Some Analogies in Inorganic Chemistry (in memory of A. A. Pasynskii)
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RETICAL INORGANIC CHEMISTRY I bring this fact with a radiant face As a valuable contribution to science. Sasha Chorny, “Koumiss Verses” (1909)
Some Analogies in Inorganic Chemistry (in memory of A. A. Pasynskii) I. B. Sivaev* Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Moscow, 119991 Russia *e-mail: [email protected] Received May 8, 2020; revised July 30, 2020; accepted July 31, 2020
Abstract―Based on a comparison of the spectral data of dimethylsulfonium derivatives of polyhedral boron hydrides and dimethylsulfide complexes of tantalum and niobium pentahalides, an analogy has been recognized between the Lewis acidity of quasiborinium cations formed upon the removal of the hydride ion from polyhedral boron hydrides, on the one hand, and tantalum and niobium pentahalides, on the other. Keywords: polyhedral boron hydrides, niobium and tantalum pentahalide complexes, Lewis acidity DOI: 10.1134/S0036023620120165
One of the distinguishing features peculiar to Alexander Anatolyevich Pasynskii was his scientific curiosity and desire to find the underlying cause of a problem. Undergraduates, as a rule, were afraid of his questions when defending their term papers, but getting him as an opponent of a well-done dissertation thesis was a great success, because a non-standard view of the problem and interesting questions were always guaranteed, often giving impetus to new research. One of the questions that usually arose during the defense of dissertations devoted to the chemistry of derivatives of polyhedral boron hydrides was the following: “Since polyhedral boron hydrides are capable of forming “complexes” with various donor molecules (amines, sulfides, ethers, and nitriles), can they be considered in as a kind of analogs of transition metals?” Indeed, such derivatives are well known practically for all types of anionic polyhedral boron hydrides [1–11]. Moreover, these derivatives usually participate in reactions typical of transition metal complexes with analogous ligands, such as nucleophilic opening of the tetrahydrofuran ring [12–15] or addition to the triple bond of nitriles [16–18]. Indeed, the reactions of nucleophilic opening of cyclic oxonium derivatives [19–24] and addition to nitrilium derivatives of polyhedral boron hydrides [25–29] are well known. As a rule, the answer in such cases is reduced to the fact that polyhedral boron hydrides are three-dimensional aromatic systems [30, 31], and therefore their derivatives should be considered as
analogues of well-known highly reactive organic compounds, such as oxonium [32] or nitrilium [33] salts, and their stability is explained by the strong electrondonor effect of the boron cage [34]. It should be noted that, from the point of view of organic chemistry, this is a completely correct formulation, but it does not answer the question posed from the point of view of coordination chemistry, within which the formation of complexes can be considered as the interaction of transition metals (Lewis acids) with ligands (Lewis bases). In fa
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