Nitrosylkomplexe des Molybdän(+II) Die Kristallstrukturen von [Mo(NO)Cl3 · POCl3]2 und von [AsPh4]2[Mo(NO)Cl5] · 2 CH2Cl2

Nitrosyl Complexes of Molybdenum (+II). Crystal Structures of Mo(NO)Cl₃ · POCl₃]₂ and AsPh₄]₂Mo(NO)Cl₅] · 2 CH₂Cl₂ Solutions of MoCl₅ in POCl₃ react with NOCl forming the nitrosyl compound Mo(NO)Cl₃ · 2POCl₃ ( I ), which in CH₂Cl₂ cleaves off one solvate molecule, yielding the dimeric complex Mo(NO)Cl₃ · POCl₃]₂ ( II ). Reaction with AsPh₄Cl in dichloro methane leads to the nitrosyl complexes AsPh₄Mo(NO)Cl₄] · CH₂Cl₂ ( III ) and AsPh₄]₂Mo(NO)Cl₅] · 2CH₂Cl₂ ( IV ), respectively. The i.r. spectra are recorded and assigned. Mo(NO)Cl₃ · POCl₃]₂ crystallizes monoclinic in the space group P2₁/c with two dimeric units per unit cell. The crystal structure was determined by X-ray diffraction methods (R = 0.040; 1391 observed, independent reflexions). Complex II is linked by chlorine bridges, forming a dimeric, centrosymmetric molecule of symmetry C_i. The N? O bond of the nitrosyl ligand is extremely short (108 pm), the Mo? N bond (181 pm) corresponds to a double bond. In trans position to the NO ligand, which is coordinated in linear array, there is the O atom of the solvate molecule POCl₃. AsPh₄]₂Mo(NO)Cl₅] · 2 CH₂Cl₂ crystallizes triclinic in the space group P1 with two units per unit cell (R = 0.039; 1967 observed, independent reflexions). The molybdenum atom is coordinated octahedrally by five Cl ligands and a nitrosyl group, as well coordinated in linear array (Mo? N? O 174°). The nitrosyl ligand exerts a significant trans-effect (r Mo? Cl_(trans) = 247 pm, r MoCl_4(eq)(average) = 239 pm).