Aspects of transmetallation reactions of 2-Me2NCH2C6H4- and 2,6-(Me2NCH2)C6H3-Metal (Pd,Pt, Hg,Tl) complexes with metal carboxylates and low-valent metal (Pd,Pt) complexes |
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Authors: | Antonius F.M.J. Van Der Ploeg Gerard Van Koten Kees Vrieze |
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Affiliation: | Anorganisch Chemisch Laboratorium, J.H. van ''t Hoff Instituut, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam Netherlands |
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Abstract: | A study has been made of reactions involving organometallic compounds containing ortho-Me2NCH2 substituted aryl ligands. The single step syntheses of the new compounds [(2-Me2NCH2C6H4)2TlCl], [ [{(S)-2-Me2NCH(Me)C6H4}2TlCl], [{(S)-2-Me2NCH(Me)C6H4}TlCl2], [{2,6-(Me2NCH2)2C6H3}TlClBr] and [{2,6-(Me2NCH2)2C6H3}HgCl] are described. Stable internal NTl coordination at low temperatures has been established for the C-chiral thallium compounds. Reactions of the other Tl and Hg compounds and of [(2-Me2NCH2C6H4)2Hg] with Pd(O2CMe)2, and also of the reverse reaction of cis-[(2-Me2NCH2C6H4)2Pd] with Hg(O2CR)2 or Tl(O2CR)3, gave transmetallation of one organo ligand and led to a single mono-organopalladium compound and corresponding by-products. Reaction of cis-[(2-Me2NCH2C6H4)2Pd] with Pd(O2CR)2 gave the dimeric compound [{(2-Me2NCH2C6H4)Pd(O2CR)}2]. cis-[(2-Me2NCH2C6H4)2Pt] did not react with Pd(O2CMe)2, while reaction of trans-[(2-Me2NCH2C6H4)2Pt] or cis-[(2-Me2NC6H4CH2)2Pt] with Pd(O2CMe)2 resulted in decomposition. Upon heating, trans-[(2-Me2NCH2C6H4)2Pt] was isomerized to cis-isomer. A redox reaction between [(2-Me2NCH2C6H4)2Hg] and [Pt(COD)2] (COD 1,5-cyclo-octadiene) and [Pd2(DBA)3] (DBA dibenzylideneacetone) gave the cis-isomers of [(2-Me2NCH2C6H4)2M] (M Pd, Pt).The results are discussed in terms of influence of internal coordination of the CH2NMe2 group. It is concluded that although internal coordination of the CH2NMe2 ligand can stabilize metal—carbon bonds it cannot prevent cleavage of such bonds by electrophiles. In this respect, there is no difference in the behaviour of Hg(O2CR)2 and Tl(O2CR)3. The reactions are influenced by the metal—nitrogen bond strength, which follows the order PtN > PdN > HgN, TlN. The reactivity of Pt compounds is greatly influenced by their structure and type of ligand. It is proposed that cleavege of PdC bonds occurs mainly by a mechanism involving direct electrophilic attack at the carbon centre. |
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Keywords: | To whom correspondence should be addressed. |
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