<C-6> is a normal mapping (I guess you want to switch to alternate buffer).
But the way you call it is incorrect -- calling it as an ex-command. Normal mode commands in vimscript should be called with
:normal! sequenceofkeypresses. For
<C-6> it would be
:normal ^^ where
^^ is generated by pressing
<C-v><C-6>. Even more, with
normal you would have issues using
<bar> and would have to wrap it into
:exe "normal ..." as described in
Having said this, it would be way easier to use
b# command to do the same...
nnoremap <silent><Leader>bd :b#<Bar>bd#<CR>
:b# is short for
:buffer # -- switch to alternate buffer.
And to answer your direct question you can map it like this:
nnoremap <silent><leader>bd <C-6>:bd #<CR>
nnoremap is used instead of
noremap -- map only for normal mode. I doubt you want this mapping to work in insert/select/visual modes. If you do, then you have to change it per mode (they should be slightly different)
<C-6> is executed in the same normal mode, so no
normal ex command is needed