Monophosphanylcalix[6]arene Ligands: Synthesis Characterization, Complexation, and Their Use in Catalysis

Novel phosphanylcalix[6]arenes having mono‐ O ‐diphenylphosphanylmethyl ( 3 ) and mono‐ O ‐(4‐diphenylphosphanylphenyl)methyl substituents ( 5 ) have been synthesized. The structures of these monophosphanylcalix[6]arenes were determined by NMR spectroscopy, mass spectrometry, and X‐ray crystal structure analysis. The X‐ray structure reveals that 3 adopts a flattened 1,2,3‐alternate conformation in the crystalline state, while the NMR spectra show that 3 and 5 have a cone conformation in solution. Structure optimization and energy calculations for 3 and 5 at the B3LYP/LANL2DZ‐CONFLEX5/MMFF94s level of theory show that the cone conformation is slightly more stable than the 1,2,3‐alternate conformation by 0.36 kcal mol –1 for 3 and 0.96 kcal mol –1 for 5 . Complexation of 3 with [PtCl 2 (COD)] and [Rh(COD) 2 ]BF 4 gives cis ‐coordinated [PtCl 2 ( 3 ) 2 ] and [Rh(COD)( 3 ) 2 ]BF 4 , respectively. The X‐ray analysis of [PtCl 2 ( 3 ) 2 ] shows that 3 adopts a cone conformation upon complexation. Combination of 3 and 5 with [Rh(COD) 2 ]BF 4 provides an active catalyst for the hydroformylation of a variety of terminal alkenes.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)