Single crystals of the {Fe (II)(pyrazine)[Pt(CN) 4]} spin crossover complex were synthesized by a slow diffusion method. The crystals exhibit a thermal spin transition around room temperature (298 K), which is accompanied by a 14 K wide hysteresis loop. X-ray single-crystal analysis confirms that this compound crystallizes in the tetragonal P4/ mmm space group in both spin states. Within the thermal hysteresis region a complete bidirectional photoconversion was induced between the two phases (high spin right arrow over left arrow low spin) when a short single laser pulse (4 ns, 532 nm) was shined on the sample.

Functionalization of CO2 is a challenging goal and precedents exist for the generation of HCOOH, CO, CH3OH, and CH4 in mild conditions. In this series, CH2O, a very reactive molecule, remains an elementary C1 building block to be observed. Herein we report the direct observation of free formaldehyde from the borane reduction of CO2 catalyzed by a polyhydride ruthenium complex. Guided by mechanistic studies, we disclose the selective trapping of formaldehyde by in situ condensation with a primary amine into the corresponding imine in very mild conditions. Subsequent hydrolysis into amine and a formalin solution demonstrates for the first time that CO2 can be used as a C1 feedstock to produce formaldehyde.

Trinuclear linear 3d-4f-3d complexes (3d = Mn(II), Fe(II), Co(II), Zn(II) and 4f = La(III), Gd(III), Tb(III), Dy(III)) were prepared by using a tripodal nonadentate Schiff base ligand, N,N',N''-tris(2-hydroxy-3-methoxybenzilidene)-2-(aminomethyl)-2-methyl-1,3-propanediamine. The structural determinations showed that in these complexes two distorted trigonal prismatic transition metal complexes of identical chirality are assembled through 4f cations. The Mn and Fe entities crystallize in the chiral space group P2(1)2(1)2(1) as pure enantiomers; the cobalt complexes exhibit a less straightforward behavior. All Mn, Fe, and Co complexes experience M(II)-Ln(III) ferromagnetic interactions. The Mn-Gd interaction is weak (0.08 cm(-1)) in comparison to the Fe-Gd (0.69 cm(-1)) and Co-Gd (0.52 cm(-1)) ones while the single ion zero field splitting (ZFS) term D is larger for the Fe complexes (5.7 cm(-1)) than for the cobalt ones. The cobalt complexes behave as single-molecules magnets (SMMs) with large magnetization hysteresis loops, as a consequence of the particularly slow magnetic relaxation characterizing these trinuclear molecules. Such large hysteresis loops, which are observed for the first time in Co-Ln complexes, confirm that quantum tunnelling of the magnetization does not operate in the Co-Gd-Co complex.

Hydrogenation of benzonitrile into benzylamine is catalyzed under very mild conditions by the ruthenium bis(dihydrogen) complex RuH(2)(H(2))(2)(PCyp(3))(2), incorporating two tricyclopentylphosphines. Two key intermediates have been isolated, resulting from the activation of benzonitrile at early stages of activation, i.e., either N-coordination through the nitrile function or first hydrogenation with benzylimine formation, followed by, thanks to C-H activation, coordination at ruthenium as an orthometalated ligand.

Treatment of Ru(eta4-C8H12)(eta6-C8H10) with 3 bar H2 in the presence of 2 equiv of tricyclopentylphosphine (PCyp3) in pentane resulted in the isolation of the new bis(dihydrogen) complex RuH2(eta2-H2)2(PCyp3)2 (2), characterized by NMR and single-crystal X-ray and neutron diffraction. The single-crystal neutron diffraction study is the first carried out for a bis(dihydrogen) complex. The coordination geometry around the metal center is a distorted octahedron defined by the two phosphines in a trans configuration (making an angle of 168.9(1) degrees ), two cis dihydrogen ligands, and two hydrides trans to them, defining the equatorial plane. The H-H bond distances (0.825(8) and 0.835(8) A) are characteristic of two "unstretched" dihydrogen ligands. H/D exchange between the Ru-H and the C-D bonds of deuterated benzene is observed within 1 h, leading to the formation of various isotopomers RuHxD6-x(PCyp3)2 (with x = 0-6). 2 is a catalyst precursor for ethylene coupling (20 bar, 293 K) to a functionalized arene (Murai reaction). We found a 90% conversion of acetophenone to 2-ethylacetophenone within 35 min, whereas 10 h was needed in the same conditions using the analogous tricyclohexylphosphine complex, RuH2(eta2-H2)2(PCy3)2, the best catalyst precursor, at room temperature, prior to this work.

One and two: The C2 compound pinBOCH2OCHO (see scheme; HBpin=pinacolborane) and several C1 compounds have been obtained from the borane‐mediated reduction of CO2 under mild conditions with the catalyst precursor [RuH2(H2)2(PCy3)2]. Mechanistic investigation highlights the role of a series of new carbonyl ruthenium complexes that were characterized by multinuclear NMR spectroscopy, IR spectroscopy, and X‐ray diffraction studies.

Anionic two-coordinate complexes of first-row transition-metal(I) centres are rare molecules that are expected to reveal new magnetic properties and reactivity. Recently, we demonstrated that a N(SiMe3)2(-) ligand set, which is unable to prevent dimerisation or extraneous ligand coordination at the +2 oxidation state of iron, was nonetheless able to stabilise anionic two-coordinate Fe(I) complexes even in the presence of a Lewis base. We now report analogous Cr(I) and Co(I) complexes with exclusively this amido ligand and the isolation of a [Mn(I){N(SiMe3)2}2]2(2-) dimer that features a Mn-Mn bond. Additionally, by increasing the steric hindrance of the ligand set, the two-coordinate complex [Mn(I){N(Dipp)(SiMe3)}2](-) was isolated (Dipp=2,6-iPr2-C6H3). Characterisation of these compounds by using X-ray crystallography, NMR spectroscopy, and magnetic susceptibility measurements is provided along with ligand-field analysis based on CASSCF/NEVPT2 ab initio calculations.

Starting from RuHCl(H2)(PCy3)2, a terminal ruthenium mesitylborylene complex was obtained via double B-H bond activation of mesitylborane and concomitant release of dihydrogen, such a process being remarkably reversible.