X-Ray structure analysis of the salts [N(PPh3)2][M4H3(CO)12](M = Ru or Os); confirmation of the existence of discrete structural isomers for a hydridocarbonyl cluster in the solid state

Abstract

X-Ray analysis has shown that the salt [N(PPh₃)₂][Ru₄H₃(CO)₁₂] crystallizes in two forms, (1) and (2), which correspond to two different structural isomers (tautomers) of the anion. These have overall geometries of virtual C₂[(1)] and C_3v[(2)] symmetry, and provide the first confirmation of the existence of such isomers in the solid state. Crystals of (1) and (2) are triclinic, space group P. For (1), a= 17.361(4), b= 11.735(2), c= 12.321(2)Å, α= 94.61 (2), β= 98.44(2), γ= 88.52(2)°, Z= 2; refinement of atomic parameters using 7 210 data converged at R= 0.0473. For (2), a= 15.608(3), b= 15.370(3), c= 11.219(2)Å, α= 99.26(2), β= 103.27(2), γ= 105.72(2)°, Z= 2; refinement of atomic parameters using 10 945 data converged at R= 0.0432. Although three crystalline modifications, (3), (4), and (5), of the corresponding salt [N(PPh₃)₂][Os₄H₃(CO)₁₂] were isolated, X-ray analysis has shown that in all three the same isomer of the monoanion, of virtual C₂ symmetry, is present. Crystals of the osmium salt (3), which are isomorphous with those of the ruthenium salt (1), are triclinic, space group P, a= 17.378(4), b= 11.691(2), c= 12.308(2)Å, α= 94.40(2), β= 98.62(2), γ= 88.41(2)°, Z= 2. Modification (4) crystallizes as a 0.5CH₂Cl₂ solvate, orthorhombic, space group Pna2₁, a= 17.648(4), b= 19.597(4), c= 15.429(3)Å, Z= 4. Modification (5) is monoclinic, space group P2₁/c, a= 11.683(2), b= 28.976(4), c= 14.733(3)Å, β= 100.13(2)°, Z= 4. Complete structure analysis was carried out for modification (4) only, for which refinement of atomic parameters using 3 347 data converged at R= 0.0426.