Physical Properties of Transition Metal Formyl Complexes

PHYSICAL PROPERTIES OF TRANSITION METAL FORMYL COMPLEXES 

Formyl complexes are characterized by distinct spectroscopic features. The most frequently used diagnostic probe has been H NMR. Chemical shifts in the 8 12-17 range (several ppm downfield from normal aldehyde or formamide H-NMR resonances) (69) are observed. However, since chemical shifts measured in the presence of trialkylborane by-products can show marked temperature dependence (32, 38, 47, 66), absolute values must be treated with caution. 

IR spectra of both anionic and neutral formyl complexes show tv=( between 1530 and 1630 cm 1 which are medium in intensity relative to 

Most aldehydes also show two weak i c-h in the 2830-2695 cm-1 region (72). Similar absorptions have been observed in some formyl complexes (28, 29, 52 -54, 67). However, these are not intense enough to be diagnostic, and confirmation of this assignment by study of the corresponding deuteroformyls (—CDO) would seem desirable. 

Several structural features of 39 suggest that resonance structure 51b significantly contributes to its ground state. First, the formyl C=0 distance, 1.220(12) A, is as long or longer than the corresponding C=0 bond distance in formamide (1.193 A) (74). Second, the plane of the formyl 

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III. Physical Properties of Transition Metal Formyl Complexes. 13... 

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