Mesocyclic thioether-aminophosphonite ligands, {-OC10H6(mu-S)C10H6O-}PNC4H8O(2a, 4-(dinaphtho[2,1-d:1', 2'-g][1,3,6,2]dioxathiaphosphocin-4-yl)morpholine) and {-OC10H6(A-S)C10H6O-}PNC4H8NCH3 (2b, 1-(dinaphtho[2,1-d:1', 2'-g][1,3,6,2]dioxathiaphosphocin-4-yl)-4-methylpiperazine) are obtained by reacting {-OC10H6(mu-S)C10H6O} PCl (1) with corresponding nucleophiles. The ligands 2a and 2b react with (PhCN)(2)PdCl2 or M(COD)Cl-2 (M = Pd-II or PtII) to afford P-coordinated cis-complexes, [{(-OC10H6(mu-S)C10H6O-)PNC4H8X-kappa P}(2)MCl2] (3a, M = Pd-II, X) O; 3b, M = Pd-II, X = NMe; 4a, M = Pt-II, X = O; 4b, M = Pt-II, X = NMe). Compounds 2a and 2b, upon treatment with [Pd(eta(3)-C3H5)Cl](2) in the presence of AgOTf, produce the P,S-chelated cationic complexes, [{(-OC10H6(mu-S)C10H6O-)PNC4H8X-kappa P, kappa S} Pd(eta(3)-C3H5)](CF3SO3) (5a, X) O and 5b, X = NMe). Treatment of 2a and 2b with ( PhCN) 2PdCl2 in the presence of trace amount of H2O affords P, S-chelated anionic complexes, [{(-OC10H6(mu-S)C10H6O-)P(O)-kappa P, kappa S}PdCl2](H2NC4H8X) (6a, X = O and 6b, X = NMe), via P-N bond cleavage. The crystal structures of compounds 1, 2a, 2b, 4a, and 6a are reported. Compound 6a is a rare example of crystallographically characterized anionic transition metal complex containing a thioether-phosphonate ligand. Most of these palladium complexes proved to be very active catalysts for the Suzuki-Miyaura reaction with excellent turnover number (( TON), up to 9.2 x 10(4) using complex 6a as a catalyst).