Synthesis and metal coordination chemistry of (phenyl)(pyridin-2-ylmethyl)phosphinodithioic acid, [2-C 5 H 4 N]CH 2 P(S)(SH)(Ph)

A three-step synthesis for the bifunctional ligand (phenyl)(pyridin-2-ylmethyl)phosphinodithioic acid, [2-C5H4N]CH2P(S)(SH)(Ph) (3-H), was developed. The molecule was characterized by spectroscopic methods, and single crystal X-ray diffraction analysis, and the molecule found to exist in a zwitterionic form (3′). Protonation constants for 3′ were measured spectrophotometrically in 0.1M NaClO4 aqueous solution. The coordination chemistry of 3′ toward CdCl2 and PtCl2 was explored, and the complexes [Cd(3′)Cl2]2 and [Pt(3−)2]·CHCl3 were isolated and structurally characterized by single crystal X-ray diffraction methods. Complexation constants for 3′ with Cd(II), Zn(II) and La(III), as a function of pH, were measured by titration techniques. An initial effort to prepare the [pyridin-bis(2,6-yl-methylphosphinodithioic acid)] analog of 3-H led to the formation and isolation of (phenyl)(6-methylpyridin-2-ylmethyl)phosphinodithioic acid, [2-C5H3N(6-CH3)]CH2P(S)(SH)(Ph) (6-H), that was characterized by spectroscopic methods and single crystal X-ray diffraction analysis. As found with 3-H, 6-H, adopts a zwitterionic structural form (6′).