Reactions of N-heterocyclic ligands with substitutionally labile organometallic complexes, [(η5-C5R5)Fe(CO)2E]BF4

The ether complexes [Cp(CO)2Fe(OEt2)]BF4 (Cp = η5-C5H5) (1) and [Cp∗(CO)2Fe(THF)]BF4 (Cp∗ = η5-C5(CH3)5) (2) react with 1,3,5,7-tetraazaadamantane (HMTA) to give stable water-soluble dinuclear complexes [{(η5-C5R5)(CO)2Fe}2(μ-HMTA)](BF4)2 (R = H; R = CH3) and mononuclear complexes [(η5-C5R5)(CO)2Fe(HMTA)]BF4 (R = H; R = CH3). The reaction of 1 with 1,4-diazabicyclo[2.2.2]octane (DABCO) gave good yields of the dinuclear and mononuclear complexes, [{Cp(CO)2Fe}2(μ-DABCO)](BF4)2 (6a) and [Cp(CO)2Fe(DABCO)]BF4 (6b), respectively, depending on reagent ratios. Similar reactions with 2 gave very low yields of the mononuclear complex [Cp∗(CO)2Fe(DABCO)]BF4 (6c) as the only product. The reactions of [Cp(CO)2Fe(HMTA)]BF4 (3b) and [Cp∗(CO)2Fe(HMTA)]BF4 (4b) with NaBPh4 in acetone proceeded smoothly at room temperature to give the corresponding BPh4- salts. Reaction of 4b with 1 at room temperature gave the dinuclear complex [{Cp(CO)2Fe}2(μ-HMTA)](BF4)2 (3a) as the major product, while the same reaction conducted at 0 °C led to the unstable mixed ligand complex [{Cp(CO)2Fe}(μ-HMTA){Fe(CO)2Cp∗}](BF4)2. The reactions of 1 and 2 with 1-methylimidazole (1-meIm) gave high yields of [(η5-C5R5)(CO)2Fe(1-meIm)]BF4 (R = H (7); R = CH3 (8)), of which the NMR, IR and single crystal X-ray studies reveal the coordination of 1-methylimidazole to be via the ‘pyridine nitrogen’ of the imidazole ring. Single-crystal X-ray diffraction studies reveal that compounds 3a and 8 crystallize in the orthorhombic P212121 and Pna21 space groups, respectively. Compound 7 however, crystallized in the monoclinic P21/c space group with three independent molecular cations and anions each in the asymmetric unit.