Trianionic pincer ligands, a CR(III)/CR(V) catalytic system and its use for catalytic aerobic oxidation of organic substrates
An embodiment of the invention is a novel Cr(V)OCO 3− trianionic pincer ligand complex. Another embodiment of the invention is a catalytic method for oxidation of a substrate aerobically in the presence of a source of oxygen, where the novel Cr(V)OCO 3− trianionic pincer ligand complex acts as the catalyst. The substrate can be a phosphine, amine, sulfide, alkene, alkane or a second metal complex. Another embodiment of the invention is directed to NCN pincer ligands that can form trianionic pincer ligand complexes.
1. A Cr(V)OCO 3− trianionic pincer ligand complex comprising the structure:
where: R is independently a C3 to C12 alkyl or aryl group; R′ is independently a H, C1 to C12 alkyl or aryl group; and L is an oxygen comprising ligand.
2. The pincer ligand complex of claim 1 , wherein R is t-butyl, R′ is H and L is tetrahydrofuran (THF).
3. A catalytic method for oxidation of a substrate comprising the steps of:
providing a Cr(V)OCO 3− trianionic pincer ligand complex of claim 1 ;
providing a source of oxygen molecules; and
providing a substrate, wherein said substrate is oxidized and said Cr(V)OCO 3− trianionic pincer ligand complex is reduced by the substrate to give a Cr(III) complex and oxidizing said Cr(III) complex to said Cr(V)OCO 3− trianionic pincer ligand complex.
4. The method of claim 3 , wherein said substrate comprises a phosphine, amine, sulfide, alkene, alkane or a second metal complex.
5. The method of claim 3 , wherein said Cr(V)OCO 3− trianionic pincer ligand complex comprises:
6. A method of preparing Cr(V)OCO 3− trianionic pincer ligand complex of claim 1 comprising the steps of:
providing an OCOH 3 pincer ligand;
converting said OCOH 3 pincer ligand to an OCOHM 2 pincer complex;
exchanging said OCOHM 2 pincer complex with a Cr(III) salt; and
oxidizing said Cr(III) to Cr(V).
7. The method of claim 6 , wherein said OCOH 3 pincer ligand comprises ( t BuOCO)H 3 .
8. The method of claim 6 , wherein said OCOHM 2 pincer complex comprises an OCOHK 2 pincer complex by reaction of said OCOH 3 pincer ligand with KH.
9. The method of claim 6 , wherein said Cr(III) salt comprises CrCl 2 Me(THF) 3 .
10. The method of claim 6 , wherein said oxidation comprises oxidation in an oxygen comprising gas.
11. An NCN pincer ligand, comprising a structure selected from:
wherein R is 2,6-bis-(i-propyl)phenyl, 3,5-bis-(methyl)phenyl, 3,5-bis-(i-propyl)phenyl 3,5-bis-(trifluoromethyl)phenyl, mesytyl, or tri-i-propylsilyl.
12. The NCN pincer ligand of claim 11 , wherein the ligand is:
wherein R is mesytyl.
13. The NCN pincer ligand of claim 11 , wherein the ligand is:
wherein R is 3,5-bis-(trifluoromethyl)phenyl.
14. The NCN pincer ligand of claim 11 , wherein the ligand is:
wherein R is 3,5-bis-(trifluoromethyl)phenyl.
15. The NCN pincer ligand of claim 11 , wherein the ligand is:
wherein R is tri-i-propylsilyl.
16. The NCN pincer ligand of claim 11 , wherein the ligand is:
17. A Cr(III)NCN 3− trianionic pincer ligand complex comprising the structure:
where R is 2,6-bis-(i-propyl)phenyl, 3,5-bis-(methyl)phenyl, 3,5-bis-(trifluoromethyl)phenyl, 3,5-bis-(i-propyl)phenyl, mesytyl, or tri-i-propylsilyl and L is any neutral coordinating ligand.
18. The Cr(III)NCN 3− trianionic pincer ligand complex of claim 17 , wherein the complex is: