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Russian Chemical Bulletin, International Edition, Vol. 69, No. 8, pp. 1594—1597, August, 2020

Brief Communications Unique triple ruthenacarborane cluster* J. J. Jones, A. P. M. Robertson, G. M. Rosair, and A. J. Welch Institute of Chemical Sciences, School of Engineering & Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS, U.K. Tel.: +44 (0)131 451 3217. E-mail: [email protected] Dehalogenation of [1,2-Ph2-3,3-(PPh3)2-3-Cl-closo/pseudocloso-3,1,2-RuC2B9H9]− affords, in addition to the unusual "symbiotic"** cluster [(1,2-Ph2-pseudocloso-3,1,2-RuC2B9H9) (1´,8´-Ph2-closo-2´,1´8´-RuC2B9H9)], a trace amount of a triple cluster species [(1,2-Ph2pseudocloso-3,1,2-RuC2B9H9)(1´,8´-Ph2-closo-2´,1´,8´-RuC2B9H9)(1″,8″-Ph2-closo-2″,1″,8″RuC2B9H9)], comprising three (Ph2RuC2B9H9) units linked by η6- coordination of Ph rings to the Ru atoms of the adjacent cluster. The structure of the triple cluster was established by X-ray crystallography, and the potential consequences of its formation are discussed. Kew words: ruthenacarborane, triple cluster, NMR spectroscopy, X-ray diffraction.

In an attempt to prepare hypercloso metallacarboranes (species with n vertices but only n skeletal electron pairs), we recently investigated the consequences of dehalogenation of the anion [1,2-Ph2-3,3-(PPh3)2-3-Cl-closo/pseudocloso-3,1,2-RuC2B9H9]− (1).1 Note that this anion is prepared in situ and not isolated, so the closo or pseudocloso nature of its structure is unknown; the CcageHcompound [3,3-(PPh3)2-3-Cl-closo-3,1,2-RuC2B9H9]− has a closo structure,2 but CcagePh analogues are usually deformed into pseudocloso clusters by Ph···Ph contacts.3 * On the occasion of the 65th anniversary of the foundation of A. N. Nesmeyanov Institute of Organoelement Compounds of the Russian Academy of Sciences. ** "Symbiotic" clusters are the clusters in which the substituent (Ph in this case) of one unit is coordinated to the metal center (Ru in this case) of the other unit and vice versa.

Treatment of compound 1 with AgBF4 in CH2Cl2 afforded a complex mixture of products, which could be separated by preparative thin-layer chromatography (TLC). One of the isolated products was subsequently identified as the "symbiotic" double ruthenacarborane cluster 2 (Scheme 1).1 In compound 2, the unprimed cage adopts a 3,1,2-RuC2B9 configuration but the presence of Ph rings on adjacent cage C atoms, forced to lie nearly co-planar, results in a deformed, pseudocloso shape in which the C···C connectivity is considerably extended. In contrast, the primed cage has undergone isomerization to a 2,1,8-RuC2B9 form and has a regular closo icosahedral geometry since the cage C atoms are now separated. The two ruthenacarborane clusters are symbiotically linked, with one Ph group from each cage η6-bonded to the Ru atom of the other cage, having displaced the two PPh3 ligands.

Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1594—1597, August, 2020. 1066-5285/20/6908-1594 © 2020 Springer Science+Business Media LLC

Unique triple ruthenacarb