N-Heterocyclic carbene adducts of the heavier group 15 tribromides. Normal to abnormal isomerism and bromide ion abstraction. Issue 36 (2nd August 2017)

• Record Type: Journal Article
• Authors: Waters, Jordan B.; Chen, Qien; Everitt, Thomas A.; Goicoechea, Jose M.
• Is Part Of: Dalton transactions. Volume 46:Issue 36(2017)
• Page Start: 12053
• Page End: 12066
• Publication Date: 2017-08-02
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c7dt02431b
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : The reactivity of the heavier group 15 tribromides, SbBr3 and BiBr3, towards 1, 3-bis(2, 6-diisopropylphenyl)-imidazol-2-ylidene (IPr) is described. Abstract : The reactivity of the heavier group 15 tribromides, SbBr3 and BiBr3, towards 1, 3-bis(2, 6-diisopropylphenyl)-imidazol-2-ylidene (IPr) is described. These reactions quantitatively afford Lewis acid–base adducts, (IPr)EBr3 (E = Sb1 ; Bi2 ), which readily react with AlBr3 yielding cationic species [(IPr)EBr2 ] + (E = Sb3 ; Bi4 ). Under thermal treatment, the N-heterocyclic carbene ligands in1 and2 will readily isomerise to afford the abnormally-bonded (or mesoionic) complexes (aIPr)EBr3 (E = Sb5 ; Bi6 ). As with1 and2, bromide abstraction from such compounds readily affords the cationic complexes [(aIPr)EBr2 ] + (E = Sb7 ; Bi8 ). Finally, in an effort to elucidate the isomerisation process which allows for the conversion of1 and2 to the abnormally bonded systems (compounds5 and6 ), compound1 was reacted with a further equivalent of IPr to afford the cationic species [(aIPr)2 SbBr2 ] + (9 ). This strongly suggests that the normal to abnormal isomerisation of the N-heterocylic carbene ligands in compounds1 and2 is mediated by the presence of free IPr. Compound [9 ]Br can be used to access the dicationic species [(aIPr)2 SbBr] 2+ (10 ), which we have identified spectroscopically. Single crystal X-ray structures and spectroscopic data for all compounds are discussed.