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.