Synthesis and structure of [Pt3(μ-dppm)2(μ-PPh2)L 2](O3SCF3) (dppm = bis(diphenylphosphino)methane; L = CO, t-BuNC)

Article abstract of DOI:10.1021/om980635v

Treatment of [Pt₂(μ-dppm)₂Cl₂] with 2 mequiv of AgO₃SCF₃ and bicyclo[2.2.1]hept-2-ene, respectively, in MeOH/CH₂Cl₂ results in a P-C cleavage of one dppm ligand to give [Pt₂-(μ-dppm)(μ-PPh₂)(η ²-bicyclo[2.2.1]hept-2-ene)₂](O₃SCF ₃) (1a) and the methoxyphosphonium salt [PMePh₂(OMe)](O₃SCF₃). Treatment of 1a with CO (1 atm) or 2 mequiv of t-BuNC gives [Pt₂(μ-dppm)(μ-PPh₂)L₂](O ₃SCF₃) where L = CO (1b) or t-BuNC (1c). The reaction of 1b or le with 1 mequiv of dppm and [Pt(η²-bicyclo[2.2.1]hept-2-ene)₃], respectively, gives [Pt₃(η-dppm)₂(μ-PPh₂)L ₂](O₃SCF₃) where L = CO (2a) or t-BuNC (2b). The new compounds were characterized by multinuclear NMR, FAB-MS, IR, and chemical analysis, 1a, 2a, and 2b additionally by single-crystal X-ray diffraction. In la, the orientation of the C=C double bonds is nearly in plane with the other ligands coordinated to the Pt atoms. The molecular structures of 2a and 2b show Pt₃ triangles whose edges are spanned by two dppm ligands and one PPh₂ ligand. There are bonds between the platinum atoms bridged by the dppm ligands (2.6456(8) and 2.6733(6) A? for 2a and 2.6463(11) and 2.6534(12) A? for 2b) while the separations of the Pt atoms bridged by the PPh₂ ligand are very long (2a, 3.5949(6) A?; 2b, 3.470(1) A?) and are clearly considered as nonbonding. The CO or t-BuNC ligands are coordinated terminally to the Pt atoms bridged by the PPh₂ ligand. The P atom of the phosphido group exhibits a short intramolecular contact to the third Pt atom of 2.954(3) A? (2a) or 2.933(5) A? (2b), which is significantly below the sum of the van der Waals radii of phosphorus and platinum.