You can check the VMware Compatibility Guide to find the different CPU's supported "EVC Modes" (for vMotion) and the "Fault Tolerant Compatible Set". For HA the different CPU types are not as important, because HA only restarts VM's.
From a quick look into the HCL, the two CPUs you mentioned (I assume you meant E5-2690) should support vMotion/EVC, but not FT because of different FT Compatibility sets (Nehalem vs. Sandy-Bridge).
For FT compatibility see also http://kb.vmware.com/kb/1008027
André