We report the preparation of N‐heterocyclic carbene (NHC)‐stabilized compounds containing P=B double bonds. The reaction of the highly functionalized phosphinoborane Mes*(SiMe3)P?B(Cl)Cp* with Lewis bases allows access to base‐stabilized phosphinidene boranes Mes*P=B(L)Cp* (L=4‐dimethylaminopyridine (DMAP), NHC) by Me3SiCl elimination. The formation of these species is shown to proceed through transient borylphosphide anions generated by Me3Si abstraction. 相似文献
Singly NHC‐coordinated (aminoboryl)aminoborenium salts react with Na2[Fe(CO)4] to yield stable coordination complexes of aminoborylene‐stabilized aminoborylenes, which exhibit exceptional σ‐donor properties. Upon photolytic CO extrusion from the metal center, the diboron ligand adopts a novel η3‐BBN coordination mode, where bond‐strengthening backdonation from the metal center into the vacant B?B π‐orbital is observed. This bonding situation can be alternatively described as a Fe‐diaminodiborene complex. In a related reduction of CAAC‐stabilized (aminoboryl)aminoborenium with KC8, the reduced species can be captured with nucleophiles to form three‐coordinate (diaminoboryl)borylenes, where both amino groups have migrated to the distal boron atom. Collectively, these reactions illustrate the isomeric flexibility imparted by amino groups on this reduced diboron system, thus opening multiple avenues of novel reactivity. 相似文献
Recent years have seen rapid advances in the chemistry of small molecules containing electron‐precise boron–boron bonds. This Review provides an overview of the latest methods for the controlled synthesis of B−B single and multiple bonds as well as the ever‐expanding range of reactivity displayed by B−B multiple bonds. 相似文献
An experimental and theoretical study of the first compound featuring a Si?P bond to a two‐coordinate silicon atom is reported. The NHC‐stabilized phosphasilenylidene (IDipp)Si?PMes* (IDipp=1,3‐bis(2,6‐diisopropylphenyl)imidazolin‐2‐ylidene, Mes*=2,4,6‐tBu3C6H2) was prepared by SiMe3Cl elimination from SiCl2(IDipp) and LiP(Mes*)SiMe3 and characterized by X‐ray crystallography, NMR spectroscopy, cyclic voltammetry, and UV/Vis spectroscopy. It has a planar trans‐bent geometry with a short Si? P distance of 2.1188(7) Å and acute bonding angles at Si (96.90(6)°) and P (95.38(6)°). The bonding parameters indicate the presence of a Si?P bond with a lone electron pair of high s‐character at Si and P, in agreement with natural bond orbital (NBO) analysis. Comparative cyclic voltammetric and UV/Vis spectroscopic experiments of this compound, the disilicon(0) compound (IDipp)Si?Si(IDipp), and the diphosphene Mes*P?PMes* reveal, in combination with quantum chemical calculations, the isolobal relationship of the three double‐bond systems. 相似文献
Like the importance of benzyne, witnessed in modern arene chemistry for decades, 1,2‐dehydro‐o‐carborane (o‐carboryne), a three‐dimensional relative of benzyne, has been used as a synthon for generating a wide range of cage, carbon‐functionalized carboranes over the past 20 years. However, the selective B functionalization of the cage still represents a challenging task. Disclosed herein is the first example of 1,3‐dehydro‐o‐carborane featuring a cage C? B bond having multiple bonding characters, and is successfully generated by treatment of 3‐diazonium‐o‐carborane tetrafluoroborate with non‐nucleophilic bases. This presents a new methodology for simultaneous functionalization of both cage carbon and boron vertices. 相似文献
Reaction of the arylchlorosilylene‐NHC adduct ArSi(NHC)Cl [Ar=2,6‐Trip2C6H3; NHC=(MeC)2(NMe)2C:] 1 with one molar equiv of lithium diphenylphosphanide affords the first stable NHC‐stabilized acyclic phosphinosilylene adduct 2 (ArSi(NHC)PPh2), which could be structurally characterized. Compound 2 , when reacted with one molar equiv selenium and sulfur, affords the silanechalcogenones 4 a and 4 b (ArSi(NHC)(?E)PPh2, 4 a : E=Se, 4 b : E=S), respectively. Conversion of 2 with an excess of Se and S, through additional insertion of one chalcogen atom into the Si?P bond, leads to 3 a and 3 b (ArSi(NHC)(?E)‐E‐P(?E)Ph2, 3 a : E=Se, 3 b : E=S), respectively. Additionally, the exposure of 2 to N2O or CO2 yielded the isolable NHC‐stabilized silanone 4 c , Ar(NHC)(Ph2P)Si?O. 相似文献
A new stable heterocyclic germylene, in which the divalent germanium atom lies between a nitrogen atom and a phosphanylidene phosphorane group, was synthesized. Experimental and theoretical studies revealed the peculiar effect of phosphanylidene phosphorane substituent, which is a stronger π‐donor towards germanium than an amino group is. Because of the weak phosphorus–germanium π‐bond, this new germylene compound shows an enhanced reactivity compared to classical N‐heterocyclic germylenes. 相似文献
The reactions of a diborene with elemental selenium or tellurium are shown to afford a diboraselenirane or diboratellurirane, respectively. These reactions are reminiscent of the sequestration of subvalent oxygen and nitrogen in the formation of oxiranes and aziridines; however, such reactivity is not known between alkenes and the heavy chalcogens. Although carbon is too electronegative to affect the reduction of elements with lower relative electronegativity, the highly reducing nature of the B?B double bond enables reactions with Se0 and Te0. The capacity of multiple bonds between boron atoms to donate electron density is highlighted in reactions where diborynes behave as nucleophiles, attacking one of the two Te atoms of diaryltellurides, forming salts consisting of diboratellurenium cations and aryltelluride anions. 相似文献
E?Si transfer : Anionic compounds capable of transferring a silicon‐containing double bond are reviewed (see figure), particularly reagents with Si?Si moieties (Tip=2,4,6‐iPr3C6H2, M=Li, Na, K) and their applications towards main‐group and transition‐metal electrophiles, as well as their reactivity towards organic compounds. A few recently reported derivatives with Si?C (Ad=1‐adamantyl) and Si?P moieties are included for completeness.
The first 4π‐electron resonance‐stabilized 1,3‐digerma‐2,4‐diphosphacyclobutadiene [LH2Ge2P2] 4 (LH=CH[CHNDipp]2 Dipp=2,6‐iPr2C6H3) with four‐coordinate germanium supported by a β‐diketiminate ligand and two‐coordinate phosphorus atoms has been synthesized from the unprecedented phosphaketenyl‐functionalized N‐heterocyclic germylene [LHGe‐P=C=O] 2 a prepared by salt‐metathesis reaction of sodium phosphaethynolate (P≡C?ONa) with the corresponding chlorogermylene [LHGeCl] 1 a . Under UV/Vis light irradiation at ambient temperature, release of CO from the P=C=O group of 2 a leads to the elusive germanium–phosphorus triply bonded species [LHGe≡P] 3 a , which dimerizes spontaneously to yield black crystals of 4 as isolable product in 67 % yield. Notably, release of CO from the bulkier substituted [LtBuGe‐P=C=O] 2 b (LtBu=CH[C(tBu)N‐Dipp]2) furnishes, under concomitant extrusion of the diimine [Dipp‐NC(tBu)]2, the bis‐N,P‐heterocyclic germylene [DippNC(tBu)C(H)PGe]2 5 . 相似文献
The syntheses of sulfur‐ and selenium‐bridged cyclic compounds containing boron stabilized by N‐heterocyclic carbenes (NHCs) have been achieved by the reductive insertion of elemental chalcogens into boron–boron multiple bonds. The three pairs of bonding electrons between the boron atoms in the triply bonded diboryne enabled six‐electron reduction reactions, resulting in the formation of [2.2.1]‐bicyclic systems wherein bridgehead boron atoms are spanned by three chalcogen bridges. A similar reaction using a diborene (boron–boron double bond) resulted in the reductive transfer of both pairs of bonding electrons to three sulfur atoms, yielding a NHC‐stabilized trisulfidodiborolane. The demonstration of these six‐ and four‐electron reductions lends support to the presence of three and two pairs of bonding electrons between the boron atoms of the diboryne and diborene, respectively, a fact that may be useful in future discussions on bond order. 相似文献
The reaction of the bulky bis(imidazolin‐2‐iminato) ligand precursor (1,2‐(LMesNH)2‐C2H4)[OTs]2 ( 1 2+ 2[OTs]?; LMes=1,3‐dimesityl imidazolin‐2‐ylidene, OTs=p‐toluenesulfonate) with lithium borohydride yields the boronium dihydride cation (1,2‐(LMesN)2‐C2H4)BH2[OTs] ( 2 + [OTs]?). The boronium cation 2 + [OTs]? reacts with elemental sulfur to give the thioxoborane salt (1,2‐(LMesN)2‐C2H4)BS[OTs] ( 3 + [OTs]?). The hitherto unknown compounds 1 2+ 2[OTs]?, 2 + [OTs]?, and 3 + [OTs]? were fully characterized by spectroscopic methods and single‐crystal X‐ray diffraction. Moreover, DFT calculations were carried out to elucidate the bonding situation in 2 + and 3 +. The theoretical, as well as crystallographic studies reveal that 3 + is the first example for a stable cationic complex of three‐coordinate boron that bears a B?S double bond. 相似文献
Metal‐free regioselective carboboration of arylnitriles with L2PhB: ( 1 : L=oxazol‐2‐ylidene) catalyzed by Et3B afforded the unprecedented acyclic 2‐aza‐4‐borabutadienes 2 , thus demonstrating a new strategy to construct a B,C,N‐mixed π‐system involving B=C and C=N bonds. Thermal isomerization of 2 gave C‐borylimines ( 3 ), and diverse reactivity of 2 a towards several substrates, such as H+, F+, O2, S, Se, and isonitriles, allowed construction of boron‐containing heterocycles with various ring sizes, thus illustrating the utility of 2 as a synthetic building block. 相似文献
In contrast to the well‐established chemistry of ketones (R2C?O), the reactivity of the elusive heavier congeners R2E?O (E=Si, Ge, Sn, Pb) is far less explored because of the high polarity of the E?O bonds and hence their tendency to oligomerize with no activation barrier. Very recently, great advances have been achieved in the synthesis of isolable compounds with E?O bonds, including the investigation of donor‐stabilized isolable silanones and the first stable “genuine” germanone. These compounds show drastically different reactivities compared to ketones and represent versatile building blocks in silicon–oxygen and germanium–oxygen chemistry. This and other exciting achievements are described in this Minireview. 相似文献
The complexation of two equivalents of a cyclic (alkyl)(amino)carbene (CAAC) to tetrabromodiborane, followed by reduction with four equivalents of sodium naphthalide, led to the formation of the CAAC‐stabilized linear diboracumulene (CAAC)2B2. The capacity of the CAAC ligand to facilitate B2→CAAC donation of π‐electron density resulted in important differences between this species and a previously reported complex featuring a B?B triple bond stabilized by cyclic di(amino)carbenes, including a longer B? B bond and shorter B? C bonds. Frontier orbital analysis indicated sharing of valence electrons across the entire linear C‐B‐B‐C unit in (CAAC)2B2, which is supported by natural population analysis and cyclic voltammetry. 相似文献
MP2/aug‐cc‐pVTZ calculations were performed on complexes of boron and aluminum trihydrides and trihalides with hydrogen cyanide (ZH3‐NCH and ZX3‐NCH; Z=B, Al; X=F, Cl). The complexes are linked through the B???N and Al???N interactions, which are named as triel bonds and which are classified as π‐hole bonds. It was found that they possess numerous characteristics of typical covalent bonds, since they are ruled mainly by processes of the electron charge shift from the Lewis base to the Lewis acid unit. Other configurations of the ZH3‐NCH and ZX3‐NCH complexes linked by the dihydrogen, hydrogen, and halogen bonds were found. However, these interactions are much weaker than the corresponding π‐hole bonds. The quantum theory of atoms in molecules and the natural bond orbital approaches were applied to characterize the complexes and interactions analyzed. The crystal structures of triel trihydrides and triel trihalides were also analyzed for comparison with the results of calculations. 相似文献