The synthesis and characterisation of 4,1,2-MC2B10 metallacarboranes

Abstract

Reduction of the tethered carborane 1,2-(CH2)3-1,2-closo-C2B10H10 followed by treatment with CoCl2/NaCp, [(p-cymene)RuCl2]2(p-cymene=C6H4MeiPr-1,4), (PMe2Ph)2PtCl2 or (dppe)NiCl2(dppe=Ph2PCH2CH2PPh2) affords reasonable yields of the new 13-vertex metallacarboranes 1,2-(CH2)3-4-Cp-4,1,2-closo-CoC2B10H10 (1), 1,2-(CH2)3-4-(p-cymene)-4,1,2-closo-RuC2B10H10 (2), 1,2-(CH2)3-4,4-(PMe2Ph)2-4,1,2-closo-PtC2B10H10 (3) and 1,2-(CH2)3-4,4-(dppe)-4,1,2-closo-NiC2B10H10 (4), respectively. All compounds were characterised spectroscopically and crystallographically. The cobalt and ruthenium species 1 and 2 have Cs symmetry in both solution and the solid state, having henicosahedral cage structures featuring a trapezoidal C1C2B9B5 face. The platinum and nickel compounds 3 and 4 have asymmetric docosahedral cage structures in the crystal (the more so for 4 than for 3) although both appear, by 11B and 31P NMR spectroscopy, to have Cs symmetry in solution. Low-temperature experiments on the more soluble platinacarborane could not freeze out the diamond-trapezium-diamond fluctional process that we assume is operating in solution, and we therefore conclude that this process has a relatively low activation barrier, probably <35 kJ mol-1.

The Mechanism of Reduction and Metalation of para Carboranes: The Missing 13‐Vertex MC2B10 Isomer

“…Thirteen‐vertex heteroboranes generally adopt the docosahedral architecture predicted for the (as yet) unknown species [B 13 H 13 ] 2− ,1 although the first 13‐vertex carborane2 and some MC 2 B 10 metallacarboranes3 adopt an alternative henicosahedral structure. In the docosahedron (Scheme ), vertex 1 is of degree four, vertices 4 and 5 are of degree six, and all other vertices are of degree five.…”

“…Thus, reduction and metalation of either 1,2‐ closo ‐C 2 B 10 H 12 or its derivatives affords 4,1,6‐MC 2 B 10 species,5 which can be progressively isomerized to 4,1,8‐ and 4,1,12‐isomers by thermolysis. 4,1,2‐MC 2 B 10 compounds are afforded upon reduction and metalation of C,C‐tethered carboranes 3. Two years ago we extended this list by describing the new isomer 4,1,10‐MC 2 B 10 , formed by reduction and metalation of 1,12‐ closo ‐C 2 B 10 H 12 or its C,C ‐dimethyl analogue 6…”

Supraicosahedral polyhedra in carboranes and metallacarboranes: The role of local vertex environments in determining polyhedral topology and the anomaly of 13-vertex closo polyhedra

“…This converts the docosahedron with 22 triangular faces into a henicosahedron with 20 triangular faces and one trapezoidal face with both carbon atoms now at favored degree 4 vertices, the metal atom at the remaining degree 6 vertex, and all ten boron vertices having the preferred degree of five. Known examples of such cl-13-AEIVae henicosahedral metallaboranes [41] include l-1,2-(CH 2 ) 3 -4-(g 5 -C 5 H 5 )Co-1,2-C 2 B 10 H 10 and l-1,2-(CH 2 ) 3 -4-(g 6 -pcymene)Ru-1,2-C 2 B 10 H 10 .…”

The Mechanism of Reduction and Metalation of para Carboranes: The Missing 13‐Vertex MC2B10 Isomer

“…Thirteen-vertex heteroboranes generally adopt the docosahedral architecture predicted for the (as yet) unknown species [B 13 H 13 ] 2À , [1] although the first 13-vertex carborane [2] and some MC 2 B 10 metallacarboranes [3] adopt an alternative henicosahedral structure. In the docosahedron (Scheme 1), vertex 1 is of degree four, vertices 4 and 5 are of degree six, and all other vertices are of degree five.…”

“…4,1,2-MC 2 B 10 compounds are afforded upon reduction and metalation of C,C-tethered carboranes. [3] Two years ago we extended this list by describing the new isomer 4,1,10-MC 2 B 10 , formed by reduction and metalation of 1,12-closo-C 2 B 10 H 12 or its C,C-dimethyl analogue. [6] The only remaining members of the docosahedral 4,1,x-MC 2 B 10 family are the 4,1,5-and 4,1,11-isomers.…”