"Try and fall sick .."-the composer, chemist, and surgeon Aleksandr Borodin.
Although Aleksandr Porfir’evič Borodin is considered one of the outstanding Russian composers of the 19th century, he left only a very small volume of musical work. He is particularly renowned for the world-famous “Polovtsian Dances” from the opera “Prince Igor” and for his membership in “The Mighty Handful”. Also noteworthy, aside from the forementioned opera “Prince Igor”, are his three symphonies, two string quartets, and a symphonic poem “In the Steppes of Central Asia”. The reason for his small œuvre is that he considered himself a sunday composer, composing for fun and only in his rare spare time or when he was ill. In fact, he was a professor of chemistry, and chemistry was avowedly his first passion. There were also other fields, besides chemistry, to which he was more committed than composition. Despite this declared priority for chemistry, Aleksandr Borodin is mostly unknown as a chemist to chemists of today, and—much to my regret—even as composer. This surely is not justified, since he is the discoverer of outstanding reactions, although unfortunately at a time when it was uncommon to name reactions after their inventors. This Essay is intended to shed light on all the various facets of Borodin, with a special focus on his chemical work.
Comproportionation of cationic and anionic tungsten complexes having an N-heterocyclic carbene ligand to give the isolable 17-electron tungsten radical CpW(CO)2(IMes)(•).
A series consisting of a tungsten anion, radical, and cation, supported by the N-heterocyclic carbene 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes) and spanning formal oxidation states W(0), W(I), and W(II), has been synthesized, isolated, and characterized. Reaction of the hydride CpW(CO)(2)(IMes)H with KH and 18-crown-6 gives the tungsten anion [CpW(CO)(2)(IMes)](-)[K(18-crown-6)](+). Electrochemical oxidation of [CpW(CO)(2)(IMes)](-) in MeCN (0.2 M (n)Bu(4)N(+)PF(6)(-)) is fully reversible (E(1/2) = -1.65 V vs Cp(2)Fe(+•/0)) at all scan rates, indicating that CpW(CO)(2)(IMes)(•) is a persistent radical. Hydride transfer from CpW(CO)(2)(IMes)H to Ph(3)C(+)PF(6)(-) in MeCN affords [cis-CpW(CO)(2)(IMes)(MeCN)](+)PF(6)(-). Comproportionation of [CpW(CO)(2)(IMes)](-) with [CpW(CO)(2)(IMes)(MeCN)](+) gives the 17-electron tungsten radical CpW(CO)(2)(IMes)(•). This complex shows paramagnetically shifted resonances in the (1)H NMR spectrum and has been characterized by IR spectroscopy, low-temperature EPR spectroscopy, and X-ray diffraction. CpW(CO)(2)(IMes)(•) is stable with respect to disproportionation and dimerization. NMR studies of degenerate electron transfer between CpW(CO)(2)(IMes)(•) and [CpW(CO)(2)(IMes)](-) are reported. DFT calculations were carried out on CpW(CO)(2)(IMes)H, as well as on related complexes bearing NHC ligands with N,N' substituents Me (CpW(CO)(2)(IMe)H) or H (CpW(CO)(2)(IH)H) to compare to the experimentally studied IMes complexes with mesityl substituents. These calculations reveal that W-H homolytic bond dissociation energies (BDEs) decrease with increasing steric bulk of the NHC ligand, from 67 to 64 to 63 kcal mol(-1) for CpW(CO)(2)(IH)H, CpW(CO)(2)(IMe)H, and CpW(CO)(2)(IMes)H, respectively. The calculated spin density at W for CpW(CO)(2)(IMes)(•) is 0.63. The W radicals CpW(CO)(2)(IMe)(•) and CpW(CO)(2)(IH)(•) are calculated to form weak W-W bonds. The weakly bonded complexes [CpW(CO)(2)(IMe)](2) and [CpW(CO)(2)(IH)](2) are predicted to have W-W BDEs of 6 and 18 kcal mol(-1), respectively, and to dissociate readily to the W-centered radicals CpW(CO)(2)(IMe)(•) and CpW(CO)(2)(IH)(•).
The Tsadik and His Soul’s Sparks: From Kabbalah to Hasidism
The present study shows the continuity between the Safedian Kabbalistic view of the relations between the sparks of a certain soul, and the Hasidic theory, that was conceived of as innovated by and characteristic of 18th century Hasidism, as to the responsibility of the Tsadik for the sparks that belongs to his soul. In the two literatures, the rescue of a spark of one's soul is related to the beautiful captive woman that is conceived of as an externalization of an inner dimension of the righteous person, immersed in a shell.