Remarkable Reactions of Cyclooctatetraene Diiron‐Bridging Carbyne Complexes with Amino and Amido Compounds: Nucleophilic Addition to and Breaking of the Cyclooctatetraene Ring

The reactions of the cationic, diiron‐bridging carbyne complexes [Fe 2 (μ‐CAr)(CO) 4 (η 8 ‐C 8 H 8 )]BF 4 ( 1 , Ar=C 6 H 5 ; 2 , Ar= p ‐CH 3 C 6 H 4 ; 3 , Ar= p ‐CF 3 C 6 H 4 ) with LiN(C 6 H 5 ) 2 in THF at low temperature gave novel N‐nucleophilic‐addition products, namely, the neutral, diiron‐bridging carbyne complexes [Fe 2 (μ‐CAr)(CO) 4 (η 7 ‐C 8 H 8 N(C 6 H 5 ) 2 )] ( 4 , Ar=C 6 H 5 ; 5 , Ar= p ‐CH 3 C 6 H 4 ; 6 , Ar= p ‐CF 3 C 6 H 4 )). Cationic bridging carbyne complexes 1 – 3 react with (C 2 H 5 ) 2 NH, ( i C 3 H 7 ) 2 NH, and (C 6 H 11 ) 2 NH under the same conditions with ring cleavage of the COT ligand to produce the novel diiron‐bridging carbene inner salts [Fe 2 {μ‐C(Ar)C 8 H 8 NR 2 }(CO) 4 ] ( 7 , Ar=C 6 H 5 , R=C 2 H 5 ; 8 , Ar= p ‐CH 3 C 6 H 4 , R=C 2 H 5 ; 9 , Ar= p ‐CF 3 C 6 H 4 , R=C 2 H 5 ; 10 , Ar=C 6 H 5 , R= i C 3 H 7 ; 11 , Ar= p ‐CH 3 C 6 H 4 , R= i C 3 H 7 ; 12 , Ar= p ‐CF 3 C 6 H 4 , R= i C 3 H 7 ; 13 , Ar=C 6 H 5 , R=C 6 H 11 ; 14 , Ar= p ‐CH 3 C 6 H 4 , R=C 6 H 11 , 15 , Ar= p ‐CF 3 C 6 H 4 , R=C 6 H 11 ). Piperidine reacts similarly with cationic carbyne complex 3 to afford the corresponding bridging carbene inner salt [Fe 2 {μ‐C(Ar)C 8 H 8 N(CH 2 ) 5 }(CO) 4 ] ( 16 ). Compound 9 was transformed into a new diiron‐bridging carbene inner salt 17 , the trans isomer of 9 , by heating in benzene. Unexpectedly, the reaction of C 6 H 5 NH 2 with 2 gave a novel COT iron–carbene complex [Fe 2 {C(C 6 H 4 CH 3 ‐ p )NHC 6 H 5 }(μ‐CO)(CO) 3 (η 8 ‐C 8 H 8 )] ( 18 ). However, the analogous reactions of 2‐naphthylamine with 2 and of p ‐CF 3 C 6 H 4 NH 2 with 3 produce novel chelated iron–carbene complexes [Fe 2 {C(C 6 H 4 CH 3 ‐ p )NC 10 H 7 }(CO) 4 (η 2 :η 3 :η 2 ‐C 8 H 9 )] ( 19 ) and [Fe 2 {C(C 6 H 4 CF 3 ‐ p )NC 6 H 4 CF 3 ‐ p }(CO) 4 (η 2 :η 3 :η 2 ‐C 8 H 9 )] ( 20 ), respectively. Compound 18 can also be transformed into the analogous chelated iron–carbene complex [Fe 2 {C(C 6 H 4 CH 3 ‐ p )NC 6 H 5 }(CO) 4 (η 2 :η 3 :η 2 ‐C 8 H 9 )] ( 21 ). The structures of complexes 6, 9, 15, 17, 18 , and 21 have been established by X‐ray diffraction studies.