Wednesday, May 31, 2017

Synthesis and activation potential of an open shell diphosphine #chempaperaday 300

This is one of the most exciting papers I have read in a few months. 

Graphical abstract: Synthesis and activation potential of an open shell diphosphine 
First of all, I really like the synthesis of all these complexes even the starting materials like Tp*W(CO)3. A lot of work! And then there are these unexpected (to me) diphenylphosphino-acetylene complexes. I actually don't know how many of these as ligands have been isolated, but I don't think they are more than a handful. So, we know almost nothing about them as ligands. This whole complex can be tuned by different substituents on the phosphines or on the metal center! You can use it as a metalloligand and synthesize bimetallic complexes! Lots of opportunities here.. The groups spent a lot of time and effort to find out the H-atom source (SI28). They did labeling experiments, KIE, tried to keep everything super dry, tried some interesting set ups etc. but couldn't find out the source. The source is most likely the solvent as they mentioned. So much greatness for a 4-page Communication. Really great work.

Tuesday, May 30, 2017

Uranyl Coordination by the 14-Membered Macrocycle Dibenzotetramethyltetraaza[14]annulene #chempaperaday 299

Another actinide paper. It looks like the goal of this study was to isolate a cis-UO2 complex. But, as you can see all three structurally characterized complexes display a trans stereochemistry. There is a 7Li NMR spectrum and some Raman spectra for those interested. You don't see them very often.

Abstract Image

Reductive Elimination of Diphosphine from a Thorium–NHC–Bis(phosphido) Complex #chempaperaday 298

After being sick for almost a week, I am back. You can't often see reductive elimination from thorium centers, because simply it is not easy to reduce Th(IV) to Th(III) or Th(II). That's why this group is focused on using a non-innocent ligand to facilitate these reactions. Here you can see the formation of a diphosphine and a thorium complex using bpy. They were able to study the kinetics of the reaction too. 
Abstract Image

Tuesday, May 23, 2017

Carbon–Fluorine Reductive Elimination from Nickel(III) Complexes #chempaperaday 297

This is "the first direct evidence of a C-F reductive elimination from a 1st row transition metal fluoride complex". They were able to structurally characterize one of these complexes and provide more evidence for the proposed Ni(III) intermediates. 

A fantastic paper and study. The barrier for reductive elimination of Ni-F was also found to be less than the Pd-F complexes. I am glad nickel is getting more and more attention. I like octahedral nickel complexes and I think we will see more of those in the future.

Monday, May 22, 2017

Terminal Parent Phosphanide and Phosphinidene Complexes of Zirconium(IV) #chempaperaday 296

I don't post papers about early metals (not 1st row ones; 2nd and 3rd row), and I think this may even be the first one I am sharing here. If you follow Prof. Liddle's group, you are probably aware of their U=P, Th=P complexes. I think I posted the one about thorium recently if not both. Here, they expand the same chemistry to early transition metals to investigate the M-P bond. They were able to structurally characterize both a phosphanide and a phosphinidene. They found out that the Zr-P bond is also polarized just like actinide-P bonds, and even less covalent than those (DFT). I am actually not completely surprised that it is not much covalent. 
If you look at Scheme 1, you will see that Zr-PH bond is drawn as a double bond. The distance is actually ~0.2 A larger than the sum of their covalent radii and there is an agostic interaction Zr-H (check the crystal structure). But they calculated the Mayer Bond order as 1.48 and assigned it as a double bond. Sometimes schemes are not enough to visualize what really is going on. Anyway, I like this gorup's work and try to read their work as much as possible.

Friday, May 19, 2017

N2-to-NH3 Conversion by a triphos–Iron Catalyst and Enhanced Turnover under Photolysis #chempaperaday 295

Another fantastic paper from one of my favorite groups. They were able to produce ammonia (again!) now with some hydride complexes. They also found out that photolysis improves the yield.  I bet they tried or they are still working on it but I am wondering if you can reduce 2 and then make a hydride or dihydride complex. As always, very nice synthetic work and characterization.