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Intramolecular CH activation by dicationic Pt(II) complexes

✍ Scribed by Antek G. Wong-Foy; Lawrence M. Henling; Mike Day; Jay A. Labinger; John E. Bercaw

Book ID
104421972
Publisher
Elsevier Science
Year
2002
Tongue
English
Weight
240 KB
Volume
189
Category
Article
ISSN
1381-1169

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✦ Synopsis

The dicationic complexes [(ArN=C(Me)-C(Me)=NAr)Pt(solv) 2 ]X 2 , (Ar = 2,6-(CH 3 ) 2 C 6 H 3 ; 5a:

-, PF 6 -, SbF 6 -) were synthesized from the corresponding Pt dichlorides with two equivalents of AgX. The reactions of 5a with 1-phenylpyrazole, 2-phenylpyridine, 2-vinylpyridine, and 2-(2-thienyl)pyridine afford the cyclometalated products 11-14 via intramolecular C-H activation of an sp 2 C-H bond of the unsaturated sidegroup. Pyridines with saturated groups at the 2-position do not undergo a similar cyclometalation reaction. In trifluoroethanol-d 3 solution, 6 undergoes cyclometalation of one of the cyclohexyl groups, an example of sp 3 C-H bond activation. The latter reaction proceeds only partway to completion, implying that an equilibrium has been reached; in the case where X = OTf -the equilibrium favors the starting dication.

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Reversible heterolytic CH cleavage by intramolecular CH activation at diazabutadiene ligands at iridium
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instead give products Cp \* IrClCH 2 C(=NHAr)CMe=N(Ar) + Cl -in which the dab ligand has undergone C-H activation at one of methyl groups of the dab bridge. The C-H cleavage reaction is reversible in the sense that thermally, the cyclometalated Ir complex decomposes to regenerate the free ligand.