Mehrfachbindungen zwischen hauptgruppenelementen und übergangsmetallen

Selenium acts as a bridging ligand between two iron atoms in the novel complex (μ-Se)(η 5 -C 5 H 5 )Fe(CO) 2 ] 2 ( 1 ), obtained in 60% yield from Na + [(η 5 -C 5 H 5 )Fe(CO) 2 ] and Se 2 Cl 2 . 1 displays nucleophilic reactivity towards protic acids (e.g., HBF 4 ·OEt 2 ) and methyl triflate, CF 3 SO 3 CH 3 , thus giving the protonated and methylated ionic species [(μ-SeR)(η 5 -C 5 H 5 )Fe(CO) 2 2 ] + (R = H: 2a , BF 4 salt; R = CH 3 : 2b , PF 6 salt) in quantitative yields. Rapid deprotonation of 2a occurs in the presence of bases such as diethylamine. Analogous protonation and methylation reactions have been observed with the tellurium complex (μ-Te)[(η 5 -C 5 H 5 )Cr(CO) 3 ] 2 ( 3 ); the ionic compounds [(μ-TeH)(η 5 -C 5 H 5 )Cr(CO) 3 2 ]BF 4 ( 4a ) and [(μ-TeCH 3 ) (η 5 -C 5 H 5 )Cr(CO) 3 2 ]PF 6 ( 4a ), respectively, are obtained. In contrast, the electron-deficient tellurium ligand of the manganese complex (μ 3 -Te)[(η 5 -C 5 H 5 )Mn(CO) 2 ] 3 ( 5 ) is neither attacked by Bronsted acids nor by electrophilic methylating agents (e.g., CF 3 SO 3 CH 3 ) but is rather methylated by methyllithium to give the anionic species [(μ 3 -TeCH 3 )η 5 -C 5 H 5 )Mn(CO) 2 3 ] − that can be isolated pure as the PPN + salt 6 .