not add export csv and xls

Hello,
I use DataTables way of dynamic sql connection.
I would like to add buttons export csv and xml, but it does not appear.
Or am I mistaken me.

		oTable = $('#tbl_result').dataTable( 
		{
			"sDom": 'T<"top"fl>rt<"bottom"pi>' ,
			"sPaginationType": "full_numbers",
			"bAutoWidth"	: false,	
			"bProcessing": true,
			"bSortClasses" 	: false, 
			"iDisplayLength": 15,
			"bStateSave"	: false,	
			"bServerSide": true,
			"oLanguage": {
				"sUrl": "/includes/js/DataTables.fr.js"
			},
			"sAjaxSource": "sql-objects.php",
		   "oTableTools": {
				"aButtons": [ "csv", "xls" ],
				{
					"aButtons":    [ "csv", "xls", "" ]
					"sExtends":    "collection",
				}
			}, 
			"fnRowCallback": function( nRow, aData, iDataIndex ) 
			{
				$('td:eq(1)', nRow).html( DateFr(aData['date']) ) ;
				$('td:eq(2)', nRow).html( ( aData['etat'] == '0' ? 'Inscrit' :  'En attente') ) ;
				$('td:eq(3)', nRow).html( '<a user="' + aData['mail'] + '" class="delete" href="?id_abonne='+ aData['mail'] +'"><img border="0" class="icon16 infobulle" src="/back_office/images/template/icon16-delete.png"></a>');
			},
			"aoColumns"		:
			[
				{ "mData": "mail" },
				{ "mData": "date" },
				{ "mData": "etat" },
				{ "mData": "cle", "bSortable": false}
			],
			"aaSorting"		:
			[
				[0,'desc']
			]
		});

thank you