Tantalum isocyanide complexes: Tai(CNDipp)6 (dipp is 2,6-diisopropylphenyl) and ionic [ta(CNDipp)7][ta(CNDipp)6], a formal disproportionation product of the 17-electron ta 0 metalloradical ta(CNDipp)6

William W. Brennessel, Alexander Romanenkov, Victor G. Young, John E. Ellis

Research output: Contribution to journalArticlepeer-review


Treatment of tetraethylammonium hexacarbonyltantalate, [Et 4 N][Ta(CO) 6 ], with 1.1 equivalents of molecular iodine (I 2 ) in tetrahydrofuran (THF) at 200 K, followed by the addition of 6.0 equivalents of 2,6-diisopropylphenyl isocyanide (CNDipp) and slow warming to 293 K over a 24 h period gave the tantalum(I) iodide derivative hexakis(2,6-diisopropylphenyl isocyanide-κC)iodidotantalum(I), [TaI(C 13 H 17 N) 6 ] or TaI(CNDipp) 6 , 1. Recrystallization of this substance from pentane provided deep-red nearly black parallelepipeds of the product, which was characterized by single-crystal X-ray diffraction. Addition of 1 in THF at 200 K to a suspension of an excess (5.8 equivalents) of caesium graphite (CsC 8 ), followed by warming, filtration, and solvent removal, afforded a dark-green oily solid of unknown composition, from which several red–brown rhombohedral plates of the ditantalum salt heptakis(2,6-diisopropylphenyl isocyanide-κC)tantalum hexakis(2,6-diisopropylphenyl isocyanide-κC)tantalate, [Ta(C 13 H 17 N) 7 ][Ta(C 13 H 17 N) 6 ] or [Ta(CNDipp) 7 ][Ta(CNDipp) 6 ], 2, were harvested. Salt 2 is a unique substance, as it is the only known example of a salt containing a homoleptic cation, [ML x ] + , and a homoleptic anion, [ML y ] , with the same transition metal and π-acceptor ligand L. In solution, 2 undergoes full comproportionation to afford the recently reported 17-electron paramagnetic zerovalent tantalum complex Ta(CNDipp) 6 , the only known isolable TaL 6 complex of Ta 0 .

Original languageEnglish (US)
Pages (from-to)135-140
Number of pages6
JournalActa Crystallographica Section C: Structural Chemistry
StatePublished - 2019

Bibliographical note

Funding Information:
Funding for this research was provided by: National Science Foundation and the donors of the Petroleum Research Fund, administered by the American Chemical Society, including an ACS–PRF stipend for AR, an undergraduate student from the Higher Chemical College, Moscow, Russia, in 2001–2002.

Publisher Copyright:
© 2019 International Union of Crystallography.


  • 2,6-diisopropylphenyl
  • Crystal structure
  • Homoleptic
  • Isocyanide
  • Low valent
  • Monocapped trigonal prism
  • Seven-coordinate
  • Tantalum


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