Beiträge zur Strukturchemie phosphorhaltiger Ketten und Ringe, IV*. Die Kristall- und Molekülstruktur des Bicyclotetraphosphans t-Bu₆P₈

Abstract

The bicyclic phosphorus compound 2,2',3,3',4,4'-Hexa(ferf-butyl)-1,1'-bicyclotetraphosphane /-Bu 6 P 8 , C 24 H 54 P 8 , crystallizes at room temperature in the monoclinic space group P2 1 jn (No. 14) with a = 1141.6(3)pm, b = 1805.7(2)pm, c = 1764.8(3)pm, β = 108.32(2)° and Ζ = 4 formula units. The crystal structure has been solved by 'direct methods' and refined to R = 0.076 with 5361 independent reflections.The molecule with approximate symmetry C 2h consists of two σ-bonded, trans positioned and slightly folded four-membered rings of phosphorus atoms. The exocyclic bridge between the two rings [</(P-P) = 221.8 pm] and the average endocyclic bond length [d(Ρ-P) = 22.1 pm] are nearly identical, although the individual values in both rings are slightly different. The arrangement of the substituents tert-butyl is all -trans in each case. The average bond lengths d(P-C) = 189.0 pm and d(C -C) = 152.4 pm are as expected.

The reactivity of cyclo-(P5tBu4)– towards group 13, 14 and 15 metal chlorides: complexation and formation of cyclooligophosphanes, {cyclo-(P5tBu4)}2 and {cyclo-(P4tBu3)PtBu}2, by reductive elimination

“…While the first example of this class of compounds, cyclo-(PPh) 5 , was synthesised as early as 1877, 2 the number of bicyclic compounds obtained in pure form, mainly by Baudler et al, is still small, 3-6 and only three structurally characterised examples are known to date: {cyclo-(P 3 R 2 )} 2 (R = t Bu, Cp) 4 and {cyclo-(P 4 t Bu 3 )} 2 . 6 Theoretical studies performed on oligocyclic P n molecules and clusters (n = 2, 4, 6,…, 28) indicate that these compounds should be thermodynamically stable at low temperatures. 7 Bicyclic oligophosphanes should be accessible by oxidative coupling of cyclooligophosphanide anions cyclo-(P n R n−1 ) − , [8][9][10] and this method was already employed in the preparation of {cyclo-(P 3 R 2 )} 2 (R = t Bu, Cp).…”

Facile synthesis ofcyclo-(P4tBu3)-containing oligo- and pnictaphosphanes

“…The use of 1 as a cyclo-(P4 17 The number of bis-cyclooligophosphanes and bicyclic compounds obtained in pure form is still small, 27,[52][53][54][55][56][57][58][59][60] and to the best of our knowledge only six structurally characterised compounds are known to date, namely P6R4 (R = t Bu, Cp), 52,58 {cyclo-(P5 t Bu4}2, 17 {cyclo-(P4 t Bu3)P t Bu}2, 17 {cyclo-(P4 t Bu3)}2 61 and its pentalane analogue 25 .…”

Dynamic Gold(I) Complexes of Hexa‐tert‐butyl‐octaphosphane

“…Since the rotation around the internal P-P bond presents the sole degree of freedom in phosphane 1, a relaxed surface scan (BP86-D3/def2-SVP level, SI) was performed to elucidate the mechanism of the dynamic process of complex 2. The obtained rotational profile (Figure 2, τ′ for 360°range) shows three major minima which correspond to a monodentate complex with an antiperiplanar conformation similar to the solid-state structure of the free phosphane [15,16] (2c, τ′ = 160°), a bidentate complex with synperiplanar conformation (2b, τ′ = 24°) as well as a gauche conformation (2a, τ′ = 272°), which is structurally analogous to 4. Complex 2a moreover represents the energetically most favored form and is thus the only species observable at -85 °C.…”

“…[11] More recently, we shifted our attention to neutral cyclophosphanes like cyclo-(P 5 Ph 5 ) [12] and found that even such simple and well-known molecules still hold surprises. [13] In this work, we report on the facile synthesis of {cyclo-(P 4 tBu 3 )} 2 (1) for which so far merely the preparation [14] and crystal structure [15,16] have been reported, but no reactivity studies.…”

“…We have studied the flexibility of the ligand by conducting a relaxed surface scan (PBE0-D3/def2-TZVP level, Figure S30, SI) of the dihedral angle between the bridge P atoms and their lone pairs of electrons (defined as τ). Two minima were thus identified corresponding to an antiperiplanar (τ = 180°, as in the solid state) [15,16] and a gauche (τ = 55°) conformation which are practically isoenergetic and are furthermore separated by low rotational barriers of ΔG act +13.7 kJ mol -1 . An additional maximum with ΔG rel +29.5 kJ mol -1 corresponding to a synperiplanar conformation (τ = 0) indicates that 1 can indeed freely rotate around the internal P-P bond.…”