Premium
Oxidative Addition of Halogens to Homoleptic Perfluoromethyl or Perfluorophenyl Derivatives of Platinum(II): A Comparative Study
Author(s) -
Menjón Babil,
MartínezSalvador Sonia,
GómezSaso Miguel A.,
Forniés Juan,
Falvello Larry R.,
Martín Antonio,
Tsipis Athanassios
Publication year - 2009
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.200900323
Subject(s) - homoleptic , oxidative addition , chemistry , halogen , reductive elimination , platinum , reactivity (psychology) , derivative (finance) , medicinal chemistry , stereochemistry , alkyl , catalysis , metal , organic chemistry , medicine , alternative medicine , pathology , financial economics , economics
Chlorocarbon solvents (solv=CH 2 Cl 2 , CHCl 3 ) are suggested to play an active role in the oxidative addition of halogens, X 2 (X=Cl, Br, I), to homoleptic d 8 perfluoromethyl and ‐phenyl platinum( II ) species [Pt(R F ) 4 ] 2− (R F =CF 3 , C 6 F 5 ). The perfluoromethyl group, CF 3 , has been found to be considerably less prone to undergo reductive elimination processes, and is, therefore, more suitable for stabilizing organoplatinum( IV ) derivatives (see scheme).The equilibrium geometries of the homoleptic perfluorinated organoplatinate( II ) anions [Pt(CF 3 ) 4 ] 2− and [Pt(C 6 F 5 ) 4 ] 2− have been computed at the B3P86/LANL2DZ level of theory. Remarkably good agreement with the experimentally determined structures has been obtained by X‐ray diffraction methods. The reactivity of [NBu 4 ] 2 [Pt(CF 3 ) 4 ] ( 1 ) towards halogens (Cl 2 , Br 2 , and I 2 ) has been investigated by using a combined experimental and theoretical approach. The perfluoromethyl derivative 1 has been found to undergo clean oxidative addition of the three halogens under investigation, giving rise to [NBu 4 ] 2 [ trans ‐Pt(CF 3 ) 4 X 2 ] (X=Cl ( 7 ), Br ( 10 ), I ( 13 )) in a quantitative and stereoselective way. In the low‐temperature reaction of the perfluorophenyl derivative [NBu 4 ] 2 [Pt(C 6 F 5 ) 4 ] ( 3 ) with Cl 2 or Br 2 , the corresponding oxidative‐addition products [NBu 4 ] 2 [ trans ‐Pt(C 6 F 5 ) 4 X 2 ] (X=Cl ( 14 ), Br ( 15 )) can also be obtained. In the case in which X=Br and working in CHCl 3 at −55 °C, it has been possible to detect the formation of an intermediate species to which we assign the formula [ trans ‐Pt(C 6 F 5 ) 4 Br(ClCHCl 2 )] − ( 16 ). The solvento complex 16 is thermally unstable and prone to undergo reductive elimination of C 6 F 5 C 6 F 5 . In the presence of PhCN, complex [NBu 4 ][ trans ‐Pt(C 6 F 5 ) 4 Br(NCPh)] ( 17 ) was isolated and structurally characterized. The reaction of 3 with I 2 gave no organoplatinum( IV ) compound. Our comparative study reveals that the CF 3 group is especially suited to stabilize organometallic compounds in high oxidation states. This ability can be attributed to a combination of factors: its hardness, its high group electronegativity, its small size, and its reluctance to undergo reductive elimination processes.