The reactions of diazomethane, the silylene fragments Me 2 Si and Ph 2 Si, and stannylene fragment Me 2 Sn with the metallophosphenium ion complex CpW(CO) 2 {P(Ph)[N(SiMe 3 ) 2 ]} were examined and the new species Cp(CO) 2 W(ER 2 )P(Ph)[N(SiMe 3 ) 2 ] (ER 2 = CH 2 , SiMe 2 and SiPh 2 ) were isolated and characterized. The molecular structures for the compounds with R 2 E = CH 2 and SiMe 2 were determined by single crystal X-ray diffraction techniques.