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12‐Vertex Zwitterionic Bis‐phosphonium‐ nido ‐carborates through Ring‐Opening Reactions of 1,2‐Diphosphetanes
Author(s) -
Schulz Jan,
Kreienbrink Anika,
Coburger Peter,
Schwarze Benedikt,
Grell Toni,
Lönnecke Peter,
HeyHawkins Evamarie
Publication year - 2018
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201800172
Subject(s) - chemistry , phosphonium , iodide , methyl iodide , medicinal chemistry , alkyl , carborane , halide , lithium (medication) , geminal , stereochemistry , crystallography , polymer chemistry , inorganic chemistry , organic chemistry , medicine , endocrinology
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 of Ia , red crystals of a lithiated intermediate, [{1‐Li(THF)P t Bu‐6‐P t Bu‐4,1,6‐ closo ‐Li(THF)C 2 B 10 H 10 }{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 C 2 B 4 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. Compounds 1 a and 1 b exhibit short C cluster −P bonds and large C cluster ⋅⋅⋅C cluster 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 of 1 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.