The reduction of N,C,N-chelated 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'-iPr2C6H3)-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-chelated 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'-iPr2C6H3)-4,6-(tBu)2]Bi (9) as an unprecedented two-coordinated 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 (1)H and (13)C 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 dibismuthene) 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.

N,C,N-Chelated pnictinidenes ArE [where E = As (1), Sb (2) or Bi (3); Ar = CH-2,6-(CH[double bond, length as m-dash]Nt-Bu)] were used as ligands for the coordination of transition metal carbonyls. Thus, the reaction of 1-3 with [M(CO)THF] (where M = Cr, W) or [Mo(CO)(MeN)] gave complexes [(ArE)M(CO)] [where E = As and M = Cr (1a), Mo (1b), W (1c); E = Sb and M = Cr (2a), Mo (2b), W (2c); E = Bi and M = Cr (3a), Mo (3b), W (3c)]. Analogously, the treatment of 1-3 with [Fe(CO)] resulted in the formation of the complexes [(ArE)Fe(CO)] [where E = As (1d), Sb (2d) or Bi (3d)]. All compounds were characterized by H andC NMR spectroscopy, Raman, IR and UV-Vis spectroscopy. The molecular structures of the majority of the compounds (except 1b and 1c) were also determined by the single-crystal X-ray diffraction analysis. Furthermore, the structure and bonding of the title compounds have also been thoroughly investigated using a computational approach.

The reduction of N,C,N-chelated antimony(III) chlorides [C H -2,6-(CH=NR) ]SbCl (R=Ph (1), tBu (2), Dip (3); Dip=2,6-iPr C H ) with an appropriate amount of KC or Li[AlH ] resulted in the formation of rare examples of monomeric stibinidenes [C H -2,6-(CH=NR) ]Sb (R=Ph (4), tBu (5), Dip (6)). Similarly, the reduction of compounds 1 or 2 by two equivalents of K[B(sBu) H] led to the stibinidenes 4 and 5. In contrast, the analogous reaction of compound 3 resulted in the formation of an unprecedented stibinidene [C H -2-(CH=NR)-6-(CH NHR)]Sb (7) (R=Dip), in which the hydrogen atoms that come from the K[B(sBu) H] are incorporated into the ligand backbone. To gain further insight into this intriguing reactivity with K[B(sBu) H] and to assess the influence of the substitution at both the antimony atom and pendant substituents, we prepared compounds [C H -2-(CH=NDip)]Sb(Ph)Cl (8) and [C H -2-(CH=NDip)-4,6-(tBu) ]SbCl (9). The treatment of compound 8 with K[B(sBu) H] smoothly led to the 1-Ph-2-Dip-1H-2,1-benzazastibole (11), whereas the reaction of compound 9 with K[B(sBu) H] resulted in either tBu-substituted 1-Cl-2-Dip-1H-2,1-benzazastibole (13) or the formation of unprecedented Sb-Sb dimer bis(2-Dip-1H-2,1-benzazastibole) (12) depending on the reaction stoichiometry. The miscellaneous reactivity of antimony(III) precursors with reducing agents together with the structure and bonding of the resulting products has also been investigated from a theoretical point of view.

The reaction of stibinidene and bismuthinidene ArM [where Ar=C6 H3 -2,6-(CH=NtBu)2 ; M=Sb (1), Bi (2)] with transition metal (TM) carbonyls Co2 (CO)8 and Mn2 (CO)10 produced unprecedented ionic complexes [(ArM)2 Co(CO)3 ](+) [Co(CO)4 ](-) and [(ArM)2 Mn(CO)4 ](+) [Mn(CO)5 ](-) [where M=Sb (3, 5), Bi (4, 6)]. The pnictinidenes 1 and 2 behaved as two-electron donors in this set of compounds. Besides the M→TM bonds, the topological analysis also revealed a number of secondary interactions contributing to the stabilization of cationic parts of titled complexes.

N,C,N-chelated antimony(III) and bismuth(III) chlorides L 1,2 MCl 2 (1−4: for L 1 , M = Sb (1), Bi (3); for L 2 , M = Sb (2), Bi (4)) containing ligands L 1,2 (wherewere prepared by reactions of lithium precursors with SbCl 3 or BiCl 3 . The identities of 1−4 were established both in solution ( 1 H and 13 C NMR spectroscopy) and, in the case of 1−3, in the solid state using single-crystal X-ray diffraction analysis. Treatment of antimony derivatives 1 and 2 with 2 molar equiv of R′Li (R = Me, n-Bu, Ph) yielded the set of substituted 1,3-(R′) 2 -2-R-7-(CHNR)-1H-2,1-benzazastiboles 5−10 (where R = t-Bu, 2,6-Me 2 C 6 H 3 and R′ = Me, n-Bu, Ph) as a result of a nucleophilic attack of one of the lithium compounds across the imino CN functionality. In contrast, analogous reactions between bismuth congeners 2 and 4 and R′Li (2 equiv, R′ = Me, Ph) gave L 1,2 BiR′ 2 (11−13: for L 1 , R′ = Me (11), Ph (12); for L 2 , R′ = Me ( 13)) as products of substitution of chlorine atoms. Compounds 5−13 were characterized by the help of 1 H and 13 C NMR spectroscopy. The molecular structures of 8, 9, and 13 were unambiguously established using single-crystal X-ray diffraction analysis.