Regioselective versus complete chalcogen transfer reactions of the bis(bidentate) phosphine cis,trans,cis-1,2,3,4-tetrakis(diphenylphosphino)cyclobutane: full characterization of new, hemilabile ligands and their complexes with palladium(ii) and platinum(ii)

Abstract

The bis(bidentate) phosphine cis,trans,cis-1,2,3,4-tetrakis(diphenylphosphino)cyclobutane (dppcb) has been regioselectively oxidized by sulfur to the novel, hemilabile disulfide cis,trans,cis-2,3-bis(diphenylphosphinothioyl)-1,4-bis(diphenylphosphino)cyclobutane (2,3-trans-dppcbS₂, I). Also the tetrachalcogenides cis,trans,cis-1,2,3,4-tetrakis(diphenylphosphinoyl)cyclobutane (dppcbO₄, II), cis,trans,cis-1,2,3,4-tetrakis(diphenylphosphinothioyl)cyclobutane (dppcbS₄, III), and cis,trans,cis-1,2,3,4-tetrakis(diphenylphosphinoselenoyl)cyclobutane (dppcbSe₄, IV) have been obtained. Regioselective selenization of the previously prepared disulfide cis,trans,cis-1,3-bis(diphenylphosphinothioyl)-2,4-bis(diphenylphosphino)cyclobutane (1,3-trans-dppcbS₂) leads to the unique, mixed chalcogenide cis,trans,cis-1,3-bis(diphenylphosphinoselenoyl)-2,4-bis(diphenylphosphinothioyl)cyclobutane (trans-dppcbSe₂S₂, V). All of the new ligands I–V have been fully characterized by X-ray structure analyses showing folded cyclobutane rings. The coordination chemistry of the previously prepared hemilabile diselenide cis,trans,cis-1,3-bis(diphenylphosphinoselenoyl)-2,4-bis(diphenylphosphino)cyclobutane (1,3-trans-dppcbSe₂), 1,3-trans-dppcbS₂, I, III, and IV with PdCl₂ or PtCl₂ has been studied. The novel complexes [Pd₂Cl₄(1,3-trans-dppcbSe₂-P,P′,Se,Se′)] (1), [Pt₂Cl₄(1,3-trans-dppcbS₂-P,P′,S,S′)] (2), [PtCl₂(2,3-trans-dppcbS₂-P,P′)] (3), [Pt₂Cl₄(dppcbS₄-S,S′,S″,S‴)] (4), [PtCl₂(2,3-trans-dppcbSe₂-P,P′)] (5), and [Pt₂Cl₄(2,3-trans-dppcbSe₂-P,P′,Se,Se′)] (6) have been obtained. 6 has been fully characterized by an X-ray structure analysis.