Substitution/omission method

The preceding discussion of substitution mechanisms barely scratches the surface of a field that has occupied the attention of many of tbe world s best coordination chemists. It is an area which seems to have an infinity of problems as well as methods of attack. It is unfortunate that it is not possible here to present a more comprehensive theory of substitution mechanisms. The discussion presented errs on the side of omission of fine points and controversial interpretations. For every experiment designed to confirm a mechanism, an alternative explanation can usually be found. As one noted researcher once said "(The members of the other school of thought] are extremely ingenious at coming up with alternative explanations for all of the conclusive experiments that we seem to do. 28 This should serve to remind us of the truism that u is not possible to prove that a particular mechanism is the correct one it is only possible sometimes to prove that an alternative mechanism is not correct. To this might be added a corollary Often it is extremely difficult to prove that the alternative is impossible. 

Surprisingly missing from this collection of preparative methods is the direct reaction between commercially available Mn(CO)sBr and NaCsHs. This omission suggests that the reaction proceeds in poor yields, which is consistent with our experience. In 1988, however. Smart and coworkers found MnBr(CO)3(pyridine)2 to be an effective reagent in making a substituted... 

It is evident that Eq. (383) and, therefore, Eqs. (394) and (396) can only be applied if and P are known values. However, in most case, these values are unknown because we do not know the BET surface area (N2, 77 K) of the adsorbent. Thus, our aim is to prove that it is possible to calculate the values of u (N2, 77 K) form the isotherms of Type I without a multilayer plateau thus, the separate determination of the nitrogen isotherm at 77 K can be omitted. This omission does not mean that the BET(N2, 77 K) method is no longer necessary. To the contrary, the following proposed calculation of (f is based on the BET(N2, 77 K) method, but the proposed method refers to the possibility that a (N2, UK) can be substituted by a (X, T), where X is the absorptive to be investigated and T, (T < T is the temperature of the isotherm of the adsorptive X. 

Summarizing this method, it should again be underlined that this calculation of cr (N2, 77 K) is only a substitution of the original BET method. The occasional but suitable omission of the nitrogen isotherm at 77 K does not mean that the well-known and widely used BET method is no... 

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