From Dibismuthenes to Three- and Two-Coordinated Bismuthinidenes by Fine Ligand Tuning: Evidence for Aromatic BiC3N Rings through a Combined Experimental and Theoretical Study

摘要

The reduction of N,C,-zchelated bismuth chlorides [C6H3-2,6-(CH=NR)(2)]BiCl2 [where R=tBu (1), 2',6'-Me2C6H3 (2), or 4'-Me2NC6H4 (3)] or N, C-chelated analogues [C6H2-2-(CH=N-2',6'-iPr(2)C(6)H(3))-4,6-(tBu)(2)]BiCl2(4) and [C6H2-2-(CH2NEt2)-4,6( tBu)(2)]BiCl2 (5) is reported. Reduction of compounds 1-3 gave monomeric N,C,N-zchelated bismuthinidenes [C6H3-2,6(CH= NR)(2)]Bi [where R=tBu (6), 2',6'-Me2C6H3 (7) or 4'-Me2NC6H4 (8)]. Similarly, the reduction of 4 led to the isolation of the compound [C6H2-2-(CH= N-2',6'-ziPr(2)C(6)H(3))-4,6(tBu)(2)]Bi (9) as an unprecedented two-zcoordinated bismuthinidene that has been structurally characterized. In contrast, the dibismuthene {[C6H2-2-(CH2NEt2)-4,6-(tBu)(2)]Bi}(2) (10) was obtained by the reduction of 5. Compounds 6-10 were characterized by using H-1 and C-13 NMR spectroscopy and their structures, except for 7, were determined with the help of single-crystal X-ray diffraction analysis. It is clear that the structure of the reduced products (bismuthinidene versus di-bismuthene) is ligand-dependent and particularly influenced by the strength of the N -> Bi intramolecular interaction(s). Therefore, a theoretical survey describing the bonding situation in the studied compounds and related bismuth(I) systems is included. Importantly, we found that the C3NBi chelating ring in the two-coordinated bismuthinidene 9 exhibits significant aromatic character by delocalization of the bismuth lone pair.