no viable alternative at character ']' when updating columnfamily
===

I'm new to Cassandra, but am trying to update a column family to have secondary indexes on some of the columns.  After creating my column family, I run the following line of code:

    db.ExecuteNonQuery("CREATE COLUMN FAMILY Targets with comparator = UTF8Type and column_metadata=[{column_name: Age, validation_class: UTF8Type, index_type: KEYS}];");

The problem is I get the following error:<br>
**line 1:141 no viable alternative at character ']'**

I can run that exact statement using the CLI without any issues.

Suggestions?