Phosphido-bridged tungsten-iridium and iron-iridium 1,5-cyclooctadiene complexes

Article abstract of DOI:10.1021/om00137a001

The new heterobimetallic complexes (CO)₄M(μ-PPh₂)₂IrH(COD) (COD = 1,5-cyclooctadiene; 2, M = W; 3, M = Mo; 4, M = Cr) have been prepared by the reaction of [Ir(μ-Cl)(COD)]₂ with the corresponding Li[M(CO)₄(PPh₂H)(PPh₂)] reagent. The methyl complex (CO)₄W(μ-PPh₂)₂IrCH₃(COD) (5) derives from a modification of the above syntheses. These complexes have been spectroscopically characterized with 2 fully defined by an X-ray diffraction study: P2₁, a = 11.260 (3) A?, b = 15.221 (4) A?, c = 11.756 (3) A?, β = 111.80 (2)°, V = 1870.8 (8) A?³, Z = 2, R = 0.0418, R_w = 0.0407. The W and Ir atoms are bridged by the two μ-PPh₂ ligands with the W further coordinated by four CO's and the Ir by a hydride and the COD ligand. The WIr(μ-P)₂ core of the molecule is planar, and the W-Ir distance of 2.893 (1) A? implies a metal-metal bond between these atoms. The Fe-Ir complex (CO)₃Fe(μ-PPh₂)₂IrH(COD) (7) was prepared by an analogous reaction using Li[Fe(CO)₃(PPh₂H)(PPh₂)]. From this complex derives the chloro derivative (CO)₃Fe(μ-PPh₂)₂IrCl(COD) (8), which has been crystallographically characterized: P2₁/n, a = 11.438 (2) A?, b = 25.149 (3) A?, c = 11.750 (2) A?, β = 108.85 (1)°, V = 3198.7 (9) A?³, Z = 4, R = 0.0379, R_w = 0.0394. The Fe and Ir atoms are bridged by the two μ-PPh₂ ligands with the Fe further coordinated by three CO's and the Ir by a chloride and the COD ligand. The FeIr(μ-P)₂ core of the molecule is bent, and the Fe-Ir distance of 2.703 (1) A? implies a metal-metal bond between these atoms. The COD ligand of the W-Ir complex 2 can be replaced by two CO's at 1000 psi pressure and 100°C to give (CO)₄W(μ-PPh₂)₂IrH(CO)₄ (6). Likewise, the Fe-Ir complex 7 reacts with CO + PPh₃ to give the known compound (CO)₃Fe(μ-PPh₂)₂IrH(CO)(PPh₃), but under much milder conditions than the reactions of 2 with CO. These results show an influence of the adjacent metal W or Fe on the reactivity of the Ir center.