Solvation of uranyl formate/acetate
This is a uranyl ion, one of the most common forms of dissolved uranium:



Because the two U=O bonds can form a single delocalised region, there's a strong tendency towards linearity (c.f. carbon dioxide). It tends to dissolve in water by gaining equatorial water ligands (4 or 5), some of which it may then hydrolyse, depending on the pH:



The axial oxygen atoms are also valid targets for hydrogen bonding, typically gaining one hydrogen bond each.



The difficulty in dissolving uranyl formate in particular suggests that the formate ion is quite well-bound, and it seems that in this case you get a combination of water and formate ligands in the complex around the uranyl. I was expecting the formate to be a bi-dentate ligand, but according to the results of a combined computational and experimental study 1, it's uni-dentate (which incidentally allows it to form polymeric chains in solution).

Here's a picture from that study showing a computationally obtained structure of a mixed water/formate-ligated uranyl structure.




2013, Dalton Trans., Christian Lucks, André Rossberg, Satoru Tsushima, Harald Foerstendorf, Karim Fahmya, Gert Bernharda, DOI:10.1039/C3DT51711J