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The reaction of 1,1'-Li 2 [(2,2'-C 2 B 10 H 10 ) 2 ] with the cyclometallated gold(III) complex (C^N)AuCl 2 afforded the first examples of gold(III) dicarboranyl complexes. The reactivity of these complexes is subject to the trans-influence exerted by the dicarboranyl ligand, which is substantially weaker than that of non-carboranyl anionic C-ligands. In line with this, displacement of coordinated pyridine by chloride is only possible under forcing conditions. While treatment of (C^N)Au{(2,2'-C 2 B 10 H 10 ) 2 } (2) with triflic acid leads to Au-C rather than Au-N bond protonolysis, aqueous HBr cleaves the Au-N bond to give the pyridinium bromo complex 7. The trans-influence of a series of ligands including dicarboranyl and bis(dicarboranyl) was assessed by means of DFT calculations. The analysis demonstrated that it was not sufficient to rely exclusively on geometric descriptors (calculated or experimental) when attempting to rank ligands for their trans influence. Complex (C^N)Au(C 2 B 10 H 11 ) 2 containing two non-chelating dicarboranyl ligands was prepared similar to 2. Its reaction with trifluoroacetic acid also leads to Au-N cleavage to give trans-(Hpy^C)Au(OAc F )(C 2 B 10 H 11 ) 2 (8). In crystals of 8 the pyridinium N-H bond points towards the metal centre, while in 7 it is bent away. The possible contribution of gold(III)⋅⋅⋅H-N hydrogen bonding in these complexes was investigated by DFT calculations. The results show that, unlike the situation for platinum(II), there is no evidence for an energetically significant contribution by hydrogen bonding in the case of gold(III)., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Three isomers of [(Cp*Ru)2 C2 B10 H12 ], the first examples of 14-vertex heteroboranes containing 14-skeletal electron pairs, have been synthesized by the direct electrophilic insertion of a {Cp*Ru(+) } fragment into the anion [4-Cp*-4,1,6-RuC2 B10 H12 ](-) . All three compounds have the same unique polyhedral structure having an approximate Cs symmetry and featuring a four-atom trapezoidal face. X-ray diffraction studies could confidently identify only one of the two cage C atoms in each structure. The other C atom position has been established by a combination of i) best fitting of computed and experimental (11) B and (1) H NMR chemical shifts, and ii) consideration of the lowest computed energy for series of isomers studied by DFT calculations. In all three isomers, one cage C atom occupies a degree-4 vertex on the short parallel edge of the trapezium., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Two-electron reduction of 1,1'-bis(o-carborane) followed by reaction with [Ru(η-mes)Cl2 ]2 affords [8-(1'-1',2'-closo-C2 B10 H11 )-4-(η-mes)-4,1,8-closo-RuC2 B10 H11 ]. Subsequent two-electron reduction of this species and treatment with [Ru(η-arene)Cl2 ]2 results in the 14-vertex/12-vertex species [1-(η-mes)-9-(1'-1',2'-closo-C2 B10 H11 )-13-(η-arene)-1,13,2,9-closo-Ru2 C2 B10 H11 ] by direct electrophilic insertion, promoted by the carborane substituent in the 13-vertex/12-vertex precursor. When arene=mesitylene (mes), the diruthenium species is fluxional in solution at room temperature in a process that makes the metal-ligand fragments equivalent. A unique mechanism for this fluxionality is proposed and is shown to be fully consistent with the observed fluxionality or nonfluxionality of a series of previously reported 14-vertex dicobaltacarboranes., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Three examples of the rare 8,1,2-closo-MC2B9 isomeric form of an icosahedral metallacarborane have been isolated as unexpected trace products in reactions. Seeking to understand how these were formed we considered both the nature of the reactions that were being undertaken and the nature of the coproducts. This led us to propose a mechanism for the formation of the 8,1,2-closo-MC2B9 species. The mechanism was then tested, leading to the first deliberate synthesis of an example of this isomer. Thus, deboronation of 4-(η-C5H5)-4,1,8-closo-CoC2B10H12 selectively removes the B5 vertex to yield the dianion [nido-(η-C5H5)CoC2B9H11](2-), oxidative closure of which affords 8-(η-C5H5)-8,1,2-closo-CoC2B9H11 in moderate yield., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)