Octahedral Hexapalladium Pseudo‑T d Pd6(μ3‑CO)4(PEt3)6 with 80 Electron-Deficient Cluster Valence Electrons (CVEs) and a Comparison with Octahedral Hexapalladium Pseudo‑C 2v Pd6(μ3‑CO)4(PMe3)7 with 82 CVEs: Computational Analysis and Resulting Implications

• Published in: Inorganic chemistry 2023-01, Vol.62 (1), p.18-24
• Main Authors: Ivanov, Sergei A., Mednikov, Evgueni G., Dahl, Lawrence F.
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.2c03542

The elusive octahedral hexapalladium Pd6(μ3-CO)4(PEt3)6 (1) was obtained by the reaction of Pd10(CO)12(PEt3)6 with TlCo­(CO)4 in tetrahydrofuran under N2 at 55 °C. Its pseudo-T d octahedral structure, established from a CCD X-ray diffractometry study at 100 K, has the highest ideal symmetry of any of the characterized octahedral-based CO/PR3-ligated homopalladium Pd n clusters (n = 6, 7, 8, 10). Each Pd atom in 1 is coordinated to a PEt3 ligand, and each nonadjacent triangular Pd3 face is capped by a triply bridging μ3-CO ligand. The 31P­{1H} NMR and IR spectra of 1 are in accordance with its solid-state molecular structure. Cluster 1 has a total of 80 cluster valence electrons (CVEs), the lowest reported for octahedral-based metal polyhedra that normally conform to the Wade–Mingos bonding rule with an 86 CVE count. Comparative density functional theory calculations involving natural population analysis are presented for trimethylphosphine analogues of the triethylphosphine (1-Me) and the previously reported octahedral hexapalladium trimethylphosphine Pd6(μ3-CO)4(PMe3)7 (2), which has pseudo-C 2v symmetry with 82 total CVEs.