Cobalt complexes cyclopentadiene

C4H 2OSi, Silane, methoxytrimethyl-, 26 44 CH4N, Propane, 2-isocyant-2-methyl-ruthenium complex, 26 275 C][l,4]-dithiin-2-thione, 26 389 CHfc, 1,3-Cyclopentadiene cobalt complex, 26 191-197, 309 chromium, molybdenum, and tungsten complexes, 26 343 iron complex, 26 232-241 mercury-molybdenum-ruthenium complex, 26 333... 

Cyclopentadiene(diene)cobalt complexes, the largest catagory of diene complexes of Co, may be prepared by direct complexation, by preparation of the dienes within the coordination sphere of Co and by nucleophilic addition to ( j5-dienyl)CoCp cations. In comparison to (diene)CoCp complexes, there are considerably fewer examples of (diene)RhCp and (diene)IrCp complexes known. 

A complex of Fe2+ with cyclopentadiene and the B9C2Hii2 ion (a) and the cobalt complex, [Co(B9C2H11)2] (b). There is one hydrogen atom attached to each boron atom in these structures. The hydrogen atoms have been omitted to simplify the drawing. 

Another cobalt complex having only hydrocarbon ligands, (1,3-butadiene)cyclopentadienylcobalt, has been obtained as a volatile red solid melting at 103°-105°C by reaction of the diene with dicyclopenta-dienylcobalt or (1-benzoyl-1,3-cyclopentadiene)cyclopentadienylcobalt (489). The compound decomposes slowly in air. 

The chiral iron(III) Lewis acid 3, derived from an oxazoline ligand, catalyzes Diels-Alder reactions of A -acryloyl-l,3-oxazolidinone (1) and cyclopentadiene (2) with good enantiomeric excess30. Nickel complexes of chiral phosphanes also catalyze Diels-Alder reactions albeit with low enantiomeric excess, not exceeding 15% cc31. Much better results are achieved for cobalt complexes with chiral phosphanes in the presence of a Lewis acid31,32. 

C,oH, Benzene, l-isoprq>yl-4-methyl-, tulhenium complex, 21 75 C oH t, 1,3-Cyclopentadiene, 1,2,3,4,5 penta-methyl, 21 181 cobalt complexes, 23 15-19 iridium and riiodium complex, 22 173, 174 CijHit, Benzene, hexamethyl-, nithenium complexes, 21 74-77 CajMnjOi, Calcium manganese oxide, 22 73 CdCl2N O9C2 H]0. Cadmium(II), aqua-... 

C10H15N, Benzenemethanamine, N,N,4-trimethyl-, lithium complex, 26 152 C10H15P, Phosphine, diethylphenyl-, nickel complex, 28 101 platinum complex, 28 135 CioHigAsi, Arsine, 1,2-phenylenebis(dimethyl-, gold complex, 26 89 nickel complex, 28 103 CioHie, 1,3-Cyclopentadiene, 1,2,3,4,5-pen-tamethyl-, 28 317 chromium complex, 27 69 cobalt complexes, 28 273, 275 iridium complex, 27 19 samarium complex, 27 155 titanium complex, 27 62 ytterbium complex, 27 148 CioH,gBrN04S, Bicyclo[2.2.1]heptane-7-methanesulfonate, 3-bromo-1,7-di-methyl-2-oxo-, U.IRHENDO, ANTPi]-, ammonium, 26 24... 

The cobalt complex 117 reacted with but-2-yne in the presence of HBF, to afford the cycloheptadienyl complex 118 (Scheme 7.45) [63]. The alkyne moiety is inserted into the C-C bond of the cyclopentadiene ring. 

Other examples are shown on pp. 107,108 and 121. An interesting feature of unsubstituted-cyclopentadiene complexes, e.g. 3.17, is that their infrared spectra show a broad, intense C-H stretch at the unusually low frequency of 27C0 cm i. For the cobalt complex, 3.17, the assignment is confirmed by the spectrum of the deuterated analogue the anomalous C-H stretch is absent and a corresponding C-D band appears [15]. 

The cationic aqua complexes prepared from traws-chelating tridentate ligand, R,R-DBFOX/Ph, and various transition metal(II) perchlorates induce absolute enantio-selectivity in the Diels-Alder reactions of cyclopentadiene with 3-alkenoyl-2-oxazoli-dinone dienophiles. Unlike other bisoxazoline type complex catalysts [38, 43-54], the J ,J -DBFOX/Ph complex of Ni(C104)2-6H20, which has an octahedral structure with three aqua ligands, is isolable and can be stored in air for months without loss of catalytic activity. Iron(II), cobalt(II), copper(II), and zinc(II) complexes are similarly active. 

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