Hybrid Dibismuthines and Distibines: Preparation and Properties of Antimony and Bismuth Oxygen, Sulfur, and Nitrogen Donor Ligands

The hybrid dibismuthines O{(CH2)2BiPh2}2, MeN(CH2-2-C6H4BiR2)2, and S(CH2-2-C6H4BiR2)2 (R = Me, Ph), have been prepared and characterized by microanalysis, 1H and 13C{1H} NMR spectroscopy, and FAB mass spectrometry. The X-ray structures of O{(CH2)2BiPh2}2 and S(CH2-2-C6H4BiPh2)2 show close to symmetrical hypervalent interactions between the O or S atoms and both bismuth centers. The antimony analogue S(CH2-2-C6H4SbMe2)2 is quaternized by MeI to [S(CH2-2-C6H4SbMe3)2]I2, which also shows a hypervalent S···Sb interaction, but in this case to only a single antimony center. Complexes of these and related ligands with the CpFe(CO)2 + group, of the type [{CpFe(CO)2}2L][BF4]2 (L = O{(CH2)2BiPh2}2, MeN(CH2-2-C6H4BiR2)2, S(CH2-2-C6H4BiR2)2, O{(CH2)2SbR2}2, S(CH2-2-C6H4SbMe2)2, MeN(CH2-2-C6H4SbMe2)2, Ph2Sb(CH2)3SbPh2), have been prepared and characterized by microanalysis (antimony complexes only), 1H and 13C{1H} NMR and IR spectroscopy, and ES+ mass spectrometry. The X-ray crystal structure of [{CpFe(CO)2}2{O{(CH2)2SbMe2}2}][BF4]2 shows a hypervalent Sb···O contact to one of the antimony centers, whereas no hypervalent contacts are seen in the structure of [{CpFe(CO)2}2{MeN(CH2-2-C6H4SbMe2)2}][BF4]2. IR (carbonyl region) and NMR spectroscopy indicate that, uniquely, [{CpFe(CO)2}2{MeN(CH2-2-C6H4BiPh2)2}][BF4]2 shows hypervalent N···Bi interactions in both the solid and solution, but for the other dibismuthine complexes, there is evidence for inequivalence of the iron centers (and hence hypervalency) only in the solid state. Spectroscopic data indicate that hypervalent interactions are absent in [{CpFe(CO)2}2{MeN(CH2-2-C6H4SbMe2)2}][BF4]2 and [{CpFe(CO)2}2{S(CH2-2-C6H4SbMe2)2}][BF4]2, but present in solid [{CpFe(CO)2}2{O{(CH2)2SbR2}2}][BF4]2. The preparation and X-ray structure of [CpFe(CO)2{BiPh2(o-C6H4OMe)}][BF4] is also reported, but attempts to isolate [CpFe(CO)2(BiPhMe2)]][BF4] resulted in rapid scrambling of the substituents at bismuth to give [CpFe(CO)2(BiPh3−n Me n )][BF4] (n = 0−3).