You cannot specify datafile for table creation as datafile is at physical level and table, tablespaces are at logical level. Seems you have the same kinda scenario what I have mentioned in the following thread.
The only option you have is reorganizing your tablespace. either using exp/imp or OEM REORG utility.
The first datafile may be fragmented, for which it is not able to create the initial extent.You can find out from the dba_free_space view, the no. of continous free space available.Since there is no continous free space of 400 MB it is giving this problem.
If you have another datafile in which the continous space is available, you can specify after the table creation the datafile the table has to use, using the :
alter table <tablename> allocate extent 'datafile' size;