Hydroxymethyl species

The dihaptoformaldehyde complex 0s(Tj2-CH20)(C0)2(PPh3)2 reacts with hydrogen halides, affording hydroxymethyl species. Further reaction leads to the formation of halomethyl complexes, probably via the intermediacy of methylene complexes (60) (73) ... 

The years 1978 and 1979 have witnessed continuing activity on the catalytic reduction of CO and models for it. Both Casey and Gladysz have established that the neutral formyl complex (C5H5)Re(CO)(NO)(CHO) which they synthesized (59b,c) is the first intermediate in the borohydride reduction of coordinated CO to methyl as reported by Graham and co-workers (55). When the neutral formyl complex is reacted with BH3 THF, the species (C5H5)Re(CO)(NO)(CH3) results. A similar reduction does not occur when H2 is used as the reductant, however (59b). While the previous report by Nesmeyanov et al. (86) of a hydroxymethyl species in the BH4 reduction process is now viewed as incorrect (59b,e), Casey has recently described (59e) unequivocal characterization of this species, and has shown how the formyl complex (C5H5)Re(CO)(NO)(CHO) can lead to its formation as shown in (23a). 

Some chemistry of [CpRe(CO)(NO)(CHO)], formed by reduction of [CpRe-(CO)a(NO)] [PF,] with K[B(OPr )3H], is summarized in Scheme 12. The complex [CpRe(CO)(NO)(CHaOH)] is the first unsubstituted hydroxymethyl species to be isolated and is of singificance to Fischer-Tropsch studies. The hydroxymethyl species can also be obtained by treatment of [CpRe(CO)a(NO)] [PF ] with NaEAlEtaHaJ. 

Fig. 6. Freeman and Lewis stabilized structure and the likely results of orr/to-polymerization. As polymerization consumes o-hydroxymethyl groups, the hydrogen-bonded species cannot fomi.

In a first reaction step the formaldehyde 2 is protonated, which increases its reactivity for the subsequent electrophilic aromatic substitution at the benzene ring. The cationic species 4 thus formed loses a proton to give the aromatic hydroxymethyl derivative 5, which further reacts with hydrogen chloride to yield the chloromethylated product 3 ... 

Pd, or Ni (Scheme 5-3). First, P-H oxidative addition of PH3 or hydroxymethyl-substituted derivatives gives a phosphido hydride complex. P-C bond formation was then suggested to occur in two possible pathways. In one, formaldehyde insertion into the M-H bond gives a hydroxymethyl complex, which undergoes P-C reductive elimination to give the product. Alternatively, nucleophilic attack of the phosphido group on formaldehyde gives a zwitterionic species, followed by proton transfer to form the O-H bond [7]. 

The overall catalytic reactions involved in the two step synthesis of hydroxymethyl ated PBD are given by Equations 1-6. It can be seen from reactions (1-6) that the addition of -CHO functional group can occur in three ways resulting in the formation of three types of hydroformyl ated PBD repeating units as shown by species A, B or C. Subsequent hydrogenation of units A, B and C result in the formation of hydroxymethylated PBD repeating units A, ... 

Hydrogenolytic treatment of ( )-28 in methanol in the presence of 10% Pd/C at room temperature and 15 psi of pressure for 24 h gave the amino alcohol 178 as the only product, the species 177 having only a short lifetime (3 h) and saturation of the pyrrole nucleus proceeded slowly and partially under these conditions but it was facilitated by the additional presence of hydrogen chloride which afforded 2-hydroxymethyl pyrrolizidine 179 in 51% yield (Scheme 24) <1998JOC9279>. 

To summarize briefly, our approach involves initial attack by a relatively nucleophilic metal hydride on coordinated CO. Such reactivity has been demonstrated repeatedly for main-group metal hydrides perhaps the most elegantly worked-out system involves CpRe(C0)2(N0)+ (Cp = Tl-C H ) which, under varying conditions, can be converted to an entire range of products containing CO at different stages of reduction, including formyl, carbene, hydroxymethyl and methyl species (Scheme l). Reactions lead-... 

This was the first example in which models for presumed Fischer-Tropsch intermediates have been isolated and their sequential reduction demonstrated. Neither methane nor methanol was observed from further reduction of the methyl and the hydroxymethyl complexes. The use of THF/H20 as solvent was crucial in this sytem in THF alone CpRe(C0)(N0)CH3 was the only species observed, probably because the initial formyl complex was further reduced by BH3.— When multihydridic reagents are reacted with metal carbonyl complexes, formyl species are usually not observed. The rapid hydrolysis of BH3 by aqueous THF allowed NaBH to act as a... 

Solutions of the nickel(O) and palladium(O) complexes of 1,3,5-triaza-7-phosphaadamantane, PTA (82) and tris(hydroxymethyl)phosphine (98) in water catalyze the oligomerization and telomerization of 1,3-butadiene at 80 °C. Although high yields and good selectivities to octadienyl products (87 %) were obtained, the complexes (or the intermediate species formed in the reaction) dissolve sufficiently in the organic phase ofthe monomer and the products to cause substantial metal leaching [17],... 

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