| Abstract
| - Hybrid phosphine crown ether ligands have been obtained from PhP(OMe)2 and P(OPh)3and carbanions generated by low-temperature Li/Br exchange reactions involving 4‘-bromo-N-phenylaza-15-crown-5 and n-butyllithium. The A1 ν(CO) values for the Ni(CO)3L complexesof these phosphines have been found to be 2063.7 and 2060.8 cm-1, for the bis (1b) and tris(1c) crown species, respectively, indicating the significant electron-donating abilities of thenitrogen atoms. Addition of NaSCN salts in dichloromethane causes these frequencies toincrease by 2.40 (1b) and 3.70 cm-1 (1c), indicating that the P(III) centers detect the presenceof crown-coordinated ions. The oxide of 1c has been prepared and the X-ray structureobtained. A prominent feature of that structure, R3̄ symmetry, is that the nitrogen atomsare nearly planar and the ring carbon-to-nitrogen distances are 1.375 Å, features that arealso consistent with a significant amount of sp2 C−N double-bond character. The phenylrings are arranged in a typical propeller shape with torsion angles of 132.4°.
- PhP(4-N-phenylaza-15-crown-5)2, P(4-N-phenylaza-15-crown-5)3, and OP(4-N-phenylaza-15-crown-5)3 have been synthesized, and the donor properties of the first two have been studied by examining the IR spectra of their Ni(CO)3L complexes in the presence and absence of ions. The X-ray structure of the oxide has been determined, and a prominent feature is that the nitrogen atoms are essentially planar, indicating, as observed in the IR spectra, a significant degree of electron pair/benzene ring conjugation.
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