PRINCIPAL PROPERTIES OF MONODENTATE PHOSPHORUS LIGANDS - PREDICTIVE MODEL FOR THE CARBONYL ABSORPTION FREQUENCIES IN NI(CO)(3)L COMPLEXES

By use of the principal component analysis method, the principal prope rties of 45 different monodentate phosphorus ligands, each described b y fifteen molecular descriptors, have been calculated. A principal com ponent model composed of live principal components was determined acco rding to cross-validation and accounted for 90% of the variance in the original data table. This model divided the P ligands into two classe s, a small one which contained six polyhalogenated P ligands, and anot her which contained 39 different P ligands. Another principal componen t analysis was carried out on the large class of P ligands. This model described 90.5% of the total variance by using four principal compone nts. Among these a subset of compounds were used for validating the re levance of the molecular descriptor variables. Two experimentally meas ured IR-frequencies, the carbonyl frequencies v(A1) and v(E) were used as independent variables and correlated to the molecular descriptors using the partial least-squares regression (PLSR) method. The PLSR mod els showed that the calculated molecular descriptors contained relevan t information concerning the investigated compounds to be used for der iving the principal properties of the monodentate phosphorus ligands. The PLSR models for the two different IR frequencies were used to pred ict the CO frequencies for P ligands where the IR frequencies have not been reported in the literature.