Inorganic Chemistry, Vol.41, No.12, 3218-3229, 2002
Diverse evolution of [{Ph2P(CH2)(n)PPh2}Pt(mu-S)(2)Pt{Ph2P(CH2)(n)PPh2}] (n=2, 3) metalloligands in CH2Cl2
The nucleophilicity of the {Pt2S2} core in [{Ph2P(CH2)(n)PPh2}Pt(mu-S)(2)Pt{Ph2P(CH2)(n)PPh2}] (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 P-31, H-1, and C-13 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)(n)PPh2}(S2CH2)], n = 3 (7), 2 (8), and [Pt{Ph2P(CH2)(n)PPh2}Cl-2], 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 [Pt-2(dppp)(2){mu-(SCH2SCH2S)-S'S}]Cl-2 (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 (SCH2SCH2 S)(2-) ligand in 11 has been established. The X-ray structure of 11 is totally unprecedented and consists of a hinged {(dppp)Pt(mu-S)(2)Pt(dppp)} core capped by a CH2SCH2 fragment.