Organometallic Chemistry of Ga⁺: Formation of an Unusual Gallium Dimer in the Coordination Sphere of Ruthenium

Abstract

New insights into the distinct organometallic chemistry of the Ga(+) ion are presented. Ga(+) reacts as a strong electrophile with the electron rich ligand trismethylene-methane (C(CH(2))(3) (2-)) attached at Ru by insertion into a Ru--C bond. The resulting "gallamethylallyl" ligand behaves like strong nucleophile similar to known monovalent GaR species. This donor property leads to the dimeric structure of the product [{Ru(GaCp*)(3)[eta(3)-(CH(2))(2)C{CH(2)(mu-Ga)}]}(2)][(BAr(F))(2)] (4) (Cp*=C(5)Me(5), [BAr(F)]=[B{C(6)H(3)(CF(3))(2)}(4)]). Very unexpectedly, the two gallium ligands in this dimer are found in close vicinity to each other with a distance in the range of Ga--Ga bonds. Indeed, AIM calculations confirm a weak attractive closed shell Ga--Ga interaction. Finally, a novel example of a complex with substituent-free Ga(+) as a ligand was found in the compound [Ru(PCy(3))(2)(GaCp*)(2)(Ga)][BAr(F)] (6) (Cy=C(6)H(11), cyclohexyl), the very short Ru--Ga bond length confirming the assumption that Ga(+) represents a pure sigma/pi-accepting ligand in this case.

Substituent‐Free Gallium by Hydrogenolysis of Coordinated GaCp*: Synthesis and Structure of Highly Fluxional [Ru2(Ga)(GaCp*)7(H)3]

“…The 1 H NMR shifts of the hydrides as well as of the GaCp* groups are in agreement with shifts of ruthenium complexes of these ligands. [14,15] Accordingly, the 13 The origin of the highly symmetric or fluxional nature of 1 in solution is puzzling. A chemically meaningful static structure of such a high symmetry for a Ru 2 Ga core structure surrounded by seven GaCp* and three hydride ligands is not conceivable.…”

“…The formation of EÀH species by the insertion of ECp* into the RuÀH bond was not observed in those cases. [14] The RuÀGa1 bonds of 1 are 2.322(1) (to Ru2) and 2.387(1) (to Ru1) whereas the Ru À GaCp* bond lengths average to 2.365 (2.313(1)-2.440 (1) ). These data are quite comparable to the Ru À Ga distances in related RuÀGaCp* complexes and clusters.…”

“…These data are quite comparable to the Ru À Ga distances in related RuÀGaCp* complexes and clusters. [14,15] Following usual electron-counting rules, 1 can be viewed as being formally composed of the unsaturated neutral 16 electron fragment {(GaCp*) 3 (H) 2 Ru II } and the saturated neutral 18 electron fragment {(GaCp*) 4 . [9] Note, that the Pt dimer [Pt 2 H(Ga)-(GaCp*) 7 ] 2+ is isoelectronic to 1 (a total of 34 valence electrons for both M 2 Ga 8 core structures).…”

Ein substituentenfreier Galliumligand durch Hydrogenolyse von koordiniertem GaCp*: Synthese und Struktur des hoch fluktionalen [Ru2(Ga)(GaCp*)7(H)3]

“…Bei diesen Verbindungen wurde keine Bildung einer E-H-Spezies durch Insertion von ECp* in die Ru-H-Bindung beobachtet. [14] Die Ru-Ga1-Abstände in 1 betragen 2.322(1) (Ru2-Ga1) und 2.387(1) (Ru1-Ga1), wohingegen die Ru-GaCp*-Bindungslängen im Durchschnitt 2.365 ergeben (2.313(1)-2.440 (1) ). Diese Daten entsprechen den Ru-Ga-Abständen verwandter Ru-GaCp*-Komplexe und -Cluster.…”

“…Diese Daten entsprechen den Ru-Ga-Abständen verwandter Ru-GaCp*-Komplexe und -Cluster. [14,15] Unter Verwendung üblicher Elektronenzählregeln (mit dem 2e-Donorligand H À und dem "nackten" Ga-Ligand als 0e-Donor Ga + ) setzt sich 1 formell zusammen aus einem ungesättigten neutralen 16e-Fragment {(GaCp*) 3 (H) 2 Ru II } und einem gesättigten 18e-Fragment {(GaCp*) 4 (H)Ru 0 (Ga)}. Die lineare Ru-Ga-Ru-Anordnung von 1 begründet sich durch die starken s-und p-Akzeptoreigenschaften von "nacktem" Ga + , wie DFT-Rechnungen für [(GaCp*) 4 PtGa] + und [Pt 2 H(Ga)-(GaCp*) 7 ] 2+ belegen.…”