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)

Abstract

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)(2)M (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 ((o)Mesmif)(2)Fe (2-Fe) and ((o)Me(2)smif)(2)Fe (3-Fe) were similarly prepared. Metatheses of MX(2) variants with 2 equiv of Li(smif) or Na(smif) generated 1-M (M = Cr, Mn, Fe, Co, Ni, Zn, Ru). Metathesis of VCl(3)(THF)(3) with 2 Li(smif) with a reducing equiv of Na/Hg present afforded 1-V, while 2 Na(smif) and IrCl(3)(THF)(3) in the presence of NaBPh(4) gave [(smif)(2)Ir]BPh(4) (1(+)-Ir). Electrochemical experiments led to the oxidation of 1-M (M = Cr, Mn, Co) by AgOTf to produce [(smif)(2)M]OTf (1(+)-M), and treatment of Rh(2)(O(2)CCF(3))(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 CNC(nb) (nonbonding) orbitals of the smif backbone to ligand π*-type orbitals are intense (ε ≈ 10,000-60,000 M(-1)cm(-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.

Scalable Synthesis of Piperazines Enabled by Visible‐Light Irradiation and Aluminum Organometallics

“…The UV-VIS spectrum of 2 a (Scheme 2 b) presents strong absorptions at λ =394 and 570 nm, and are within the range of the intraligand bands (CNC nbo →Py π* ) observed by Wolczanski and co-workers in transition-metal smif complexes [ λ =(420±40) and (590±30) nm]. [14b,c], [15] We have also monitored the reaction in the presence and absence of visible light (Scheme 2 c), thus observing a clear relationship between light irradiation periods and the formation of 3 a . All these results are fully consistent with the excited diradical intermediate 2 a *, which we reasonably propose.…”

“…b) UV-VIS spectrum of 2 a, featuring intraligand charge-transfer transitions. [14b] c) Formation of 3 a is clearly accelerated by visible light.…”

Synthetic Approaches to (smif)2Ti (smif = 1,3-di-(2-pyridyl)-2-azaallyl) Reveal Redox Non-Innocence and C–C Bond-Formation

“…5 The o -C H resonances of δ 7.17 and 8.15 for 1 were ~3 ppm greater than the average o -C H chemical shift for 2 - 4 (δ 4.28(60)), and the p -C H proton chemical shifts of 1 (δ 6.59, 6.62) were about 2 ppm greater than the corresponding average shift (δ 4.39(20)) for 2 - 4 . The m -C H nearest the quaternary center changed the least, but the average shift from species 2 - 4 of δ 4.83(22) was still over 1 ppm lower than the corresponding values for 1 (δ 5.95, 6.40).…”

“…5,39–41 Fig. 2 shows normalized K-edge titanium spectra for (smif){Li(smif-smif)}Ti ( 1 ) and [(smif)Ti] 2 (μ-κ 3 ,κ 3 -N,N(py) 2 -smif,smif) ( 2 ), which was generated in ~90% purity via removal of 1 via crystallizations.…”

“…6 In (smif) 2 Cr, spectroscopic and calculational investigations provided evidence that the compound was best formulated as (smif(−))(smif(2−))Cr III , and related studies of (smif) 2 V suggested that the HOMO of the compound possessed roughly even amounts of ligand and metal character (i.e., “V(2.5+)”). 5 …”