Having a full name in single column may be really a can of worms!

When you are sure both first and last names are always single names, you can use worksheet formulas - no need for VBA:
a) for leftmost name
=LEFT($A2,IF(ISERROR(FIND(" ",$A2;1)),LEN($A2),FIND(" ",$A2,1)))
b) for rightmost name
=IF(ISERROR(FIND(" ",$A2,1)),"",MID($A2,FIND("|",IF(ISERROR(FIND( " ",$A2,1)),"",SUBSTITUTE($A2," ","|",FIND(" ",$A2,1)-1)))+1,250))

When there is only a single name in FullName column ($A), the 2nd formula returns an empty string.
Instead of character "|" you can use any other character not being used in any of names.

Of course the formulas aren't helping when people have many-part first names (NB! Not first and middle names, but several first names!) or many-part last names (p.e. some women add husbands family name to her maiden family name) - but then doesn't VBA help too. And I hate to think about Spanish names at all