Web Release Date: November 1,
A Direct Route to Platinum NCN-Pincer Complexes Derived from 1,3-Bis(imino)benzenes and an Investigation into Their Activity as Catalysts for Carbon-Carbon Bond Formation
Department of Chemistry, Queen Mary, University of London, Mile End Road, London, E1 4NS, U.K.
Received July 16, 2002
Abstract:
1,3-Bis(imino)lbenzenes [1,3-C6H4(CH=NR)2], obtained from condensation of 1,3-isophthalaldehyde with primary amines (R = tBu, Cy, Bu, Bn, Ph), were heated with K2PtCl4 at
reflux for 48 h in glacial acetic acid to give ((2,6-bis(N-R-substituted)imino)phenyl)platinum(II) chloride complexes (15-52% yield). X-ray crystal structures of the R = tBu and R = Ph
complexes are reported. The byproducts were found to be 1,3-isophthalaldehyde and
N-acetylamines. Quantitative chloride abstraction with AgBF4 (R = tBu) or AgOTf (R =
tBu, Cy) provided the corresponding cationic complexes containing water coordinated to
platinum, as established by an X-ray crystal structure of ((2,6-bis(N-tert-butyl)imino)phenyl)aquoplatinum(II) trifluoromethanesulfonate. Use of 4-5 mol % of ((2,6-bis(N-cyclohexyl)imino)phenyl)aquoplatinum(II) trifluoromethanesulfonate accelerated the rate of the Michael
reaction between ethyl 
-cyanoacetate and methyl vinyl ketone and the Diels-Alder reaction
between acrylonitrile and cyclopentadiene.
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