Editing Nickel(II) pincer complexes demonstrate that the remote substituent controls catalytic carbon dioxide reduction

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{{#doiinfobox: 10.1039/c7cc09507d}}

===Abstract===
====Summary====
A photochemical reduction of CO<sub>2</sub> to CO was shown using the nickel complex {{#moleculelink:|link=UDPGSTPOVCEDJN-UHFFFAOYSA-L|image=false|width=300|height=200}} in comparison to the inactive derivative {{#moleculelink:|link=XLAXHWSGDXWDSW-UHFFFAOYSA-N|image=false|width=300|height=200}} as catalyst in combination with the iridium-based photosensitizer {{#moleculelink:|link=NSABRUJKERBGOU-UHFFFAOYSA-N|image=false|width=300|height=200}}. Turnover numbers (TONs) of 10.6 for CO with the cobalt complex {{#moleculelink:|link=UDPGSTPOVCEDJN-UHFFFAOYSA-L|image=false|width=300|height=200}} were reached in acetonitrile. The experiments were conducted under visible-light irradiation using BIH and TEA as sacrificial electron donors (see section SEDs below).
====Advances and special progress====
The authors showed the importance of remote substituents by a drastic change in activity through a change in a remote substituent. 

====Additional remarks====
The designed photocatalyst could be turned on and off via (de)protonation.

===Content of the published article in detail===
The article contains results for the reduction of CO<sub>2</sub> to CO under visible-light catalysis using nickel complexes as catalysts. The catalytic system performs best (referring to the TON of CO production) in acetonitrile with the cobalt catalyst {{#moleculelink:|link=UDPGSTPOVCEDJN-UHFFFAOYSA-L|image=false|width=300|height=200}}.
===Catalyst===
{{#moleculelink:|link=UDPGSTPOVCEDJN-UHFFFAOYSA-L|image=true}}
<chemform smiles="C1C2N3C=CN(C)C3[Ni+2](N#CC)3C4N(C(N=23)=CC=1)C=CN4C.F[P-](F)(F)(F)(F)F.F[P-](F)(F)(F)(F)F" inchi="1S/C13H17N5.C2H3N.2F6P.Ni/c1-15-6-8-17(10-15)12-4-3-5-13(14-12)18-9-7-16(2)11-18;1-2-3;2*1-7(2,3,4,5)6;/h3-9H,10-11H2,1-2H3;1H3;;;/q;;2*-1;+2" inchikey="XLAXHWSGDXWDSW-UHFFFAOYSA-N" height="200px" width="300px" float="none">
  -INDIGO-11282314472D

  0  0  0  0  0  0  0  0  0  0  0 V3000
M  V30 BEGIN CTAB
M  V30 COUNTS 36 38 0 0 0
M  V30 BEGIN ATOM
M  V30 1 C 6.95985 -3.47507 0.0 0
M  V30 2 C 8.69015 -3.47459 0.0 0
M  V30 3 C 7.82664 -2.97497 0.0 0
M  V30 4 C 8.69015 -4.47553 0.0 0
M  V30 5 C 6.95985 -4.48002 0.0 0
M  V30 6 N 7.82882 -4.97503 0.0 0
M  V30 7 N 6.02651 -5.12971 0.0 0
M  V30 8 C 6.18292 -6.11739 0.0 0
M  V30 9 N 5.29191 -6.57142 0.0 0
M  V30 10 C 4.58481 -5.86432 0.0 0
M  V30 11 C 5.03884 -4.9733 0.0 0
M  V30 12 N 9.62349 -5.15472 0.0 0
M  V30 13 C 10.6112 -4.9983 0.0 0
M  V30 14 C 11.0652 -5.88932 0.0 0
M  V30 15 N 10.3581 -6.59642 0.0 0
M  V30 16 C 9.46708 -6.14239 0.0 0
M  V30 17 C 5.13549 -7.55911 0.0 0
M  V30 18 C 10.5145 -7.58411 0.0 0
M  V30 19 Ni 7.85 -6.225 0.0 0 CHG=2
M  V30 20 N 7.85 -7.75 0.0 0
M  V30 21 C 7.85 -8.75 0.0 0
M  V30 22 C 7.85 -9.75 0.0 0
M  V30 23 F 12.092 -4.675 0.0 0
M  V30 24 P 12.958 -4.175 0.0 0 CHG=-1
M  V30 25 F 13.824 -4.675 0.0 0
M  V30 26 F 12.958 -3.175 0.0 0
M  V30 27 F 12.092 -3.675 0.0 0
M  V30 28 F 13.824 -3.675 0.0 0
M  V30 29 F 12.958 -5.175 0.0 0
M  V30 30 F 12.359 -8.075 0.0 0
M  V30 31 P 13.225 -7.575 0.0 0 CHG=-1
M  V30 32 F 14.091 -8.075 0.0 0
M  V30 33 F 13.225 -6.575 0.0 0
M  V30 34 F 12.359 -7.075 0.0 0
M  V30 35 F 14.091 -7.075 0.0 0
M  V30 36 F 13.225 -8.575 0.0 0
M  V30 END ATOM
M  V30 BEGIN BOND
M  V30 1 2 3 1
M  V30 2 2 4 2
M  V30 3 1 1 5
M  V30 4 1 2 3
M  V30 5 2 5 6
M  V30 6 1 6 4
M  V30 7 1 7 8
M  V30 8 1 8 9
M  V30 9 1 9 10
M  V30 10 2 10 11
M  V30 11 1 11 7
M  V30 12 1 12 13
M  V30 13 2 13 14
M  V30 14 1 14 15
M  V30 15 1 15 16
M  V30 16 1 16 12
M  V30 17 1 7 5
M  V30 18 1 12 4
M  V30 19 1 9 17
M  V30 20 1 15 18
M  V30 21 10 6 19
M  V30 22 10 8 19
M  V30 23 10 16 19
M  V30 24 10 19 20
M  V30 25 3 20 21
M  V30 26 1 21 22
M  V30 27 1 23 24
M  V30 28 1 24 25
M  V30 29 1 24 26
M  V30 30 1 24 27
M  V30 31 1 24 28
M  V30 32 1 24 29
M  V30 33 1 30 31
M  V30 34 1 31 32
M  V30 35 1 31 33
M  V30 36 1 31 34
M  V30 37 1 31 35
M  V30 38 1 31 36
M  V30 END BOND
M  V30 END CTAB
M  END
</chemform>

==Photosensitizer ==
{{#moleculelink: |link=NSABRUJKERBGOU-UHFFFAOYSA-N|image=true}}

===Investigation ===
{{#experimentlist:|form=Photocatalytic_CO2_conversion_experiments|name=Table 1}}
====Sacrificial Electron Donor====
In this study, the experiments were done with the sacrificial electron donors BIH ({{#moleculelink:|link=VDFIVJSRRJXMAU-UHFFFAOYSA-N|image=false|width=300|height=200}}) and TEA ({{#moleculelink: |link=ZMANZCXQSJIPKH-UHFFFAOYSA-N|image=false|width=300|height=200}}).
====Additives====
In this study, {{#moleculelink:|link=ITMCEJHCFYSIIV-UHFFFAOYSA-N|image=false|width=300|height=200}} and proton sponge were used as additives to (de)protonate the catalytically active nickel complex. Moreover, a control experiment under nitrogen atmosphere was conducted.
[[Category:Photocatalytic CO2 conversion to CO]]