- C-C bond formation and related reactions at the CNC backbone in (smif)FeX (smif = 1,3-di-(2-pyridyl)-2-azaallyl): Dimerizations, 3 + 2 cyclization, and nucleophilic attack; Transfer hydrogenations and alkyne trimerization (X = N(TMS)2, dpma = (Di-(2-pyridyl-methyl)-amide))
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Molecular orbital analysis depicts the CNCnb backbone of the smif (1,3-di-(2-pyridyl)-2-azaallyl) ligand as having singlet diradical and/or ionic character where electrophilic or nucleophilic attack is plausible. Reversible dimerization of (smif)Fe{N(SiMe3)2} (1) to [{(Me3Si)2N}Fe]2(μ-κ3, κ3-N,py2-smif,smif) (2) may be construed as diradical coupling. A proton transfer within the backbone-methylated, and o-pyridine-methylated smif of putative (bMe2 oMe2smif)FeN(SiMe3)2 (8) provides a route to [{(Me3Si)2N}Fe]2(μ- κ4,κ4-N,py2,C-(bMe, bCH2,oMe2(smif)H))2 (9). A 3 + 2 cyclization of ditolyl-acetylene occurs with 1, leading to the dimer [{2,5-di(pyridin-2-yl)-3,4-di-(p-tolyl-2,5-dihydropyrrol-1-ide)}FeN(SiMe 3)2]2 (11), and the collateral discovery of alkyne cyclotrimerization led to a brief study that identified Fe(N(SiMe 3)2(THF) as an effective catalyst. Nucleophilic attack by (smif)2Fe (13) on tBuNCO and (2,6-iPr 2C6H3)NCO afforded (RNHCO-smif)2Fe (14a, R = tBu; 14b, 2,6-iPrC6H3). Calculations suggested that (dpma)2Fe (15) would favorably lose dihydrogen to afford (smif)2Fe (13). H2-transfer to alkynes, olefins, imines, PhNNPh, and ketones was explored, but only stoichiometric reactions were affected. Some physical properties of the compounds were examined, and X-ray structural studies on several dinuclear species were conducted.
- Frazier, Brenda A.,Williams, Valerie A.,Wolczanski, Peter T.,Bart, Suzanne C.,Meyer, Karsten,Cundari, Thomas R.,Lobkovsky, Emil B.
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supporting information
p. 3295 - 3312
(2013/05/08)
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- Synthesis and Characterization of (smif)2Mn (n = 0, M = V, Cr, Mn, Fe,Co, Ni, Ru; N = +1, M = Cr, Mn, Co, Rh, Ir; Smif =1,3-di-(2-pyridyl)-2-azaallyl)
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A series of Werner complexes featuring the tridentate ligand smif, that is, 1,3-di-(2-pyridyl)-2-azaallyl, have been prepared. Syntheses of (smif) 2M (1-M; M = Cr, Fe) were accomplished via treatment of M(NSiMe 3)2(THF)n (M = Cr, n = 2; Fe, n = 1) with 2 equiv of (smif)H (1,3-di-(2-pyridyl)-2- azapropene); ortho -methylated ( oMesmif)2Fe (2-Fe) and (oMe2smif)2Fe (3-Fe) were similarly prepared. Metatheses of MX2 variants with 2 equiv of Li(smif) or Na(smif) generated 1-M (M = Cr, Mn, Fe, Co, Ni, Zn, Ru). Metathesis of VCl3(THF)3 with 2 Li(smif) with a reducing equiv of Na/Hg present afforded 1-V, while 2 Na(smif) and IrCl3(THF) 3 in the presence of NaBPh4 gave [(smif) 2Ir]BPh4 (1+-Ir). Electrochemical experiments led to the oxidation of 1-M (M = Cr, Mn, Co) by AgOTf to produce [(smif)2M]OTf (1+-M), and treatment of Rh2(O2CCF3)4 with 4 equiv Na(smif) and 2 AgOTf gave 1+-Rh. Characterizations by NMR, EPR, and UV-vis spectroscopies, SQUID magnetometry, X-ray crystallography, and DFT calculations are presented. Intraligand (IL) transitions derived from promotion of electrons from the unique CNCnb (nonbonding) orbitals of the smif backbone to ligand π*-type orbitals are intense (σ ≈ 10 000-60 000 M -1cm-1), dominate the UV-visible spectra, and give crystals a metallic-looking appearance. High energy k-edge spectroscopy was used to show that the smif in 1-Cr is redox noninnocent, and its electron configuration is best described as (smif(-))(smif(2-))Cr(III); an unusual S = 1 EPR spectrum (X-band) was obtained for 1-Cr.
- Frazier, Brenda A.,Bartholomew, Erika R.,Wolczanski, Peter T.,DeBeer, Serena,Santiago-Berrios, Mitk'el,Abruna, Hector D.,Lobkovsky, Emil B.,Bart, Suzanne C.,Mossin, Susanne,Meyer, Karsten,Cundari, Thomas R.
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p. 12414 - 12436
(2012/01/31)
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