Co-Authors:
Poverenov, E., Department of Organic Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
Iron, M.A., Computational Chemistry Unit, Department of Chemical Research Support, Weizmann Institute of Science, Rehovot 76100, Israel
Gandelman, M., Department of Organic Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel, Schulich Faculty of Chemistry, TechnionIsrael Institute of Technology, Haifa 32000, Israel
Ben-David, Y., Department of Organic Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
Milsteins, D., Department of Organic Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel
Abstract:
The pincer-type complexes [(PCN)PtR] [R = H, 2; Me, 4; PCN = C 6H4[CH2P(tBu)2](CH2) 2N(CH3)2} react with MeLi or Et 3BHNa, to give anionic cis-Pt(Me).H complexes [(PCN*)Pt(H)(Me) J-Li+(Me irons to P; PCN* denotes the PCN ligand in which the amine arm is not coordinated) and [(PCN*)Pt(Me)(H)]-Na+ (H trans to P). Only the isomer in which the incoming nucleophile is situated trans to the phosphane ligand is formed. These first d8 anionic alkyl hydride complexes were fully characterized spectroscopically, The hemilabile PCN ligand allows for reversible de-coordination of the amine arm, thereby providing a desirable balance of stability vs. reactivity. Theoretical calculations on model systems indicate a concerted mechanism in which the nucleophilic attack and the amine dissociation occur concurrently. The (unobserved) methane reductive elimination from the stable anionic methyl hydride complex [(PCN*)Pt(Me)(H)]-Li+ (3) is thermodynamically and kinetically unfavorable, as indicated by DFT. This complex reacts with electrophiles, such, as water and methyl iodide, to yield exclusively methane and the corresponding organometallic product (either 2 or 4). This reactivity was also further examined by DFT. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.
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