Metal carbonyls bond angles from

The two weaker bonds from Hg to N atoms in a plane perpendicular to the C-Hg-C plane may account for the departure of the C—Hg—C bond angle from 180°. In the ions to be discussed now the C—N bond is collinear with the metal-carbon bond the system M—C—O in metal carbonyls is also linear. 

C. The structure, which involves two bridging carbonyl groups as shown in Fig. 26.8a, can perhaps be most easily rationalized on the basis of a bent Co-Co bond arising from overlap of angled metal orbitals (d sp hybrids). However, in solution this structure is in equilibrium with a second form (Fig. 26.8b) which has no bridging carbonyls and is held together solely by a Co-Co bond. 

FlO. 1. Theoretical curves of OC—M—CO bond angle in M(CO)3 groups with approximate trigonal symmetry, with transition metal M enneacoyalent (u = 9) or octacovalent (< = 8), as functions of the bond number n from n = 1 (single bond from metal to carbonyl) to n = 2 (double bond). 

Figure 4. Relationship between the calculated Fe-Fe distance and the Fe-Fe-CO bond angle (y) of the carbonyl group trans to the substituents E in the model compound [Fe2(//-CFl2)(CO)gl (structure 8, circles, adapted from ref. [16]). Also shown are the experimental valuesf for [Fe2(/ E)(CO)gj compounds 8 in which E is a carbene or a vinyl group (circles), and for [Fe2T2(CO)8l complexes of structure 6 (triangles) in which T is a transition metal.

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