Wydział Chemii

Tomasz Ruman

Zbigniew Ciunik

Anna M. Trzeciak

Stanisław Wołowiec

Józef J. Ziółkowski

2003

Organometallics

22

1072-1080

10.1021/om020873x

Naukowa

Angielski

Artykuł

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 κ² 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 Tp^Ph,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.

Conformation, Ligands, Molecular structure, Molecules, Pyrazolyl

https://doi.org/10.1021/om020873x

https://www.acs.org/content/acs/en.html