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The continued development of redox-active ligands requires an understanding as to how ligand modifications and related factors affect the locus of redox activity and spin density in metal complexes...

Diphosphines are highly versatile ancillary ligands in coordination chemistry and catalysis because their structures and donor–acceptor properties can vary widely depending on the substituents atta...

Phosphorus K-edge X-ray absorption spectroscopy (XAS) is a highly effective experimental method for investigating metal-phosphorus bonding and electronic structure. Here, we provide a comprehensive...

The synthesis, coordination chemistry, and reactivity of two diphosphines containing the cyclic triaminoborane 1,8,10,9-triazaboradecalin (TBD) are described. To evaluate the ligand-centered reactivity of PhTBDPhos and iPrTBDPhos, the complexes (PhTBDPhos)MCl2 and (iPrTBDPhos)MCl2, where M = Ni and Pd, were prepared and characterized by elemental analysis, multinuclear NMR spectroscopy (1H, 13C, 31P, and 11B), and single-crystal X-ray diffraction (XRD). Despite very low boron Lewis acidity in the TBD backbone, (PhTBDPhos)NiCl2 (1) and (PhTBDPhos)PdCl2 (3) react with H2O, alcohols, and hydrated fluoride reagents in the presence of NEt3 to yield trans H–O or H–F addition across the bridgehead N–B bond. In contrast, iPrTBDPhos shows no appreciable reactivity when bound to NiCl2 (2) and PdCl2 (4), which is attributed to the sterically-bulky isopropyl substituents blocking substrate access to boron in the TBD backbone. The new complexes {[(PhTBDPhos-H2O)Ni]2(μ-OH)2}Cl2 (5), {[(PhTBDPhos-H2O)Pd]2(μ-OH)2}Cl2 (6), (PhTBDPhos-MeOH)NiCl2 (7), (PhTBDPhos-MeOH)PdCl2 (8), (PhTBDPhos-C3H5OH)PdCl2 (9), and {[(PhTBDPhos-HF)Ni]2(μ-OH)2}Cl2 (10) were isolated, and all but 6 were structurally characterized by single-crystal XRD. Multinuclear NMR studies revealed that isolated, crystallographically-authenticated samples of 5–9 lose ligand-bound water or alcohol with reappearance of starting materials 1 and 3 when dissolved in NMR solvents. Addition of NEt3 attenuated the water and alcohol loss from 5–9 to allow 1H, 13C, 31P, and 11B NMR data to be collected for all the compounds, confirming the determined structures. Additional reactivity experiments with NaOMe and fluoride reagents suggested that participation of the bridgehead nitrogen in the TBD backbone is important for promoting reactivity at boron when PhTBDPhos is bound to Ni and Pd. The term “cooperative ligand-centered reactivity” (CLR) is proposed to define chemical reactions that appear to require participation of more than one atom on the ligand, such as those reported here.

The synthesis and characterization of the new arsenic dithiocarbamate complex As[S2CNPh2]3 and three new phosphonium dithiocarbamates [PPh4][S2CNR2], where R2 = Et2, (CH2)5 and Ph2, are reported. As[S2CNPh2]3 was prepared by treating AsI3 with three equivalents of NaS2CNPh2 in a 2:1 mixture of H2O and EtOH. The precipitate that formed was recrystallized from hot toluene to yield yellow prisms of As[S2CNPh2]3 suitable for single-crystal X-ray diffraction (XRD). Attempts to prepare the known compound As[S2CN(CH2)5]3 using a similar route resulted in a mixture of As[S2CN(CH2)5]3 and the mixed iodide species As[S2CN(CH2)5]2I. Single-crystals of both compounds were isolated from concentrated Et2O/CHCl3 solutions and their structures are described here for the first time. [PPh4][S2CNR2] salts were prepared for comparison to arsenic dithiocarbamates by metathesis reactions with PPh4Br and NaS2CNR2 in acetonitrile. All three salts could be obtained in high-purity from MeCN/Et2O solutions and crystal structures of [PPh4][S2CNEt2] and [PPh4][S2CN(CH2)5] reveal charge-separated phosphonium cations and dithiocarbamate anions. The five new crystal structures are used to compare dithiocarbamate bond distances and angles in the presence and absence of arsenic. Nuclear magnetic resonance (NMR) spectra, infrared (IR) spectra, microanalyses, and melting points of the compounds are reported.

Experimental data on the reactions of argon with BF n + monocations ( n = 0–3) and BF n 2+ dications ( n = 1, 2) and dications reveal the formation of the new argon species ArBF 2+ and ArBF 2 + . Theoretical calculations on the stability of these ions using density functional theory confirm the formation of the rare-gas compounds, but their formation is only exothermic for the reaction Ar + BF 2 2+ → ArBF 2+ + F. According to theory, the corresponding neon compounds all involve endothermic pathways and could hence only be formed via involvement of excited states.