Organometallics最新文献

Phosphine ligands bearing amidine groups were designed for the synthesis of complexes in which a metal center and ligands cooperate. Several palladium amidinate complexes were synthesized from these ligands. The reaction of these complexes with various organic molecules containing an acidic OH group gave the palladium amidine complexes. In the reaction, the O–H bond was activated by metal–ligand cooperation (MLC).

Structures and bonding of various borallyl complexes stabilized in the coordination sphere of osmium have been demonstrated. For example, the Os-borallyl species [(PPh₃)(H)₂Os(η⁵-B₃H₅(C₅H₄NS)₂)] (2) has been synthesized from the prolonged thermolysis of [(Ph₃P)Os(κ²-N,S-(C₅H₄NS))₂(κ¹-S-(C₅H₄NS))] (1) with an excess amount of BH₃·THF. The structural features of 2 suggest the presence of one linear triborane unit [B₃H₅(C₅H₄NS)₂] which is stabilized in the coordination sphere of osmium through an η³ bonding mode. Strikingly, the Os center in 2 possesses unique secondary interactions through two mercaptopyridinyl sulfur atoms, along with the primary η³-borallyl bonding. Furthermore, we have explored the reaction of [Cp*Os(PPh₃)₂Cl] (4) with BH₃·THF that furnished another borallyl species, [Cp*(PPh₃)(H)Os(η³-B₃H₇)] (5). Notably, species 2 and 5 are both structurally and electronically linked to arachno-B₄H₁₀ in which the “hinge-tip” vertex is replaced by osmium. A detailed comparative analysis in combination with theoretical calculation offered valuable insights into the bonding scenarios in both borallyl species and aided us to assess their relative stability.

This manuscript describes the synthesis of Os complexes supported by the diarylamido/bis(phosphine) PNP pincer ligand. Compound (PNP)OsH(CO) (3-Os) was prepared by analogy with the previously reported 3-Ru. However, attempts to make (PNP)OsH₃ (4-Os) analogously to 4-Ru resulted in the formation of an unexpected compound (5-Os) that is a product of addition of a BH₃ unit across the Os-N bond in 4-Os. Nonetheless, 4-Os was prepared via an alternative route. Unlike 4-Ru, 4-Os appears to be a classical trihydride. Compounds 3-Ru, 3-Os, 4-Os, 4-Ru, and 5-Os were tested as potential catalysts for (a) dehydrogenative borylation of terminal alkynes (DHBTA) and (b) dehydrogenative borylation of benzene. No catalytic C-H borylation was observed for any of them, but all of them catalyzed unselective hydroboration of 4-MeC₆H₄CCH.

This manuscript describes the synthesis of Os complexes supported by the diarylamido/bis(phosphine) PNP pincer ligand. Compound (PNP)OsH(CO) (3-Os) was prepared by analogy with the previously reported 3-Ru. However, attempts to make (PNP)OsH₃ (4-Os) analogously to 4-Ru resulted in the formation of an unexpected compound (5-Os) that is a product of addition of a BH₃ unit across the Os–N bond in 4-Os. Nonetheless, 4-Os was prepared via an alternative route. Unlike 4-Ru, 4-Os appears to be a classical trihydride. Compounds 3-Ru, 3-Os, 4-Os, 4-Ru, and 5-Os were tested as potential catalysts for (a) dehydrogenative borylation of terminal alkynes (DHBTA) and (b) dehydrogenative borylation of benzene. No catalytic C–H borylation was observed for any of them, but all of them catalyzed unselective hydroboration of 4-MeC₆H₄CCH.

Two straightforward synthetic procedures leading to air- and moisture-stable trans-[Pd(NHC)(NH₂ⁿBu)Cl₂] precatalysts are presented. These complexes, obtained by adding n-butylamine to [Pd(NHC)(μ-Cl)Cl]₂ or trans-[Pd(NHC)(DMS)Cl₂] precursors (DMS, dimethyl sulfide), demonstrate superior catalytic activity compared to their DMS counterparts in Buchwald–Hartwig amination reactions. Utilizing a more sustainable solvent (2-MeTHF), the catalyst loading was halved to 0.1 mol %, establishing this new system as a highly efficient and environmentally more friendly alternative to previous systems.

Our lab has studied a complex with an Al–Fe bond capable of cooperative substrate activation processes. This reactivity was previously found to depend on Al–Fe homolytic bond dissociation followed by substrate coordination to the Al^III center of the resulting redox noninnocent radical intermediate. The current study investigates ligand influences on the Al–Fe bond dissociation free energy (BDFE_Al–Fe) and the Gibbs free energy of H₂O coordination at aluminum (ΔG_OH2) for a series of variants with systematic changes in their ligand substitution patterns. DFT calculations combined with multivariate linear regression analysis provided predictive models for ligand effects on both BDFE_Al–Fe and ΔG_Al–OH2 for three synthetically tunable positions in the molecular architecture when using appropriate electronic (σ_para, σ_meta) and steric (wSterimol, %V_bur) descriptors. Chemical interpretations of the predictive models were facilitated by the use of these intuitive descriptors. Linear scaling relationships relating BDFE_Al–Fe and ΔG_OH2 provided further insight. We expect our findings to inform designs of future Al-containing heterobinuclear complexes for small molecule activation processes and cleavage reactions of strong or inert bonds.

In recent years, NHC-derived zwitterions [NHC·CS(X)] (X = S and NR) have gained a great deal of attention owing to their various applications in fields such as organic synthesis, organometallics, and more recently in catalysis. In this work, we report that the reaction of free triarylated triazol-5-ylidenes (MIC) with equimolar amounts of dithiocarboxylate and isothiocyanate derivatives allows for the preparation of a series of MIC·SC₂ and MIC·CSNAr zwitterions in good yields. Their potential as ligands for transition metals was demonstrated by the synthesis of ruthenium(II) complexes with the general formulas [RuCl(p-cymene)(MIC·CS₂)]PF₆ and [RuCl(p-cymene)(MIC·CNSAr)]PF₆. The zwitterions and the ruthenium complexes were fully characterized by NMR spectroscopy, X-ray crystallography, TGA, and elemental analysis. The new ruthenium complexes were successfully applied as catalysts in the transfer hydrogenation of a series of aldehydes and ketones showing good efficiency under low catalyst loadings and providing excellent conversions.

Coinage metal complexes, particularly Cu(I) and Au(I), supported by N-heterocyclic carbenes are of broad interest in organometallic synthesis, catalysis, and luminescent materials. The d¹⁰ coinage metals can adopt varied linear, trigonal planar, and tetrahedral geometries. However, two-coordinate, linear Cu(I) and Au(I) complexes supported by sterically demanding monodentate or chelating carbenes are generally observed. In most cases, chelating ligands generate multinuclear species with linear geometries at the corresponding Cu(I) centers rather than mononuclear complexes. In this report, we synthesized two bis(carbene) ligands anchored by a flexible bipyridine and a rigid naphthyridine backbone with tunable proximal and distal steric properties at the wingtips to examine the influence of backbone rigidity and directionality of carbene donors on the formation of trigonal planar coinage metal species. The bipyridine-bis(carbene) (ImPy)₂ ligand exclusively stabilizes dinuclear chloride complexes of Cu(I) and Ag(I), whereas the naphthyridine-bis(carbene) (NBC) stabilizes mononuclear, trigonal planar chloride complexes of Cu(I) and Ag(I) and a dinuclear chloride Au(I) complex.

Dinitrogen complexes have garnered significant attention due to their potential applications across various fields. The synthesis and characterization of novel dinitrogen complexes are essential to advancing this area of research. In this study, we report the bulk synthesis and first successful single crystal X-ray structure analysis of [Cr(PCy₃)₂(CO)₃(N₂)] using high-pressure nitrogen at 50 atm. The presence of the nitrogen ligand was confirmed by infrared (IR) spectroscopy and elemental analysis, and the interesting disorder phenomenon between N₂ and CO ligands was also observed. The elimination process of the N₂ ligand was monitored by a combination of thermogravimetry (TG) and temperature-programmed desorption (TPD), and the changes in the color, IR spectrum, and UV–vis spectrum of the complexes before and after elimination were investigated. These experimental results agree well with the results of density functional theory (DFT) calculations.

Replacing wasteful metal-based reducing agents with H₂ is an important goal for green chemistry. For this reason, we outline our design principles for building catalysts that use electrons from hydrogen to activate organohalides for reaction. These designs rely on an electron-withdrawing ligand to support low-valent metal centers, an electron-donating ligand to support oxidative addition, and the capacity for vacant sites to allow substrate docking. We begin by outlining our previous work in this field before describing a new rhodium complex that activates a particularly stubborn organohalide, 2,2-dibromopropane, using electrons from hydrogen. We then react this activated organohalide with styrene to generate a synthetically useful fragment of murraol in an efficient manner.