The role of ligands in rhodium‐ and iridium‐catalyzed
By attaching pyridine groups to a diaza[6]helicene, a helical, bis‐ditopic, bis‐
- Award ID(s):
- 1855470
- NSF-PAR ID:
- 10238440
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- ChemPlusChem
- Volume:
- 85
- Issue:
- 11
- ISSN:
- 2192-6506
- Page Range / eLocation ID:
- p. 2446-2454
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
Abstract Para hydrogen Induced Polarization (PHIP) and SABRE (signal amplification by reversible exchange) chemistry has been studied in the benchmark systems, [Rh(diene)(diphos)]+and [Ir(NHC)(sub)3(H)2]+, and shown to have a great impact on the degree of hyperpolarization observed. Here, we examine the role of the flanking moieties in the electron‐rich monoanionic bis(carbene) aryl pincer ligand,ArCCC (Ar=Dipp, 2,6‐diisopropyl or Mes, 2,4,6‐trimethylphenyl) on the cobalt‐catalyzed PHIP and PHIP‐IE (PHIP via Insertion and Elimination) chemistry that we have previously reported. The mesityl groups were exchanged for diisopropylphenyl groups to generate the (DippCCC)Co(N2) catalyst, which resulted in faster hydrogenation and up to 390‐fold1H signal enhancements, larger than that of the (MesCCC)Co‐py (py=pyridine) catalyst. Additionally, the synthesis of the (DippCCC)Rh(N2) complex is reported and applied towards the hydrogenation of ethyl acrylate withpara hydrogen to generate modest signal enhancements of both1H and13C nuclei. Lastly, the generation of two (MesCCC)Ir complexes is presented and applied towards SABRE and PHIP‐IE chemistry to only yield small1H signal enhancements of the partially hydrogenated product (PHIP) with no SABRE hyperpolarization. -
Abstract The design, synthesis, and characterization of the novel polymerizable ligand 3,5‐bis(3,4‐ethylenedioxythien‐2‐yl)‐
N,N ‐bis(2‐diphenylphosphinoethyl)‐phenylamine is achieved. The corresponding molybdenum complexes (EDOT)2PNP‐Mo(CO)n wheren = 3,4 with carbonyls as ancillary ligands are also synthesized, and characterized by1H NMR,31P{1H} NMR, HRMS, FTIR (both the solution state spectrum between KBr discs and the solid‐state spectrum with attenuated total reflectance [ATR] apparatus). Single crystal X‐ray analysis of (EDOT)2PNP‐Mo(CO)3complex is performed. The monomer complexes and the free ligand are electropolymerized to obtain the corresponding polymers that are studied electrochemically. The Mo/P and Mo/S ratios as well as the metal oxidations in the conducting metallopolymers are analyzed by X‐ray photoelectron spectroscopy. -
Abstract A series of isomeric bis(alkylthiocarbamate) copper complexes have been synthesized, characterized, and evaluated for antiproliferation activity. The complexes were derived from ligand isomers with 3‐methylpentyl (H2L2) and cyclohexyl (H2L3) backbone substituents, which each yield a pair of linkage isomers. The thermodynamic products CuL2a/3ahave two imino N and two S donors resulting in three five‐member chelate rings (555 isomers). The kinetic isomers CuL2b/3bhave one imino and one hydrazino N donor and two S donors resulting in four‐, six‐, and five‐member rings (465 isomers). The 555 isomers have more accessible CuII/Ipotentials (E1/2=−811/−768 mV vs. ferrocenium/ferrocene) and lower energy charge transfer bands than their 465 counterparts (E1/2=−923/‐854 mV). Antiproliferation activities were evaluated against the lung adenocarcinoma cell line (A549) and nonmalignant lung fibroblast cell line (IMR‐90) using the MTT assay. CuL2awas potent (A549EC50=0.080 μM) and selective (IMR‐90EC50/A549EC50=25) for A549. Its linkage isomer CuL2bhad equivalent A549 activity, but lower selectivity (IMR‐90EC50/A549EC50=12.5). The isomers CuL3aand CuL3bwere less potent withA549EC50 values of 1.9 and 0.19 M and less selective withIMR‐90EC50/A549EC50ratios of 2.3 and 2.65, respectively. There was no correlation between reduction potential and A549 antiproliferation activity/selectivity.
-
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. -
Abstract A new series of mono‐ and bis‐alkynyl CoIII(TIM) complexes (TIM=2,3,9,10‐tetramethyl‐1,4,8,11‐tetraazacyclotetradeca‐1,3,8,10‐tetraene) is reported herein. The
trans ‐[Co(TIM)(C2R)Cl]+complexes were prepared from the reaction betweentrans ‐[Co(TIM)Cl2]PF6and HC2R (R=tri(isopropyl)silyl or TIPS (1 ), ‐C6H4‐4‐tBu (2 ), ‐C6H4‐4‐NO2(3 a ), andN ‐mesityl‐1,8‐naphthalimide or NAPMes(4 a )) in the presence of Et3N. The intermediate complexes of the typetrans ‐[Co(TIM)(C2R)(NCMe)](PF6)(OTf),3 b and4 b , were obtained by treating3 a and4 a , respectively, with AgOTf in CH3CN. Furthermore, bis‐alkynyltrans ‐[Co(TIM)(C2R)2]PF6complexes,3 c and4 c , were generated following a second dehydrohalogenation reaction between3 b and4 b , respectively, and the appropriate HC2R in the presence of Et3N. These new complexes have been characterized using X‐ray diffraction (2 ,3 a ,4 a , and4 c ), IR,1H NMR, UV/Vis spectroscopy, fluorescent spectroscopy (4 c ), and cyclic voltammetry.