Cationic, neutral, and anionic platinum(II) complexes based on an electron-rich PNN ligand. New modes of reactivity based on pincer hemilability and dearomatization

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Cationic, neutral, and anionic platinum(II) complexes based on an electron-rich PNN ligand. New modes of reactivity based on pincer hemilability and dearomatization

Year: 

2008

Source of publication :

Organometallics

Authors :

פוברנוב, ילנה

.

Volume :

Co-Authors: 

Vuzman, D., Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, 76100, Israel
Poverenov, E., Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, 76100, Israel
Shimon, L.J.W., Unit of Chemical Research Support, Weizmann Institute of Science, Rehovot, 76100, Israel
Diskin-Posner, Y., Unit of Chemical Research Support, Weizmann Institute of Science, Rehovot, 76100, Israel
Milstein, D., Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, 76100, Israel

From page: 

2627

To page: 

2634

(

Total pages: 

8

)

Link :

Cationic, neutral, and anionic platinum(II) complexes based on an electron-rich PNN ligand. New modes of reactivity based on pincer hemilability and dearomatization

Abstract: 

The synthesis and reactivity of new Pt(II) complexes, including anionic d8 complexes, based on the electron-rich, hemilabile PNN-type pincer ligand C5H3N-2-(CH2PtBu 2)(CH2NEt2) are described. Formation of these complexes involves dearomatization/aromatization processes of the ligand. The chloride complex [(PNN)PtCl]+Cl- (1) was prepared and reacted with the base tBuOK to give the deprotonated, neutral chloride complex (PNN*)PtCl (2) (PNN* = C5H 3N-2-(CHPtBu2)(CH2NEt2)). Reaction of 2 with nBuLi gave the corresponding neutral hydride complex (PNN*)PtH (3), which was readily protonated by triflic acid to give the cationic hydride complex [(PNN)PtH]+OTf- (4). Unexpectedly, reaction of complex 2 with 1 equiv of RLi resulted in opening of the chelate ring, to give the corresponding anionic, dearomatized complexes Li+[(PNN*)Pt(Cl)(R)]- (R = methyl, 5; phenyl, 6). Notably, these complexes are relatively stable although they bear no stabilizing π acceptors that can lower the electron density at the metal center. Complexes 5 and 6 readily undergo protonation by HCl to form the corresponding neutral, aromatic complexes (PNN)Pt(Cl)(R) (R = methyl, 7; phenyl, 8), in which the hemilabile amine "arm" remains decoordinated and does not undergo protonation. Minor amounts of the dearomatized chloride complex 2 are also formed as a result of elimination of RH. Reaction of complexes 5 and 6 with water results in selective protonation-aromatization to give the corresponding complexes 7 and 8. © 2008 American Chemical Society.