ИСТИНА

Bis(dicarbollide) complexes of the iron group transition metals [3,3’-M(1,2-C2B9H11)2]- (M = Fe, Co, Ni) were recognized as analogues of the corresponding metallocenes immediately after their synthesis in the mid-1960s. However, despite a certain similarity between the cyclopentadienide (C5H5)- and dicarbollide (1,2-C2B9H11)2- ligands, there are a number of differences between them, which leads to a difference in the properties of transition metal complexes based thereof. The first and most obvious difference is the larger charge of the dicarbollide ligand. Another distinguishing feature of the dicarbollide ligand is its greater donor capacity, which leads to more efficient stabilization of the higher oxidation states of transition metals compared to the cyclopentadienide ligand. In addition to the differences associated with the donor ability of cyclopentadienide and dicarbollide ligands and the electronic structure of sandwich complexes based on them, there are a number of differences due to the structure of the ligands themselves. In contrast to the cyclopentadienide ligand, the hydrogen atoms in the pentagonal face of the dicarbollide ligand are not located in the ligand plane, but are directed from the center of the icosahedron, decreasing the ligand cone angle. the substitution of hydrogens by other atoms or groups leads to an even greater decrease in the ligand cone angle. This is most noticeable in bis(dicarbollide) complexes of transition metals, where the interaction between substituents in the dicarbollide ligands becomes one of the main factors determining the properties of the complexes. The interaction between different types of substituents in dicarbollide ligands and their influence on the stabilization of various rotational conformers (rotamers) of transition metal bis(dicarbollide) complexes [3,3’-M(1,2-C2B9H11)2]- will be considered [1]. The formation of intramolecular CH···X hydrogen bonds between the dicarbollide ligands is determined by the size of the proton acceptor atom X rather than its electronegativity. Due to the stabilization of rotamers with different dipole moments, the intramolecular hydrogen bonds between the ligands in transition metal bis(dicarbollide) complexes can have a significant impact on the biological properties of their derivatives. In the presence of external complexing metals, weak intramolecular CH···X hydrogen bonds can be broken to form stronger X—>M donor-acceptor bonds. This process is accompanied by mutual rotation of dicarbollide ligands and can be used in sensors and molecular switches based on transition metal bis(dicarbollide) complexes.