Symmetry and Group Theory- Point Group Tips and Practice 6

I couldn't help but write about this interesting metal complex tonight.Two of the authors are Richard Schrock (a Nobel Prize winner) and another great chemist Stephen Lippard. Here is the paper and the structure :

This is a very interesting geometry (at least for me), because the O=W-O-W=O is linear! Honestly, I didn't know that you could get an oxygen in between two metals in a linear way. I know bridging oxygens, but I have never seen/known and imagined something like this.

Anyway, to make it easier I will draw a simpler structure assuming the R groups are spherical and determine the point group of the metal complex. As you can see from the figure above, the R groups are staggered. 

There is a nice and comprehensive discussion about IR and Raman active vibrations in the paper and it is written that the symmetry is D3. But, I don't know why they don't say anything about its being D3d. I don't think I am wrong. If anyone knows more about it, please let us know.  May be I am missing something.

Related posts:

http://chemdiary.blogspot.com/search/label/symmetry