Unusual reactions of cationic bridging carbyne complexes of dimethylsilane-bridged bis(η5-cyclopentadienyl)diiron tricarbonyl with carbonylmetal anions

The reactions of the dimethylsilane-bridged cationic carbyne complexes of diiron, [Fe2(μ-CO)(μ-CAr)(CO)2{(η5-C5H4)2Si(CH3)2}]BBr4 (1, Ar=C6H5; 2, Ar=p-CF3C6H4), with carbonylmetal anionic compounds Na[M(CO)5CN] (4, M=Cr; 5, M=Mo; 6, M=W) in THF at low temperature afford diiron bridging carbene complexes [Fe2(μ-CO){μ-C(Ar)NCM(CO)5}(CO)2{(η5-C5H4)2Si(CH3)2}] (9, M=Cr, Ar=C6H5; 10, M=Mo, Ar=C6H5; 11, M=W, Ar=C6H5; 12, M=Cr, Ar=p-CF3C6H4; 13, M=Mo, Ar=p-CF3C6H4; 14, M=W, Ar=p-CF3C6H4). In contrast to the reaction of 1 and 2, cationic carbyne complex [Fe2(μ-CO)(μ-CC6H4CH3-p)(CO)2{(η5-C5H4)2Si(CH3)2}]BBr4 (3) reacts with 4–6 under the same conditions to produce novel cationic bridging carbyne complexes [Fe2(μ-CO)(μ-CC6H4CH3-p)(CO)2{(η5-C5H4)2Si(CH3)2}]+[M(CO)5CN]− (15, M=Cr; 16, M=Mo; 17, M=W). Analogous cationic bridging carbyne complex [Fe2(μ-CO)(μ-CC6H4CH3-p)(CO)2{(η5-C5H4)2Si(CH3)2}]+[Fe(CO)4CN]− (18) can also be obtained from the reaction of 3 with Na[Fe(CO)4CN] (7). Complex 15 or 16 reacts with NaSR (R=CH3, C6H5, p-CH3C6H4) to give bridging mercaptocarbene complexes [Fe2(μ-CO){μ-C(SR)C6H4CH3-p}(CO)2{(η5-C5H4)2Si(CH3)2}] (19, R=CH3; 20, R=C6H5; 21, R=p-CH3C6H4) in high yields. The related reaction of 1 with NaN(SiMe3)2 affords a novel benzonitrile-coordinated diiron complex [Fe2(μ-CO)2(CO)NCC6H5{(η5-C5H4)2Si(CH3)2}] (22). Unexpectedly, the reactions of 1 and 2 with 7 yield diiron bridging arylcarbene complexes [Fe2(μ-CO){μ-C(H)Ar}(CO)2{(η5-C5H4)2Si(CH3)2}] (23, Ar=C6H5; 24, Ar=p-CF3C6H4). The products 23 and 24 and bridging p-tolyl-carbene complex [Fe2(μ-CO){μ-C(H)C6H4CH3-p}(CO)2{(η5-C5H4)2Si(CH3)2}] (25) were also obtained from the reactions of 1–3 with [(PPh3)2N][Cr(CO)4NO] (8). The structures of 14, 15, 22, and 23 have been established by X-ray crystallography.