TY - JOUR
T1 - Diene-metal π bonding. Some unexpected effects of Group 5 donor ligands on carbon-13 nuclear magnetic resonance parameters and X-ray crystal structures
AU - Pearson, Anthony J.
AU - Raithby, Paul R.
PY - 1981
Y1 - 1981
N2 - A number of η4-cyclohexadiene-Fe(CO)2L and η4-2-methoxycyclohexadiene-Fe(CO)2L complexes have been prepared and their 13C n.m.r. spectra recorded. Methoxy-substituent effects suggest a depopulation rather than the expected enhanced population of the diene I.u.m.o. (lowest unoccupied molecular orbital) as the π-acceptor strength of L decreases. X-Ray crystal-structure determinations for L = PPh3 were in agreement, and an explanation is proposed. Complexes [Fe(CO)2(PPh3)(C6H8)] (7) and [Fe(CO)2(PPh3)(C6H7OMe)] (8) both crystallise in the monoclinic space group P21/c with Z = 4. The cell parameters are a = 10.289(4), b = 24.651(10), c = 9.282(4) Å, and β = 109.37(3)° for (7) and a = 14.444(7), b = 18.052(10), c = 9.229(4) Å, and β = 100.57(4)° for (8). The structures were solved by a combination of Patterson and Fourier-difference techniques, and refined by blocked-cascade least squares to R = 0.053 for 3 325 unique observed reflections (7) and to R = 0.062 for 2 952 reflections (8).
AB - A number of η4-cyclohexadiene-Fe(CO)2L and η4-2-methoxycyclohexadiene-Fe(CO)2L complexes have been prepared and their 13C n.m.r. spectra recorded. Methoxy-substituent effects suggest a depopulation rather than the expected enhanced population of the diene I.u.m.o. (lowest unoccupied molecular orbital) as the π-acceptor strength of L decreases. X-Ray crystal-structure determinations for L = PPh3 were in agreement, and an explanation is proposed. Complexes [Fe(CO)2(PPh3)(C6H8)] (7) and [Fe(CO)2(PPh3)(C6H7OMe)] (8) both crystallise in the monoclinic space group P21/c with Z = 4. The cell parameters are a = 10.289(4), b = 24.651(10), c = 9.282(4) Å, and β = 109.37(3)° for (7) and a = 14.444(7), b = 18.052(10), c = 9.229(4) Å, and β = 100.57(4)° for (8). The structures were solved by a combination of Patterson and Fourier-difference techniques, and refined by blocked-cascade least squares to R = 0.053 for 3 325 unique observed reflections (7) and to R = 0.062 for 2 952 reflections (8).
UR - https://www.scopus.com/pages/publications/37049097132
U2 - 10.1039/DT9810000884
DO - 10.1039/DT9810000884
M3 - Article
AN - SCOPUS:37049097132
SN - 1472-7773
SP - 884
EP - 891
JO - Journal of the Chemical Society, Dalton Transactions
JF - Journal of the Chemical Society, Dalton Transactions
IS - 3
ER -