AddControl does not show content filled in textarea using jQuery

Question

When i have a textarea in a page that i fill with jQuery and i then create an editor instance using mceAddControl the old value of the textarea gets displayed in the editor an not the filled in one. Why is that so? What can i do before initialization to get the filled in String taken into the editor?

Code:

$('#content_2').html('new Content); // content_2 is the textarea id


tinymce.execCommand('mceAddControl',true,'content_2');