Aiding Factors in the Formation of Azaplatinacyclobutane Rings – X‐ray and Crystal Structure of [Pt{CH(Ph)CH 2 NEt 2 ‐κC,κN}( N , N , N′ , N′ ‐tetramethylethylenediamine)] + and of Its Open‐Chain Precursor

Autor: Giovanni Natile, Luciana Maresca, Nicola G. Di Masi, Giuseppe Lorusso, Concetta Pacifico, Carmen R. Barone
Rok vydání: 2007
Předmět:
Zdroj: European Journal of Inorganic Chemistry. 2007:2144-2150
ISSN: 1099-0682
1434-1948
DOI: 10.1002/ejic.200601219
Popis: The addition products 2 of a secondary amine to a coordinated olefin, in the cationic complexes [PtCl(η2-CH2=CHR)(tmeda)]+ (tmeda = N,N,N′,N′-tetramethylethylenediamine; R = Me, 1a; Ph, 1b, H, 1c), undergo in basic medium an intramolecular nucleophilic substitution with elimination of the chlorido ligand and formation of an azaplatinacyclobutane ring 3. The ring-closing process occurs notwithstanding the absence of a labilizing ligand trans to the leaving chlorido ligand and of bulky substituents on the amino–ethanide chain. If the addition product 2 is a mixture of Markovnikov and anti-Markovnikov isomers, the ring-closing reaction is faster for the anti-Markovnikov form, and this leads to an increase of the relative amount of the anti-Markovnikov isomer in the cyclized species 3. The difference in the rate of formation of the azaplatinacyclobutane ring between the two isomers has been interpreted on the basis of a more favorable stereochemistry in the case of the anti-Markovnikov form. The X-ray crystal structures of [Pt{CH(Ph)CH2NEt2-κC,κN}(tmeda)]+ (3bn) and of its open-chain precursor, [PtCl{CH(Ph)CH2NHEt2}(tmeda)]+ (2bn) fully support this hypothesis.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Databáze: OpenAIRE
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