this command works: tp @p[x=15,y=64,z=13,r=3] 15 64 17
this command also works: tp Maarten359 15 64 17
but this command doesn't work!:tp Maarten359[x=15,y=64,z=13,r=3] 15 64 17
I tried variations like:tp Maarten359 [x=15,y=64,z=13,r=3] 15 64 17 and: tp @Maarten359[x=15,y=64,z=13,r=3] 15 64 17.
but it still doesn't work. 
what I expected to happen was: this command would work:tp Maarten359[x=15,y=64,z=13,r=3] 15 64 17
what actually happened: nothing
 
      
      
Player selectors (@, then type) are a special syntax. It's not "anything and then [] on the end". It's @a or @p or @r and then [] on the end for extra options.
You cannot specify specific players, and you cannot use player selector arguments with anything other than player selectors.