Synthesis and structure of [Pt-3(mu-dppm)(2)(mu-PPh2)L-2] (O3SCF3) (dppm =bis(diphenylphosphino)methane; L = CO, t-BuNC)

Treatment of [Pt-2(mu-dppm)(2)Cl-2] 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 [Pt-2(mu-dppm)(mu-PPh2)(eta(2)-bicyclo [2.2.1]hept- 2-ene)(2)](O3SCF3) (la) and the methoxyphosphonium salt [PMePh2(OMe)](O3SCF 3). Treatment of la with CO (1 atm) or 2 mequiv of t-BuNC gives [Pt-2(mu-dp pm)(mu-PPh2)L-2](O3SCF3) where L = CO (Ib) or t-BuNC (Ic). The reaction of Ib or Ic with 1 mequiv of dppm and [Pt(eta(2)-bicyclo[2.2.1]hept-2-ene)(3)] , respectively, gives [Pt-3(mu-dppm)(2)(mu-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, la, 2a, and 2b additionally by single- crystal X-ray diffraction, In la, the orientation of the C=C double bonds i s nearly in plane with the other ligands coordinated to the Pt atoms, The m olecular structures of 2a and 2b show Pt-3 triangles whose edges are spanne d by two dppm ligands and one PPh2 ligand, There are bonds between the plat inum atoms bridged by the dppm ligands (2.6456(8) and 2.6733(6) Angstrom fo r 2a and 2.6463(11) and 2.6534(12) Angstrom for 2b) while the separations o f the Pt atoms bridged by the PPh2 ligand are very long (2a, 3.5949(6) Angs trom; 2b, 3.470(1) Angstrom) 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 intramo lecular contact to the third Pt atom of 2.954(3) Angstrom (2a) or 2.933(5) Angstrom (2b), which is significantly below the sum of the van der Waals ra dii of phosphorus and platinum.