Dimolybdenum Complexes Containing Pairs of Bridging Diphosphine and Carboxylate Ligands. Synthesis and Structures of trans-Mo[feaf](O[feaf]CCH[feb0])[feaf](μ-dppa)[feaf](BF[feb2])[feaf]and trans-Mo[feaf]X[feaf](O[feaf]C(CH[feaf])抜CH[feb0])[feaf](μ-dppa)[feaf](n=2,10 or 12; X=Cl or Br;dppa=N,N-Bis(diphenylphosphino)amine)