Pentamethylcyclopentadienylselenium derivatives IV. Synthesis and characterisation of methyl(pentamethylcyclopentadienyl) selenium and its pentacarbonyltungsten complex [W(CO)5{Se(C5Me5)Me}]

The novel alkyl(pentamethylcyclopentadienyl)selenium derivative Se(C 5 Me 5 )Me has been prepared by treatment of LiC 5 Me 5 sequentially with Se and MeI. It reacts with [W(CO) 5 THF] to form [W(CO) 5 {Se(C 5 Me 5 )Me}]. Spectroscopic characterisation of the new compounds includes the measurement of the first reported value for the coupling constant 1 J ( 77 Se- 183 W).