Hi
SharePoint 2010 works on .Net framework 3.5.
So you can install 4.5 framework, but make sure that SharePoint Website application pools should be mapped to 3.5 framework only.
You can create separate application pool for the tool which requires 4.5 framework.
Refer this msdn blog also-
http://blogs.msdn.com/b/sharepointdev/archive/2011/07/14/net-framework-support-in-sharepoint-2010.aspx
Thanks,
Danny
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