The structure of dinitrosylbis(triphenylphosphine)osmium(-II) hemibenzene, Os(NO)2(P(C6H5)3)2•1/2C6H6, has been determined using three-dimensional X-ray diffraction techniques. This structure completes those of M(NO)2(P(C6H5)3)2 of the Fe triad. The conditions and requirements leading to bent and linear nitrosyl ligands in four-coordinate complexes are discussed and compared with those for similar five- and six-coordinate complexes. A set of empirical rules is presented which allows the a priori prediction in many cases of whether the bent or linear form of the nitrosyl ligand will be present. The Os compound crystallizes from benzene-hexane as hemisolvated crystals in space group C2h5-P21/n with four formula units in a cell of dimensions a = 17.034 (5) Å, b = 18.735 (5) Å, c = 10.799 (3) Å, and β = 96.81 (1)°, Based on 3455 unique reflections with Fo2> 3σ (Fo2), the structure was solved and refined by full-matrix, least-squares methods to values of R of 0.031 and Rw of 0.039. The structure consists of discrete molecules of the complex and of benzene, the latter being located on centers of inversion. The osmium complex is four-coordinate with pseudotetrahedral geometry and linear nitrosyl ligands. Although ESCA spectra show that the nitrosyl ligands are very effective at removing electron density from the metal, the coordination geometry is best rationalized on the basis of Os(-II), which is a d10 system. This structure is remarkably similar to its Ru analog. The short Os-N and N-O distances point to the extensive metal-nitrogen and nitrogen-oxygen multiple bonding. Important angles and distances are Os-N(1) = 1.771 (6) Å, Os-N(2) = 1.776 (7) Å N(l)-O(1) = 1.195 (8) Å, N(2)-O(2) = 1.211 (7) Å, N(1)-Os-N(2) = 139.1 (3)°, Os-N(l)-O(1) = 178.7 (7)°, Os-N(2)-O(2) = 174.1 (6)°, and P(1)-Os-P(2) = 103.51 (6)°.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry