Preparation of the First Ditantalum(III) Complex Containing a Ta−Ta Bond without Bridging Ligands

Abstract

Anionic organic amides have proven to be versatile ligands in the chemistry of di-and trivalent vanadium. In addition to the stabilization of rare V-N 2 -V moieties, 1 these ligands can be involved in a number of vanadium metal center mediated transformations which include C-H σ-bond metathesis, 2 Htransfer, 3 dinitrogen cleavage, 4 azide coordination, 5 stabilization of alkyl groups, 6 and formation of metallacycles. 7 These observations prompted us to study the chemistry of low-valent niobium and tantalum amides for which only little information is available in terms of preparation and characterization. 8 We have recently reported that the reaction of [NbCl 4 (THF) 2 ] with Cy 2 NLi affords a Nb(V) niobaaziridine complex where the metallacycle is formed Via C-H σ-bond activation. 9 Given the potential offered by this type of reactivity, we are currently attempting to expand the accessibility to medium-valent Taamide derivatives through preparation of complexes with the formula [(R 2 N) n TaCl (5-n) ], which may work as a starting material for further reduction. In this paper, we describe our preliminary observations. The reaction of TaCl 5 with 4 equiv of Cy 2 NLi in diethyl ether at -78°C gave, upon mixing, an instantaneous color change and formation of a brown-reddish mixture. 10 After elimination

Chemistry of Group 4 metals supported by carbazole ligation

“…This distance is slightly longer (ca. 0.05 Å) than the Ti-N values of 1.912(9) and 1.923( 14) Å reported for the related compound 113.29 (7) 93.17 [Zr(cb-3Bu t ) 2 (NMe 2 ) 2 (NHMe 2 )] 2. To a toluene solution (20 mL) of [Zr(NMe 2 ) 4 ] (1.00 g, 3.74 mmol) was added 3-tertbutylcarbazole (1.75 g, 7.84 mmol).…”

“…[2][3][4] Within this context the search for new types of amido ligation is also a rapidly expanding area of chemistry with chelating, tripodal and hybrid metalloceneamide ligands all being developed to support novel organometallic and inorganic chemistry at early transition metal centers. [5][6][7][8][9][10][11][12] In the context of this background we have been exploring the inorganic and in particular organometallic chemistry of ligands derived from the carbazole (cbH) nucleus. This is a class of ligands that have so far been underutilized.…”

Tantallaaziridines: from synthesis to catalytic applications

“…While these early reports suggested the formation of such tantallaaziridines, it took 18 years before the first tantallaaziridines generated via β-H abstraction could be crystallographically characterized. 51 Following upon this synthetic strategy, it was established that alkane elimination is a high-yielding and reliable synthetic approach for the synthesis of early transition metallaaziridines generally. 43,52,53 For example, Bercaw and co-workers established that Cp*Ta(NMe 2 )Me 3 is stable and isolable at temperatures below 0 °C, but at room temperature undergoes β-H abstraction to generate methane and a tantallaaziridine (Scheme 13).…”

Highlights in the Renaissance of Amidometal Chemistry

“…Noteworthy is the first ditantalum complex with a Ta À Ta bond which is not stabilized by further bridging ligands. [192] A homobimetal complex with an unbridged TaÀTa bond is formed in the reaction of TaCl 5 with four equivalents of LiNCy 2 . The metal ± metal distance is 2.8484(7) .…”