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, [Fe-2(mu-CO)(mu-CAr)(CO)(2) {(eta(5)- C5H4)(2)Si(CH3)(2)}]BBr4 (1, Ar = C6H5; 2, Ar = p-CF3C6H4), with carbonylmetal anionic compounds Na[M(CO)(5)CN] (4, M = Cr; 5, M = Mo; 6, M = W) in THF at low temperature afford diiron bridging carbene complexes [Fe-2(mu-CO){mu-C(Ar)NCM(CO)(5)}(CO)(2) {(eta(5)-C5H4)(2)Si(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 [Fe-2(mu-CO)(mu-CC6H4CH3-p)(CO)(2){(eta(5)-C5H4)(2)Si(CH3)(2)}]BBr4 (3) reacts with 4-6 under the same conditions to produce novel cationic bridging carbyne complexes [Fe-2(mu-CO)(mu-CC6H4CH3-p)(CO)(2){(eta(5)- C5H4)(2)Si(CH3)(2)}](+)[M(CO)(5)CN](-) (15, M = Cr; 16, M = Mo; 17, M = W). Analogous cationic bridging carbyne complex [Fe-2(mu-CO)(mu-CC6H4CH3-p)(CO)(2){(eta(5)-C5H4)(2)Si(CH3)(2)}](+)[Fe(CO)(4)CN](-) (18) can also be obtained from the reaction of 3 with Na[Fe(CO)(4)CN] (7). Complex 15 or 16 reacts with NaSR (R = CH3, C6H5, p-CH3C6H4) to give bridging mercaptocarbene complexes [Fe-2(mu-CO){mu-C(SR)C6H4CH3-p} (CO)(2){(eta(5)-C5H4)(2)Si(CH3)(2)}] (19, R = CH3; 20, R = C6H5; 21, R = p-CH3C6H4) in high yields. The related reaction of 1 with NaN(SiMe)(2) affords a novel benzonitrile-coordinated duron complex [Fe-2(mu-CO)(2)(CO)NCC6H5 {(eta(5)-C5H4)(2)Si(CH3)(2)}] (22). Unexpectedly, the reactions of 1 and 2 with 7 yield duron bridging arylcarbene complexes [Fe-2(mu-CO){mu-C(H)Ar}(CO)(2) {(eta(5)-C5H4)(2)Si(CH3)(2)}] (23, Ar = C6H5; 24, Ar = p-CF3C6H4) The products 23 and 24 and bridging p-tolyl-carbene complex [Fe-2(mu-CO) {mu-C(H)C6H4CH3-p} (CO)(2){(eta(5)-C5H4)(2)Si(CH3)(2)}] (25) were also obtained from the reactions of 1-3 with [(PPh3)(2)N][Cr(CO)(4)NO] (8). The structures of 14, 15, 22, and 23 have been established by X-ray crystallography. (C) 2002 Elsevier Science B.V. All rights reserved.