Heptaphosphanortricyclenes with Oligosilyl Substituents: Syntheses and Reactions

Abstract

Three new nortricyclic P 7 R 3 derivatives with R = (SiMe 3 ) 2 -MeSi-(2), (SiMe 3 ) 2 PhSi-(3), and cyclo-Si 6 Me 11 -(4) were synthesized from red phosphorus, sodium/potassium alloy, and a chlorooligosilane, and their structures were elucidated with X-ray diffraction. Reactions of 2 and 3 and of tri(hypersilyl)heptaphosphane 1 [hypersilyl = (SiMe 3 ) 3 Si-] with KOtBu and LiOtBu were performed, which led to different results depending on the size of the substituent. With KOtBu, Si-P bonds were cleaved in 2 and 3, and the mono-and dianions [ 18-crown-6]+ salt of 2b suitable for X-ray diffraction could be grown successfully. Compound 1 reacted in an unprecedented way with KOtBu at -60°C. An Si-Si bond was cleaved, and a transient silyl anion formed, which immediately rearranged into a transient heptaphosphanide anion [Hyp 2 P 7 ] -(1a) under expulsion of bis(trimethylsilyl)silylene.

Metalated Oligosilanylstibines

“…In a 1,2-silyl shift, the tris(trimethylsilyl)silyl group migrates to the anionic silicon atom, leading to the formation of a stibide. Similar reactivity is already known for oligosilanylated phosphines 15 , 38 and likely reflects the increased ability to stabilize a negative charge of antimony compared to silicon.…”

Hydropnictination Reactions of Carbodiimides and Isocyanates with Protonated Heptaphosphide and Heptaarsenide Zintl Ions

“…The remaining four vertices each form three bonds to adjacent atoms and are neutral with formal oxidation states of zero. [6][7][8][9][10][11][12][13][14][15][16][17] Similarly, alkyl exchange reactions between [P 7 ] 3and R 3 P 7 or reactions of the heptaphosphide trianion with alkyl halides and tosylates can be used to access disubstituted monoanionic species [R 2 P 7 ] -[R = Me, Et, nBu, Bn, iPr, iBu, (EtO)C(O)CH 2 , (EtO)C(O)CHMe]. [2,3] The lack of NMR-active nuclei has impeded studies into the fluxionality of the heavier congeners, although it is reasonable to assume that these species are also fluxional, particularly considering the lower E-E bond dissociation enthalpies of the heavier group 15 elements.…”

An Actinide Zintl Cluster: A Tris(triamidouranium)μ3‐η2:η2:η2‐Heptaphosphanortricyclane and Its Diverse Synthetic Utility

“…The U–N and P–P bond lengths are unexceptional. A common parameter used to assess the extent of ionic character in [P 7 ] 3− trianions is the Q value,[1, 7e, 23] where Q = h / a ( h =distance from the apical P-center to the center-point of the lower rim of three P-centers; a =average P–P distance in the lower rim). For ionic systems, the Q value is typically 1.3–1.4 (for example, in P 7 (SiR 3 ) 3 derivatives), and for 2 the Q value is 1.39, which is suggestive of predominantly electrostatic U–P bonding.…”

“…In principle, [P 7 ] 3À is an attractive precursor to organophosphorus derivatives; however, although Group 1 derivatives can be prepared straightforwardly in liquid ammonia, high-temperature melts have a reputation for detonating in the presence of traces of moisture, and Na/K reduction of phosphorus in ethers gives non-stoichiometric mixtures. [7] Unlike main-group and late-transition-metalmediated activation of P 4 , [8,9] examples of early metalmediated transformations of P 4 are far less common. [10] In Group 3 and 4f-block chemistry, despite the potentially strongly reducing nature of these metals, activation of P 4 is surprisingly rare, [11] presumably because of the hard-soft mismatch between the electropositive metal and soft phosphorus.…”