title: Reaction of a terminal phosphinidene complex with azulenes: eta1-complexes, C--H bond insertions, and 1,4-adducts.
abstract: Reaction of an in situ generated phosphinidene complex [PhPW(CO)(5)] with the aromatic azulene and guaiazulene leads to unexpected 1,4-adducts of the seven-membered ring and to C--H bond insertion of the five-membered ring. A DFT analysis suggests that the reaction is initiated by formation of a eta(1)-complex between the phosphinidene and the five-membered ring of the aromatic substrate. Four conformations of this complex were identified. Two convert without barrier to the slightly more stable syn- and anti-1,2-adducts. These undergo pericyclic 1,7-sigmatropic rearrangements with remarkably low barriers to give 1,4-adducts, with an inverted configuration at the phosphorus center. An X-ray crystal structure is presented for one of the 1,4-adducts of guaiazulene. The other two eta(1)-complexes insert with modest barriers into a C--H bond of the five-membered ring.
authors.affiliation: Vrije Universiteit, FEW, Department of Chemistry De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands.
authors.forename: Rosa E
authors.initials: RE
authors.lastname: Bulo
authors.forename: Andreas W
authors.initials: AW
authors.lastname: Ehlers
authors.forename: Frans J J
authors.initials: FJ
authors.lastname: de Kanter
authors.forename: Marius
authors.initials: M
authors.lastname: Schakel
authors.forename: Martin
authors.initials: M
authors.lastname: Lutz
authors.forename: Anthony L
authors.initials: AL
authors.lastname: Spek
authors.forename: Koop
authors.initials: K
authors.lastname: Lammertsma
authors.forename: Bing
authors.initials: B
authors.lastname: Wang