אסיף מאגר המחקר החקלאי

Nucleophilic de-coordination and electrophilic regeneration of "hemilabile" pincer-type complexes: Formation of anionic dialkyl, diaryl, and dihydride PtII complexes bearing no stabilizing π-acceptors

Year:

2004

Source of publication :

Authors :

Volume :

10

Co-Authors:

Poverenov, E., Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, 76100, Israel
Gandelman, M., 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
Rozenberg, H., Unit of Chemical Research Support, Weizmann Institute of Science, Rehovot, 76100, Israel
Ben-David, Y., Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, 76100, Israel
Milstein, D., Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, 76100, Israel

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Abstract:

Novel anionic dialkyl, diaryl, and dihydride platinum(II) complexes based on the new πlong-armπ hemilabile PCN-type ligand C6H 4[CH2P(tBu)2](CH2) 2N(CH3)2 with the general formula Li + [Pt(PCN)(R)2]- (R = Me (4), Ph (6) and H (9)) were prepared by reaction of [Pt(PCN)(R)] complexes (obtained from the corresponding chlorides) with an equivalent of RLi, as a result of the opening of the chelate ring. Alkylating agents based on other metals produce less stable products. These anionic d8 complexes are thermally stable although they bear no stabilizing π acceptors. They were characterized by 1H, 31P{1H}, 13C, and 7Li NMR spectroscopy; complex 9 was also characterized by single crystal X-ray crystallography, showing that the Li + ion is coordinated to the nitrogen atom of the open amine arm and to the hydride ligand (trans to the P atom) of a neighboring molecule (H-Li = 2.15 Å), resulting in a dimeric structure. Complexes 4 and 9 exhibit high nucleophilic reactivity, upon which the pincer complex is regenerated. Reaction of 4 with water, methyl iodide, and iodobenzene resulted in the neutral complex [Pt(PCN)(CH3)] (3) and methane, ethane, or toluene, respectively. Labeling studies indicate that the reaction proceeds by direct electrophilic attack on the metal center, rather than attack on the alkyl ligand. The anionic dihydride complex 9 reacted with water and methyl iodide to yield [Pt(PCN)(H)] (8) and H2 or methane, respectively.

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