165901-75-7Relevant academic research and scientific papers
Structural characterization and simple synthesis of {Pd[P(o-Tol)3]2}, dimeric palladium(II) complexes obtained by oxidative addition of aryl bromides, and corresponding monometallic amine complexes
Paul, Frédéric,Patt, Joe,Hartwig, John F.
, p. 3030 - 3039 (2008/10/09)
The palladium(0) complex {Pd[P(o-Tol)3]2} was prepared by addition of P(o-Tol)3 to crude "[Pd(DBA)2]", which is an approximately equimolar mixture of Pd2(DBA)3 and Pd(DBA)3, followed by crystallization from the reaction medium by addition of ether. The formation of {Pd[P(o-Tol)3]2} appeared to be driven by its insolubility in the benzene/ether solvent mixture. Benzene solutions of "[Pd(DBA)2]" and P(o-Tol)3 did not contain amounts of the L2Pd compound that could be detected by 31P NMR spectroscopy. {Pd[P(o-Tol)3]2} was characterized crystallographically and showed an exactly linear geometry. Similar Pd(O) compounds {Pd[P(2,4-dimethylphenyl)3]2}, {Pd[P(2-methyl-4-fluorophenyl)3]2}, and the low-coordinate trialkylphosphine complex {Pd[P(t-Bu)a]2} were also prepared by this method, but [Pd(PCy3)2-(DBA)] was produced from reactions involving PCy3 and "[Pd(DBA)2]", and [Pd(TMPP)(DBA)2] was isolated after addition of tris(1,3,5-trimethoxyphenyl)phosphine (TMPP) to "[Pd(DBA)2]". The oxidative addition of aryl halides to {Pd[P(o-Tol)3]2} at room temperature led to dimeric products {Pd[P(o-Tol)3](Ar)(Br)}2. An example of these compounds was characterized crystallographically as well as by solution molecular weight analysis. This aryl halide complex was shown to be dimeric in the solid state as well as in solution. The NMR spectra of the large triarylphosphine complexes showed temperature dependent behavior, presumably due to isomerizations and ligand rotations that occurred on the NMR time scale. The aryl halide compounds did not form four-coordinate monometallic species in the presence of excess P(o-Tol)3, but they did undergo cleavage to four-coordinate monometallic complexes upon addition of primary and secondary amines.
