Organic and inorganic derivatives of tantalum are widely used in the synthesis of various classes of organic compounds . Modern advances in using VB group metal compounds include oxidation, reduction, water splitting, alkylation, dealkylation, polymerization, aromatization, protein synthesis, and other reactions . We have previously shown that tantalum pentachloride can initiate carboaluminations of alkynes with organoaluminum compounds . New synthetic possibilities for niobium, an electronic analogue of tantalum, have been discovered through the chlorothiolation reaction of 2-alkynylamines with methanesulfonyl chloride and stoichiometric amounts of niobium(V) chloride in the presence of metallic magnesium . It has been assumed that the observed transformation is initiated by the "NbCl 4 " complex, which is generated as a result of the reduction of NbCl 5 using metallic magnesium in a toluene solution. It is known that monomeric coordination complexes of low-valent niobium, such as NbCl 4 L 2 , are paramagnetic . Another synthetic finding of the use of metal compounds from the VB group is presented in this study. We have, for the first time, performed a highly selective arylation of alkyl-substituted aldehydes using benzene, under the action of a system of reagents consisting of TaCl 5 and Mg .