Cobalt ethylene complexes

Cobalt atom reactions with ethylene were also studied (121). By using techniques similar to those described for Cu (122) and Ni (101), it has proved possible to synthesize a novel series of mononuclear and binuclear cobalt-ethylene complexes, Co(C2H4) , = 1, or 2, and... 

Cobalt vapor was generated by directly heating a 0.01-in. ribbon filament of the metal and cocondensed with C2H4/Ar matrices at 12-15K. A series of mono- and binuclear cobalt-ethylene complexes Co(C2H4) (where / = 1, 2) and Co2(C2H4)OT (where m = 1, 2) as well as a suspected tetranuclear species Co4(C2H4)f have been detected by spectroscopic methods. 

Electronic spectra have been recorded for the 1,5-pentamethylene-tetrazole adducts MX2(l,5-pmtta) (M = Mn, Fe, Co, Ni, and Cu X = Cl and Br) (32) and for the complex salts [M(l,5-pmtta)6][C104]2 (M = Fe, Co, Ni, and Cu) (51, 52). Data for the complex salts indicate that 1,5-pentamethylenetetrazole is a stronger ligand than ethylene-diamine in the nickel(II) system but only slightly stronger than water in cobalt(II) complexes (51). 

A somewhat similar catalytic acetoxylation of ethylene to vinyl acetate by 02 has been carried out in acetic acid in the presence of a Pd(OAc)2-pyCo(TPP)N02 system.472 A stoichiometric epoxidation of alkenes such as 1-octene or propene by cobalt-nitro complexes has been shown to occur in the presence of thallium(III) benzoate. Oxygen labeling studies showed that the epoxide oxygen atom comes only from the nitro ligand (equation 197).473... 

A great majority of the hitherto known dianionobis(ethylene-diamine)cobalt(III) complexes have traditionally been prepared by... 

Other Co(II)-complexes that were applied in the photosensitized reduction of C02 to CO (and concomitant H2-evolution) include Co(II)-ethylene glycol dimethyl ether complexes [178], and different tetraaza-macrocyclic Co(II)-complexes such as 27,28. A closely related system, where Ni(II)-tetraaza macrocycle (29) substitutes the cobalt homogeneous complexes in the photosystem including Ru(bpy) + as photosensitizer and ascorbic acid as electron donor, has been reported by Tinnemans [181] and Calvin [182],... 

Cobalt(i) complexes [Co(chel)], where chel = NN -ethylene(acetylacetonedi-imi-nato), iViV -ethylenebis(iViV -dimethylsalicylideneiminato), NN -ethylenebis(salicyli-... 

As has been demonstrated in Section 3.1.2.4, complexation of amino groups offers a quite different concept for reversible protection. Making use of this principle, the coordination of chromium carbyne complexes with amino acids was described as a new amino protection. Similarly, bis(ethylene-diamine)cobalt(III) complexes of amino acids constitute a new interesting method for protection which recently was extended to the development of a new type of anchoring in solid-phase synthesis (Scheme 69). First, a t-BOC amino acid is condensed with the aquabis(ethylenediamine)cobalt(lII) complex of p-aminomethylbenzoic acid. The handle obtained in this way is then linked to aminomethyl polystyrene to give the anchored amino acid (69). Due to the sufficient stability of the complex toward... 

Influence of Catalyst Preparation. Pebrine reported on the influence of the synthesis conditions of HZSM-5 on the selectivity toward light olefins. Synthesizing ZSM-5 in the presence of a tetra-urea-cobalt(II) complex resulted in an ethylene yield of 24.3 wt% of the hydrocarbon fraction at 43.7% methanol conversion, whereas the conventionally prepared ZSM-5 yielded only 18 wt% ethylene at the same conditions and conversion. Heering et al. mentioned that the conversion of dimethylether on ZSM-5 catalysts crystallized from a sodium-free gel with 1,6-dicunino-hexane as organic base was more selective toward both ethylene and propylene than on a conventionally prepared zeolite in the sodium form from a gel containing tetrapropylammonium. 

The discovery of the Kubas complex was a defining event in the historical development of coordination chemistry. By 1920, the Lewis ideas on the role of electron pairs in bonding had already associated the coordinate bond with the donation of a lone pair to a metal. For example, donation of the ammonia lone pair to was implicated in the classical Werner cobalt-ammonia complexes. Subsequent developments extended the coordination concept beyond lone-pair donors. Around 1950, a series of discoveries by Wilkinson, Chatt, Fischer, and others showed how the electrons of unsaturated ligands such as cyclopentadienide ion and ethylene can also bind to metal ions. These complexes stimulated the modem development of organometallic chemistry and homogeneous catalysis. 

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