Chelating or bridging Pd(ii) and Pt(ii) metalloligands from the functional phosphineligandN-(diphenylphosphino)-1,3,4-thiadiazol-2-amine. New heterometallic Pd(ii)/Pt(ii) and Pt(ii)/Au(i) complexes

Abstract

The reaction of two equivalents of the functional phosphine ligand N-(diphenylphosphino)-1,3,4-thiadiazol-2-amine Ph₂PNHCNNCHS (2) with [PdCl₂(NCPh)₂] in the presence of NEt₃ gives the neutral, P,N-chelated complex cis-[Pd(Ph₂PNCNNCHS)₂] ([Pd(2_−H)₂], 3b), which is analogous to the Pt(II) analoguecis-[Pt(Ph₂PNCNNCHS)₂] ([Pt(2_−H)₂], 3a) reported previously. These complexes function as chelating metalloligands when further coordinated to a metal through each of the CH-N atoms. In the resulting complexes, each endo-cyclic N donor of the thiadiazole rings is bonded to a different metal centre. Thus, the heterodinuclear palladium/platinum complexes cis-[Pt(Ph₂PNCNNCHS)₂PdCl₂] ([Pt(2_−H)₂·PdCl₂], 4a) and cis-[Pd(Ph₂PNCNNCHS)₂PtCl₂] ([Pd(2_−H)₂·PtCl₂], 4b) were obtained by reaction with [PdCl₂(NCPh)₂] and [PtCl₂(NCPh)₂], respectively. In contrast, reaction of 3a with [AuCl(tht)] occurred instead at the P-bound N atom, and afforded the platinum/digold complex cis-[Pt{Ph₂PN(AuCl)CNNCHS}₂] ([Pt(2_−H)₂(AuCl)₂], 5). For comparison, reaction of 4a with HBF₄ yielded cis-[Pt(Ph₂PNHCNNCHS)₂PdCl₂](BF₄)₂ ([H₂4a](BF₄)₂, 6), in which the chelated PdCl₂ moiety is retained. Complexes 3b, 4a·CH₂Cl₂, 4b·0.5C₇H₈, 5·4CHCl₃ and 6 have been structurally characterized by X-ray diffraction.