Alkoxyacetyl complexes

We have delineated viable coordinated ligand reactions and their attendant intermediates for the stoichiometric conversion of CO ligands selectively to the C2 organics ethane, ethylene, methyl (or ethyl) acetate, and acetaldehyde. We now outline results from three lines of research (1) T -Alkoxymethyl iron complexes CpFe(C0)2CH20R (2) are available by reducing coordinated CO on CpFe(C0)3+ (1) [Cp = r -CsHs]. Compounds 2 then form t -alkoxyacetyl complexes via migratory-insertion (i,e. CO... 

Conversion of Alkoxyacetyl Complexes CpFe(C0)PPh3(COCH9OR) to Ethylene or to Ethane... 

The alkoxyacetyl complexes CpFe(C0)PPh3(COCH2OR) (6a,b) were transformed to the known (56,57) ethyl complex... 

We converted the alkoxyacetyl complexes 9 to the ethyl complex 8, by employing the aforementioned acyl ligand activation and BH reduction procedures, as outlined in Scheme 2. The a, -dialkoxyethylidene salts 9a, b resulted from alkylation of 6a,b with EtsO+PFg" in CH2CI2 recrystallization from CH2CI2-ether provided 9 in 72% yields as air-stable yellow PFg" salts. 

In order to produce free alkyl acetates, the alkoxyacetyl complexes 5-7 must first isomerize to carboalkoxymethyl compounds... 

The same results obtain whether carboalkoxy compounds 12,13 or alkoxyacetyl complexes 6,7 are treated with excess acid. Alkyl acetate liberated in these experiments, of course, derives from two CO ligands on CpFe(CO)3+ (1). 

Intermediates occurring in the acid-promoted isomerization of an alkoxyacetyl complex, CpFe(C0)2C0CH20Me (5a) to its carboalkoxymethyl compound CpFe(C0)2CH2C02Me (11a) have been observed by IR. Upon addition of acid to 5a, its IR terminal v (2025,... 

The alkoxyacetyl complexes 5 and 6 also serve as precursors, via reactions of the coordinated C2 ligands depicted in Scheme 4, for acetaldehyde. Activation of 5 and 6 as a,3-dialkoxyethylidene... 

Alkoxyacetyl complex 5a also forms bimetallic P2 alkoxy-acetyl compounds Cp(C0)2Fe(CO[M(C0)nCp]CH20Me)+ 32,M=Fe,n=2 and 3s3,M=Mo,n=3, but these adducts are less stable than the corresponding y2"acetyl adducts 28,29. Only 33 was isolable, although... 

We have demonstrated that NaBH3CN in alcohol reduces a CO ligand on CpFe(CO)3+ and generates an alkoxymethyl iron complex. Versatile alkoxyacetyl complexes CpFe(C0)L(C0CH20R)... 

Bimetallic activation of acetyl and alkoxyacetyl ligands — through formation of cationic P2 acyl complexes — to reaction with nucleophilic hydride donors was established. Cationic transition metal compounds possessing an accessible coordination site bind a neutral T -acyl ligand on another complex as a cationic P2 acyl system. These i2 3icyl systems activate the acyl ligand to reduction analogous to carbocation activation. Several examples of i2-acyl complexation have been reported previously. 

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