¹⁷ O, ¹³ C and ¹ H NMR spectra of 1,2‐dialkoxyethenes

Transformations of Group 7 Carbonyl Complexes: Possible Intermediates in a Homogeneous Syngas Conversion Scheme

“…An attractive approach to further progress would be addition of an electrophile to the acyl oxygen of 13 to form a new carbene complex, which might add hydride to form an alkyl and grow the chain via another CO insertion or could undergo protonolysis of the Mn-C bond to give a C 2 organic product. Addition of MeOTf to acyl complex 13 gives no immediately detectable reaction, but over a period of 24 h the MeOTf 1 H NMR signal disappears and a new product grows in, whose 1 H NMR spectrum corresponds to trans-1,2-dimethoxyethene, 41 accompanied by growth of a 31 P NMR signal at 42 ppm, identified as belonging to Mn(PPh 3 )(CO) 4 (OTf) (14). 42 The yield of this reaction is greater than 80% by 1 H NMR.…”

“…If EtOTf is used as the alkylating agent, the reaction proceeds similarly to give the asymmetrically substituted olefin trans-1-ethoxy-2-methoxyethene, whose 1 H NMR spectrum matches literature data. 41 With triethyloxonium tetrafluoroborate, in contrast, alkylation of the acyl oxygen occurs over a period of several hours, forming the originally expected cationic carbene complex [Mn(PPh 3 )(CO) 4 (dC-(OEt)CH 2 OMe)][BF 4 ] (15), identified by its 1 H NMR signals (ethyl triplet and quartet at δ 4.28 and 1.36, respectively; methylene singlet at δ 4.12; methoxy singlet at δ 3.68). 15 decomposes over time to liberate trans-1-ethoxy-2-methoxyethene.…”

Electronic control of the competitive π donation in heteroatom substituted CpFe(CO)2(olefin)BF4 complexes and the resulting influence on the symmetry of the metal to olefin bond

“…As such, they reveal the competitive p donation between the oxygen at C 1 and the nitrogen at C 2 . We know from Taskinen's work with mixed cis-dialkoxyethylenes [11], as well as our previous work with various Fp olefin complexes [5], that when competition for p-p overlap exists, the 13 C shift of the carbon bonded to the dominant p donor will move downfield while the remaining olefin carbon moves upfield. The distance between these peaks (in an analogous series) is therefore a reasonable measure of each heteroatom's ability to compete for p overlap with the olefin.…”

“…(2)), thereby activating [4] displacement is not a prerequisite for nucleophilic substitution chemistry on the coordinated olefin [6], limited displacement has been observed (both experimentally and theoretically) to facilitate substitution at the site of heteroatom substitution [4,[7][8][9] ð2Þ When the entering nucleophile is an alcohol (or alkoxide), the unsymmetric dialkoxy intermediate product results in a competition between similar p donors. In such cases, the Fp moiety favors one side by some small [10] amount, often displaced away from the larger alkoxy fragment [11]. The use of these alkoxy disubstitution reactions has been extended to the synthesis of multi-oxygen containing heterocyclic products [12].…”

“…Comparison of the olefin 13 C shifts for the Single (1-9) and disubstituted(10)(11)(12)(13)(14) Fp + olefin complexes. The arrows show the shift of the 13 C peaks in response to increasing electron withdraw at the para position.…”