Synthesis, structure and reactivity of ferrio-chloro-phosphanes, -arsanes and -stibanes [(CO)2(η5-C5Me5)FePn(Cl)R] (Pn = P, As, Sb); R = tetramethylcyclopentadienyl, 2,7-di-tert-butylfluorenyl, 2,7-di-tert-butyl-9-trimethylsilylfluorenyl) as precursor to novel metallo-phosphaalkenes, -arsaalkenes, and -stibaalkenes

Abstract

Reaction of one equivalent of the complexes [FeCp*(CO)₂PnCl₂] (Pn = P, As, Sb) with tetramethylcyclopentadienyllithium afforded compounds [FeCp*(CO)₂{Pn(Cl)(C₅Me₄H)}]. Dehydrochlorination by means of tert-butyllithium led to decomposition. Only in the case of the phosphorus compound was evidence for the initial formation of a phosphaalkene given by ³¹P NMR spectroscopy. Similarly treatment of equimolar amounts of [FeCp*(CO)₂PnCl₂] with 2,7-di-tert-butyl-9-H-fluorenyllithium or 2,7-di-tert-butyl-9-trimethylsilylfluorenyllithium yielded the asymmetrically substituted ferriopnicogenanes [FeCp*(CO)₂{Pn(Cl)-9-R-Fl*}] (Pn = P, As, Sb; R = H, Me₃Si; Fl* = 2,7-di-tert-butylfluorenylidene). Dehydrohalogenation of [FeCp*(CO)₂{Pn(Cl)-9-H-Fl*}] with lithium diisopropylamide resulted in the formation of the anticipated phosphaalkene [FeCp*(CO)₂{P = Fl*}], whereas in the case of the arsenic and antimony derivatives the novel ferriopnicogenanes [FeCp*(CO)₂{Pn(9-H-Fl*)₂}] (Pn = As, Sb) were obtained as products. The new compounds were characterized by elemental analyses and spectra (IR, ¹H, ¹³C, ²⁹Si, ³¹P NMR). The molecular structures of [FeCp*(CO)₂{Pn(Cl)(C₅Me₄H]}] (Pn = As, Sb), [FeCp*(CO)₂{As(Cl)(9-Me₃Si-Fl*)}] and [FeCp*(CO)₂{Sb(9-H-Fl*}₂] were elucidated by single X-ray diffraction analyses.