Chemistry of di- and tri-metal complexes with bridging carbene or carbyne ligands. Part 15. Reactions of the complex [W(CR)(CO)2(η-C5H5)](R = C6H4Me-4) with iron carbonyls; crystal structures of [Fe2W(µ3-CR)(µ-CO)(CO)8(η-C5H5)] and [FeW2(µ3-RC2R)(CO)5L(η-C5H5)2](L = CO or O)

Abstract

The compound [W(CR)(CO)₂(η-C₅H₅)](R = C₆H₄Me-4) in diethyl ether at room temperature reacts with [Fe₂(CO)₉] to give the dimetal complex [FeW(µ-CR)(CO)₆(η-C₅H₅)](1), and the two trimetal species [Fe₂W(µ₃-CR)(µ-CO)(CO)₈(η-C₅H₅)](2) and [FeW₂(µ₃-RC₂R)(CO)₆(η-C₅H₅)₂](3). Compound (2) with PMe₂Ph or Ph₂PCH₂PPh₂(dppm) affords [Fe₂W(µ₃-CR)(µ-CO)(CO)₆L₂(η-C₅H₅)][L = PMe₂Ph (4), L₂= dppm (5)], complexes in which the phosphine ligands are bonded to the two iron atoms. From the reaction between the complexes [Fe₃(CO)₁₂] and [W(CR)(CO)₂(η-C₅H₅)], the trimetal compounds (2), (3), and [FeW₂(O)(µ₃-RC₂R)(CO)₅(η-C₅H₅)₂](6) were isolated. Spectroscopic data (infrared and n.m.r.) for the new compounds are reported, and discussed in relation to their structures, which were firmly established for (2), (3), and (6) by single-crystal X-ray diffraction studies. Crystals of (2) are orthorhombic, space group P2₁2₁2₁, Z= 4, in a unit cell with lattice parameters a= 10.078(8), b= 13.115(8), and c= 16.785(8)Å. The structure was refined to R 0.030 (R′ 0.031) for 5 837 reflections having 2θ⩽ 60°(Mo–K_αX-radiation) collected at 200 K. The molecule consists of a Fe₂W triangle [Fe–W 2.805(2) and 2.756(2), Fe–Fe 2.538(2)Å] capped by a triply bridging tolylidyne ligand [µ₃-C–W 2.093(5), µ₃-C–Fe 1.969(5) and 2.036(5)Å]. The Fe–Fe bond is bridged by a CO group, the remaining carbonyl ligands being terminally bonded, two to the tungsten and three to each iron. Crystals of (3) are triclinic, space group P, Z= 2, in a unit cell with a= 8.622(2), b= 12.799(4), c= 13.443(8)Å, α= 90.72(4), β= 108.45(4), and γ= 93.34(2)°. The structure has been refined to R 0.037 (R′ 0.039) for 4 337 reflections having 2θ⩽ 50° collected at room temperature. The molecule consists of a FeW₂ triangle, the W–W distance [2.747(1)Å] suggesting double bonding. The Fe–W separations [2.731(1) and 2.745(1)] are perceptibly different, and the shorter is transversely bridged by a RC₂R alkyne group; one of the carbon atoms of the alkyne triply bridges the metal triangle [µ₃-C–W 2.289(5) and 2.264(7), µ₃-C–Fe 2.011(5)Å]. There are five terminally bound CO ligands, three attached to the iron atom and one to each tungsten. In addition, the tungsten atom σ-bonded to the alkyne carries a CO group which semi-bridges the W–W edge [W–C-0 164.9(7)°]. Crystals of (6) are triclinic, space group P, Z= 2, in a unit cell with a= 8.694(2), b= 12.540(4), c= 13.365(7)Å, α= 88.03(4), β= 108.44(3), and γ= 97.54(2)°. The structure has been refined to to R 0.049 (R′ 0.050) for 3 916 reflections having 2θ⩽ 50° collected at room temperature. The molecule has a structure very similar to that of (3) except that an oxygen atom has replaced the terminal CO ligand bonded to the tungsten atom µ-η² co-ordinated to the alkyne.