Carbon monoxide bonding geometry

Further examples of coordinate bonds are found in metal carbonyl complexes. Metal carbon (carbon monoxide) bond distances in a selection of (first-row) transition-metal carbonyls and transition-metal organometallics are examined in Table 5-11. As expected, Hartree-Fock models do not perform well. The 6-3IG model is clearly superior to the STO-3G and 3-2IG models (both of which lead to completely unreasonable geometries for several compounds), but still exhibits unacceptable errors. For example, the model shows markedly different lengths for the axial and equatorial bonds in iron pentacarbonyl, in contrast to experiment where they are nearly the same. Hartree-Fock models cannot be recommended. 

When heated, azodicarbonamide breaks apart into gaseous carbon monoxide, nitrogen, and ammonia. Azodicarbonamide is used as a foaming agent in the polymer indushy. (a) Add nonbonding electron pairs and multiple bonds as required to complete the Lewis stmcture of this molecule, (b) Determine the geometry around each inner atom. 

Insertion of carbon monoxide into Csp2—Zr bonds occurs readily at ambient temperatures or below to produce a,(5-unsaturated, reactive acyl zirconocene derivatives [27—29]. Early work by Schwartz demonstrated the potential of such intermediates in synthesis [5d], as they are highly susceptible to further conversions to a variety of carbonyl compounds depending upon manipulation. More recently, Huang has shown that HC1 converts 16 to an enal, that addition of a diaryl diselenide leads to selenoesters, and that exposure to a sulfenyl chloride gives thioesters (Scheme 4.11) [27,28]. All are obtained with (F)-stereochemistry, indicative of CO insertion with the expected retention of alkene geometry. 

Qulnkert et. al. (O photoellmlnated carbon monoxide from cls-l,3-dlphenyl-2-lndanone (Figure 5). In solution, the major product Is the more stable trans-substltuted benzocyclobutane. However, the els geometry Is maintained In the corresponding solid phase reaction because the crystalline state Impedes rotation about carbon-carbon single bonds In the reaction Intermediate. 

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