Synthesis, Structure, and Bonding of the Cation [{(C6H5)3PAu}5C]⊕

Scherbaum, Franz; Grohmann, Andreas; Müller, Gerhard; Schmidbaur, Hubert

doi:10.1002/anie.198904631

Cited by 192 publications

(73 citation statements)

References 18 publications

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“…[9,10] Recently,arelated structural motive has been identified in the iron-molybdenum nitrogenase cofactor, which contains hexacoordinated C 4À .…”

Section: C]mentioning

confidence: 99%

“…[9,10] Recently,arelated structural motive has been identified in the iron-molybdenum nitrogenase cofactor, which contains hexacoordinated C 4À . [11] Taking ac ompletely different approach, Akiba and co-workers prepared formally hypercoordinated organic species through special ligand design, where an electrophilic carbon atom is intramolecularly coordinated by two/four neighboring methoxy groups.…”

Section: C]mentioning

confidence: 99%

See 1 more Smart Citation

Crystal Structure Determination of the Pentagonal‐Pyramidal Hexamethylbenzene Dication C₆(CH₃)₆²⁺

Malischewski

Seppelt

2016

Angew Chem Int Ed

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In contrast to the well-known 2-norbornyl cation, the structure of which was am atter of long debate until its pentacoordinated nature was recently proven by an X-ray structure,t he pentagonal-pyramidal dication of hexamethylbenzeneh as received considerably less attention. This species was first prepared by Hogeveen in 1973 at low temperatures in magic acid (HSO 3 F/SbF 5 ), for whichh ep roposed an onclassical structure (containing ah exacoordinated carbon) based on NMR spectroscopya nd reactivity studies,b ut no Xray crystal structure has been reported. C 6 (CH 3 ) 6 2+ can be obtained through the dissolution of hexamethyl Dewar benzeneepoxideinHSO 3 F/SbF 5 and crystallized as the SbF 6À salt upon addition of excess anhydrous hydrogen fluoride.T he crystal structure of C 6 (CH 3 ) 6 2+ (SbF 6 À ) 2 ·HSO 3 Fc onfirms the pentagonal pyramidal structure of the dication. The apical carbon is bound to one methyl group (distance 1.479(3) )and to the five basal carbon atoms (distances 1.694(2)-1.715(3) ).The tetravalencyo fc arbon and the hexagonal-planar ring structure of benzene are fundamental axioms of organic chemistry,a nd were developed 150 years ago by KekulØ. [1,2] Chemists have long been fascinated by finding exceptions from these rules.S tarting in the 1960s,v alence isomers of benzene were prepared through elaborate organic syntheses, [3][4][5][6] while hypercoordinated carbon compounds entered the stage through the pioneering work of Olah on superacids and non-classical cations. [7,8] Theb onding situation in protonated methane (CH 5 + ), which is the most prominent representative of pentacoordinated carbon, is best described as a3-center 2-electron bond between H 2 and CH 3 + ,but its isolation in bulk is elusive.The replacement of hydrogen with organogold species lead to the isolation of penta-and hexacoordinated methanium salts by Schmidbaur.T hese carbido clusters,[ (Ph 3 PAu) 5 C]+ and [(Ph 3 PAu) 6 C] 2+ ,a re significantly stabilized by aurophilic interactions. [9,10] Recently,arelated structural motive has been identified in the iron-molybdenum nitrogenase cofactor, which contains hexacoordinated C 4À .[11] Taking ac ompletely different approach, Akiba and co-workers prepared formally hypercoordinated organic species through special ligand design, where an electrophilic carbon atom is intramolecularly coordinated by two/four neighboring methoxy groups. TheC À Odistances are in the range of 2.43(1)-2.45(1) and 2.641(5)-2.750(5) ,r espectively, [12,13] thus indicating only weak interactions.Instark contrast, hypercoordinated carbon with much shorter bonds can be found in carboranes. Nevertheless,t hese common structural motives of boron chemistry are only subtly changed by replacing boron with an isolobal carbon fragment. Surprisingly,e ven hexagonalplanar carbon has been considered viable (based on theoretical calculations by Exner and Schleyer) in boron compounds, for example,inC B 6 2À . [14] Recently,t he isolation of the non-classical norbornyl cation and its crystal structure ana...

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“…[9,10] Recently,arelated structural motive has been identified in the iron-molybdenum nitrogenase cofactor, which contains hexacoordinated C 4À .…”

Section: C]mentioning

confidence: 99%

Section: C]mentioning

confidence: 99%

Crystal Structure Determination of the Pentagonal‐Pyramidal Hexamethylbenzene Dication C₆(CH₃)₆²⁺

Malischewski

Seppelt

2016

Angew Chem Int Ed

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“…Schmidbaur and coworkers have prepared a variety of higher coordinate boron (6), carbon (7,8), nitrogen (9), oxygen (10), phosphorus (11), and sulfur (12) ϩ and CLi 6 2ϩ , respectively, were also calculated to be stable minima (13-15).…”

mentioning

confidence: 99%

“…Schmidbaur and coworkers have prepared a variety of higher coordinate boron (6), carbon (7,8), nitrogen (9), oxygen (10), phosphorus (11), and sulfur (12) complexes with gold and determined their x-ray crystal structures. They have prepared trigonal bipyramidal (7) complexes involving five-and sixcoordinate carbon, respectively, representing the isolobal (5) analogs of CH 5 ϩ and CH 6 2ϩ .…”

mentioning

confidence: 99%

Structures and stabilities of higher coordinate onium-boronium dications (X ⁺ BH ₃ ⁺ and X ⁺ BH ₅ ⁺ ; X = NH ₃ , PH ₃ , H ₂ O, and H ₂ S)

Rasul

Prakash²,

Oláh³

2002

Proc. Natl. Acad. Sci. U.S.A.

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Structures of higher coordinate onium-boronium dications (X ؉ BH3 ؉ 1-4a and X ؉ BH5 ؉ 1-4d; X ‫؍‬ NH3, PH3, H2O, and H2S) were calculated by using the ab initio method at the MP2͞6-311؉G** level. All of the dications 1-4a contain a four-coordinate boron atom with a three-center two-electron bond involving boron and two hydrogens. On the other hand, all the dications 1-4d contain a six-coordinate boron atom with two three-center two-electron bonds. The thermodynamics of the complexations of 1-4a and H2 to form 1-4d were computed. Deprotonations of 1-4d were found to be substantially endothermic. Higher coordinate compounds involving a main group element are of both theoretical (1-4) and experimental (5) interest. Schmidbaur and coworkers have prepared a variety of higher coordinate boron (6), carbon (7,8), nitrogen (9), oxygen (10), phosphorus (11), and sulfur (12) ϩ and CLi 6 2ϩ , respectively, were also calculated to be stable minima (13-15).We previously reported (16) computed structures of the four-coordinate boronium ion BH 4 ϩ and the six-coordinate boronium ion BH 6 ϩ . The structure of BH 4 ϩ is planar with a three-center two-electron (3c-2e) bond (16). The structure of BH 6 ϩ contains two 3c-2e bonds (16). Results and DiscussionCalculations were carried out with the GAUSSIAN 98 program system (23). The geometry optimizations were performed at the MP2͞6-311ϩG** level. Vibrational frequencies at the MP2/6-311ϩG**͞MP2/6-311ϩG** level were used to characterize stationary points as minima (number of imaginary frequency ϭ 0) and evaluate zero-point vibrational energies that were scaled by a factor of 0.96 (24). For improved energy, single-point energies at MP4(SDTQ)6-311ϩG** on MP2͞6-311ϩG** optimized geometries were computed. Final energies were calculated at the MP4(SDTQ)/6-311ϩG**͞MP2/6-311ϩG** ϩ zero-point vibrational energy level. Thermodynamics of the selected complexation and protonation processes are given in Table 1. The calculated energies are given in Table 2. MP2͞6-311ϩG** geometrical parameters and final energies will be discussed throughout unless stated otherwise. (Fig. 1) was found to be a minimum on the potential energy surface. The structure 1a can also be considered as ammonium-substituted BH 4 ϩ . The structure is characterized with a four-coordinate boron atom having a 3c-2e bond involving boron and two hydrogens. In dication 1a the boronium ion (-BH 3 ϩ ) unit and the ammonium ion (-NH 3 ϩ ) unit are separated by a distance of 1.505 Å. The structures of phosphonium-boronium H 3 P ϩ BH 3 ϩ 2a, oxonium-boroniumϩ 3a, and sulfonium-boronium H 2 S ϩ BH 3 ϩ 4a dications ( Fig. 1) were also calculated and found to be minima on the potential energy surface. Similar to 1a, each of the 2-4a structures also contains a 3c-2e bond involving boron and two hydrogens.Deprotonation energies of 1-4a were computed and are listed in Table 1. Deprotonation of 1a to give monocation H 3 N ϩ BH 2 1b was calculated to be slightly exothermic by 2.8 kcal͞mol. The Abbreviation: 3c-2e, three-center two-electron. ...

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“…The synthesis of ligand precursors, 1,8-dimethoxy-9-trifluoromethanesulfonyloxyanthracene (3) and 9-bromo-1,8-dimethoxyanthracene (4), is illustrated in Scheme 1. The introduction of a carbon atom at the 9-position was successful from 1,8-dimethoxy-9-trifluoromethanesulfonyloxyanthracene (3) by Pd-catalyzed CO insertion with DMSO as a solvent and Pd(PPh3)4 as a catalyst in 52% yield.14a The expected cation (1) could be prepared by treatment of the ester (5) with excess Me3O+BF4-.…”

Section: Syntheses Of Ligand Precursors Bearing the Anthracene Skeletmentioning

confidence: 99%

Synthesis of Hypervalent Pentavalent Carbon and Boron Compounds

Yamamoto

Akiba

2004

J. Syn. Org. Chem., Jpn.

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Various carbon and boron compounds bearing a 1,8-disubstituted anthracene skeleton were synthesized and characterized by X-ray analysis. They showed three types of structures based on the kinds of substituents. The first one is symmetrical and is a loose pentacoordinate structure, which has the sp2 carbon or boron atom and the two weak apical interactions. The next one is an unsymmetrical tetracoordinate structure, which has the sp3 central atom. The last one is symmetrical and is a tight pentacoordinate structure, which resulted from the special feature of the fluorine substituents on the boron. The existence of hypervalent interaction was proved by the Atoms In Molecules Theory, experimental electron distribution analysis and a comparison among the structures of tight and loose pentacoordinate species. The synthesis and structures of hypervalent carbon compounds with a 2,6-bis(aryloxymethyl)benzene ligand are also discussed.

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Synthesis, Structure, and Bonding of the Cation [{(C₆H₅)₃PAu}₅C]^⊕

Cited by 192 publications

References 18 publications

Crystal Structure Determination of the Pentagonal‐Pyramidal Hexamethylbenzene Dication C₆(CH₃)₆²⁺

Crystal Structure Determination of the Pentagonal‐Pyramidal Hexamethylbenzene Dication C₆(CH₃)₆²⁺

Structures and stabilities of higher coordinate onium-boronium dications (X ⁺ BH ₃ ⁺ and X ⁺ BH ₅ ⁺ ; X = NH ₃ , PH ₃ , H ₂ O, and H ₂ S)

Synthesis of Hypervalent Pentavalent Carbon and Boron Compounds

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Synthesis, Structure, and Bonding of the Cation [{(C6H5)3PAu}5C]⊕

Cited by 192 publications

References 18 publications

Crystal Structure Determination of the Pentagonal‐Pyramidal Hexamethylbenzene Dication C6(CH3)62+

Crystal Structure Determination of the Pentagonal‐Pyramidal Hexamethylbenzene Dication C6(CH3)62+

Structures and stabilities of higher coordinate onium-boronium dications (X + BH 3 + and X + BH 5 + ; X = NH 3 , PH 3 , H 2 O, and H 2 S)

Synthesis of Hypervalent Pentavalent Carbon and Boron Compounds

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Synthesis, Structure, and Bonding of the Cation [{(C₆H₅)₃PAu}₅C]^⊕

Crystal Structure Determination of the Pentagonal‐Pyramidal Hexamethylbenzene Dication C₆(CH₃)₆²⁺

Crystal Structure Determination of the Pentagonal‐Pyramidal Hexamethylbenzene Dication C₆(CH₃)₆²⁺

Structures and stabilities of higher coordinate onium-boronium dications (X ⁺ BH ₃ ⁺ and X ⁺ BH ₅ ⁺ ; X = NH ₃ , PH ₃ , H ₂ O, and H ₂ S)