The structure of hydridonitrosyltris(triphenylphosphine)iridium(I) perchlorate, [IrH(NO)(P(C6Hr4)3)3] [ClO4], has been determined from three-dimensional X-ray data collected by counter methods. The compound crystallizes in the space group Pbc21 of the orthorhombic system with four molecules in a unit cell of dimensions a = 11.335 (9), b = 21.992 (17), and c = 19.170 (15) Å. The observed and calculated densities are 1.53 (±0.02) and 1.54 g cm-3, respectively. Least-squares refinement has led to a final value of the conventional R factor (on F) of 0.047 for the 1342 reflections having F2 > 3σ(F2). The structure consists of well-separated monomeric ions and the geometry around the metal is described as distorted trigonal bipyramidal with the hydrido and nitrosyl ligands occupying the axial positions and the triphenylphosphine ligands the equatorial positions. The iridium atom lies 0.51 Å above the plane of the three phosphorus atoms. The hydrogen atom was not located in the structural determination. However its position has been inferred because the geometry of the other ligands around the metal is very similar to that found for the complexes RhH(CO)(P(C6H5)3)3 and CoH(N2)(P(C6H5)3)3 for which the hydrogen atoms have been located. The iridium-nirrogen-oxygen bond angle of 175 (3)° suggests that this complex is best formulated as an NO+ complex of iridium(I). Other important bond lengths in the molecule are as follows (Å): Ir-P, 2.346 (9), 2.341 (8), 2.334 (8); Ir-N, 1.68 (3); N-O, 1.21 (3). The bonding of the nitrosyl group in this complex is compared with that found in other iridium complexes, which have the nitrosyl ligand coordinated as NO-. Also the geometries of the five-coordinate complexes MH(X)(P(C6H5)3)3 (M = Co, X = N2; M = Rh, X = CO; M = Ir, X = NO+) seem to be influenced by the degree of double bonding of the M-X bond, and it is proposed that electron-pair repulsions are responsible for the distortions from the ideal trigonal-bipyramidal geometry.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry