TUNGSTEN-183-PHOSPHORUS-31 SPIN-SPIN COUPLING INTERACTIONS IN PENTACARBONYLTUNGSTEN COMPLEXES

The magnitudes of 183W-31P nuclear spin-spin coupling constants have been determined in a series of LW(CO)5 complexes and are found to increase linearly with a correlation coefficient of greater than 0.95 as the electronegativity of the substituents on the phosphorus ligand L increases: P(CH2O)3CC4H9 < P(SCH2)3CC5H11 < P(N(CH3)CH2)3CC5H11 < P(OCH2)3CCH3 < PF3. This trend can be interpreted in terms of the increasing s character of the 183W-81P bond and the rise in positive charge on phosphorus as more electronegative substituents are bound to phosphorus. Carbonyl stretching frequencies for these complexes have been assigned to A11, B1, A12, and E modes and to the 13CO satellites of the E band. The approximate method of Cotton and Kraihanzel was used to obtain the force constants k1, k2, and ki. The stretching frequencies of the E mode were found to increase in the series: P(N(CH3)CH2)3CC5H11 < P(CH2O)3CC4H9 < P(OCH2)3CC5H11 < P(SCH2)3CC5H11 < PF3. Attempts to correlate the 183W-31P coupling constants with the A11 or E mode frequencies and k1 produced correlation coefficients of 0.70, 0.79 and 0.51, respectively. Evaluation of the ligands in terms of σ and π-donating capacities after the method of Graham resulted in correlation coefficients of 0.55 and 0.35, respectively. © 1969, American Chemical Society. All rights reserved.