Novel phosphanylcalixarenes having mono-O-diphenylphosphanylmethyl (3) and mono-O-(4-diphenylphosphanylphenyl)methyl substituents (5) have been synthesized. The structures of these monophosphanylcalixarenes 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 [PtCl2(COD)] and [Rh(COD) 2]BF4 gives cis-coordinated [PtCl2(3) 2] and [Rh(COD)(3)2]BF4, respectively. The X-ray analysis of [PtCl2(3)2] shows that 3 adopts a cone conformation upon complexation. Combination of 3 and 5 with [Rh(COD) 2]BF4 provides an active catalyst for the hydroformylation of a variety of terminal alkenes.
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