Tantalum organometallic compounds: Analysis and classification of crystallographic data

Niobium and Tantalum

“…1 The reader is referred to that chapter for a thorough introduction to this area, for an excellent historical context, for discussion o f the unusual NMR properties o f niobium complexes, and for the exhaustive collection o f organometallic compounds reported through 1980. Reviews o f the structural chemistry o f niobium 2 and tantalum 3 are also of note. The Dictionary of Organometallic Compounds, first published in 1984, provides a valuable compilation of niobium and tantalum compounds 4 in a series supplemented with annual updates.…”

“…However, recently isolated complexes Ag 3 M 3 (CO) 12 (dmpe) 3 (1) do appear to contain M° [M(CO) 4 (dmpe)] units which are loosely coordinated to a trinuclear metallic silver cluster, 18 and completely substituted Ta(dmpe) 3 has been described. 37 In spite o f the lack of neutral carbonyls, salts of the 18-electron anions [M(C0) 6 ]~ are readily accessible and constitute useful precursors in carbonyl chemistry.…”

“…These species are prepared by reductive carbonylation of (rj-C 5 R 5 )MC1 4 (using Na or Zn) under high CO pressures, often in the presence of aluminum-copper as halogen acceptor, 40 ' 41 although a low-pressure route has been reported. Thus, high yields of CpM(CO) 4 can also be obtained from reacting dinuclear [M 2 (u-X) 3 (CO) 8 ]~ with LiCp. 17 (rj-C 5 R 5 )M(CO) 4 compounds exhibit a rich reactivity; like [M(CO) 6 ]~, (r|-C 5 R 5 )M(CO) 4 species undergo both oxidation and reduction.…”

“…127 The mechanism o f carbon-carbon bond formation in this reaction, particularly any identifiable intermediate species, is of obvious interest with respect to Fischer-Tropsch (F-T) chemistry. Thus, when the more sterically bulky electrophile Pr' 3 SiCl is added to a solution o f Na[Ta(CO) 2 (dmpe) 2 ], the plum-red carbyne complex Ta(=COSiPr' 3 )(dmpe) 2 (CO) (3) can be isolated in high yield. 1 Upon reaction o f (3) with TMS-C1, coupling of the carbyne and carbonyl ligands ensues to provide Ta(Pr' 3 SiOC=CO-TMS)(dmpe) 2 Cl (4), thereby supporting the intermediacy o f (3) in the formation o f the alkyne complexes.…”

Synthesis and Characterization of Niobium (V) and Tantalum(V) Chelates with 2-aminothiophenol and 2-aminophenol

“…These d°-complexes have no stereochemical preferences and exhibit a variety of coordination numbers [2][3][4] having very interesting insights into structure and bonding [5][6][7] . Some hexacoordinate complexes with thioamide ligands are reported in our earlier paper [8][9][10][11] .…”