Hydrogen atom abstraction from carbon-, phosphorus-, silicon-, and tin-hydrogen bonds by the triplet excited state of the tetrakis(.mu.-pyrophosphito)diplatinum(II) tetraanion. Spectroscopic observation of the mixed-valence hydride complex Pt2(.mu.-P2O5H2)4H4-

Hydrogen Production by Molecular Photocatalysis

“…The photoreaction mechanism shown in Figure was deciphered by Gray and co-workers by undertaking a series of comprehensive studies. Initial photon absorption generates the Pt 2 II,II , 3 (dσ*pσ) excited state, which abstracts a hydrogen atom from isopropanol and forms the mixed valence hydride complex, Pt 2 II,III H. The existence of this mixed valence complex was verified directly in pulse radiolysis spectra . This mixed-valence intermediate abstracts a second H atom to form the valence symmetric dihydride, Pt 2 III,III (H) 2 by analogy with previous work concerning the thermal oxidation chemistry of Pt 2 II,II cores .…”

“…Initial photon absorption generates the Pt 2 II,II , 3 (dσ*pσ) excited state, which abstracts a hydrogen atom from isopropanol and forms the mixed valence hydride complex, Pt 2 II,III H. The existence of this mixed valence complex was verified directly in pulse radiolysis spectra. 123 This mixedvalence intermediate abstracts a second H atom to form the valence symmetric dihydride, Pt 2 III,III (H) 2 by analogy with previous work concerning the thermal oxidation chemistry of Pt 2 II,II cores. 124 This intermediate was independently synthesized, and a binuclear axial dihydride formulation was confirmed.…”

Molecular catalysts for hydrogen production from alcohols

“…177 From detailed studies of this system it was concluded that the rst step is the abstraction of the a-hydrogen from 2-propanol by 3 Pt * 2 to form a divalent-trivalent dinuclear monohydride-bridged species Pt II (m-H)Pt III (120) (detected by transient absorption spectroscopy). 178 Pinacol is found as a byproduct from the photoreaction and supports the suggestion of the formation of isopropyl radical intermediates. The mixed valence intermediate Pt II (m-H)Pt III (120) abstracts a second H atom to form the trivalent dihydride, Pt III (m-H) 2 Pt III (121), in analogy to the previously reported work on the thermal oxidation chemistry of Pt 2 complexes.…”

Transition Metal Complex Catalyzed Photo- and Electrochemical (De)hydrogenations Involving C=O and C=N Bonds

“…The authors suggested that the dinuclear platinum complex abstracts in a HAT process the -CH atom from the alcohol forming a carbon-centered radical and the mixed valent Pt II Pt III species [Pt 2 (-P 2 O 5 H 2 ) 4 H] 4-, which readily disproportionates generating the dihydrido platinate [Pt 2 (-P 2 O 5 H 2 ) 4 H 2 ] 4and 29. 78,79 A second HAT step from the isopropyl radical to [Pt 2 (-P 2 O 5 H 2 ) 4 ] 4leads to the formation of acetone. The method is not limited to propan-2-ol and also applicable to primary and secondary aliphatic and benzylic alcohols, 80 Broad band irradiation >300 nm yields the corresponding aldehydes or ketones in TONs between 15-140 and with fairly efficient quantum yields.…”