TY - JOUR
T1 - Steric and electronic balance in metal- phosphine coordination
T2 - The phosphine twist
AU - Lichtenberger, Dennis L.
AU - Jatcko, Mark E.
N1 - Funding Information:
D.L.L. acknowledges support of thc Department of Energy (Division of Chemical Sciences, Office of Basic Energy Sciences, Office of Energy Research; Contract No. DE-FG02-86ERl3501) for the study of the electronic structure of organometallic molecules, the National Science Foundation (CHE-930084 1) for assistance in support for instrumentation, and the Materials Characterization Program (Arizona). We also thank Professor T.L. Brown for enlightening and inspiring discussions.
PY - 1994/6/1
Y1 - 1994/6/1
N2 - The relationship between the bite angles of cis phosphines and the electron distribution and bonding to the metal is studied by gas phase valence photoelectron spectroscopy. The complexes selected for the electronic structure comparison are cis-Mo(CO)4(PMe3)2, Mo(CO)4DMPE (DMPE = 1, 2-bis dimethylphosphinotethane), Mo(CO)4DMPM (DMPM = bis(dimethylphosphino) methane), cis- W(CO)4(PMe3)2, W(CO)4DMPE, and cis-W(CO)4DMPM. The Mo carbonyl complexes give simple photoelectron spectra with the valence ionizations originating from the phosphine lone pairs bonding to the metals and from the metal d6configurations. The W complexes give similar spectra, but have an additional electronic spin-orbit perturbation. The ionizations from the phosphine lone pairs that donate to the metals in a bond formation show the effects of the different bite angles of the ligands. However, the total interaction and charge distribution of the phosphines with the metals look very similar in each case. The metal-based ionizations also show very similar bonding and charge distribution in each case. The similarity of the cis-(PMe3)2 and DMPE spectra is interesting in light of the ⋍15° difference in P-M-P angles. The metal-based ionizations of the DMPM complexes are slightly different from those of the other complexes, primarily because of through-space interactions with the methylene carbon in the phosphine backbone. The similarity in electronic interactions with the metal in these complexes is traced to a twist of the phosphine coordination to the metal which adjusts for the steric or bite angle constraints of the ligands with a minimum effect on the bonding to the metal. This results in slightly bent metal-phosphorus bonds.
AB - The relationship between the bite angles of cis phosphines and the electron distribution and bonding to the metal is studied by gas phase valence photoelectron spectroscopy. The complexes selected for the electronic structure comparison are cis-Mo(CO)4(PMe3)2, Mo(CO)4DMPE (DMPE = 1, 2-bis dimethylphosphinotethane), Mo(CO)4DMPM (DMPM = bis(dimethylphosphino) methane), cis- W(CO)4(PMe3)2, W(CO)4DMPE, and cis-W(CO)4DMPM. The Mo carbonyl complexes give simple photoelectron spectra with the valence ionizations originating from the phosphine lone pairs bonding to the metals and from the metal d6configurations. The W complexes give similar spectra, but have an additional electronic spin-orbit perturbation. The ionizations from the phosphine lone pairs that donate to the metals in a bond formation show the effects of the different bite angles of the ligands. However, the total interaction and charge distribution of the phosphines with the metals look very similar in each case. The metal-based ionizations also show very similar bonding and charge distribution in each case. The similarity of the cis-(PMe3)2 and DMPE spectra is interesting in light of the ⋍15° difference in P-M-P angles. The metal-based ionizations of the DMPM complexes are slightly different from those of the other complexes, primarily because of through-space interactions with the methylene carbon in the phosphine backbone. The similarity in electronic interactions with the metal in these complexes is traced to a twist of the phosphine coordination to the metal which adjusts for the steric or bite angle constraints of the ligands with a minimum effect on the bonding to the metal. This results in slightly bent metal-phosphorus bonds.
KW - cis-complexes
KW - phosphine ligand bonding
KW - photoelectron spectra
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U2 - 10.1080/00958979408024239
DO - 10.1080/00958979408024239
M3 - Article
AN - SCOPUS:0013249986
SN - 0095-8972
VL - 32
SP - 79
EP - 101
JO - Journal of Coordination Chemistry
JF - Journal of Coordination Chemistry
IS - 1-3
ER -