INVESTIGATIONS ON SYSTEMS OF THE TYPE PCL3 MCL3/ARENE (M = AL, GA), I- REACTIONS WITH MONOHALOBENZENES - MULTINUCLEAR NMR SPECTROSCOPIC CHARACTERIZATION OF ARYLDICHLOROHYDROGENPHOSPHONIUM SALTS - CRYSTAL-STRUCTURE OF PARA-FLUOROPHENYLDICHLOROPHOSPHONIUM TETRACHLOROALUMINATE/

The reactions of the monohalobenzenes with AlCl3 (GaCl3) and PCl3 have been monitored by P-31 NMR spectroscopy. Primary product of the react ion with fluorobenzene and AlCl3 is the thermolabile para-fluorophenyl dichlorophosphonium tetrachloroaluminate, which was characterized by H -1, C-13, F-19, Al-27 and P-31 NMR spectroscopy as well as by a crysta l structure analysis (space group P2(1)/c, a = 7.0720(10), b = 12.659( 3), c = 15.413(3) Angstrom, beta = 90.93(3)degrees, Z = 4, T = -110 de grees C). For the phosphonium ion we found a very good agreement of th e experimental structural parameters and those obtained by ab initio q uantum chemical calculations at the B3LYP 6-31++G(d,p) level of theory . Both, the experimentally determined and the calculated structure sho w a significant chinoid distortion of the para-disubstituted benzene r ing. From the primary product the reaction proceeds to give exclusivel y para-fluorophenyl(phenyl)dichlorophosphonium tetrachloroaluminate. W ith GaCl3 and fluorobenzene analogous tetrachlorogallates were observe d, however, some by-products were recognized: para-fluorophenylchlorof luorophosphonium and para-fluorophenyldifluorophosphonium tetrachlorog allate at the beginning of the reaction, bis(para-fluorophenyl)chlorop hosphonium tetrachlorogallate at a later stage of the reaction. The re action of chlorobenzene with PCl3 and AlCl3 yields analogous products as compared to the reaction with fluorobenzene. However, appreciable a mounts of ortho- and some meta-chlorophenyldichlorophosphonium tetrach loroaluminate are by-products. If GaCl3 is used instead of AlCl3, nume rous by-products and reaction intermediates are detectable. The major one is para-chlorophenyldihydrogenchlorophosphonium tetrachlorogallate . No principal differences were observed, when AlCl3 and GaCl3, respec tively, reacted with bromobenzene and PCl3 giving phenylbromodichlorop hosphonium and para-bromophenylbromodichlorophosphonium salts as well as some amounts of the ortho- and meta-bromophenyl derivatives. With i odobenzene the corresponding reactions exclusively give phenyldichloro iodophosphonium tetrachloroaluminate and -gallate, respectively.