The Doubly Base‐Stabilized Diborane(4) [HB(μ‐hpp)]2 (hpp = 1,3,4,6,7,8‐hexahydro‐2H‐pyrimido[1,2‐a]pyrimidinate): Synthesis by Catalytic Dehydrogenation and Reactions with S8 and Disulfides

Schulenberg, Nikola; Ciobanu, Oxana; Kaifer, Elisabeth; Wadepohl, Hubert; Himmel, Hans‐Jörg

doi:10.1002/ejic.201000637

Cited by 59 publications

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“…All solvents were rigorously dried by applying standard procedures prior to their use. The synthesis of [HB(m-hpp)] 2 (1) was accomplished as reported previously in reference [5].…”

Section: Methodsmentioning

confidence: 99%

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Synthesis and Characterization of a Doubly Base‐Stabilized B₃H₆⁺ Analogue

Schulenberg¹,

Wadepohl²,

Himmel³

2011

Angew Chem Int Ed

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There is long-standing interest in the electronic structure of small-ring compounds containing boron.[1] However, the simple boron hydride B 3 H 6 + , being isoelectronic to the smallest aromatic organic compound, namely the 2p system C 3 H 3 + , has not yet been prepared. The possible structure of B 3 H 6 + was assessed in a number of quantum-chemical calculations using various levels of theory. [2,3] These calculations predicted a C 3v -symmetric, nonplanar global minimum structure with three bridging hydrogen atoms (see Scheme 1). The D 3h -symmetric planar form does not represent an energy minimum, is approximately 175 kJ mol À1 higher in energy than the C 3v -symmetric global energy minimum. B 3 H 6 + was therefore declared to be the "first three-membered nonplanar 2p aromatic" species.[2a]Korkin, Schleyer, and McKee also considered other isomers in their calculations.[3] They found in total four energy minimum structures, which are displayed in Scheme 1. According to their ab initio (MP2) calculations, a C 2v -symmetric isomer featuring a B 3 triangle with one short (150.1 pm) and two longer B À B bonds (184.9 pm) as well as two bridging hydrogen atoms (see Scheme 1) lies 49 kJ mol À1 higher in energy than the C 3v -symmetric global energy minimum. In two further C S -and C 2v -symmetric isomers a B-B-B chain is established. The energies of these two isomers are already 60 and 77 kJ mol À1 higher than the C 3v global energy minimum structure. Up to date, none of these isomers or even a derivative of B 3 H 6 + have been structurally characterized. Herein we report the synthesis and complete characterization of a doubly base-stabilized B 3 H 6 + analogue. In our studies we used the doubly base-stabilized diborane(4) [HB(m-hpp)] 2 (1), which was synthesized as described previously by catalytic dehydrogenation of the adduct H 3 B·hppH (Scheme 2).[4] We recently reported on different aspects of the reactivity of 1. For example, sulfuration was shown to give [HB(m-hpp)] 2 (m-S), [5] and protonation leads to the cation and doubly base-stabilized B 2 H 5[6] Moreover, the complexes [{HB(m-hpp)} 2 ZnX 2 ] and [{HB(m-hpp)} 2 ZnMe 2 ] were obtained as the products of reaction with zinc halides ZnX 2 (X = Cl, Br) or dimethylzinc, respectively.[7] These reactions demonstrated the high nucleophilicity of 1. In the light of this chemical behavior, we tested the reaction of 1 with BR 2 + (R = H or alkyl) cationic species. In the course of our research, we treated 1 with Nborabicyclo[3.3.1]nonan-9-yl (9-BBN) bis-(trifluoromethanesulfonyl)imide (2 a) and trifluoromethanesulfonate (2 b) (see Scheme 3), which are known as easily accessible sources of a highly electrophilic boronium ion.[8] We indeed observed the formation of a single reaction product.Both salts 3 a and 3 b could be crystallized from toluene or toluene/petroleum ether (40/60) solutions. However, only for the crystals of 3 b was a good-quality structure derived on the basis of the X-ray diffraction data. The unit cell contains two slightly different cationic unit...

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“…All solvents were rigorously dried by applying standard procedures prior to their use. The synthesis of [HB(m-hpp)] 2 (1) was accomplished as reported previously in reference [5].…”

Section: Methodsmentioning

confidence: 99%

“…For example, sulfuration was shown to give [HB(m-hpp)] 2 (m-S), [5] and protonation leads to the cation and doubly base-stabilized B 2 H 5…”

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confidence: 99%

Synthesis and Characterization of a Doubly Base‐Stabilized B₃H₆⁺ Analogue

Schulenberg¹,

Wadepohl²,

Himmel³

2011

Angew Chem Int Ed

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“…[10] [a] Anorganisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany Fax: +49-6221-545707 E-mail: hans-jorg.himmel@aci.uni-heidelberg. Recently, we showed that the doubly base-stabilized diborane(4) [HB(μ-hpp)] 2 (see Scheme 1) (hpp = 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidinate) can easily be prepared by catalytic dehydrogenation of the adduct H 3 B·hppH, [11][12][13] and also reported its structural properties. Oxidative insertion reactions into its B-B bond were in the focus of our first reactivity studies.…”

Section: Introductionmentioning

confidence: 99%

“…[12] Sulfuration with elemental sulfur gives eventually, after passing several coloured (and spectroscopically characterized) intermediate stages, the neutral hydride [HB(μ-hpp)] 2 (μ-S). [13] Here we now analyse a new aspect of the reactivity of [HB(μ-hpp)] 2 , namely its use as a ligand. In contrast to B 2 H 4 (PMe 3 ) 2 and related diborane(4) species, [HB(μ-hpp)] 2 exhibits no rotational freedom around the B-B bond, and the B-H groups are already ideally oriented for complex formation.…”

Section: Introductionmentioning

confidence: 99%

Zinc Halide and Alkylzinc Complexes of a Neutral Doubly Base‐Stabilized Diborane(4)

et al. 2011

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“…[4] Kürzlich berichteten wir über verschiedene Aspekte der Reaktivität von 1. Es wurde beispielsweise gezeigt, dass Sulfurierung [HB(mhpp)] 2 (m-S) ergibt, [5] während Protonierung zu dem kationischen B 2 H 5…”

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Synthese und Charakterisierung eines doppelt basenstabilisierten B₃H₆⁺‐Analogons

2011

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Seit langem besteht Interesse an der elektronischen Struktur kleiner cyclischer Borverbindungen.[ [7] Diese Reaktionen zeigen den stark nukleophilen Charakter von 1. Angesichts dieser Reaktivität überprüften wir die Reaktion zwischen 1 und dem Kation BR 2 + (R = H oder Alkyl).In unseren Untersuchungen setzten wir 1 mit N-Borabicyclo[3.3.1]nonan-9-yl(9-BBN)-bis(trifluormethansulfonyl)-imid (2 a) und -trifluormethansulfonat (2 b) ein (Schema 3), die als leicht zugängliche Quellen eines stark elektrophilen Boronium-Ions bekannt sind. [8] In der Tat beobachteten wir jeweils die Bildung eines einzigen Reaktionsprodukts.Beide Salze

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The Doubly Base‐Stabilized Diborane(4) [HB(μ‐hpp)]₂ (hpp = 1,3,4,6,7,8‐hexahydro‐2H‐pyrimido[1,2‐a]pyrimidinate): Synthesis by Catalytic Dehydrogenation and Reactions with S₈ and Disulfides

Cited by 59 publications

References 58 publications

Synthesis and Characterization of a Doubly Base‐Stabilized B₃H₆⁺ Analogue

Synthesis and Characterization of a Doubly Base‐Stabilized B₃H₆⁺ Analogue

Zinc Halide and Alkylzinc Complexes of a Neutral Doubly Base‐Stabilized Diborane(4)

Synthese und Charakterisierung eines doppelt basenstabilisierten B₃H₆⁺‐Analogons

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The Doubly Base‐Stabilized Diborane(4) [HB(μ‐hpp)]2 (hpp = 1,3,4,6,7,8‐hexahydro‐2H‐pyrimido[1,2‐a]pyrimidinate): Synthesis by Catalytic Dehydrogenation and Reactions with S8 and Disulfides

Cited by 59 publications

References 58 publications

Synthesis and Characterization of a Doubly Base‐Stabilized B3H6+ Analogue

Synthesis and Characterization of a Doubly Base‐Stabilized B3H6+ Analogue

Zinc Halide and Alkylzinc Complexes of a Neutral Doubly Base‐Stabilized Diborane(4)

Synthese und Charakterisierung eines doppelt basenstabilisierten B3H6+‐Analogons

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The Doubly Base‐Stabilized Diborane(4) [HB(μ‐hpp)]₂ (hpp = 1,3,4,6,7,8‐hexahydro‐2H‐pyrimido[1,2‐a]pyrimidinate): Synthesis by Catalytic Dehydrogenation and Reactions with S₈ and Disulfides

Synthesis and Characterization of a Doubly Base‐Stabilized B₃H₆⁺ Analogue

Synthesis and Characterization of a Doubly Base‐Stabilized B₃H₆⁺ Analogue

Synthese und Charakterisierung eines doppelt basenstabilisierten B₃H₆⁺‐Analogons