The first paper came out in 2010 and reported synthesis and characterization of a Ni(II)-dithiolene complex. The authors formulated the compound as NiII(L2−)(L−.)][PPh4] and claim that complex "shows strikingly similar EPR and reduction potential values to those observed with native Ni-containing hydrogenases." I should mention that CV of the compound was reported in MeCN. You can read the paper and ask questions, but the most interesting thing they did not provide a proton NMR spectrum for this paramagnetic compound. But, they assigned a signal at 4.1 ppm to a S-H. Interesting.
Anyway, shortly after a "comment" was published and proposed a new oxidation state assignment for the Ni atom and the ligand. A "Response" followed and honestly I don't think they added any new evidence or supporting argument for their own assignment.
I still think, they are worth reading.