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Hydrogenolysis of Dinuclear PCN R Ligated Pd II μ‐Hydroxides and Their Mononuclear Pd II Hydroxide Analogues
Author(s) -
Bailey Wilson D.,
Phearman Alexander S.,
Luconi Lapo,
Rossin Andrea,
Yakhvarov Dmitry G.,
D'Accolti Lucia,
Flowers Sarah E.,
Kaminsky Werner,
Kemp Richard A.,
Giambastiani Giuliano,
Goldberg Karen I.
Publication year - 2019
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201900507
Subject(s) - hydrogenolysis , chemistry , medicinal chemistry , hydroxide , hydride , ligand (biochemistry) , stereochemistry , palladium , oxidative addition , catalysis , inorganic chemistry , organic chemistry , metal , biochemistry , receptor
The hydrogenolysis of mono‐ and dinuclear Pd II hydroxides was investigated both experimentally and computationally. It was found that the dinuclear μ‐hydroxide complexes {[(PCN R )Pd] 2 (μ‐OH)}(OTf) (PCN H =1‐[3‐[(di‐ tert ‐butylphosphino)methyl]phenyl]‐1 H ‐pyrazole; PCN Me =1‐[3‐[(di‐ tert ‐butylphosphino)methyl]phenyl]‐5‐methyl‐1 H ‐pyrazole) react with H 2 to form the analogous dinuclear hydride species {[(PCN R )Pd] 2 (μ‐H)}(OTf). The dinuclear μ‐hydride complexes were fully characterized, and are rare examples of structurally characterized unsupported singly bridged μ‐H Pd II dimers. The {[(PCN Me )Pd] 2 (μ‐OH)}(OTf) hydrogenolysis mechanism was investigated through experiments and computations. The hydrogenolysis of the mononuclear complex (PCN H )Pd‐OH resulted in a mixed ligand dinuclear species [(PCN H )Pd](μ‐H)[(PCC)Pd] (PCC=a dianionic version of PCN H bound through phosphorus P, aryl C, and pyrazole C atoms) generated from initial ligand “rollover” C−H activation. Further exposure to H 2 yields the bisphosphine Pd 0 complex Pd[(H)PCN H ] 2 . When the ligand was protected at the pyrazole 5‐position in the (PCN Me )Pd−OH complex, no hydride formed under the same conditions; the reaction proceeded directly to the bisphosphine Pd 0 complex Pd[(H)PCN Me ] 2 . Reaction mechanisms for the hydrogenolysis of the monomeric and dimeric hydroxides are proposed.