Formaldehyde molecular orbital scheme

Figure 7 Proposed molecular orbital scheme for uncomplexed and complexed formaldehyde...

Co2(CO)q system, reveals that the reactions proceed through mononuclear transition states and intermediates, many of which have established precedents. The major pathway requires neither radical intermediates nor free formaldehyde. The observed rate laws, product distributions, kinetic isotope effects, solvent effects, and thermochemical parameters are accounted for by the proposed mechanistic scheme. Significant support of the proposed scheme at every crucial step is provided by a new type of semi-empirical molecular-orbital calculation which is parameterized via known bond-dissociation energies. The results may serve as a starting point for more detailed calculations. Generalization to other transition-metal catalyzed systems is not yet possible. 

These deviations from linearity indicate the existence of an oligomeric distribution of chiral ligands. Noyori proposed a rationale as follows Due to the different dissociability (stability) of homochiral and heterochiral dimer, the enantiopurity of the remaining reactive catalyst (monomer) is improved as compared with that of the submitted chiral ligand 6 (Scheme 9.5) [11]. Heterochiral dimer is thermodynamically more stable than homochiral dimer, which is consistent with Noyori s rationale mentioned above [12a]. An ab initio molecular orbital study was also reported in a simplified model reaction between formaldehyde and dimethylzinc catalyzed by achiral 2-aminoethanol [12b]. 

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