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Air‐Stable Trifluorophosphoranes: Preparation, X‐Ray Crystal Structure Determinations, and Reactions
Author(s) -
Plack Volker,
R. Goerlich Jens,
Thönnessen Holger,
G. Jones Peter,
Schmutzler Reinhard
Publication year - 1999
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/(sici)1521-3749(199908)625:8<1278::aid-zaac1278>3.0.co;2-o
Subject(s) - chemistry , pseudorotation , trigonal bipyramidal molecular geometry , toluene , crystal structure , crystallography , ether , halogen , nuclear magnetic resonance spectroscopy , oxidative addition , medicinal chemistry , stereochemistry , molecule , organic chemistry , catalysis , alkyl
The trifluorophosphoranes TrtRPF 3 (R = tert. ‐Bu ( 1 ), Ph ( 2 ), NEt 2 ( 3 )) were obtained by the oxidative addition of TrtF (Trt = triphenylmethyl) to the difluorophosphines RPF 2 . At room temperature only 1 exhibited dynamic behaviour in solution, but at –5 °C the pseudorotation was slow enough to permit the differentiation of 1 J (PF ax ) and 1 J (PF eq ) by 31 P NMR spectroscopy. X‐ray structure analyses of 1 , 2 , and 3 confirm the expected trigonal bipyramidal geometry at phosphorus, with axial fluorine substituents. The trifluorophosphoranes 1 – 3 are of such stability towards water that hydrolysis was effected only under vigorous, basic conditions. The action of HCl or HBr on Trt(NEt 2 )PF 3 ( 3 ) led, in a complex reaction, to the formation of TrtPF 4 ( 5 ), besides 3 and PF 3 . As first observed for 1 by NMR spectroscopy at elevated temperature, in the case of 1 and 2 an equilibrium exists between TrtRPF 3 and TrtF/RPF 2 . Accordingly, it was possible to trap TrtF or RPF 2 by addition of I 2 , PCl 3 , AlCl 3 , and tetrachloro‐ o ‐benzoquinone (TOB) to solutions of 1 or 2 . 3 was unreactive towards I 2 and PCl 3 , whereas treatment with AlCl 3 caused formation of (Et 2 N)PCl 2 by cleavage of the P–C bond, and halogen exchange. If a mixture of toluene and ether was used, LiAlH 4 reduced 1 and 2 to the corresponding secondary phosphines 8 and 9 , while if only diethyl ether was employed under the same conditions, P–C bond rupture occurred in 2 , and a mixture of PhPH 2 and TrtH was obtained.