Dipnictogen Radical Chemistry: A Dithorium-Supported Distibene Radical Trianion
Jingzhen Du, Kevin Dollberg, John A. Seed, Floriana Tuna, Ashley J. Wooles, Carsten von Hänisch, Stephen T. Liddle
Abstract
High Resolution Image Download MS PowerPoint Slide Although two examples of σ-bonded trans -bent [RSbSbR] •– (R = bulky organo- or Ga-groups) that formally contain the Sb 2 •3– radical trianion moiety are known in p-block chemistry, d- or f-element Sb 2 •3– radical trianion complexes, with or without R-substituents, have remained elusive. Here, we report that reduction of a 77:23 mix of [{Th(Tren TIPS )} 2 (μ-η 2:η 2 -Sb 2 )] ( 3a, Tren TIPS = {N(CH 2 CH 2 NSiPr i 3 ) 3 } 3– ):[{Th(Tren TIPS )} 2 (μ-SbH)] ( 3b ) with 1.5 equiv of KC 8 in the presence of 1.1 equiv of 2.2.2-cryptand yields the emerald green Sb 2 •3– radical complex [K(2.2.2-cryptand)][{Th(Tren TIPS )} 2 (μ-η 2:η 2 -Sb 2 )] ( 4 ), providing an f-block Sb 2 •3– radical trianion complex, and the heaviest actinide-N 2 radical analogue. When the recrystallization conditions are modified, a small crop of red crystals determined to be [K(2.2.2-cryptand)] 3 [{Th(Tren TIPS )(μ-η 3:η 3 -Sb 3 )} 2 (μ-K)] ( 5 ) were also isolated, highlighting the complexity of heavy group 15 homodiatomic reduction chemistry. SQUID magnetometry and EPR spectroscopy suggest that the Sb 2 •3– radical trianion in 4 is fairly well isolated, due to electrostatic binding to Th, with pseudoaxial g -values reflecting the distinctive Sb 2 •3– radical trianion side-on bridging π-bonded coordination mode. Spectroscopically validated computational analysis of 3a and 4 confirms the stronger donating capability, and weaker Sb–Sb bond, of Sb 2 •3– radical trianion compared to the Sb 2 2– dianion form.