title: Oligonuclear molecular models of intermetallic phases: a case study on [Pd2Zn6Ga2(Cp*)5(CH3)3].
abstract: The synthesis, characterization, and theoretical investigation by means of quantum-chemical calculations of an oligonuclear metal-rich compound are presented. The reaction of homoleptic dinuclear palladium compound [Pd(2)(μ-GaCp*)(3)(GaCp*)(2)] with ZnMe(2) resulted in the formation of unprecedented ternary Pd/Ga/Zn compound [Pd(2)Zn(6)Ga(2)(Cp*)(5)(CH(3))(3)] (1), which was analyzed by (1)H and (13)C NMR spectroscopy, MS, elemental analysis, and single-crystal X-ray diffraction. Compound 1 consisted of two C(s)-symmetric molecular isomers, as revealed by NMR spectroscopy, at which distinct site-preferences related to the Ga and Zn positions were observed by quantum-chemical calculations. Structural characterization of compound 1 showed significantly different coordination environments for both palladium centers. Whilst one Pd atom sat in the central of a bi-capped trigonal prism, thereby resulting in a formal 18-valence electron fragment, {Pd(ZnMe)(2)(ZnCp*)(4)(GaMe)}, the other Pd atom occupied one capping unit, thereby resulting in a highly unsaturated 12-valence electron fragment, {Pd(GaCp*)}. The bonding situation, as determined by atoms-in-molecules analysis (AIM), NBO partial charges, and molecular orbital (MO) analysis, pointed out that significant Pd-Pd interactions had a large stake in the stabilization of this unusual molecule. The characterization and quantum-chemical calculations of compound 1 revealed distinct similarities to related M/Zn/Ga Hume-Rothery intermetallic solid-state compounds, such as Ga/Zn-exchange reactions, the site-preferences of the Zn/Ga positions, and direct M-M bonding, which contributes to the overall stability of the metal-rich compound.
authors.affiliation: Inorganic Chemistry II-Organometallics & Materials, Faculty of Chemistry and Biochemistry, Ruhr University Bochum, 44870 Bochum, Germany.
authors.forename: Timo
authors.initials: T
authors.lastname: Bollermann
authors.forename: Mariusz
authors.initials: M
authors.lastname: Molon
authors.forename: Christian
authors.initials: C
authors.lastname: Gemel
authors.forename: Kerstin
authors.initials: K
authors.lastname: Freitag
authors.forename: Rüdiger W
authors.initials: RW
authors.lastname: Seidel
authors.forename: Moritz
authors.initials: M
authors.lastname: von Hopffgarten
authors.forename: Paul
authors.initials: P
authors.lastname: Jerabek
authors.forename: Gernot
authors.initials: G
authors.lastname: Frenking
authors.forename: Roland A
authors.initials: RA
authors.lastname: Fischer