Diverse evolution of [{Ph₂P(CH₂)_n PPh₂}Pt(μ-S)₂Pt {Ph₂P(CH₂)_nPPh₂}] (n = 2, 3) metalloligands in CH₂Cl₂

The nucleophilicity of the {Pt2S2} core in [{Ph2P(CH2)n PPh2}Pt(μ-S)2Pt{Ph2 P(CH2)nPPh2}] (n = 3, dppp (1); n = 2, dppe (2)) metalloligands toward the CH2Cl2 solvent has been thoroughly studied. Complex 1, which has been obtained and characterized by X-ray diffraction, is structurally related to 2 and consists of dinuclear molecules with a hinged {Pt2S2} central ring. The reaction of 1 and 2 with CH2Cl2 has been followed by means of 31P, 1H, and 13C NMR, electrospray ionization mass spectrometry, and X-ray data. Although both reactions proceed at different rates, the first steps are common and lead to a mixture of the corresponding mononuclear complexes [Pt{Ph2P(CH2)nPPh2} (S2CH2)], n = 3 (7), 2 (8), and [Pt{Ph2P(CH2)nPPh2} Cl2], n = 3 (9), 2 (10). Theoretical calculations give support to the proposed pathway for the disintegration process of the {Pt2S2} ring. Only in the case of 1, the reaction proceeds further yielding [Pt2(dppp)2{μ-(SCH2SCH2S)-S, S′}]Cl2 (11). To confirm the sequence of the reactions leading from 1 and 2 to the final products 9 and 11 or 8 and 10, respectively, complexes 7, 8, and 11 have been synthesized and structurally characterized. Additional experiments have allowed elucidation of the reaction mechanism involved from 7 to 11, and thus, the origin of the CH2 groups that participate in the expansion of the (SCH2S)2- ligand in 7 to afford the bridging (SCH2SCH2S)2- ligand in 11 has been established. The X-ray structure of 11 is totally unprecedented and consists of a hinged {(dppp)Pt(μ-S)2Pt(dppp)} core capped by a CH2SCH2 fragment.