Methylation of [Pt2(μ-SR)(μ-S)(PPh3) 4]: En route to mixed-thiolato bridged complexes

Abstract

Sequential and independent alkylation of [Pt2(μ-S) 2(PPh3)4] by RX followed by methylation with Me2SO4 led to the first successful isolation of novel diplatinum complexes [Pt2(μ-SR)(μ-SCH3)(PPh 3)4](PF6)2 (3) (R = CH 2C6H5 (a), CH2CHCH2 (b), C5H10CO2CH2CH3 (c), C2H4CO2-CH2CH3 (d), CH2CH2CN (e), C2H4CH-(O) 2C2H4 (f), and C2H 4SC6H5 (g)) with asymmetric thiolato bridges. The synthetic methodology can tolerate a range of electronically and sterically contrasting thiolate substituents with different chemical functionalities. The X-ray crystal structures of 3a-c, g confirm the unusual heterodialkylation with two different thiolato bridging ligands in a syn-exo conformation. A secondary product [Pt2(μ-SC2H4SC6H 5) (μ-SCH3)(PPh3](PF6) 2 (4), which arises from intramolecular phosphine displacement by the thio pendant at the neighboring SC2H4SC6H 5 bridge, has been trapped and characterized. This is an unusual diplatinum complex with three different bridging thio ligands and three different phosphines. The heteroalkylation is screened in situ by ESI-MS, and the resultant spectral data provide a convenient guide for one-pot syntheses of {M2(SR)(SR′)} from{M2S}. The isolation and X-ray crystal structure of a homoalkylated analogue [Pt2(μ-SCH 3)2(PPh3)4](PF6) 2 (6) is included for comparison. © 2006 Wiley-VCH Verlag GmbH & Co. KGaA.