On heterocyclic systems containing bismuth(III) 2. Eight-membered heterocycles Cl/Br/I-M(CH2CH2CH2)2X with lewis acidic group 15 atoms M As, Sb, Bi and donor atoms X NR, S: a contribution to the value of the electronegativity of bismuth(III)
摘要:
Paths to the ligands (Cl/Br-CH2CH2CH2)(2)NR/O/S/Se, R = Me, Bz, iPr, iBu, to the diGrignard reagents (Cl/BrMg-CH2CH2CH2)(2)NR/O/S, R = Me, Bz, iPr, iBu and to the eight-membered group 15 heterocycles (C1/Br/I-As/Sb/Bi(CH2CH2CH2)(2)NR/S, R = Me, Bz, iBu are given. C-13-NMR, TR and Raman spectra are discussed; for the compound ClSb(CH2CH2CH2)(2)NMe the crystal structure analysis is given: the antimony atom is clearly Lewis acidic with psi-trigonal-bipyramidal coordination and a transannular Sb ... N interaction of 2.385(2) Angstrom. For such a configuration the values of the C-13-NMR chemical shifts of the alpha-CH2-groups (e.g. Cl-As/Sb/Bi(alpha CH2CH2CH2)(2)NMe 34.6, 25.9, 46.6 ppm) display clearly a sequence N > Bi > P approximate to As > Sb for the Paulins electronegativities of the group 15 elements: a value as high as 2.3 for bismuth is suggested.