Chemistry of di- and tri-metal complexes with bridging carbene or carbyne ligands. Part 42. Synthesis of the compounds [N(PPh3)2][Fe2W(µ-CO)(µ-NO)(µ3-CR)(CO)6(η-C5H5)](R = Me or C6H4Me-4) and the X-ray crystal structure of the tolylmethylidyne complex

Abstract

The compounds [Fe₂W(µ₃-CR)(µ-CO)(CO)₈(η-C₅H₅)](R = Me or C₆H₄Me-4) and [N(PPh₃)₂][NO₂] react in tetrahydrofuran at room temperature to afford the salts [N(PPh₃)₂][Fe₂W(µ-CO)(µ-NO)(µ₃-CR)(CO)₆(η-C₅H₅)]. An X-ray diffraction study was carried out on the species with R= C₆H₄Me-4, which crystallises with a molecule of tetrahydrofuran. The anion contains an essentially isosceles triangle of metal atoms [Fe–W 2.702(2) and 2.71 6(2), Fe–Fe 2.607(3)Å], capped by the CC₆H₄Me-4 group [µ₃-C–Fe 1.969(13) and 2.008(10), µ₃-C–W 2.055(11)Å]. Each iron atom carries three terminally bound CO molecules. The tungsten atom is bonded by the cyclopentadienyl ligand, and in addition is attached to a CO and an NO group. These carbonyl and nitrosyl groups asymmetrically bridge the two Fe–W edges of the metal triangle [W–C–0160.0(9), W–N–O 157.0(10)°]. Protonation of the salt [N (PPh₃)₂][Fe₂W(µ-CO)(µ-NO)(µ₃-CC₆H₄Me-4)(CO)₆(η-C₅H₅)] with HBF₄·Et₂O affords thedi-irontungsten complex [Fe₂W(µ-CC₆H₄Me-4)(µ₃-NOH)(CO)₇(η-C₅H₅)]. A structurally related species [Fe₂W(µ-CC₆H₄Me-4)(µ₃-NC₆H₄Me-4)(CO)₇(η-C₅H₅)] is obtained by heating a mixture of [Fe₂W(µ₃-CC₆H₄Me-4)(µ-CO)(CO)₈(µ-C₅H₅)] with McC₆H₄N₃–4 in tetrahydrofuran. Spectroscopic data (i.r. and n.m.r.) for the new complexes are reported and discussed.