INFRARED AND C-13 NMR-STUDY OF PHOSPHINE MONOSUBSTITUTED GROUP-VI B METAL-CARBONYLS

IR and 13C NMR data are presented for a series of LM(CO)5 compounds with L = (CH3)3P, (C2H5)3P and (C6H5)3P for M = Cr, Mo, W and L = PCl3, C6H5PCl2 and (C6H5)2PCl for M = Cr. The correlation between the A1(eq) ν(CO) stretching frequency and the sum of Taft's σ*i,X parameters for the phosphorus substituents is discussed in terms of σ- and π-bonding. Relative inductive and mesomeric parameters, derived according to both the treatment of Graham and of Dobson, are compared. A linear correlation has also been found between ν(CO) and δ 13C(O) for axial as well as equatorial CO groups. Finally 2JPMC(O) ax, 2JPMC(O) eq and 1JWC(O) eq are discussed in view of the recent literature; a negative sign is proposed for some PC(O) coupling constants in LCr(CO)5 compounds in order to obtain logical trends for the carbonyls of the three transition metals Cr, Mo and W. © 1979.