Is Rfc2898DeriveBytes class accessible via com?

Note:sorry I'm not sure if this is the right place for this topic.

I was trying to use Rfc2898DeriveBytes in a php application so I wrote: 

$obj = new COM('System.Security.Cryptography.Rfc2898DeriveBytes');

but I got this error:
Fatal error: Uncaught exception ‘com_exception’ with message ‘Failed to create COM object `System.Security.Cryptography.Rfc2898DeriveBytes’: Invalid syntax

After doing some research I thought the class may not be accessible this way, I opened GAC and didn't find mscorelib.dll v4.0 in which the class is.

is this the reason I wasn't able to use it? or is there something else? Thanks.