title: Conversion of trans-diboran(4)yl platinum complexes into their cis-bisboryl analogues.
abstract: The diboran(4)yl trans-[(iPr3 P)2 Pt(Br){B(NMe2 )B(NMe2 )Br}] (1) is readily converted into its cis-bisboryl analogues 2 and 3 by reaction with the chelating bisphosphines 1,2-bis(dicyclohexylphosphino)ethane (dcpe) and 1,1-bis(dicyclohexylphosphino)methane (dcpm), respectively. A plausible mechanism of this transformation consists of a sequence of reductive diborane(4) elimination and subsequent reoxidative addition of its BB bond to the low-valent platinum centers. Thus, the forced cis configuration of the phosphine ligands induces a change in the preferred reaction site of the diborane(4) with respect to oxidative addition. The reactions proceed with high selectivities, and the cis-bisboryl complexes 2 and 3 were isolated in moderate yields (55 and 46 %). Moreover, their identity was clearly verified by NMR spectroscopy and X-ray diffraction studies.
authors.affiliation: Institut für Anorganische Chemie, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg (Germany), Fax: (+49) 931-31-84623. h.braunschweig@uni-wuerzburg.de.
authors.forename: Holger
authors.initials: H
authors.lastname: Braunschweig
authors.forename: Alexander
authors.initials: A
authors.lastname: Damme
authors.forename: Thomas
authors.initials: T
authors.lastname: Kupfer
keywords: boron; chelates; isomerization; phosphane ligands; platinum