Halogen bonding stretching-force constants

Fig. 19 Variation of the intermolecular stretching force constant ka with nucleophilicity Nb for several series of halogen-bonded complexes B- XY, where B is one of a series of Lewis bases and XY is Cl2, Br2, BrCl, C1F or IC1. N% were assigned by use of Eq. 4 with the choice of ICi = 10.0, hence the perfect straight line for the B- -IC1 series. The lines for the other series are those obtained by least-squares fits to the ka values using the Mb determined from the B- IC1 series. Points for E P- -IC1, E N- -C1F and EEN- BrCl are anomalous and were excluded from the fits (see text for discussion)... 

II. Halogeno complex ions. Table 4 lists the observed frequencies and the calculated values of the metal-halogen stretching force constants. The bond, between Pt(IV) and Cl is stronger than that between Pt(II) and Cl. This is also the case for Pd(IV) and Pd(II). This result is in agreement with that of the pure quadrupole resonance study (8). 

Figure 5.4 Comparison of intermolecular stretching force constants hydrogen bond versus halogen bond.

FIG. 3.4. Plots of the dependencies between experimental atomic equilibrium charges of halogens in CH3a and (a) difference of electronegativity between halogen and carbon, (b) stretching force constant of the bond aC, and (c) interatomic distance aC (Reproduced from Ref. [81] widi permission. Copyright [1984] American Chemical Society). 

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