title: Facile activation of dihydrogen by a phosphinito-bridged Pt(I)-Pt(I) complex.
abstract: The phosphinito-bridged Pt(I) complex [(PHCy(2))Pt(mu-PCy(2)){kappa(2)P,O-mu-P(O)Cy(2)}Pt(PHCy(2))](Pt-Pt) (1) reversibly adds H(2) under ambient conditions, giving cis-[(H)(PHCy(2))Pt(1)(mu-PCy(2))(mu-H)Pt(2)(PHCy(2)){kappaP-P(O)Cy(2)}](Pt-Pt) (2). Complex 2 slowly isomerizes spontaneously into the corresponding more stable isomer trans-[(PHCy(2))(H)Pt(mu-PCy(2))(mu-H)Pt(PHCy(2)){kappaP-P(O)Cy(2)}](Pt-Pt) (3). DFT calculations indicate that the reaction of 1 with H(2) occurs through an initial heterolytic splitting of the H(2) molecule assisted by the phosphinito oxygen with breaking of the Pt-O bond and hydrogenation of the Pt and O atoms, leading to the formation of the intermediate [(PHCy(2))(H)Pt(mu-PCy(2))Pt(PHCy(2)){kappaP-P(OH)Cy(2)}](Pt-Pt) (D), where the two split hydrogen atoms interact within a six-membered Pt-H...H-O-P-Pt ring. Compound D is a labile intermediate which easily evolves into the final dihydride complex 2 through a facile (9-15 kcal mol(-1), depending on the solvent) hydrogen shift from the phosphinito oxygen to the Pt-Pt bond. Information obtained by addition of para-H(2) on 1 are in agreement with the presence of a heterolytic pathway in the 1 --> 2 transformation. NMR experiments and DFT calculations also gave evidence for the nonclassical dihydrogen complex [(PHCy(2))(eta(2)-H(2))Pt(mu-PCy(2))Pt(PHCy(2)){kappaP-P(O)Cy(2)}](Pt-Pt) (4), which is an intermediate in the dehydrogenation of 2 to 1 and is also involved in intramolecular and intermolecular exchange processes. Experimental and DFT studies showed that the isomerization 2 --> 3 occurs via an intramolecular mechanism essentially consisting of the opening of the Pt-Pt bond and of the hydrogen bridge followed by the rotation of the coordination plane of the Pt center with the terminal hydride ligand.
authors.affiliation: Dipartimento di Ingegneria delle Acque e di Chimica del Politecnico di Bari, Via Orabona 4, I-70125 Bari, Italy. p.mastrorilli@poliba.it
authors.forename: Piero
authors.initials: P
authors.lastname: Mastrorilli
authors.forename: Mario
authors.initials: M
authors.lastname: Latronico
authors.forename: Vito
authors.initials: V
authors.lastname: Gallo
authors.forename: Flavia
authors.initials: F
authors.lastname: Polini
authors.forename: Nazzareno
authors.initials: N
authors.lastname: Re
authors.forename: Alessandro
authors.initials: A
authors.lastname: Marrone
authors.forename: Roberto
authors.initials: R
authors.lastname: Gobetto
authors.forename: Silvano
authors.initials: S
authors.lastname: Ellena
mesh_terms: D003198:Computer Simulation; D006859:Hydrogen / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D015394:Molecular Structure; D009944:Organoplatinum Compounds / Q000737:chemistry*; D013237:Stereoisomerism
chemical_list: D009944:Organoplatinum Compounds; D006859:Hydrogen