Mesocyclic thioether−aminophosphonite ligands, {−OC10H6(μ-S)C10H6O−}PNC4H8O (2a, 4-(dinaphtho[2,1-d:1‘,2‘-g][1,3,6,2]dioxathiaphosphocin-4-yl)morpholine) and {−OC10H6(μ-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(μ-S)C10H6O−}PCl (1) with corresponding nucleophiles. The ligands 2a and 2b react with (PhCN)2PdCl2 or M(COD)Cl2 (M = PdII or PtII) to afford P-coordinated cis-complexes, [{(−OC10H6(μ-S)C10H6O−)PNC4H8X-κP}2MCl2] (3a, M = PdII, X = O; 3b, M = PdII, X = NMe; 4a, M = PtII, X = O; 4b, M = PtII, X = NMe). Compounds 2a and 2b, upon treatment with [Pd(η3-C3H5)Cl]2 in the presence of AgOTf, produce the P,S-chelated cationic complexes, [{(−OC10H6(μ-S)C10H6O−)PNC4H8X-κP,κS}Pd(η3-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(μ-S)C10H6O−)P(O)-κP,κS}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 × 104 using complex 6a as a catalyst).

Council of Scientific & Industrial Research (CSIR) - India