Organotransition-Metal Metallacarboranes. 8. Mono-, Di-, and Triiron Polyarene Sandwich Complexes of Et₂C₂B₄H₄^2-Containing Fluorene, 9,10-Dihydroanthracene, or [2.2]Paracyclophane Ligands

This paper describes the synthesis of mixed-ligand carborane-iron-polycyclic arene complexes from nido-2,3-Et₂C₂B₄H₆together with structural characterization of the products via¹¹B and¹H NMR, infrared, and mass spectroscopic data. All products reported were isolated as air-stable crystalline solids. The main preparative route utilized displacement of the neutral ligand (L) from (η⁶-L)Fe(Et₂C₂B₄H₄) (L = C₈H₁₀or C₁₆H₁₈) by arenes. In an alternative approach, the previously known naphthalene species (n⁶-C₁₀H₈)-Fe(Et2C₂B₄H₄) was obtained directly from the Et₂C₂B₄H₅^_ion, FeC1₂, and the naphthaleneide dianion. A monoiron fluorene complex (n⁶-C₁₃H₁₀)Fe(Et₂C₂B₄H₄) (6) was prepared via both routes, employing displacement of C₈H₁₀from (n⁶-C₈H₁₀)Fe(Et₂C₂B₄H₄) (2) as well as direct treatment of Et₂C₂B₄H₅^-with - C₁₃H₁₀^-and FeCl₂. The thermal reaction of 6 with 2 gave a staggered triple-decker diiron species (n⁶,n⁶-C₁₃H₁₀)Fe₂(Et₂C₂B₄H₄)₂(7) and a staggered quadruple-decker triiron complex Fe[(C₁₃H₁₀)Fe-(Et₂C₂B₄H₄)]₂(8), whose proposed structures are supported by spectroscopic evidence and by X-ray crystallographic data on 6 and 7. “Decapitation” (apex BH removal) of 6 was achieved by treatment with tetramethylethylenediamine giving nido-(η⁶-C₁₃H₁₀)Fe(Et₂C₂B₃H₅).