Unusual reactions of cationic bridging carbyne complexes of bis (η5-cyclopentadienyl) diiron tricarbonyl with carbonylmetal anions.: A route to diiron bridging carbyne complexes

The reactions of cationic carbyne complexes of diiron, [Fe-2(mu-CO)(mu-CPh)(CO)2(eta(5)-C5H5)(2)]-BBr4 (1), with the anionic carbonylmetal compounds Na[M(CO)(5)CN] (3, M = Cr; 4, M = Mo; 5, M = W) in THF at low temperature afford the novel bridging carbyne complexes [Fe-2(mu-CO)(mu-CPh)(CO)(2)(eta(5)-C5H5)(2)NCM(CO)(5)] (6, M = Cr; 7, M = Mo; 8, M = W). In contrast to the reaction of 1, the cationic carbyne complex [Fe-2(mu-CO)(mu-CC6H4Me-p)(CO)(2)(eta(5)-C5H5)(2)]BBr4 (2) reacts with carbonylmetal anions 3-5 under the same conditions to produce the novel bridging p-tolyl(pentacarbonylcyanotungsten)carbene complexes [Fe-2(mu-CO){mu-C(C6H4Me-p)(CO)(2)(eta(5)-C5H5)(2)NCM(CO)(5)}] (9, M = Cr; 10, M = Mb; Ii, M = W). However, the analogous reaction of Na[Fe(CO)(4)CN] with 1 yields the diiron bridging phenylcarbene complex [Fe-2-(mu-CO){mu-C(H)Ph}(CO)(2)(eta(5)-C5H5)(2)] (12) The structures of 7, 8, and 11 have been established by X-ray crystallography.