Hexaphosphapentaprismane: A New Gateway to Organophosphorus Cage Compound Chemistry

Al-Ktaifani, Mahmoud M.; Bauer, Walter; Bergsträßer, Uwe; Breit, Bernhard; Francis, Matthew D.; Heinemann, Frank W.; Hitchcock, Peter B.; Mack, Andreas; Nixon, John F.; Pritzkow, Hans; Regitz, Manfred; Zeller, Mat­thias; Zenneck, Ulrich

doi:10.1002/1521-3765(20020603)8:11<2622::aid-chem2622>3.0.co;2-#

Cited by 55 publications

(21 citation statements)

References 67 publications

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“…From a synthetic standpoint, the synthesis of 6 by a Lewis acid promoted ring‐opening reaction of 1 represents a new approach to phosphorus–carbon clusters. These compounds were previously prepared from PC t Bu, either by thermolysis or by reaction with various transition‐metal species or Lewis acids,21, 22 synthetic approaches which have to date not provided access to molecules such as 6 . Interestingly, the cation of 6 obeys Wade's rules and is in fact the first example of a cationic phosphorus–carbon cluster.…”

Section: Methodsmentioning

confidence: 99%

Selective Preparation of the [3,5‐tBu₂‐1,2,4‐C₂P₃]⁻ Ion and Synthesis and Structure of the Cationic Species nido‐[3,5‐tBu₂‐1,2,4‐C₂P₃]⁺, Isoelectronic with [C₅R₅]⁺

et al. 2003

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Selective Preparation of the [3, There has been significant progress in the chemistry of transition-metal complexes carrying the h 5 -3,5-tBu 2 -1,2,4-C 2 P 3 ligand.[1] Although the isolobal relationship PMCH and diagonal relationship P/C suggest that complexes carrying this ligand should behave like the corresponding h 5 -cyclopentadienyl-substituted analogues, recent work has shown that the phosphorus-containing systems exhibit subtle differences in both bonding and reactivity. [2][3][4] This situation suggests that further investigations could be rewarding. In a new approach to this chemistry we focused on the reactivity of the interesting tricyclic C 2 P 3 compound 1 (Scheme 1), first reported by Regitz et al.[5] First, we used this species as a convenient starting point for a new selective synthetic approach to the aromatic ion [3,5-tBu 2 -1,2,4-C 2 P 3 ] À (3). Second, and again reflecting on the consequences of replacing CH groups by isolobal P atoms, we explored the possibility of utilizing 1 as a precursor to cations [C 2 tBu 2 P 3 ]+ . The published synthetic pathways to the anion 3, [6][7][8] which derive from earlier work by Becker et al., [9,10] involve reaction of PCtBu with alkali metals (M). However, this procedure is unselective, and to obtain pure 3 it is necessary to repeatedly recrystallize the moisture-sensitive alkali-metal salts to remove the second product of these reactions, the [2,4,5-tBu 3 -1,3-C 3 P 2 ]À ion. Therefore, we recognized that if the full potential of this area was to be realized, it was important to devise a more efficient and selective pathway to 3. We reasoned that if the tricyclic compound 1, which is readily formed in good to excellent yield by treating the readily accessible zirconium complex 2 with PCl 3 , [5] was treated with an alkali metal in THF, the anionic species A should be generated (Scheme 1). We then hypothesized that such a species should undergo consecutive ring-opening reactions (A!B!3) and thus selectively provide the desired anion.Reaction (RT, 2 h, THF) of 1 with Li or Na metal leads to quantitative formation of the lithium or sodium salt of 3, which confirms our ring-opening hypotheses. Both Li·3 and Na·3 react quantitatively with Ph 3 SnCl to give the known compound 3,5-tBu 2 -1-SnPh 3 -1,2,4-C 2 P 3 (4), which has been shown to be a valuable reagent for the syntheses of complexes of the h 5 -C 2 P 3 ligand. [7] We believed that 1 might react with Lewis acids to provide an entry point to the cationic [C 2 tBu 2 P 3 ] + manifold, related to the isoelectronic pentamethylcyclopentadienyl cation, a species that has recently attracted considerable attention. [11][12][13][14][15] In particular, in view of the isolobal relationship PMCH, and Scheme 1. a) PCl 3 ; b) M, THF, ÀMCl; c) Ph 3 SnCl, ÀMCl (* = CtBu; .. = lone pair; M = Li, Na.

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Section: Methodsmentioning

confidence: 99%

Selective Preparation of the [3,5‐tBu₂‐1,2,4‐C₂P₃]⁻ Ion and Synthesis and Structure of the Cationic Species nido‐[3,5‐tBu₂‐1,2,4‐C₂P₃]⁺, Isoelectronic with [C₅R₅]⁺

et al. 2003

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“…No cage‐inversion reactions of optically active cage compounds have been reported in the literature, and P–C cage‐rearrangement reactions are rare. Most examples are based on photochemical activation of the cages,9,13,14 and sp 2 ‐hybridized cage phosphorus atoms have been identified by Binger et al as specifically reactive centers for rearrangement processes 15. The same seems to be true for the P 5 ‐deltacyclenes.…”

Section: Discussionmentioning

confidence: 97%

“…This striking fact seems to correspond to earlier observations with P–C cages, the preparation of which is based on Becker's famous tert‐ butylphosphaalkyne t BuC≡P ( 5 ) 6,7. The stannylated version of 1 , for example, in which a SnR 3 group is bonded to P1 rather than H1, contains seven stereogenic centers, but is formed as one pair of enantiomers only,8 and three independent synthetic approaches to tetra‐ tert‐ butyl‐P 6 ‐pentaprismane yielded only two enantiomers of the same cage, which contains ten stereogenic centers 9. We believe that this approach can be adapted to asymmetric P–C cages with bulky C ‐substituents in general, and that this should open a gate to several new enantiomerically pure cages.…”

Section: Introductionmentioning

confidence: 96%

Optically Active P₅‐Deltacyclenes: A Unique Cage‐Inversion Reaction and Some Transition‐Metal Complexes of the Rearranged Cage

et al. 2015

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Cage-chiral P 5 -deltacyclene 1 is available as a pair of highly enriched P-C cage enantiomers 1′ and 1′′, which exist as pairs of epimers a and b. Deprotonation of cage atom P1 initiates a rearrangement reaction, in which P1 and the neighboring carbon atom C4, together with its substituent, change places to form optically active iso-P 5 -deltacyclene enantiomers 6′′ and 6′, again as pairs of epimers. The CD spectra of related pairs of optically active cages 1 and 6 consist of almost mirrorsymmetric curves, an indicator of mirror-symmetric cage structures. This surprising result was verified by an absolute structure determination of the W(CO) 5 complex 9a′′. With the exception of the two cage nuclei that had changed places in relation to starting material 1′, all other cage nuclei of rearrangement [a] 691 Scheme 2. Base-induced cage-rearrangement reactions of 1′ and 1′′ to form 6′′ and 6′, respectively. Expected and experimentally observed reaction pathways.

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“…P‐C cage compounds of the general composition P n ( t BuC) m X are available in some variability including highly symmetric species such as tetra‐ tert ‐butyl‐tetraphosphacubane ( 1 ), but chiral cages are formed in most cases . Due to the significant size difference of the tert ‐butyl groups and the P‐lone pairs as the peripheral components of the cages, which are based on Becker's famous tert ‐butyl‐phosphaalkyne ( 2 ), the number of stable isomers is limited for a given combination of n and m .…”

Section: Introductionmentioning

confidence: 99%

“…Due to the significant size difference of the tert ‐butyl groups and the P‐lone pairs as the peripheral components of the cages, which are based on Becker's famous tert ‐butyl‐phosphaalkyne ( 2 ), the number of stable isomers is limited for a given combination of n and m . A highly efficient diastereoselectivity results for the preparation of chiral cages like triorganylstannyl‐tetra‐ tert ‐butyl‐P 5 ‐deltacyclene 3 and tetra‐ tert ‐butyl‐P 6 ‐pentaprismane ( 4 ) (Figure ).…”

Section: Introductionmentioning

confidence: 99%

Stereoselective P₅-Deltacyclene Alkylation, an Efficient Route to New Asymmetric P-C-Cage Compounds

Keller

Höhn

Rohwer

et al. 2017

Z. Anorg. Allg. Chem.

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Tetra-tert-butyl-P 5 -deltacyclene 5 represents one of only two asymmetric P-C cage compounds, which are available in highly enantiomerically enriched versions. This paper reports about stereoselective substitution reactions of 5 to develop the chemistry of optically active P-C cages further. Electrophilic substitution of the only secondary phosphorus atom P1 of the cage with methyl and benzyl groups was achieved with 92 % and Ͼ99 % de, but the yields of the reactions are limited due to competing processes. The uncatalyzed hydrophosphination reaction of a monosubstituted allene and two α,β-unsaturated 922 carbonyl compounds with 5 proved to be the method of choice. cis-Butanone-P 5 -deltacyclene 12 is formed in 92 % yield and with Ͼ99 % de and cis-pentanone-P 5 -deltacyclene 13a is accessible with Ͼ99 % de for P1 and 92 % de for the attached carbon atom at the same time. Besides stereoselectivity, the hydrophosphination reaction of 5 performs with a good regioselectivity. The chiral cage 5 controls the stereoselectivity of its reactions for the cage elements as well as for the α position of a substituent.A novel aspect of this field of chemistry are optically active derivatives of chiral P-C cage compounds. [6][7][8] As a specific property of the derivatives of 3, a once established enantiomeric excess remains untouched by all reactions tested to date which do not disintegrate the molecules such as destannylation, [6] protonation, [7] deprotonation, [9] complexation, [7,9] oxidation, [10] and cage rearrangement including cage inversion. [9] In spite of its five P-lone pairs and a dynamic equilibrium between two epimers, P-H P 5 -deltacyclene 5 (Scheme 1) proved to be a highly selective ligand with metals of interest for catalytic applications. It forms only one single complex species in high yield for each of its enantiomers with the (benzene)Ru II Cl 2 fragment, for example. [7] Scheme 1. Preparation of P-H P 5 -deltacyclene 5 and iso-P 5 -deltacyclene 8. Journal of Inorganic and General ChemistryZeitschrift für anorganische und allgemeine Chemie ARTICLE ated [5 -H] -. [7,9] P-alkylation of a P-C cage compound has been reported for the first time for tetraphosphacubane (1), [11] and an asymmetric P-C cage has been used as well. [12] Cationic mono organylation and alkynylation products [1R] + are accessible with suitable electrophiles. 5 should form the cation [5R] + if treated in the same way as 1. A successive deprotonation of [5R] + with bases seemed to be possible and would lead to alkylated neutral cages, whose ligand properties with respect to metal cations would not be hampered by a positive charge. In spite of the bulkiness of the tetra-tert-butyl-P 5 -deltacyclene cage, the P-H function of 5 might be active as a hydrophosphination agent towards activated unsaturated organic compounds and form neutral alkyl-tetra-tert-butyl-P 5 -deltacyclene derivatives directly. In the case of prochiral organic substrates, the stereochemical aspects of the reaction are of interest for the potential use of the cages as ch...

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Hexaphosphapentaprismane: A New Gateway to Organophosphorus Cage Compound Chemistry

Cited by 55 publications

References 67 publications

Selective Preparation of the [3,5‐tBu₂‐1,2,4‐C₂P₃]⁻ Ion and Synthesis and Structure of the Cationic Species nido‐[3,5‐tBu₂‐1,2,4‐C₂P₃]⁺, Isoelectronic with [C₅R₅]⁺

Selective Preparation of the [3,5‐tBu₂‐1,2,4‐C₂P₃]⁻ Ion and Synthesis and Structure of the Cationic Species nido‐[3,5‐tBu₂‐1,2,4‐C₂P₃]⁺, Isoelectronic with [C₅R₅]⁺

Optically Active P₅‐Deltacyclenes: A Unique Cage‐Inversion Reaction and Some Transition‐Metal Complexes of the Rearranged Cage

Stereoselective P₅-Deltacyclene Alkylation, an Efficient Route to New Asymmetric P-C-Cage Compounds

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Hexaphosphapentaprismane: A New Gateway to Organophosphorus Cage Compound Chemistry

Cited by 55 publications

References 67 publications

Selective Preparation of the [3,5‐tBu2‐1,2,4‐C2P3]− Ion and Synthesis and Structure of the Cationic Species nido‐[3,5‐tBu2‐1,2,4‐C2P3]+, Isoelectronic with [C5R5]+

Selective Preparation of the [3,5‐tBu2‐1,2,4‐C2P3]− Ion and Synthesis and Structure of the Cationic Species nido‐[3,5‐tBu2‐1,2,4‐C2P3]+, Isoelectronic with [C5R5]+

Optically Active P5‐Deltacyclenes: A Unique Cage‐Inversion Reaction and Some Transition‐Metal Complexes of the Rearranged Cage

Stereoselective P5-Deltacyclene Alkylation, an Efficient Route to New Asymmetric P-C-Cage Compounds

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Selective Preparation of the [3,5‐tBu₂‐1,2,4‐C₂P₃]⁻ Ion and Synthesis and Structure of the Cationic Species nido‐[3,5‐tBu₂‐1,2,4‐C₂P₃]⁺, Isoelectronic with [C₅R₅]⁺

Selective Preparation of the [3,5‐tBu₂‐1,2,4‐C₂P₃]⁻ Ion and Synthesis and Structure of the Cationic Species nido‐[3,5‐tBu₂‐1,2,4‐C₂P₃]⁺, Isoelectronic with [C₅R₅]⁺

Optically Active P₅‐Deltacyclenes: A Unique Cage‐Inversion Reaction and Some Transition‐Metal Complexes of the Rearranged Cage

Stereoselective P₅-Deltacyclene Alkylation, an Efficient Route to New Asymmetric P-C-Cage Compounds