The first transition metal complex of a silaborate, 7-methyl-7-sila-nido-undecaborate(1 À ) (MeSiB 10 H 12 À ), a derivative of the higher homologue of the carbollide ligand, was described only two years ago. [1] In analogy to the carbon-containing cluster, the silaborate ligand will be referred to as a silollide ligand in the following. The known coordination modes of various complexes of this type that have been characterized by single-crystal structure analyses are depicted in Scheme 1.
Scheme 1. Coordination modes of 7-methyl-7-sila-nido-undecaborate(1 À ).
Type A resembles the typical h 5 coordination mode, as known for many complexes of the dicarbollide (nido-C 2 B 9 H 12 À ) [2] and carbollide (nido-CB 10 H 13 À ) [3, ligands and as is found in the mixed sandwich anions [Cp*M-(MeSiB 10 H 10 )] À (M Co, Rh, Ir) and the carbonyl complexes [(CO) 3 M(MeSiB 10 H 10 )] À (M Ru, Fe). [6] Both coordination types B and C are observed in the dinuclear complex [NBu 4 ] 2 [{HFe(MeSiB 10 H 10 )} 2 ]. [1] Herein we will describe compounds of type D which display a hitherto unknown coordination pattern in borane and heteroborane chemistry that results from an unexpected B,H activation.
Jordan [7] and co-workers adapted a method of Chandra and Lappert for the synthesis of dicarbollide complexes from transition metal amides. Application of the same reaction to the silollide ligand yields the highly air-and moisture-sensitive metallasilaborates [NEt 4 ][Nb(MeSiB 10 H 10 )-(NMe 2 ) 3 ] (1) and [NEt 4 ][Ta(MeSiB 10 H 10 )(NMe 2 ) 3 ] (2) from [nido-MeSiB 10 H 12 ] À and [Nb(NMe 2 ) 5 ] or [Ta(NMe 2 ) 5 ] [Eq. (1)]. The reaction is almost quantitative according to NMR spectroscopy.
The liquified gasses (ethene, propene, 1-butene) were first condensed into a steel cylinder and then introduced into the autoclave under pressure.
All products were unambiguously identified by GC/MS. After distillation of the products NMR spectra consistent with literature information were obtained.