Acyclic, Ring, and Cage As,C Compounds from Trimethylsilyl Ylides and AsCl3

Abstract

From the reaction of trimethylsilyl ylides with AsCl3 the dichloroarsanyl ylides 2b and 5b are obtained. As shown by X-ray structure determination, their AsCl2 groups deviate systematically from the symmetric orientation. This conformation enables an effective charge transfer from the ylide moiety to one of the As-Cl bonds, which as a consequence is up to 15 pm longer than the other. At the same time the length of the As-C bonds in 2b and 5b indicates a partial double bond. The effects observed here are of the same type as those observed for the corresponding dichlorophosphanyl ylides; they are, however, more pronounced. The 1:1 condensation of the bis(trimethylsilyl) ylide 3 and AsCl3 yields the oligomers (Ph3PCAsCl)2,3,4. The dimer 7b has a diarsetane structure. HCl adds readily to one of its As-C bonds without opening it. The trimer and the tetramer are ionic. The cation of the trimer forms a six-membered ring with a delocalized arsenium/phosphonium charge, the cation of the tetramer forms a barrelane cage with a phosphonio substituent, and the anion is AsCl4- in both cases (10, 13). An arsa-phosphocyanine cation as in 10 is also part of the diphosphonio isoarsindolide tetrachloroarsenate(III) 12. The structures of 7b.HCl, 10, and 13 reflect again an ylide to As-Cl charge transfer. The As-Cl bonds of 13 are by far the longest ones known for a chloroarsine (average 249 pm).

Phosphorus-ylides: powerful substituents for the stabilization of reactive main group compounds

“…The same p-donation effects were observed in analogous arsenic compounds and allowed the isolation of di(ylide)substituted cations such as 39, 40 and 41 which feature a delocalization of the charge within the C-E-C linkage. 58b, 61,62 The preference of certain conformers due to the repulsion between the lone pair at the ylidic carbon atom and the neighbouring phosphorus atom was also found in ylide- substituted phosphines (YPhos, Fig. 7).…”

Anellated Heterophospholes and Phospholides and Analogies with Related Non-Phosphorus Systems

“…The intermediate 54 could be detected by 31 P NMR. As analogues have also been synthesized . More representatives 55 (R = Ph, 2-pyridyl, X = Cl, Br, F 3 CSO 3 ) having other substituents at the phosphonio group and counteranions have been prepared in a similar manner .…”

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“…91 The reaction of trimethylsilyl ylides with AsCl 3 gives dichloroarsanyl ylides such as Ph 3 PNC(SiMe 3 )AsCl 2 , which slowly loses Me 3 SiCl to give the diarsetane (Ph 3 PNCAsCl) 2 . 92 A new route to aminoiminoarsanes such as Mes * NNAs-N(Bu t )SiMe 3 has been described. 93 The reaction of Cl 2 AsN(Bu t )SiMe 3 with Mes * NHLi gives Mes * NH-AsCl-N(Bu t )SiMe 3 , which is converted into the aminoiminoarsane by reaction with DBU.…”