Palladium(ii) ortho-cyano-aminothiophenolate (ocap) complexes

Abstract

A series of Pd(II) complexes containing ortho-cyano-aminothiophenolate (ocap) ligands have been prepared and their molecular structures elucidated. Hg(II) ocap complexes, [Hg{SC₆H₃XN(CN)}]_n (X = H, Me) (1), react with Na₂S to afford HgS and Na₂[ocap] which reacts in situ with K₂[PdCl₄] to afford palladium ocap complexes [Pd{SC₆H₃XN(CN)}]_n (2). A second route to these coordination polymers has also been developed from reactions of 2-aminobenzothiazole (abt) complexes, trans-PdCl₂(abt)₂ (3), with NaOH. We have not been able to crystallographically characterise coordination polymers 2, but addition of PPh₃, a range of phosphines and cyclic diamines affords mono and binuclear complexes in which the ocap ligand adopts different coordination geometries. With PPh₃, binuclear [Pd(μ-κ²,κ¹-ocap)(PPh₃)]₂ (4) results, in which the ocap bridges the Pd₂ centre acting as an S,N-chelate to one metal centre and binding the second via coordination of the cyanide nitrogen. In contrast, with diphosphines, Ph₂P(CH₂)_nPPh₂ (n = 1–4), mononuclear species predominate as shown in the molecular structures of Pd(κ²-ocap){κ²-Ph₂P(CH₂)_nPPh₂} (5–7; n = 1–3). With 2,2′-bipy and 1,10-phen we propose that related monomeric chelates Pd(κ²-ocap)(κ²-bipy) (9) and Pd(κ²-ocap)(κ²-phen) (10) result but we have been unable to substantiate this crystallographically. Addition of HgCl₂(phen) to 9a (generated in situ) affords heterobimetallic Pd(κ²-phen)(μ-κ²,κ¹-ocap)HgCl₂(κ²-phen) (11), in which Hg(II) is coordinated through the ring sulfur.