Synthesis, structure and reactivity of highly functionalized arsanyl- and stibanyl-diazomethanes

Reaction of the ferriophosphane and ferrioarsane [Cp*(CO)2FeE(SiMe3){C(OSiMe3)CPh2}] (2a, E=P; 2b, E=As) with an equimolar amount of hexachloroethane proceeded smoothly to afford the chlorinated derivatives [Cp*(CO)2FeE(Cl){C(OSiMe3)CPh2}] (3a, E=P; 3b, E=As). Only 3b could be converted into the pnictogen functionalized diazoalkane [Cp*(CO)2FeAs{C(N2)SiMe3}{C(OSiMe3)CPh2}] (4b) by treatment with LiC(N2)SiMe3. Upon gentle heating or irradiation, compound 4b as well as its antimony analogue 4c proved to be inert towards N2-extrusion. Diazoalkane 4c and dialkyl acetylenedicarboxylates underwent [3+2] cycloadditions with the result of the (1-pyrazolyl)stibanes 9c and 9d. This process involved a sigmatropic migration of the antimony fragment from carbon to nitrogen. The novel products were characterized by elemental analyses and spectra (IR, 1H-, 13C-, 29Si-, 31P-NMR). In addition the diazoalkanes 4b and 4c as well as the (1-pyrazolyl)stibane 9d were subjected to single crystal X-ray structure determinations.