MSI files do not have an executable file extension, so the correct command line for installing an MSI silently looks something like this:
C:\Windows\System32\msiexec.exe /i <path>\filename.msi /qn
The section in bold is the executable you call to install any MSI, and the remainder of the line is the argument that needs to be passed to the EXE. The argument can also include any public property settings required by the MSI and any logging options if you want to record the success (or failure) of the silent install.