That query should work.
You could accomplish the same using an outer join.
Something like this:
SELECT c.name,acctstatus, c.statusDetail, c.sales_person, c.loggedInBy,c.loginDate, c.lastUpdateBy, c.LastUpdateOn
FROM contractor c LEFT OUTER JOIN leads_contacts lc
ON c.name = lc.company_name
WHERE lc.company_name IS NULL</pre>
… But if the problem is in the data, this will return an empty result set as well.
Do you know of some specific company that has no associated record in the leads_contacts table ? If so, I would run a query on leads_contacts for that specific company_name. If no row is returned, then your report should display at least that company.