine or phosphine-borane-is reported. It uses a Lewis base exchange at boron and provides easy access to new NHC boranes, in particular B-substituted borane ones.
EPR studies of the generation, structure, and reactivity of n-heterocyclic carbene borane radicals
Walton, John C.,Brahmi, Malika Makhlouf,Fensterbank, Louis,Lacote, Emmanuel,Malacria, Max,Chu, Qianli,Ueng, Shau-Hua,Solovyev, Andrey,Curran, Dennis P.
, p. 2350 - 2358 (2010/04/30)
N-Heterocyclic carbene boranes (NHC-boranes) are a new "clean" class of reagents suitable for reductive radical chain transformations. Their structures are well suited for their reactivity to be tuned by inclusion of different NHC ring units and by approp
