Sequential reactions of heptadentate phosphinoamine LH 3 with rare-earth metal tris-alkyl precursor (Me 3 SiCH 2 ) 3 Ln-(THF) 2 (Ln = Sc, Lu, Yb, Y, Gd) and a low-valent cobalt complex (Ph 3 P) 3 CoI afforded rare-earth metal-supported cobalt iodide complexes. Reduction of these iodide complexes under N 2 allowed the isolation of the first series of dinitrogen complexes of Co(−I) featuring dative Co(−I) → Ln (Ln = Sc, Lu, Yb, Y, Gd) bonding interactions. These compounds were characterized by multinuclear NMR spectroscopy, X-ray diffraction analysis, electrochemistry, and computational studies. The correlation of N−N vibrational frequencies with the pK a of [Ln(H 2 O) 6 ] 3+ showed that strongest activation of N 2 was achieved with the least Lewis acidic Gd(III) ion. Interestingly, these Ln−Co−N 2 complexes catalyzed silylation of N 2 in the presence of KC 8 and Me 3 SiCl with turnover numbers (TONs) up to 16, where the lutetium-supported Co(−I) complex showed the highest activity within the series. The role of the Lewis acidic Ln(III) was crucial to achieve catalytic turnovers and tunable reactivity toward N 2 functionalization.

The bis­(NHC) (NHC = N-heterocyclic carbene)-based CNC-pincer rare-earth-metal amido complexes LRE­[N­(SiMe3)2]2 (L = 4-CH3-2-{R-[N­(CH)2CN]}­C6H3]2N; L 2 , R = CH3; L 3 , R = CH­(CH3)2) were synthesized and characterized, and their catalytic activities toward hydrophosphination of heterocumulenes were developed. Reactions of bis­[2-(3-methylimidazolium)-4-methylphenyl]­amine diiodide (H3 L 2 I2) or bis­[2-(3-isopropylimidazolium)-4-methylphenyl]­amine diiodide (H3 L 3 I2) with 5 equiv of NaN­(SiMe3)2 followed by treatment with 1 equiv of RECl3 in THF at −78 °C afforded the bis­(NHC)-based CNC-pincer rare-earth-metal amido complexes LRE­[N­(SiMe3)2]2 (L 2 = [4-CH3-2-{CH3-[N­(CH)2CN]}­C6H3]2N, RE = Y (1), Eu (2), Er (3); L 3 = [4-CH3-2-{(CH3)2CH-[N­(CH)2CN]}­C6H3]2N, RE = Y (4), Er (5), Yb (6)). Complexes 4–6 can also be prepared by stepwise reactions of H3 L 3 I2 with n-BuLi in THF followed by reactions with [(Me3Si)2N]3RE­(μ-Cl)­Li­(THF)3. Stepwise reactions of H3 L 2 I2 with n-BuLi in THF followed by treatment with [(Me3Si)2N]3RE­(μ-Cl)­Li­(THF)3 generated the bis­(NHC)-based CNC-pincer rare-earth-metal amido complexes L 2 RE­[N­(SiMe3)2]2 (RE = Y (1), Er (3)) together with the fused-heterocyclic compound 3,8,9-trimethyl-8a,9-dihydro-8H-benzo­[4,5]­imidazo­[2′,1′:2,3]­imidazo­[1,2-a]­imidazo­[2,1-c]­quinoxaline (7), which formed through carbene C–C and C–N coupling. Attempts to prepare complexes of the type LRE­[N­(SiMe3)2]2 by reaction of H3 L 3 I2 with [(Me3Si)2N]3Yb­(μ-Cl)­Li­(THF)3 in THF, however, afforded mixed complexes of the bis­(NHC)-based CNC-pincer ytterbium complex L 3 Yb­[N­(SiMe3)2]2 (6) and the unexpected bis­(NHC)-based CNC-pincer monoamido ytterbium iodide L 3 YbI­[N­(SiMe3)2] (8). Investigation of the catalytic activity of complexes 1–6 and 8 indicated that all complexes displayed high activity toward the addition of the phosphine P–H bond to heterocumulenes, producing the corresponding phosphaguanidines, phosphaureas, and phosphathioureas, which represents the first example of bis­(NHC)-based CNC-pincer type rare-earth-metal amido complexes as catalysts for the catalytic addition of the phosphine P–H bond to heterocumulenes with high efficiency in the presence of a low catalyst loading at room temperature.

Heterobimetallic Ln(III)-Pd(0) complexes (Ln = Y, Sm, Gd, Yb) featuring tetranuclear structures with COD as bridges were obtained via the metallation of tris(phosphinoamido) rare-earth metal complexes [Ph2PNAd]3Ln (Ad = admantyl)...

As the oxidized state models for the active site of [FeFe]-H2ases, a series of new diphosphine-chelated dinuclear FeII(μ-X)­FeII (X = Cl, Br, I) complexes have been prepared using a simple and convenient one-pot synthetic method. Thus, treatment of the diphosphine dppv-chelated Fe dithiolate (dppv)­Fe­(CO)2(pdt) with equimolar amounts of the dppv-chelated Fe dihalides (dppv)­Fe­(CO)2X2 in the presence of a 2-fold excess of NaBF4 at room temperature gave the corresponding homodiphosphine dppv/dppv-chelated dinuclear Fe complexes [(dppv)2(CO)2Fe2(μ-pdt)­(μ-X)]­(BF4) ([1(μ-X)]­(BF4)), whereas their dppe analogues [(dppe)2(CO)2Fe2(μ-pdt)­(μ-X)]­(BF4) ([2(μ-X)]­(BF4)) could be prepared by treatment of the dppe-chelated Fe complex (dppe)­Fe­(CO)2(pdt) with dppe-chelated Fe dihalides (dppe)­Fe­(CO)2X2 and NaBF4 under similar conditions. Furthermore, the heterodiphosphine dppv/dppe-chelated dinuclear Fe complexes [(dppv)­(dppe)­(CO)2Fe2(μ-pdt)­(μ-X)]­(BF4) ([3(μ-X)]­(BF4)) could be similarly prepared by the one-pot reactions of the dppv-chelated Fe dithiolate (dppv)­Fe­(CO)2(pdt) with equimolar dppe-chelated Fe dihalides (dppe)­Fe­(CO)2X2 and a 2-fold excess of NaBF4. All the prepared new complexes [1(μ-X)]­(BF4)–[3(μ-X)]­(BF4) were fully characterized by elemental analysis and various spectroscopic techniques and particularly for some of their representatives by X-ray crystallography. In addition, on the basis of an electrochemical study, complexes [1(μ-X)]­(BF4) were found to be catalysts for H2 production from Cl3CCO2H under CV conditions.