Synthesis and Characterization of (smif)₂M^<i>n</i> (<i>n</i> = 0, M = V, Cr, Mn, Fe, Co, Ni, Ru; <i>n</i> = +1, M = Cr, Mn, Co, Rh, Ir; smif =1,3-di-(2-pyridyl)-2-azaallyl)

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(NSiMe3)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 (ε ≈ 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.