Reaction of the diiminepyridine ligand Et DIP (2,6-Et 2 -C 6 H 3 NCMe) 2 C 5 H 3 N) with TiCl 3 (THF) 3 gave the corresponding Ti(III) complex ( Et DIP)TiCl 3 (1). Reduction of 1 with 1 equiv of KC 8 produced the formally Ti(II) complex ( Et DIP)TiCl 2 (2). From this, ( Et DIP)TiClR complexes (R = Me (3a), Me 3 SiCH 2 (3b), Ph (3c)) were obtained by addition of 1 equiv of RLi. Similarly, dialkyl complexes ( Et DIP)TiR 2 (R = Me (4a), Me 3 SiCH 2 (4b)) were obtained with 2 equiv of RLi. All new complexes except 3b were characterized by single-crystal X-ray diffraction. EPR studies indicate that complex 1 is best regarded as a true Ti(III) complex with an "innocent" DIP ligand. Complexes 2−4 are all diamagnetic. In contrast to DIP complexes of the late transition metals Fe and Co, the new complexes 2−4 show strong upfield 1 H NMR shifts for the pyridine β and γ protons caused by transfer of negative charge to the DIP ligand. On the basis of this and the CN and C imine −C Py bond lengths, a description involving Ti(IV) and a dianionic ligand seems most appropriate, and DFT calculations support this interpretation. This means that reduction of Ti(III) complex 1 results in oxidation of the metal center to Ti(IV). VT-NMR studies of 4a suggest a small and temperature-dependent thermal population of a triplet state, and indeed calculations indicate that 4a has the lowest singlet− triplet energy difference of the systems studied.

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Diiminepyridines (DIP) are popular redox “non‐innocent” ligands with widespread application in late, first‐row transition metal mediated catalysis and coordination chemistry. Here, we report the isolation and characterization of a pair of phosphorus coordination complexes in the +1 and +3 oxidation states supported by the same ligand framework bearing sterically imposing and electron‐releasing tBu substituents on the imine carbons of the DIP backbone. Electrochemical analysis demonstrates that the DIP scaffold can retain its ability to serve as an electron reservoir when coordinated to a reduced pnictogen centre, with a reversible reduction observed for the PI complex.

A B S T R A C TThe goal of this study was to survey the feasibility of the biosorption of two acid dyes (Acid Blue 113 and Acid Black 1) from aqueous solution using biomass prepared from potato peel waste. Adsorption isotherms were constructed and the kinetics of dye adsorption were studied. Langmuir and Freundlich isotherms, pseudo-first-order, and pseudo-second-order kinetic models were studied. The maximum biosorption was observed at a pH of 2 and 3 for Acid Blue 113 and Acid Black 1, respectively. The biosorption of two dyes increased with increasing contact time and reached equilibrium after two hours, approximately. Acid dye removal efficiency decreased with an increase in the initial dye concentration. The sum of squares due to error and the coefficient of determination (R2) analysis showed that the pseudo-second-order kinetic and the Langmuir isotherm model are better fit for the adsorption of Acid Blue 113 and Acid Black 1 on used potato peel waste.

Reaction of the dinuclear complex [Pd{j2-N2 0 ,C1-2-(2 0 -NH 2 C 6 H 4 )C 6 H 4 }Cl] 2 (1) with ligands (L = 4-picoline, sym-collidine) gave the six-membered palladacycles [Pd{j2-N2 0 ,C1-2-(2 0 -NH 2 C 6 H 4 )C 6 H 4 }Cl(L)] (2). The complex 1 reacted with AgX (X = CF 3 SO 3 , BF 4 ) and bidentate ligands [L-L = phen (phenanthroline), dppe (bis(diphenylphosphino)ethane), bipy(2,2 0 -bipyridine) and dppp (bis(diphenylphosphino)propane)] giving the mononuclear orthopalladated complexes [Pd{j2-N2 0 ,C1-2-(2 0 -NH 2 C 6 H 4 )C 6 H 4 }(L-L)] (3) [L-L = phen, dppe, bipy and dppp]. These compounds were characterized by physicochemical methods, and the structure of [Pd{j2-N2 0 ,C1-2-(2 0 -NH 2 C 6 H 4 )C 6 H 4 }Cl(L)] (L = sym-collidine) was determined by single-crystal X-ray analysis.