N-heterocyclic carbene (NHC) adducts of iron dichloride, (IMes) 2 FeCl 2 (1a; IMes = 1,3-bis(2,4,6trimethylphenyl)imidazol-2-ylidene) and (IEtPh*) 2 FeCl 2 (1b; IEtPh* = 1,3-bis((R)-1′-phenylethyl)imidazol-2-ylidene), were prepared in good yields from the reactions of Fe{N(SiMe 3 ) 2 } 2 with imidazolium salts. While the iron atom of 1a has a tetrahedral geometry, replacement of the chlorides by methyl groups via treatment of 1a with MeLi led to the formation of the square-planar complex trans-(IMes) 2 FeMe 2 (2). The molecular structures of complexes 1a,b and 2 were identified by means of single-crystal X-ray diffraction analysis. Complexes 1a,b and 2 are good catalyst precursors in the transfer hydrogenation of 2′-acetonaphthone, and complex 2 also efficiently catalyzes the hydrosilylation of 2′-acetonaphthone.

The synthesis, structures, and reactivity of dinuclear Fe 0 complexes of N-heterocyclic carbenes (NHCs, denoted as L) are reported. The NHC adducts of ferric chloride (L)FeCl 3 were prepared from the reactions of FeCl 3 with L in toluene. The reduction of (L)FeCl 3 with KC 8 resulted in the formation of the dinuclear Fe 0 complexes Fe 2 {μ-η 1 (C):η 6 (arene)-L} 2 (2a, L = 1,3-bis(2,4,6trimethylphenyl)imidazol-2-ylidene (IMes); 2b, L = 1,3bis(2,6-diisopropylphenyl)imidazol-2-ylidene (IPr)), in which NHC ligands bridge two iron atoms using one of the arene rings as an η 6 ligand. Their magnetic properties are different: 2a is paramagnetic and 2b is diamagnetic. The dinuclear complexes 2a,b serve as precursors for monomeric (NHC)Fe 0 species, and treatment of 2a,b with 1 atm of CO led to the formation of (L)Fe(CO) 4 . Complex 2a was found to react with 1-azidoadamantane, giving rise to the dinuclear tetrazene complex (IMes)Fe(μ-NAd) 2 Fe(AdNNNNAd) (4).

Radiotherapy is commonly used in patients with head and neck cancer, and usually results in irreversible salivary glands damage and hypofunction. It is therefore important to manage such irradiation to prevent damage to the salivary glands. A previous study showed that Lactoferrin (LF) has a radioprotective effect, but the mechanism was not determined in salivary glands. In the present study, we investigated the detailed radioprotective effect of LF using both ex vivo submandibular salivary gland organ culture and ICR male mice in vivo. We found that LF had effects on both cell proliferation and CyclinD1-mediated cell-cycle progression which were regulated via the ERK1/2 and AKT signal transduction pathways. In addition, LF affected acinar cell structure and function after irradiation. These findings suggest that LF may be a useful agent to prevent irradiation effects in salivary glands.

N-heterocyclic carbene complexes of three- and four-coordinate Fe­(I), [Fe­(LR)4]­[PF6] (LR = 1,3-R2-4,5-dimethylimidazol-2-ylidene, R = Me (2), Et (3), iPr (4)) and [Fe­(LMes)2(THF)]­[PF6] (5) (LMes = 1,3-bis­(2,4,6-trimethylphenyl)­imidazol-2-ylidene), were synthesized from successive reactions of [Fe­(toluene)2]­[PF6]2 with 1 equiv of KC8 and LR (4 equiv for R = Me, Et, iPr; 2 equiv for R = Mes). The coordination geometry of the iron atom in these complexes varies depending on the nature of the R group in LR: a tetrahedral geometry was observed for 2, a square-planar one for 3 and 4, and a three-coordinate T-shaped one for 5. In solution, 4 releases LiPr ligand(s), while the LR ligands of the other Fe­(I) complexes remain firmly bound. Tetrahedral 2 and T-shaped 5 contain a high-spin (S = 3/2) Fe­(I) center, whereas square-planar 3 and 4 contain Fe­(I) in the low-spin state (S = 1/2).