Synthese, Struktur und Reaktivität von Bis(dialkylamino)diphosphanen

Bender, H. R. G.; Niecke, Edgar; Nieger, Martin; Westermann, H.

doi:10.1002/zaac.19946200712

Cited by 31 publications

(30 citation statements)

References 38 publications

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“…Im Gegensatz zu den bei Diphosphanen vor herrschenden gauche-oder /ra«s-Anordnungen der Substituenten stimmt diese K onform ation eher mit "Empirical force field"-Berechnungen für Diphosphane mit sterisch anspruchsvollen Ligan den überein, die eine halbekliptische K onform a tion Vorhersagen [23], Dies konnte bereits anhand von Strukturuntersuchungen einiger alkyl-, silylund am inosubstituierter D iphosphane (r = 5-30°) [11,24] verifiziert werden.…”

Section: Kristallstruktur-bestimmungenunclassified

Synthese amino- und silylsubstituierter Triphosphane – Struktur des 1.1.3.3-Tetrakis(di-iso-propylamino)-2-trimethylsilyl- und des 1.1.3.3-Tetraphenyl-2-tri-iso-propylsilyl-triphosphans / Synthesis of Amino- and Silyl-Substituted Triphosphines – Structure of 1,1,3,3-Tetrakis(di-iso-propylamino)-2-trimethylsilyl- and 1,1,3,3-Tetraphenyl-2-tri-iso-propylsilyl-triphosphine

Bender

Nieger

Niecke

1993

Zeitschrift Für Naturforschung B

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A variety o f triphosphines [(Et2N )2 P]2PR 4 a -h , [('Pr2 N )2P]2PR 5 a -e and [Ph,P]-,PR 9 e -g [R = Cy (a), rBu (b), Mes (c), M e3Si (d), 'BuM e2Si (e), ThexM e2Si (f), 'Pr3Si (g), Äd"(h), H (i)] has been obtained by the reaction o f the dilithiated primary phosphines R PH 2 l a -h with 2 equiv. o f the chlorophosphines (Et2 N )2PCl 2, ('Pr2N )2PCl 3 or Ph2PCl 8 . M ethanolysis o f the trimethylsilyl substituted derivative [('Pr2 N )2 P]2P(SiM e3) 5d yields the hydrogen substituted triphosphine [('Pr2 N )2 P]2PH 5i. The lithiated diphosphine ('Pr2 N )2 P -P (S iM e 3)Li 6 reacts with the chlorophosphine 2 to give the unsymmetrically substituted triphosphine ('Pr2N )2 P -P (S iM e 3 )-P ( N E t2 ) 2 7d. The com pounds have been chracterized by their N M R and mass spectra. The structures o f 4d and 9g have been determined by X-ray diffraction, repre senting the first structures o f uncomplexed triphosphines.

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Section: Kristallstruktur-bestimmungenunclassified

Synthese amino- und silylsubstituierter Triphosphane – Struktur des 1.1.3.3-Tetrakis(di-iso-propylamino)-2-trimethylsilyl- und des 1.1.3.3-Tetraphenyl-2-tri-iso-propylsilyl-triphosphans / Synthesis of Amino- and Silyl-Substituted Triphosphines – Structure of 1,1,3,3-Tetrakis(di-iso-propylamino)-2-trimethylsilyl- and 1,1,3,3-Tetraphenyl-2-tri-iso-propylsilyl-triphosphine

Bender

Nieger

Niecke

1993

Zeitschrift Für Naturforschung B

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“…The P1ÀP2 bond length in 5 a (2.334(1) , Figure 1) is substantially longer than typical PÀP distances in diphosphanes (2.217 AE 0.08 [8] ) and exceeds even the distances in the sterically overcrowded [{(Me 3 Si) 2 CH} 2 P] 2 (2.310 ), [9] which dissociates easily under homolytic cleavage of the PÀP bond to give two radicals, and in the 1,1-diaminodiphosphane (iPr 2 N) 2 PÀPPh 2 (2.250 ), [10] for which, owing to the significantly lower cation stability of (iPr 2 N) 2 P + as compared to a diazaphospholenium cation, [3] a less pronounced dipolar polarization of the PÀP bond is expected.…”

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confidence: 99%

Diphosphanes with Polarized and Highly Reactive PP Bonds

2004

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Single bonds are described in the valence-bond (VB) model in terms of resonance between covalent and ionic canonical structures (Scheme 1).[1] Whereas the covalent canonical structure is dominant for homoatomic bonds (AÀB), the weight of the appropriately polarized ionic canonical structure prevails for heteroatomic bonds with a large electronegativity difference (cA ! cB). As a result, this leads to a lower covalent bond order and a substantial bond polarityWe reported in 2000 on the hydride reactivity of 2-hydridodiazaphospholenes 1, and interpreted this behavior as a consequence of a polarization P d+ ÀH dÀ of the PÀH bond that can be explained in terms of a hyperconjugation between the six p electrons in the C 2 N 2 moiety and the s*(PÀH) orbital. [2] In the frame of the VB model, this indicates that ionic canonical structures contribute, regardless of the low electronegativity difference (c AR (H) 2.2, c AR (P) 2.06), significantly to the bonding. The cause of this effect lies in the high cation stability of the diazaphospholenium fragment which yields an energetic stabilization of canonical structures such as 1'' and 1''', and provides, for example, the driving force for the increased tendency towards dissociation of P-halogeno-1,3,2-diazaphospholenes.[3] Following this principle, a combination of a diazaphospholenium with a stable anionic phosphanide fragment should likewise render the polarization of the homoatomic PÀP bond of a diphosphane feasible. Herein we describe the synthesis and characterization of such derivatives, and the unusual reactivity of the PÀP bond resulting from the polarization will be demonstrated.First attempts at the synthesis of P-phosphanyldiazaphospholenes were made starting from lithium diphenylphosphanide (2) or lithium tetraethyl phospholide (3), [4] whose high anion stability offer particularly suitable conditions for a dipolar polarization of the PÀP bond. The reaction of 2 or 3 with an equivalent of the P-chlorodiazaphospholene 4 in THF yielded cleanly the target compounds 5 a,b, which were isolated after workup as yellow, crystalline solids that are sensitive to hydrolysis and were characterized by means of spectroscopic and analytical studies (Scheme 2).Whereas the spectroscopic data are not very unusual, [5] Xray crystal structural studies [6] furnished clear evidence for a weakening of the PÀP bond that is expected as the result of an increased weight of ionic canonical structures such as 5'''. The P1ÀP2 bond length in 5 a (2.334(1) , Figure 1) is substantially longer than typical PÀP distances in diphosphanes (2.217 AE 0.08 [8] ) and exceeds even the distances in the sterically overcrowded [{(Me 3 Si) 2 CH} 2 P] 2 (2.310 ), [9] which dissociates easily under homolytic cleavage of the PÀP bond to give two radicals, and in the 1,1-diaminodiphosphane (iPr 2 N) 2 PÀPPh 2 (2.250 ), [10] for which, owing to the significantly lower cation stability of (iPr 2 N) 2 P + as compared to a diazaphospholenium cation, [3] a less pronounced dipolar polarization of the PÀP bond is expe...

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“…The syntheses of 1 and 2 were conducted according to Domańska-Babul et al, 5 the synthesis of 3 similarly to King and Sundaram, 6 and the synthesis of 4 similarly to Bender et al 7 We obtained a much higher yield of 4 than previously reported, probably because we used the isolated ( i Pr 2 N) 2 P-P(SiMe 3 )Li (2), and the synthesis was conducted at temperatures not higher than 20 • C. Moreover, we have found that, even at room temperature, ( i Pr 2 N) 2 P-P(SiMe 3 )Li undergoes a slow decomposition leading to the formation of phosphetanes and polyphosphorus compounds. 5 We studied the reactivity of 4 towards BuLi in THF solution in order to obtain the related lithium compound ( i Pr 2 N) 2 P-P(Li)-P(N i Pr 2 ) 2 .…”

Section: Resultsmentioning

confidence: 99%

“…12 The P1-P2 distance of 224.03(13) pm is in the range of a P-P single bond, and the P-Si distance 225.97(14) pm (mean) is typical for a P-Si single bond. The coordination around the phosphorus atoms P1 and P2 is tetrahedral, with the sum of angles around these phosphorus atoms being 332.00(6) deg and 321.39 (12) deg, respectively. The arrangement around N1 and N2 is almost planar; the sum of angles around N1 is 359.5(2)deg and around N2 is 356.7(2) deg.…”

Section: Crystal Data Measurement Conditions and Refinement Parametmentioning

confidence: 99%

“…The results were however very similar to those reported previously. 7 Crystallographic data for the structures of compounds 1 and 4 have been deposited with the Cambridge Crystallographic Data Centre, CCDC-670414 (1) and CCDC-670415 (4). Copies of the data can be obtained free of charge on application to The Director, CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (Fax: int.…”

Section: Crystal Data Measurement Conditions and Refinement Parametmentioning

confidence: 99%

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