178925-18-3Relevant academic research and scientific papers
FvCr2(CO)4L2 (Fv = fulvalene; L = PMe2Ph, PMe3), metal-metal-bonded compounds which undergo spontaneous thermal homolysis to their biradical isomers. Relevant chemistry of the compounds FvCr2(CO)4L2X2 (X = H, Cl, Br, I)
Kovács, István,Baird, Michael C.
, p. 3588 - 3599 (1996)
Two new (fulvalene)dichromium carbonyl dihydrides, FvCr2(CO)4L2H2 (L = PMe2Ph (2b), PMe3 (2c)) were prepared by phosphine substitution of FvCr2(CO)6H2 (2a) and studied by variable-temperature 1H, 13C{1H}, and 31P{1H} NMR. Compound 2b assumes a 77:23 and 2c an 85:15 cis/trans isomeric ratio at -50 °C, while low-temperature NMR spectra of 2b present evidence for the meso and dl forms of the cis,cis isomer. Hydride hydrogen atom abstraction from 2b and 2c by Ph3C?, as well as hydrogenation of isoprene and 1,3,5-hexatriene by 2b and 2c, result in the formation of FvCr2(CO)4L2 (L = PMe2Ph (6a), PMe3 (6b)). Variable-temperature IR and 1H, 13C{1H}, and 31P{1H} NMR studies demonstrate that both 6a and 6b maintain facile equilibria between the trans isomers of the chromium-chromium-bonded species and the novel biradical species L(CO)2Cr(μ-Fv)Cr(CO)2L at room temperature in solution. Room-temperature reactions of 6a with alkyl halides reflect the radical character of this compound, halogen atom abstractions leading to the new dihalide compounds FvCr2(CO)4(PMe2Ph)2X2 (X = I (3b), Br (4), Cl (5)). Compounds 3b, 4, and 5 were obtained alternatively in the hydrogen-halogen atom exchange reactions of 2b with the appropriate alkyl halides. These reactions are shown to proceed via intermediate formation of the corresponding mixed hydrido halide compounds Cis-FvCr2(CO)4(PMe2Ph)2HX (containing cis-halide halves). FvCr2(CO)6I2 (3a) was prepared analogously from 2a and ethyl iodoacetate and was also identified as the product of iodine atom abstraction from ethyl iodoacetate by FvCr2(CO)6. The reaction of FvCr2(CO)6I2 with PMe2Ph provided access to Cis-(CO)2(PMe2Ph)ICr(μ-Fv)[trans-Cr(CO) 2(PMe2Ph)2]I (7); the reaction was shown to proceed via consecutive formation of the intermediates (CO)3ICr(μ-Fv)[Cr(CO)3PMe2Ph]I and Cis-(CO)2(PMe2Ph)ICr(μ-Fv)[Cr(CO)3PMe 2Ph]I.
