Untersuchungen an Systemen des Typs PCl3/MCl3/Aren (M = Al, Ga), I. Reaktionen mit Monohalogenbenzolen; Multikern-NMR-spektroskopische Charakterisierung von Aryldichlorhydrogenphosphoniumsalzen; Struktur des para-Fluorphenyldichlorphosphonium-tetrachloroaluminats

Abstract

AbstractThe reactions of the monohalobenzenes with AlCl3 (GaCl3) and PCl3 have been monitored by 31P NMR spectroscopy. Primary product of the reaction with fluorobenzene and AlCl3 is the thermolabile para-fluorophenyldichlorophosphonium tetrachloroaluminate, which was characterized by 1H, 13C, 19F, 27Al and 31P NMR spectroscopy as well as by a crystal structure analysis (space group P21/c, a = 7.0720(10), b = 12.659(3), c = 15.413(3) Å, ß = 90.93(3)°, Z = 4, T = -110 °C). For the phosphonium ion we found a very good agreement of the experimental structural parameters and those obtained by ab initio quantum chemical calculations at the B3LYP 6-31++G(d,p) level of theory. Both, the experimentally determined and the calculated structure show a significant chinoid distortion of the para-disubstituted benzene ring. From the primary product the reaction proceeds to give exclusively para-fluorophenyl-(phenyl)dichlorophosphonium tetrachloroaluminate. With GaCl3 and fluorobenzene analogous tetrachlorogallates were observed, however, some by-products were recognized: para-ftuorophenylchlorofluorophosphonium and para-fluorophenyldifluorophosphonium tetrachlorogallate at the beginning of the reaction, bis(para-fluorophenyl)chlorophosphonium tetrachlorogallate at a later stage of the reaction. The reaction of chlorobenzene with PCl3 and AlCl3 yields analogous products as compared to the reaction with fluorobenzene. However, appreciable amounts of ortho- and some meta-chlorophenyldichlorophosphonium tetrachloroaluminate are by-products. If GaCl3 is used instead of AlCl3, numerous by-products and reaction intermediates are detectable. The major one is para-chlorophenyldihydrogenchlorophosphonium tetrachlorogallate. No principal differences were observed, when AlCl3 and GaCl3, respectively, reacted with bromobenzene and PCl3 giving phenylbromodichlorophosphonium and para-bromophenylbromodichlorophosphonium salts as well as some amounts of the ortho- and meta-bromophenyl derivatives. With iodobenzene the corresponding reactions exclusively give phenyldichloroiodophosphonium tetrachloroaluminate and -gallate, respectively.