IF statement is not formatted correctly and not sure how to fix

I am trying to set the startDate of the query to fiirst_completed based on a set of 'if true' conditions. I am getting an error that the syntax is wrong.
I am open to suggestions on how to do this.
I am including the entire query that I am working with as well as the piece separately that is giving me trouble.

specific part of query that is throwing an error

SELECT 
    IF (coolingHours is null AND rowNum = min(rowNum) THEN ''',startDate,''':= first_completed END IF, 
    rowNum,l.logId,l.completed,l.next_completed,l.first_completed,
    isError,charge,totalTimeRange,startingDate,endingDate,coolingHours,
    databaseName,i.name,l.itemId, kwDifference, cost, costT,l.details,timeInSeconds
  FROM tempTable3 l
   inner join items i ON l.logId = i.logId AND i.name LIKE ''%KW PRE%'' 
   WHERE l.itemId = ''',myItemId,'''
        AND completed BETWEEN ''', startDate, ''' AND ''', endDate, '''

Select allOpen in new window

full query

DECLARE startDate VARCHAR (50);
  DECLARE endDate   VARCHAR (50);
  DECLARE mylogID   INT;
  DECLARE myItemId varchar (50);
  DECLARE myItemId2 varchar (50);
  DECLARE xHours varchar (50);

  SET startDate = FROM_UNIXTIME(fromDate/1000);
  SET endDate   = FROM_UNIXTIME(toDate/1000);
  SET mylogID   = (SELECT logID FROM logs WHERE details LIKE 'FCT%' LIMIT 1);
  SET myItemID = (SELECT i.itemId FROM items i  WHERE i.name LIKE '%KW PRE%');
  SET myItemID2 = (SELECT i.itemId FROM items i  WHERE  i.name LIKE '%KW STA%');

  SET @sql = NULL;
  SET @sql = CONCAT(
 'CREATE TEMPORARY TABLE tempTable3 AS (SELECT
    @row := @row + 1 AS rownum,
    a.logId,
    L1.recordId,
    L2.recordId AS next_recordId,
    L1.completed,
    L2.completed AS next_completed,
    L3.completed AS first_completed,
    L1.activityId AS activityJoin,
    L2.activityId AS next_activityId,
    IF(L1.activityId = L2.activityId, 1, NULL) AS isError,
     CASE
        when a.name LIKE ''%Enable%'' THEN time_to_sec(timediff(L2.completed, L1.completed)) / 3600
        ELSE NULL
        END AS coolingHours,
     TO_SECONDS(L2.completed) - TO_SECONDS(L1.completed) AS timeInSeconds,
    ((SUBSTR(l.details, INSTR(l.details, '':'') + 1))) AS charge,
    time_to_sec(timediff(''', endDate, ''', ''', startDate, ''')) / 3600 AS totalTimeRange,
    CONVERT_TZ(''', startDate, ''', ''UTC'', ''US/Pacific'') AS startingDate, 
    CONVERT_TZ(''', endDate, ''', ''UTC'', ''US/Pacific'') AS endingDate,
    ((L1.item', myItemID, ' - L1.item', myItemID2, ') * 
        (TIME_TO_SEC(TIMEDIFF(L2.completed, L1.completed)))) / 3600 AS kwDifference,
    ((L1.item', myItemID, ' - L1.item', myItemID2, ') * (SUBSTR(l.details, INSTR(l.details, '':'') + 1))) AS cost,
    ((((L1.item', myItemID, ' - L1.item', myItemID2, ') * (SUBSTR(l.details, INSTR(l.details,'':'') + 1)))
    * (TIME_TO_SEC(TIMEDIFF(L2.completed, L1.completed)) / 3600))) AS costT,
    DATABASE() AS databaseName, i.itemId ,l.details
FROM
    (SELECT @row:=0)R,
    (SELECT T1.completed
         , (SELECT MIN(T2.completed) 
            FROM log',mylogID, ' T2
            WHERE T2.completed > T1.completed) AS next_completed
         , (SELECT MAX(T2.completed) 
            FROM log',mylogID, ' T2
            WHERE T2.completed < T1.completed) AS frst_completed
    FROM log',mylogID, ' T1
    ORDER BY T1.completed
     )TimeOrder
        LEFT JOIN log', mylogID, ' L1 ON (L1.completed = TimeOrder.completed)
        LEFT JOIN log', mylogID, ' L2 ON (L2.completed = TimeOrder.next_completed)
        LEFT JOIN log', mylogID, ' L3 ON (L3.completed = TimeOrder.frst_completed)
        LEFT JOIN activities a ON L1.activityId = a.activityId
        LEFT JOIN logs l ON a.logId = l.logId
        inner join items i ON l.logId = i.logId AND i.name LIKE ''%KW PRE%'' 
    )order by L1.completed');  

 SET @sqlTemp = NULL;
  SET @sqlTemp = CONCAT(
  'SELECT 
    IF (coolingHours is null AND rowNum = min(rowNum) THEN ''',startDate,''':= first_completed END IF, 
    rowNum,l.logId,l.completed,l.next_completed,l.first_completed,
    isError,charge,totalTimeRange,startingDate,endingDate,coolingHours,
    databaseName,i.name,l.itemId, kwDifference, cost, costT,l.details,timeInSeconds
  FROM tempTable3 l
   inner join items i ON l.logId = i.logId AND i.name LIKE ''%KW PRE%'' 
   WHERE l.itemId = ''',myItemId,'''
        AND completed BETWEEN ''', startDate, ''' AND ''', endDate, '''
 '); 

PREPARE stmt FROM @sql;
 EXECUTE stmt;
 DEALLOCATE PREPARE stmt;

PREPARE stmtTemp FROM @sqlTemp;
 EXECUTE stmtTemp;
 DEALLOCATE PREPARE stmtTemp;

 DROP TEMPORARY TABLE tempTable3

Select allOpen in new window

sample of dataset

row Num      completed      next_completed      first_completed      cooling Hours
10      11/27/2013 1:05:45 AM      11/29/2013 11:18:34 PM      11/25/2013 11:21:15 PM      (null)
11      11/29/2013 11:18:34 PM      11/30/2013 7:37:45 PM      11/27/2013 1:05:45 AM      20.3197
12      11/30/2013 7:37:45 PM      11/30/2013 11:36:57 PM      11/29/2013 11:18:34 PM      (null)
13      11/30/2013 11:36:57 PM      12/1/2013 6:52:19 PM      11/30/2013 7:37:45 PM      19.2561