Alkyl and Alkylidene Tantalum−Lithium Complexes Supported by an Anionic Triazacyclononane Ligand

Abstract

A new i Pr 2 -tacn --supported alkyl tantalum species, (Me 3 SiCH 2 ) 2 (RNd)Ta(µ-CH 2 SiMe 3 )(µ-η 1 :η 3 -i Pr 2tacn)Li (R ) 2,6-i Pr 2 C 6 H 3 ; 2), was synthesized and found to undergo R-H abstraction under gentle heating to form the alkylidene (Me 3 SiCH 2 )(RNd)Ta(µ-CHSiMe 3 )(µ-η 1 :η 3i Pr 2 -tacn)Li ( 3). The syntheses and crystal structures of 2 and 3 and their precursor (( i Pr 2 -tacn)TaCl 2 (dNR) (1)) are described, as well as kinetic data for the first-order thermolysis reaction producing 3.

Lability of Ta–NHC adducts as a synthetic route towards heterobimetallic Ta/Rh complexes

“…The tantalum core adopts a pseudo-tetrahedral geometry (τ4 = 0.95) which is typical for 4coordinate d 0 Ta(V) complexes. 50,51 As expected, the Ta=Calkylidene bond length (1.90(1) Å) is significantly shorter than the Ta-Calkyl distances (2.14(1) and 2.156(1) Å), and falls in the expected range. 23,[36][37][38][39][40]52 The Rh centre adopts a square-planar coordination geometry (τ4 = 0.09) which is characteristic for 4-coordinate 16valency electrons Rh(I) species.…”

Heterobimetallic Pd–K carbene complexes via one-electron reductions of palladium radical carbenes

“…Heterobimetallic carbene complexes 73 , 74 containing K–C carbene –M units, in which the carbene is not stabilized by adjacent heteroatoms, are rare; 23 , 75 to the best of our knowledge, complexes 4 and 5 represent the only known characterized heterobimetallic carbene species possessing such binding motifs. The successful synthesis of amide substituted carbene complexes 4 and 5 from the radical precursor 1 prompted us to investigate other nucleophiles, especially those featuring an alkyl group.…”

Anionic triazacyclononanes: new supporting ligands in main group and transition metal organometallic chemistry

“…5 Using related methodology, a close analog was prepared independently. 26,27 Treatment of (THF) 2 TaCl 3 (NNAr) [Ar = 2,6-i Pr 2 C 6 H 3 ] with i Pr 2 tacnLi gave ( i Pr 2 tacn)TaCl 2 (NNAr) in moderate yield as a yellow, crystalline solid (Scheme 7). The reactivity of this complex has been extensively investigated for comparison to the Zr tacn complexes described above and to group 4 metallocene chemistry.…”