Driver binary for SAP jConnect 16.0 resides in jconn4.jar. Your application CLASSPATH variable should point to jConnect-16_0/classes/jconn4.jar.
If you are upgrading from SAP jConnect 5.x or 6.x and want to use SAP jConnect 16.0 with an existing application, you may also need to change your application code. See SAP jConnect for JDBC Programmers Reference.