skip to main content

Explore Research Products in the NSF-PAR

Title: A unique series of chromium( iii ) mono-alkynyl complexes supported by tetraazamacrocycles
Described herein is the synthesis and characterization of macrocyclic Cr III mono-alkynyl complexes. By using the meso -form of the tetraazamacrocycle HMC (HMC = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane), trans -[Cr(HMC)(C 2 Ph)Cl]OTf ( 1a ), trans -[Cr(HMC)(C 2 Np)Cl]OTf ( 2a ), trans -[Cr(HMC)(C 2 C 6 H 4 t Bu)Cl]OTf ( 3a ), and trans -[Cr(HMC)(C 2 (3,5-Cl 2 C 6 H 3 ))Cl]OTf ( 4a ) complexes have been realized. These complexes were synthesized in high yield through the reaction of trans -[Cr( meso -HMC)(C 2 Ar) 2 ]OTf ( 1b–4b ) with stoichiometric amounts of methanolic HCl. Single crystal X-ray diffraction showed that the trans -stereochemistry and pseudo-octahedral geometry is retained in the desired mono-alkynyl complexes. The absorption spectra of complexes 1a–4a display d–d bands with distinct vibronic progressions that are slightly red shifted from trans -[Cr(HMC)(C 2 Ar) 2 ] + with approximately halved molar extinction coefficients. Time-delayed measurements of the emission spectra for complexes 1a–4a at 77 K revealed phosphorescence with lifetimes ranging between 343 μs ( 4a ) and 397 μs ( 1a ). The phosphorescence spectra of 1a–4a also exhibit more structuring than the bis-alkynyl complexes due to a strengthened vibronic coupling between the Cr III metal center and alkynyl ligands.  more » « less
Award ID(s):
1764347
NSF-PAR ID:
10229815
Author(s) / Creator(s):
; ; ; ;
Date Published:
Journal Name:
Dalton Transactions
Volume:
50
Issue:
14
ISSN:
1477-9226
Page Range / eLocation ID:
4936 to 4943
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ( , European Journal of Inorganic Chemistry)
    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. Thetrans‐[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 band4 b, were obtained by treating3 aand4 a, respectively, with AgOTf in CH3CN. Furthermore, bis‐alkynyltrans‐[Co(TIM)(C2R)2]PF6complexes,3 cand4 c, were generated following a second dehydrohalogenation reaction between3 band4 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.

     
    more » « less
  2. ; ( , European Journal of Inorganic Chemistry)
    Abstract

    A pair of novel Fe‐alkynyl complexes, [FeIII(HMTI)(C2SiEt3)2]ClO4(2) and [FeII(HMTI)(C2SiEt3)(NCCH3)]ClO4(3), is described herein. Reaction of Fe(meso‐HMC)Cl(ClO4)]ClO4(1) with lithiated triethylsilylacetylene and subsequent exposure to oxygen yielded the bis‐alkynyl2containing the dehydrogenated tetraimine macrocycle (HMTI). Reduction of2by mossy zinc in acetonitrile yielded the mono‐alkynyl3. The structures of2and3were determined using single‐crystal X‐ray diffraction. Analysis of visible absorption and electrochemical data establishes the redox‐active nature of the HMTI macrocycle, and indicates significant interactions between the Fedπ and tetraimine π* orbitals. These deductions are further supported by density functional theory calculations.

     
    more » « less
  3. ; ; ( , Acta Crystallographica Section C Structural Chemistry)
    Reported in this contribution are the synthesis and crystal structures of two new Fe III complexes of 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane (HMC), namely, dichlorido(5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane)iron(III) chloride, [FeCl 2 (C 16 H 36 N 4 )]Cl or cis -[FeCl 2 ( rac -HMC)]Cl ( 1 ), and dichlorido(5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane)iron(III) tetrachloridoferrate, [FeCl 2 (C 16 H 36 N 4 )][FeCl 4 ] or trans -[FeCl 2 ( meso -HMC)][FeCl 4 ] ( 2 ). Single-crystal X-ray diffraction studies revealed that both 1 and 2 adopt a pseudo-octahedral geometry, where the macrocycles adopt folded and planar geometries, respectively. The chloride ligands in 1 are cis to each other, while those in 2 have a trans configuration. The relevant bond angles in 1 deviate substantially from an ideal octahedral coordination geometry, with the angles between the cis substituents varying from 81.55 (5) to 107.56 (4)°, and those between the trans -ligating atoms varying from 157.76 (8) to 170.88 (3)°. In contrast, 2 adopts a less strained configuration, in which the N—Fe—N angles vary from 84.61 (8) to 95.39 (8)° and the N—Fe—Cl angles vary from 86.02 (5) to 93.98 (5)°. 
    more » « less
  4. ; ; ; ; ( , Dalton Transactions)
    Palladium(0) phosphine complexes are of great importance as catalysts in numerous bond formation reactions that involve oxidative addition of substrates. Highly active catalysts with labile ligands are of particular interest but can be challenging to isolate and structurally characterize. We investigate here the synthesis and chemical reactivity of Pd 0 complexes that contain geometrically adaptable diferrocenylmercury-bridged diphosphine chelate ligands (L) in combination with a labile dibenzylideneacetone (dba) ligand. The diastereomeric diphosphines 1a (p S p R , meso -isomer) and 1b (p S p S -isomer) differ in the orientation of the ferrocene moieties relative to the central Ph 2 PC 5 H 3 –Hg–C 5 H 3 PPh 2 bridging entity. The structurally distinct trigonal LPd 0 (dba) complexes 2a ( meso ) and 2b (p S p S ) are obtained upon treatment with Pd(dba) 2 . A competition reaction reveals that 1b reacts faster than 1a with Pd(dba) 2 . Unexpectedly, catalytic interconversion of 1a ( meso ) into 1b ( rac ) is observed at room temperature in the presence of only catalytic amounts of Pd(dba) 2 . Both Pd 0 complexes, 2a and 2b , readily undergo oxidative addition into the C–Cl bond of CH 2 Cl 2 at moderate temperatures with formation of the square-planar trans -chelate complexes LPd II Cl(CH 2 Cl) ( 3a , 3b ). Kinetic studies reveal a significantly higher reaction rate for the meso -isomer 2a in comparison to (p S p S )- 2b . 
    more » « less
  5. ; ; ; ( , Acta Crystallographica Section C Structural Chemistry)
    Both trans and cis iron–CTMC complexes, namely, trans -dichlorido[(5 SR ,7 RS ,12 RS ,14 SR )-5,7,12,14-tetramethyl-1,4,8,11-tetraazacyclotetradecane]iron(III) tetrachloridoferrate, [Fe(C 14 H 32 N 4 )Cl 2 ][FeCl 4 ] ( 1a ), the analogous chloride methanol monosolvate, [Fe(C 14 H 32 N 4 )Cl 2 ]Cl·CH 3 OH ( 1b ), and cis -dichlorido[(5 SR ,7 RS ,12 SR ,14 RS )-5,7,12,14-tetramethyl-1,4,8,11-tetraazacyclotetradecane]iron(III) chloride, [Fe(C 14 H 32 N 4 )Cl 2 ]Cl ( 2 ), were successfully synthesized and structurally characterized using X-ray diffraction. The coordination geometry of the macrocycle is dependent on the stereoisomerism of CTMC. The packing of these complexes appears to be strongly influenced by extensive hydrogen-bonding interactions, which are in turn determined by the nature of the counter-anions ( 1a versus 1b ) and/or the coordination geometry of the macrocycle ( 1a/1b versus 2 ). These observations are extended to related ferric cis - and trans- dichloro macrocyclic complexes. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email