The Electronic Structure of the Tris(ethylene) Complexes [M(C2H4)3] (M=Ni, Pd, and Pt): A Combined Experimental and Theoretical Study

• Published in: Chemistry : a European journal Vol. 13; no. 36; pp. 10078 - 10087
• Main Authors: Hebben, Nicole, Himmel, Hans-Jörg, Eickerling, Georg, Herrmann, Carmen, Reiher, Markus, Herz, Verena, Presnitz, Manuel, Scherer, Wolfgang
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.01.2007; WILEY‐VCH Verlag
• Subjects: density functional calculations; Group 10 elements; olefin complexes; palladium; vibrational spectroscopy
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.200700885

In this article we analyze in detail the electronic properties of the D3h‐symmetric tris(ethylene) complexes of nickel, palladium, and platinum ([M(C2H4)3] M=Ni, Pd, Pt). In the case of [Pd(C2H4)3] the analysis is based on new experimental IR and Raman spectra for the matrix‐isolated molecules and in all cases on the results of quantum‐chemical (DFT) calculations. The experimental spectra collected for [Pd(C2H4)3] provide evidence for several previously unobserved vibrational modes, including the in‐phase and out‐of‐phase ν(CC) and δ(CH2) modes, and the in‐phase ν(MC) mode. Special consideration is given to possible inter‐ligand interactions. The interaction force constant fCC,CC between two C2H4 ligands can be directly estimated from the spectra, and its very small value (0.002 N m−1) indicates the absence of any significant inter‐ligand interaction. An analysis of the topology of the theoretical electron density distribution, ρ(r), and the corresponding Laplacian, ∇2ρ(r), for [Pd(C2H4)3] and its lighter and heavier homologues [Ni(C2H4)3] and [Pt(C2H4)3], respectively, is in full agreement with the conclusions drawn from the experimental results. The combined experimental and quantum‐chemical results provide detailed insights in the electronic properties of these prototypical ethylene complexes. The bonding properties in the tris(ethylene) complexes of Ni, Pd, and Pt have been studied by charge density analysis and vibrational spectroscopy of the matrix‐isolated [Pd(C2H4)3] complex (see picture).