Convenient routes to mono- and dinuclear (C5Me5)iron(II) complexes bearing acyl, alkynyl, aryl and thienyl ligands

Treatment of the cations [Fe(C5Me5)(CO)2(L)][PF6] (1a, L=CO; 1c, L=PPh3) with LiCCSiMe3 gives the corresponding acyl derivatives [Fe(C5Me5)(CO)2{C(O)CCSiMe3}] (2) and [Fe(C5Me5)(CO)(PPh3){C(O)CCSiMe3}] (4), respectively. The nucleophile adds at the carbonyl ligand, but in the case of 1a, competitive attack occurs at the metal centre leading to the formation of the alkynyl complex [Fe(C5Me5)(CO)2{CCSiMe3}] (3). The latter species is formed as the only product from the acetonitrile complex [Fe(C5Me5)(CO)2(CH3CN)][PF6] (1b), under the same conditions. Similarly, the dinuclear bis(acyl) complex [Fe(C5Me5)(CO)2{μ-η1,η1′-C(O)-]2(2,2′-C4H2S) (6) is obtained from 1a by using 0.5 equivalents of the dilithium salt 2,2′-Li2C4H2S/TMEDA. Complete decarbonylation by UV irradiation of 3 or 6 in the presence of dppe affords the corresponding disubstituted complexes [Fe(C5Me5)(dppe){CCSiMe3}] (5) and [Fe(C5Me5)(dppe)]2{μ-η1,η1′-2,2′-C4H2S} (7), respectively. Complexes [Fe(C5Me5)(CO)2{CH(OMe)C6H4-p-Br}] (9) and [Fe(C5Me5)(CO)2{CH(OMe)-2-C4H3S}] (10) are synthesised from the methoxycarbene complex [Fe(C5Me5)(CO)2(CHOMe)][PF6] (8); the nucleophilic addition of the organolithium reagents occurs at the carbene ligand. Dinuclear complexes such as the thiophene derivative [Fe(C5Me5)(CO)2{μ-η1,η1′-CHOMe-]2(2,2′-C4H2S) (11) and the biphenylene complex [Fe(C5Me5)(CO)2{μ-η1,η1′-CHOMe-]2(p-C6H4-C6H4) (12) are obtained by using the appropriate dilithiated nucleophiles. Protonolysis of 12 gives the bis(carbene) complex [Fe(C5Me5)(CO)2{μ-η1,η1′-CH-]2(p-C6H4-C6H4) (13), which is stable at −50°C.