503156-56-7Relevant academic research and scientific papers
Complexes of heteroscorpionate trispyrazolylborate ligands. Part 10. Structures and fluxional behavior of rhodium(I) complexes with heteroscorpionate trispyrazolylborate ligands, Tp″Rh(LL) (LL = (CO)2 or COD)
Ruman, Tomasz,Ciunik, Zbigniew,Trzeciak, Anna M.,Wolowiec, Stanislaw,Ziolkowski, Jozef J.
, p. 1072 - 1080 (2008/10/08)
Heteroscorpionate Tp″ ligands constructed of two 3-phenyl-5-methylpyrazolyl and a variable third pyrazolyl residue (3-methyl-5-phenyl-, 3,5-dimethyl-, and 3,5-diethylpyrazolyl) coordinate to rhodium(I) in a k2 fashion to form Tp″Rh(LL) complexes (where LL = COD or (CO)2). One of the two 3-phenyl-5-methylpyrazolyl and the less sterically hindered pyrazolyl coordinate through N(2) atoms, while the axially appended 3-phenyl-5-methylpyrazolyl is in side-on conformation. The Tp″Rh(COD) complexes possess C1 symmetry in the solid state. The energy of activation of the exchange between coordinated and uncoordinated pyrazolyls was estimated from variable-temperature 1H NMR measurements. Two ΔG? values were found for heteroscorpionate complexes. The ΔG?1 - ΔG?2 depends on a difference in steric demands of competing pyrazoles. For the homoscorpionate Tpph,MeRh(COD) complex two rotational isomers were identified by low-temperature 1H NMR spectroscopy, which originate from slow rotation of the dangling 3-phenyl-5-methylpyrazolyl residue. All studied Tp′Rh-(COD) complexes were found to be catalytically active in regioselective polymerization of phenylacetylene.
