94890-34-3Relevant academic research and scientific papers
Comparison of the self-reactivity of [CpCo(P'down curve sign'P)I]+ complexes, P'down curve sign'P = Ph2P(CH2)nPPh2 (n = 1-4), leading to bridged and oxidized dangling P'down curve sign'P reactions and spectral studies and the structures of [CpCo(dppm)I]I·CHCl3, CpCo[dppm(O)]I2, and ...
Bao,Landon,Rheingold,Haller,Brill
, p. 900 - 908 (2008/10/08)
Full title: Comparison of the self-reactivity of [CpCo(P'down curve sign'P)I]+ complexes, P'down curve sign'P = Ph2P(CH2)nPPh2 (n = 1-4), leading to bridged and oxidized dangling P'down curve sign'P reactions and spectral studies and the structures of [CpCo(dppm)I]I·CHCl3, CpCo[dppm(O)]I2, and Cp2Co2I4(μ-dpppent). The intrinsic stability of bis(tertiary phosphine) chelate complexes of the type [CpCo(P'down curve sign'P)I]I, where P'down curve sign'P = Ph2P(CH2)nPPh2 (n = 1-4), was investigated in CH2Cl2 and CDCl3 solution by 1H and 31P{1H} NMR spectroscopy and product isolation. Depending on P'down curve sign'P, the complexes range from indefinitely stable (n = 2, 3, ≥90 h) to reactive (n = 4, 2, containing an oxidized dangling phosphine, and Cp2Co2I4(μ-P'down curve sign'P), containing a bridged phosphine. The stability (n = 4 2(P'down curve sign'P), containing monodentate P'down curve sign'P. The importance of this species in the stability of the chelate salts of interest, [CpCo(P'down curve sign'P)I]I, is evidenced by the fact that these salts are destabilized by the presence of excess I-. Moreover, the BF4- and PF6- salts of [CpCo(P'down curve sign'P)I]+ are stable in situations where the I- salt is not. Dissociation constants, KD, are in the range of (2-7) × 10-4 M for the ion pairs [CpCo(P'down curve sign'P)I]X, X = I-, BF4-, PF6-. These relatively small values along with evidence from the 1H NMR spectra of various contact ion pairs suggest that the [CpCo(P'down curve sign'P)I]I contact ion pair is responsible for the formation of CpCoI2(P'down curve sign'P). The formation of CpCo[P'down curve sign'P(O)]I2 requires the presence of light and at least adventitious O2/H2O. These observations, although not conclusive, are most consistent with oxidation initiated by photolysis of the Co-I bond. H2O2 oxidizes [CpCo(P'down curve sign'P)I]I to CpCo[P'down curve sign'P(O)]I2 to a greater extent in complexes where the chelate ring is strained. X-ray crystal structure determinations were conducted on [CpCo(dppm)I]I·CHCl3 (I4, a = 18.271 (6) A?, c = 25.496 (8) A?, Z = 8), CpCo[dppm(O)]I2 (P21/n, a = 8.383 (4) A?, b = 10.388 (3) A?, c = 33.16 (1) A?, β = 91.43 (3)°, Z = 4), and Cp2Co2I4(μ-dpppent) (P21/c, a = 14.978 (5) A?, b = 18.556 (5) A?, c = 15.011 (5) A?, β = 103.03 (2)°, Z = 4).
