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Di‐ and Tetranuclear Palladium Complexes Incorporating Phospha‐ and Diphosphaferrocenes as Ligands
Author(s) -
Sava Xavier,
Ricard Louis,
Mathey François,
Le Floch Pascal
Publication year - 2001
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 - 10.1002/1521-3765(20010716)7:14<3159::aid-chem3159>3.0.co;2-6
Subject(s) - palladium , lone pair , chemistry , ligand (biochemistry) , atom (system on chip) , medicinal chemistry , crystallography , stereochemistry , catalysis , molecule , organic chemistry , computer science , embedded system , biochemistry , receptor
Monophosphaferrocenes 1 and 4 react with [Pd(COD)Cl 2 ] (COD=cyclooctadiene) to afford cis ‐[Pd( 1 or 4 ) 2 Cl 2 ] complexes that slowly decompose in solution to give dimeric complexes 3 and 6 of general formula [{Pd( 1 or 4 )Cl} 2 ]. In these dimers, which incorporate a Pd−Pd bond, phosphaferrocenes act as four electron donors through the phosphorus‐atom lone pair ( μ 2 ‐bonded) and through one orbital of appropriate symmetry at iron. These dimers can also be more conventionally prepared from the reaction of cis ‐[Pd( 1 or 4 ) Cl 2 ] complexes with [Pd(dba) 2 ] (dba=dibenzylidene acetone). The reaction of octaethyldiphosphaferrocene ( 7 ) with [Pd(COD)Cl 2 ] yields a dinuclear complex [Pd 2 ( 7 ) 2 Cl 4 ] ( 8 ) in which the two ligands 7 are coordinated in a trans fashion through the phosphorus‐atom lone pairs. Decomposition of 8 in solution yields a dimeric dicationic complex of general formula [{Pd 2 ( 7 ) 2 Cl} 2 ] 2+ [FeCl 4 ] 2 − ( 9 a ) incorporating four palladium atoms. In each ligand, one phospholyl ring behaves as a two‐electron donor through the phosphorus‐atom lone pair whereas the second binds two palladium centers in a μ 2 ‐fashion. A plausible mechanism that explains the formation of dimers 3, 6 , and 9 a involves the preliminary oxidation of the mono‐ or diphosphaferrocene ligand. Parallel experiments aimed at confirming this hypothesis have shown that complex 9 a can be synthesized from the reaction of FeCl 2 with complex 8 . Also presented is another synthetic approach to the synthesis of the tetranuclear complex 9 b (counterion is GaCl 4 − ) from the reaction of the palladium(0) complex [Pd( 7 ) 2 ] ( 10 ) with [Pd(COD)Cl 2 ] in the presence of GaCl 3 as chloride abstractor.