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Inorganic and nuclear chemistry
A new linked bis(tricarbadecaboranyl) dianion has been used to form the first examples of ansa-vanadabis(tricarbadecaboranyl) complexes. The Li2+[6,6-(CH2)4-nido-(5,6,9-C3B7H9)2]2– (1) dianion was produced by a carbon-insertion route involving the reaction of two equivalents of arachno-4,6-C2B7H12– with adiponitrile. The reaction of 1 with VCl3·THF produced two isomeric ansa-vanadabis(tricarbadecaboranyl) complexes, ansa-(2′,4-(CH2)4-)-commo-V-(1′-V-2′,3′,5′-C3B7H9)(1-V-2,3,4-C3B7H9) (2) and ansa-(2′,4-(CH2)4-)-commo-V-(1′-V-2′,3′,4′-C3B7H9)(1-V-2,3,4-C3B7H9) (3). Crystallographic determinations showed that in both complexes a formal V2+ ion is sandwiched between two tricarbadecaboranyl cages that are linked by the ansa-(CH2)4– group, but that the points of linker-attachment on the two cages are different. One cage of each complex has the linkage attached to the C2 cage-carbon, but in the other cage, a cage-atom rearrangement moved the C2 cage-carbon along with its attached –(CH2)4– linker to an adjacent 4-position. This rearrangement along with the long flexible –(CH2)4– linker enables the two cages in each complex to rotate into a perpendicular interlocking configuration that maximizes the bonding interaction with the metal, reduces unfavorable steric interactions between the two linked cages and encapsulates the vanadium inhibiting its interactions with other potential ligands. The isomeric structures of 2 and 3 differ as a result of their being formed from different combinations of the enantiomeric forms of the –(CH2)4–C3B7H9 cages, with the C4 and C5′ carbons on opposite sides of the tether in 2, whereas in 3 the C4 and C4′ carbons are on the same side.
Perez-Gavilan, A., Carroll, P.J., & Sneddon, L.G. (2015) Synthesis and structural characterizations of ansa-vanadabis (tricarbadecaboranyl) sandwich complexes. Journal of Organometallic Chemistry, 798 (2015): 263-267. doi.org/10.1016/j.jorganchem.2015.04.002