Here is a very good article outlining the difference between corporate coaching, counseling and mentoring. In my opinion it is well worth the read as you consider how coaching is used within your organization. "Coaching" as a professional term has of course become a fad word over the last number of years, easily bandied about in almost every circumstance you can imagine.
In general I would suggest that for leadership and executive coaching, you look outside the organization for a Coach. This ensures objectivity when it comes to your company or organization and its goals and priorities. The executive coach concentrates on you and has no reason to 'look over their shoulder'.
Here is the article.