A new method to synthesize complexes of the type [(CNC)RuII(NN)L]n+has been introduced, where CNC is a tridentate pincer composed of two (benz)imidazole derived NHC rings and a pyridyl ring, NN is a bidentate aromatic diimine ligand, L=bromide or acetonitrile, and n=1 or 2. Following this new method a series of six new complexes has been synthesized and characterized by spectroscopic, analytic, crystallographic, and computational methods. Their electrochemical properties have been studied
- NSF-PAR ID:
- 10364373
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- European Journal of Inorganic Chemistry
- Volume:
- 2022
- Issue:
- 8
- ISSN:
- 1434-1948
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
The first examples of a CNC pincer ligands with a central pyridinol derived ring were recently reported. The differences in catalytic reactivity between CNC ligands with a central pyridine ring vs. a pyridinol derived ring are substantial and highly active and robust catalysts have been synthesized and studied. In these pincer ligands, the 4-substituent can be OMe, OH, or O , and these latter two options allow for altered catalyst properties as a function of proton concn. Catalytic studies have used ruthenium(II), nickel(II), and other transition metals. We have made metal complexes that can be protonated or deprotonated reversibly in situ to switch on or off the photocatalytic performance towards CO redn. Furthermore, the methoxy group on the pyridine ring offers unique catalysis advantages not seen with the unsubstituted analog. Our best catalysts offer selective CO formation, >300 turnover cycles, and a 40 h lifetime. Highly active self-sensitized catalysts have recently been developed. Steric and electronic ligand effects are being studied with these catalysts by exptl. and computational methods.more » « less
-
Abstract Herein, we report the synthesis and characterization of two manganese tricarbonyl complexes, MnI(HL)(CO)3Br (
1 a‐Br ) and MnI(MeL)(CO)3Br (1 b‐Br ) (where HL=2‐(2’‐pyridyl)benzimidazole; MeL=1‐methyl‐2‐(2’‐pyridy)benzimidazole) and assayed their electrocatalytic properties for CO2reduction. A redox‐active pyridine benzimidazole ancillary ligand in complex1 a‐Br displayed unique hydrogen atom transfer ability to facilitate electrocatalytic CO2conversion at a markedly lower reduction potential than that observed for1 b‐Br . Notably, a one‐electron reduction of1 a‐Br yields a structurally characterized H‐bonded binuclear Mn(I) adduct (2 a’ ) rather than the typically observed Mn(0)‐Mn(0) dimer, suggesting a novel method for CO2activation. Combining advanced electrochemical, spectroscopic, and single crystal X‐ray diffraction techniques, we demonstrate the use of an H‐atom responsive ligand may reveal an alternative, low‐energy pathway for CO2activation by an earth‐abundant metal complex catalyst. -
Abstract The description of π‐donor amido moieties as ‘weak‐field’ ligands can belie the influence of metal‐ligand covalency on the overall ligand field of coordination complexes, which can in turn influence properties including the magnetic ground state and those of their excited states. In this contribution, the ligand fields of pseudo‐octahedral Ni(II) complexes supported by diarylamido pincer‐type amido ligands – three previously reported examples supported by asymmetric (2‐R‐phenanthridin‐4‐yl)(8‐quinolinyl)amido ligands (R = Cl, CF3,
t Bu;R L1 ) along with a new congener bearing a symmetricbis (8‐quinolinyl)amido ligand (BQA;L2 ) – were investigated in two ways. First, high‐frequency and ‐field electron paramagnetic resonance spectroscopy (HFEPR), SQUID magnetometry, and electronic absorption spectroscopy were used to determine the ligand field parameters. Second, the ability to electrochemically address ligand‐based oxidations despite metal‐centered SOMOs in the parentS =1 paramagnets was investigated, supported by time‐dependent density functional theory (TDDFT) identification of strong intervalence charge‐transfer (IVCT) transitions attributed to electronic communication between two Namidomoieties mediated by a Ni(II) bridge. These findings are discussed in the broader context of 3d transition metal coordination complexes of weak‐field π‐donor ligands. -
The first examples of a CNC pincer ligands with a central pyridinol derived ring were recently reported. The differences in catalytic reactivity between CNC ligands with a central pyridine ring vs. a pyridinol derived ring are substantial and highly active and robust catalysts have been synthesized and studied. In these pincer ligands, the 4-substituent can be OMe, OH, or O-, and these latter two options allow for altered catalyst properties as a function of proton concn. Catalytic studies have used ruthenium(II), nickel(II), and other transition metals. We have made metal complexes that can be protonated or deprotonated reversibly in situ to switch on or off the photocatalytic performance towards CO2 redn. Furthermore, the methoxy group on the pyridine ring offers unique catalysis advantages not seen with the unsubstituted analog. Our best catalysts offer selective CO formation, >300 turnover cycles, and a 40 h lifetime. Steric and electronic ligand effects are being studied with these catalysts by exptl. and computational methods.more » « less
-
Abstract Two novel sulfonated CNN‐pincer ligands
1b and1c and the corresponding chloro and aqua complexes K[CNNLPtCl] andCNNLPt(H2O),3b –3c and2b –2c , were prepared and fully characterized including single crystal X‐ray diffraction. Along with the previously described complexes2a and3a , the derivatives of a CNN pincer ligand1a , these complexes form a family of structurally similar compounds where the pincer core rigidity increases in the series2a (3a) <2b (3b) <2c (3c ), as deduced from their XRD data. The increased ligand rigidity affects the aqua ligand dissociation energy of theCNNLPt(H2O) complexes, as it follows from DFT calculations and as is reflected in the increased reactivity of the aqua complexes2a ,2b and2c in processes that involve aqua ligand loss. Among these processes the formation of the presumed dinuclear complexesCNNL2Pt2and, importantly, catalytic C−D bond cleavage in C6D6were studied in 2,2,2‐trifluoroethanol solutions. The C−D bond cleavage reactivity was quantified as the rate of H/D exchange between C6D6and CF3CH2OH at 80 °C.