Electronic insights into aminoquinoline-based PNN ligands: protonation state dictates geometry while coordination environment dictates N-H acidity and bond strength.

A variety of transition metal complexes bearing aminoquinoline PNH'-R ligands R = Ph (L1H), Cy (L2H) and their amido analogues are reported for rhodium(I) ([Rh(L1H)(PPh)]1 and Rh(L1)(PPh) 2), cobalt(II) (Co(L2)(Cl) 3), and iron(II) ([Fe(L1H)]5, Fe(L1)6, and [Fe(CMe)(L1H)]PF7). The acid-base and redox properties of the amido complexes 2, 6, and their protio parent complexes 1, and 5 permit the determination of the p and bond dissociation free energy (BDFE) of their N-H bonds while the ligand scaffold is coordinated to metal centres of square planar and octahedral geometry, respectively. From relative concentrations obtained by the use of P{H} NMR spectroscopy, a p value of 14 is calculated for rhodium complex 1, 6.

A One-Step Preparation of Tetradentate Ligands with Nitrogen and Phosphorus Donors by Reductive Amination and Representative Iron Complexes.

The synthesis and use of the first examples of unsymmetrical, mixed phosphine donor tripodal NPP' ligands N(CHCHPR)(CHCHPPh) are presented. The ligands are synthesized via a convenient, one pot reductive amination using 2-(diphenylphosphino)ethylamine and various substituted phosphonium dimers in order to introduce mixed phosphine donors substituted with P/P', those being Ph/Cy (), Ph/Pr (), Ph/Bu (), Ph/-Tol (), and Ph/-Tol (). Additionally, we have developed the first known synthesis of a symmetrical tripodal NP ligand N(CHCHPBu) using bench safe ammonium acetate as the lone nitrogen source ().

PNN' & PNN' ligands via reductive amination with phosphine aldehydes: synthesis and base-metal coordination chemistry.

Novel PNN' & P2NN' ligands based on 2-aminopyridine (APyPNN-R) R = Ph (1a), Cy (1b), iBu (1c), 8-aminoquinoline (AQPNN-R) R = Ph (2a), Cy (2b), iBu (2c), iPr (2d), and 2-picolylamine (P2NN-R) R = Ph (3a), Cy (3b), iBu (3c), have been synthesized via a versatile, one-pot, single-step, reductive amination of tertiary phosphine acetaldehydes with the amine by reaction with STAB (where STAB is sodium(triacetoxy)borohydride). Ligands 1b and 1c bridge between paramagnetic Co(ii) and form dimeric complexes Co2Cl4(APyPNN-R)2 (4 and 5) when reacted with cobalt dichloride. Ligands 2a-c coordinate in a tridentate fashion forming chelate complexes MCl2(AQPNN-R) M = Co(ii) (6-8), and, for 2d, the Fe(ii) complex FeCl2(AQPNN-iPr) (9).