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Imidovanadium( V ) Complexes as Reaction Partners for Kinetically Stabilized Phosphaalkynes: Synthesis of 1,2,4‐Azaphosphavanada( V )‐cyclobutenes, 1,3,5‐Triphosphabenzenes, and 1 H ‐1,2,4‐Azadiphospholes
Author(s) -
Tabellion Frank,
Peters Christoph,
Fischbeck Uwe,
Regitz Manfred,
Preuss Fritz
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(20001215)6:24<4558::aid-chem4558>3.0.co;2-6
Subject(s) - chemistry , catalysis , alkyl , medicinal chemistry , cycloaddition , adduct , vanadium , decomposition , stereochemistry , organic chemistry
Cycloaddition reactions of the kinetically stabilized phosphaalkynes 1 with the imidovanadium( V ) trihalides 9 furnish the 1,2,4‐azaphosphavanada( V )cyclobutenes 10 . The stability of these novel metallacyclic compounds depends solely on the substitutents of the imido unit. Thus, the imidovanadium( V ) species 9 with tertiary alkyl groups on the N atom form stable addition products with 1 while in the cases of compounds 9 with a lower degree of substitution at N (primary and secondary alkyl groups) the primarily formed adducts 10 undergo irreversible decomposition to afford the 1 H ‐1,2,4‐azadiphospholes 13 . Reactions of an excess of the phosphaaalkyne 1 with the vanadium complexes 9 furnish the corresponding triphosphabenzenes 8 in good yields (36–68 %). A catalytic reaction course has been demonstrated for the all‐ tert‐ butyl system 1 a/9 a in which the metallacyclic species 10 a serves as the catalytically active species. Poisoning of the catalyst leads to a second reaction pathway, which results in formation of the azatetraphosphaquadricyclanes 16 . By means of the stepwise use of different phosphaalkynes 1 a , b this methodology provides the first access to the differently substituted triphosphabenzenes through cyclotrimerization.