12‐Vertex Zwitterionic Bis‐phosphonium‐nido‐carborates through Ring‐Opening Reactions of 1, 2‐Diphosphetanes. Issue 23 (26th March 2018)

• Record Type: Journal Article
• Authors: Schulz, Jan; Kreienbrink, Anika; Coburger, Peter; Schwarze, Benedikt; Grell, Toni; Lönnecke, Peter; Hey‐Hawkins, Evamarie
• Is Part Of: Chemistry. Volume 24:Issue 23(2018)
• Page Start: 6208
• Page End: 6216
• Publication Date: 2018-03-26
• Subjects: carboranes -- heterocycles -- phosphorus -- reactive intermediates -- zwitterions; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201800172
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: Carborane‐substituted 1, 2‐diphosphetanes (Ia, b ) react with elemental lithium in THF with cleavage of the P−P bond to give a deep red solution from which, in the case ofIa, red crystals of a lithiated intermediate, [{1‐Li(THF)P t Bu‐6‐P t Bu‐4, 1, 6‐ closo ‐Li(THF)C2 B10 H10 }{Li(THF)3 }]2 ⋅ 2 THF (2 a ), are obtained. The compound is dimeric, C 2 ‐symmetric and contains six lithium and four phosphorus atoms. Two lithium atoms cap the six‐membered C2 B4 faces, resulting in two 13‐vertex closo ‐clusters (according to Wade's rules) with docosahedral geometry. The addition of methyl iodide resulted in the formation of zwitterionic bis‐phosphonium‐ nido ‐carborates 7, 10‐bis( tert ‐butyldimethylphosphonium)dodecahydro‐7, 10‐dicarba‐ nido ‐dodecaborate(2−) (1 a ) and 7, 10‐bis( N, N ‐diisopropylaminodimethylphosphonium)dodecahydro‐7, 10‐dicarba‐ nido ‐dodecaborate(2−) (1 b ) in moderate to good yields. Compounds1 a and1 b exhibit short Ccluster −P bonds and large Ccluster ⋅⋅⋅Ccluster distances in the solid state. Further insight into the ring opening and reduction potential of the alkyl halide was obtained from methylation reactions of different 1, 2‐bis‐phosphinocarboranes. The reaction of rac ‐/ meso ‐1, 2‐bis( tert ‐butylmethylphosphino)‐1, 2‐dicarba‐ closo ‐dodecaborane(12) (3 a ) with two equivalents of methyl iodide also resulted in the formation of1 a (as shown by NMR spectroscopy), whereas the reaction of 1, 2‐bis(diphenylphosphino)‐1, 2‐dicarba‐ closo ‐dodecaborane(12) with methyl triflate afforded the phosphonium salt 1‐methyl‐diphenylphosphonium‐2‐diphenylphosphino‐1, 2‐dicarba‐ closo ‐dodecaborane(12) triflate (4 ) without reduction of the cluster. Abstract : Creating clusters : Two zwitterionic 12‐vertex bis‐phosphonium‐ nido ‐carborates were obtained through a ring‐opening reaction and subsequent methylation of 1, 2‐diphosphetanes with lithium and methyl iodide (see figure). Additionally, the lithiated intermediate was isolated and DFT calculations provided insight into reactions with nucleophiles and electrophiles.