Chemistry of di- and tri-metal complexes with bridging carbene or carbyne ligands. Part 13. Synthesis of platinumirontungsten tri-metal compounds with µ3-tolylidyne groups; crystal structures of [FePtW(µ3-CR)(CO)5(PMePh2)2(η-C5H5)] and [FePtW(µ3-CR)(CO)6(PEt3)(η-C5H5)](R = C6H4Me-4)

Abstract

The dimetal compounds [PtW(µ-CR)(CO)₂(PR′₃)₂(η-C₅H₅)](R = C₆H₄Me-4, PR′₃= PMe₃, PMe₂Ph, PMePh₂, or PEt₃) react with [Fe₃(CO)₉] in tetrahydrofuran at room temperature to afford trimetal complexes [FePtW(µ₃-CR)(η-CO)(CO)₅(PMe₂Ph)₂(η-C₅H₅)], [FePtW(µ₃-CR)(CO)₅(PMePh₂)₂(η-C₅H₅)], and [FePtW(µ3-CR)(CO)₆(PR′₃)(η-C₅H₅)](PR′₃= PMe₃, PMePh₂, or PEt₃). The reaction involving [PtW(µ-CR)(CO),(PEt₃)₂(η-C₅H₅)] also gave the non-iron containing compound [Pt₂W(µ₃-CR)(CO)₄(PEt₃)₂(η-C₅H₅)]. Pathways for the formation of these heteronuclear trimetal complexes are discussed, and n.m.r. data (¹H, ³¹ P-{¹H}, ¹³C-{¹H}) are reported for the dynamic platinumirontungsten species which contain a µ₃-CFePtW core. X-Ray diffraction studies on [FePtW(µ₃-CR)(CO)₅(PMePh₂)₂(η-C₅H₅)] and on [FePtW(µ₃-CR)(CO)₆(PEt₃)(η-C₅H₅)] confirm that the molecular skeleton is the same for both; the Pt atom in the former carries two PMePh₂ ligands whereas in the latter it carries one terminal CO and one PEt₃ ligand. Interesting differences in detailed structure are revealed, however. The Fe–Pt bond lengths are similar [2.556(2) and 2.542(3)Å] for [FePtW(µ₃-CR)(CO)₅(PMePh₂)₂(η-C₅H₅)] and [FePtW(µ₃-CR)(CO)₆(PEt₃)(η-C₅H₅)] respectively, but the Fe–W and Pt–W bond lengths are significantly different [2.694(2)versus 2.784(3), and 2.883(1)versus 2.775(1)Å]. The Pt–W bond in [FePtW(µ₃-CR)(CO)₅(PMePh₂)₂(η-C₅H₅)] is among the longest so far observed. These differences, and those between the bonds of the µ₃-CR ligand, are discussed. In the pentacarbonyl species the two P–Pt distances differ, that trans to the µ₃-C atom [2.331(4)Å] being notably longer than the other [2.289(3)Å]. Both molecules are chiral and both crystallise in non-centrosymmetric space groups. Crystals of [FePtW(µ₃-CR)(CO)₅(PMePh₂)₂(η-C₅H₅)] are monoclinic, space group P2₁(no. 4) with Z= 2 in a unit cell of dimensions a= 10.005(2), b= 17.240(3), c= 12.928(4)Å, β= 115.98(2)°, and the structure has been refined to R 0.050 for 4 490 reflections. Crystals of [FePtW(µ₃-CR)(CO)₆(PEt₃)(η-C₅H₅)] are orthorhombic, space group Pna2₁(no. 33) with Z= 4 in a unit cell of dimensions a= 16.106(5), b= 8.958(5), c= 18.429(7)Å, and the structure has been refined to R 0.050 for 2 703 reflections.