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Acyclic, Ring, and Cage As,C Compounds from Trimethylsilyl Ylides and AsCl 3
Author(s) -
Breitsameter Florian,
Schmidpeter Alfred,
Nöth Heinrich
Publication year - 2000
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20001002)6:19<3531::aid-chem3531>3.0.co;2-v
Subject(s) - trimer , ylide , chemistry , trimethylsilyl , dimer , delocalized electron , tetramer , moiety , crystallography , substituent , phosphonium , ring (chemistry) , ionic bonding , stereochemistry , ion , medicinal chemistry , polymer chemistry , organic chemistry , enzyme
From the reaction of trimethylsilyl ylides with AsCl 3 the dichloroarsanyl ylides 2 b and 5 b are obtained. As shown by X‐ray structure determination, their AsCl 2 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 2 b and 5 b 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 AsCl 3 yields the oligomers (Ph 3 PCAsCl) 2,3,4 . The dimer 7 b 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 AsCl 4 − 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 7 b ⋅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).