Dear Nigha,
Regarding your question about whether HR personnel should inform the boss if they have information about any staff planning to leave the organization.
My comment would be YES, as I feel that it is our responsibility to act in the best interest of the company. However, before we give out the information, we need to find out the reasons that have caused him to consider leaving the company. Remember that 'People join good companies and leave bad bosses!' or they will move on if they feel that there are no more opportunities for personal or career growth in the company.
Having knowledge of the reasons that have caused him to plan to leave, it is then our responsibility to work out a plan (which has to be aligned with the company's policy) to retain him if he is a valued employee and also create a succession plan if we know that we will not be able to retain him.
Simply structure all your information properly and inform the boss accordingly. This includes the reason for his planning to leave, feedback from superiors and peers on his general performance in terms of teamwork, productivity, etc., the pros and cons of losing the said employee, the proposed retention package, succession plan, etc.
If we handle this subject objectively, the boss will understand, and the position of the said employee will not be jeopardized.
Our goal is to achieve what is best for the company, and it is crucial that HR plays its role responsibly.
Best Regards,
Catherine