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Proton‐Transfer Reactions on Hexanuclear Platinum Clusters: Reversible Heterolytic Cleavage of H 2 and CH Activation Affording a Linear, Cluster‐Containing Polymer
Author(s) -
Leoni Piero,
Marchetti Lorella,
Bonuccelli Veronica,
Mohapatra Swagat K.,
Albinati Alberto,
Rizzato Silvia
Publication year - 2010
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.201000809
Subject(s) - heterolysis , cluster (spacecraft) , proton , platinum , cleavage (geology) , chemistry , photochemistry , polymer , crystallography , materials science , catalysis , physics , nuclear physics , organic chemistry , computer science , programming language , fracture (geology) , composite material
The hexanuclear cluster {Pt 6 }H 2 ( 2 ) contains a sterically hindered and chemically stable {Pt 6 }=Pt 6 (μ‐P t Bu 2 ) 4 (CO) 4 core, with the six metals forming an edge‐bridged tetrahedron. The two hydrides are the reactive sites of the cluster and lie on opposite sides of the cluster, terminally bonded to the two “apical” edge‐bridging platinum centres. Indeed, cluster 2 reacts with acids of different acidity (HA=CF 3 SO 3 H, HBF 4 , p ‐CH 3 C 6 H 4 SO 3 H, CF 3 COOH, PhCOOH and CH 3 COOH), affording, after evolution of two equivalents of dihydrogen, the corresponding anion‐substituted clusters {Pt 6 }A 2 ( 4 ). We suggest that the reaction proceeds through a mechanism similar to the one generally accepted for the analogous protonation of mononuclear hydrides, with some of the intermediates partially characterised at low temperature. Interestingly, the reverse reaction, the heterolytic splitting of H 2 by clusters 4 , occurs readily under mild conditions. The anions in clusters 4 a and 4 b ( 4 a : A=CF 3 SO 3 , 4 b : A=BF 4 ) are bonded in the solid state but very easily dissociate in solution and may be substituted under mild conditions by weak ligands, such as CH 2 Cl 2 or CH 3 CN. With dialkyl ethers, the reaction proceeds further with the heterolytic splitting of a CH bond of the ethereal ligand. This process allowed us to isolate the polymer [{Pt 6 }(CH 2 OCH 2 CH 2 OCH 2 )] x ( 8 ), in which the {Pt 6 } cluster units are connected by insulating spacers arising from dimethoxyethane. The results of single‐crystal X‐ray diffraction studies on 4 a and 8 are also reported.