# Synthesis of a tungsten carbene bromide from [CpW(CO)3]-

I'm currently working through past test and exam papers in order to prepare for my organometallic test at the end of the month, but unfortunately I've gotten stuck on the following question.

Since I don't know how to build molecules on here, I've attached a screenshot of the question.

The biggest problem I have is getting the Br coordinated to the metal while I already have my alkyl $\ce{(CH2CH2CH2Br)}$ bonded to one of the carbonyls. I don't know what reagent to use to get it on there. One idea I have is using $\ce{NaBH4}$ to get a hydride onto Tungsten, then I use R-Br (where R is some alkyl) to essentially swap the H with the Br and form as a by-product, R-H, but I'm not sure if this would work. Below is my complete synthesis.

EDIT: I spoke to my professor and it was unnecessary for me to remove the $\ce{Br-}$ in one of the earlier steps. That $\ce{Br-}$ would've attacked the metal centre later on and the rest of the steps would be elementary.