The iron acetylide Cp*(dppe)FeC⋮CH (Cp*
= η5-C5Me5, dppe = Ph2PCH2CH2PPh2) reacted with
[Cp2Zr(H)Cl]
n
(Schwartz's reagent, Cp = η5-C5H5) to
produce the C⋮C-bridged complex Cp*(dppe)FeC⋮CZrClCp2 in nearly quantitative yield instead of the
expected CHCH-bridged hydrozirconation product. The
bulky ligand set around iron is postulated to prevent the
addition of hydride at the carbon α to the metal center.
Reaction of Cp*(dppe)FeC⋮CH with (dimethylamino)trimethyltin gave the condensed product Cp*(dppe)FeC⋮CSnMe3 in nearly quantitative yield.
The butadienediyl-bridged complexes [(η 5 -C 5 R 5 )Fe(dppe)] 2 (µ-CHdCHCHdCH) (R ) H, Me) and their radical cationic and dicationic forms have been prepared and characterized by cyclic voltammetry, electronic spectroscopy (UV-vis and near-IR), EPR, and X-ray crystallography (R ) Me). Comparisons with each other and with the literature complexes [(η 5 -C 5 H 5 )Fe(dppm)] 2 (µ-CHdCHCHdCH), [(η 5 -C 5 Me 5 )Fe(dppe)] 2 (µ-CtCCtC), and [(η 5 -C 5 Me 5 )-Fe(dppe)] 2 (µ-C(OMe)dCHCHdC(OMe)) have allowed for systematic evaluation of several structural variations (C 5 H 5 vs C 5 Me 5 , dppm vs dppe, µ-CHdCHCHdCH vs µ-CtCCtC, and µ-CHdCHCHdCH vs µ-C(OMe)dCHCHdC(OMe)) and their effects on spectra and electronic intermetal coupling. Some of the structural changes have opposite effects on H ab , the effective coupling parameter, and K c , the comproportionation constant. The data for the mixed-valence cations are most consistent with electronic delocalization.Many recent examples of transition metals linked with conjugated bridges have shown that such bridges can promote electronic coupling between metal centers. 1 Studies of mixed-valence (MV) ions in comparison with fully oxidized and fully reduced states have provided much insight concerning delocalization and/or intramolecular electron transfer 2 and have allowed more accurate predictions concerning potential use as molecular wires. 3 Through systematic evaluation of trends related to isolated structural variations, the role of different structural aspects has sometimes been discerned. 4 For complexes linked by conjugated hydrocarbon bridges, such systematic studies are rare. 5 We have previously described the preparation of several butadienediyl-bridged diiron complexes, [CpFeLL′] 2 (µ-CHdCHCHdCH) (1-4, Cp ) η 5 -C 5 H 5 ; Scheme 1), and the oxidation of these neutral species to dicationic and MV radical cationic species. 6 Lapinte and co-workers have reported the closely related butadiynediyl-bridged complex [Cp*Fe(dppe)] 2 (µ-CtCCtC) (7, Cp* ) η 5 -C 5 Me 5 , dppe ) Ph 2 PCH 2 CH 2 PPh 2 ) 7 and the butadienediyl-bridged complex [Cp*Fe(dppe)] 2 -(µ-C(OMe)dCHCHdC(OMe)) ( 8), 8 each also prepared in three oxidation levels. Though the MV cation forms of all of these species were found to be delocalized, class III 9 complexes, several interesting differences were
Factors such as flow and sediment characteristics affecting the spur dike's local depth of erosion have yielded considerable research results, but there is little discussion of the geometry of the spur dike's local scour holes. This study focuses on the spatial characteristics of the geometry of local scour holes in straight-wall spur dikes. The discussion shows that the spur dike arrangement clearly changes the plane geometry of the scour hole. The maximum scour depth has a power function relationship with the area of the scour hole and the scour hole-volume. Moreover, the ratio of the product of the maximum scour depth and the plane area of the scour hole to the scour hole-volume is a fixed constant. The average slope of upstream of the scour hole and along the axis direction of the spur dike is slightly larger than the angle of repose of the sediment, the slope distribution of the scour holes profiles presents an inverted "U" type, and its profile morphology and slope distribution have geometric similarity. This distribution also reflected that, the interaction between the downward flow and the horseshoe vortex inside the scour hole leads to the formation of a cusp.
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