Carbamoyl (carboxamido) complexes as precursors for metallaoxetene, isonitrile, and aminomethylidyne complexes of iron

The reaction of [Fe{C(=O)(NPr2)-Pr-i}(CO)(4)]Li with (CF3CO)(2)O in diethyl ether followed by triphenylphosphine provides carbamoyl complexes [Fe(eta( 2)-(OCNPr2)-Pr-i}(CF3)(CO)(2)(PPh3)] (1) or [Fe(eta(2)-(OCNPr2)-Pr-i)(CO)(2 )(PPh3)(2)](O2CCF3) (2a . O2CCF3) depending on the reaction conditions. The same procedure performed in dichloromethane provides the aminomethylidyne complex [Fe(=(CNPr2)-Pr-i)(CO)(3)(PPh3)](O2CCF3) (5 . O2CCF3) as well, as t races of [Fe(eta(2)-(OCNPr2)-Pr-i)(CO)(2)(PPh3)(2)](O2CCF3) (2a . O2CCF3). The reactions of 1 with moist AgBF4 or HBF4 provide [Fe(eta(2)-(OCNPr2)-Pr- i}(CO)(3)(PPh3)]BF4 (2b . BF4), via a putative difluorocarbene intermediate , [Fe(eta(2)-(OCNPr2)-Pr-i}(=CF2)(CO)(2)(PPh3)]BF4. In a similar manner, [F e(eta(2)-(OCNPr2)-Pr-i)(CF3)(CO)(dppe)] (3) (obtained from 1 and dppe) reac ts with HBF4(aq) to provide [Fe(eta(2)-(OCNPr2)-Pr-i}(CO)(2)(dppe)]BF4 (4 . BF4). A difluorocarbene complex is also implicated in the formation of the ferraoxetene [Fe{kappa(2)-C((NPr2)-Pr-i)OCF2}(CO)(HB(pz)(3)}] (6) (pz = py razol-1-yl), which results from treatment of 1 with K[HB(pz)(3)] under high dilution. Under more concentrated conditions [Fe(HB(pz)(3)}(2)] is obtaine d. The ferraoxetene undergoes an unusual acid hydrolysis with HBF4(aq)/CO t o provide the isonitrile salt [Fe((CNPr)-Pr-i)(CO)(2){HB (pz)(3)}]PF6 (7 . PF6). The salt [Fe(=(CNPr2)-Pr-i)-(CO)(3)(PPh3)]I(5 . I) is the product of the reaction of 1 with iodine, via an as yet obscure mechanism, which may h owever also involve ferraoxetene intermediates.