Synthesis and characterization of tantalum(V) dicarbollide complexes

Cp*TaCl2B4H8: synthesis, crystal structure and spectroscopic characterization of an air-stable, electronically unsaturated, chiral tantalaborane

“…Although 1 is unique in being an unsaturated cluster featuring a single metal atom, the electronic factors underlying its apparent stability, the high-lying nature of the metal d orbitals and their ability to overlap well with borane-based orbitals, have much in common 8 but a significantly shorter direct Ta-B linkage (2.249 vs. 2.37 Å). The Ta-B bond is also decidedly shorter than those found in h 5 bound tantalum carborane complexes (which are typically in the range 2.4-2.5 Å), 11,13,14 but of similar length to that found in both isomers of the h 1 complex Cp 2 Ta(H) 2 (BO 2 C 6 H 4 ) (2.263, 2.295 Å 12 ).…”

“…An alternative view of 1 is as a 16-electron organometallic complex containing either a d 0 Ta V centre coordinated to a sixelectron B 4 H 8 22 ligand or a Ta III 13 or (Me 3 -Si) 2 C 2 B 4 H 4 14 ]. In contrast to these carborane complexes, however, 1 is chiral with the plane of mirror symmetry present in other 2-metallapentaboranes such as 2-CpCoB 4 H 8 9 being eliminated by the non-symmetrical distribution of ligands about the tantalum centre (see Fig.…”

The VCD method – a simple and reliable way to distinguish cage C and B atoms in (hetero)carborane structures determined crystallographically

“…For L = π-donor ligand one L is located approximately trans to the C-C connectivity whilst for L = π-acceptor ligand one L eclipses this connectivity. The structures VUPBAJ (L = Cl, M = Ta) 92 and KISCEU (L = CO, M = Fe) 93 are typical (Fig. 7a and 7b respectively).…”

Do the discrete dianions C2B9H112− exist? Characterisation of alkali metal salts of the 11-vertex nido dicarboranes, C2B9H112−, in solution

“…This procedure was adapted from the reported synthesis of the di-lithium salt Li 2 (7,8 The Me 3 NH ϩ salt of 7,9-C 2 B 9 H 12 Ϫ (0.3 g, 1.5 mmol) was stirred under N 2 in 20 ml of an 1 : 1 ratio mixture of anhydrous Et 2 O : toluene. A solution of BuLi (1.6 M in hexane, 1.9 ml, 3 mmol) was added dropwise at 0 ЊC, and the mixture was then stirred for a further 24 h at ambient temperature, then finally refluxed for 4 h. The reaction mixture was then cooled, the solvent was removed under reduced pressure and the residue dried under vacuum (0.05 mmHg) for 1 h. Anhydrous hexane (10 ml) was added to the white residue, the suspension was stirred for 1 h and the hexane solution was then removed using a cannula.…”

“…6 However, characterisation data on these air-sensitive salts are sparse. In fact the only reported characterising data for the alkali metal salts M 2 C 2 B 9 H 11 are the 11 B and 1 H NMR data in THF-d 8 for Li 2 (7,8-C 2 B 9 H 11 ) 1, the 11 B NMR spectrum showing resonances in a 3 : 3 : 2 : 1 ratio, 7 and the 11 B NMR spectrum of Na 2 (7,8-C 2 B 9 H 11 ) 2 in THF which shows four resonances in a 6 : 1 : 1 : 1 ratio, with the chemical shifts not reported. 8 The differing 11 B NMR patterns reported for salts containing different cations with the same dianion 7,8-C 2 B 9 H 11 2Ϫ suggest some interaction between the dianion and cation.…”