Allyl strontium compounds: synthesis, molecular structure and properties

Abstract

The synthesis and attempted isolation of neutral bis(allyl)strontium [Sr(C(3)H(5))(2)] (1) resulted in the isolation of potassium tris(allyl)strontiate K[Sr(C(3)H(5))(3)] (2). In situ generated 1 shows a pronounced Brønsted basicity, inducing polymerisation of THF. Ate complex 2 crystallises as [K(THF)(2){Sr(C(3)H(5))(3)}(THF)](∞) (2·(THF)(3)). The salt-like solid state structure of 2·(THF)(3) comprises a two-dimensional network of (μ(2)-η(3):η(3)-C(3)H(5))(-) bridged potassium and strontium centres. Synthesis of allyl complexes 1 and 2 utilised SrI(2), [Sr(TMDS)(2)] (3) (TMDS = tetramethyldisilazanide), and [Sr(HMDS)(2)] (HMDS = hexamethyldisilazanide) as strontium precursors. The solid state structure of previously reported [Sr(TMDS)(2)] (3) was established by X-ray single crystal analysis as a dissymmetric dimer of [Sr(2)(TMDS)(4)(THF)(3)] (3·(THF)(3)) with multiple Si-HSr agostic interactions. The presence of ether ligands (THF, 18-crown-6) influenced the Si-HSr resonances in the NMR spectra of the amido complex 3.

Structurally Defined Allyl Compounds of Main Group Metals: Coordination and Reactivity

“…η 3 Coordination of the allyl ligand ( D ) is the archetypical bonding mode showing only π‐type MC allyl interactions 40. 57a Similarly, the bridging μ 2 ‐η 3 :η 3 coordination mode ( E ) also shows π‐type MC allyl bonding exclusively 61. Mode E leads to oligomeric cyclic42 as well as one‐43 and two‐dimensional61 polymeric arrangements in the solid state.…”

“…57a Similarly, the bridging μ 2 ‐η 3 :η 3 coordination mode ( E ) also shows π‐type MC allyl bonding exclusively 61. Mode E leads to oligomeric cyclic42 as well as one‐43 and two‐dimensional61 polymeric arrangements in the solid state. For both coordination modes, D and E , the π electrons in the allyl ligand are delocalized.…”

“…The isolation of bis(allyl)strontium and bis(allyl)barium has been reported in a patent, but these compounds were only analyzed spectroscopically 57b,c. Recent reinvestigation of the preparation of [Sr(C 3 H 5 ) 2 ] by a different synthetic route, namely the reaction of [K(C 3 H 5 )] with different strontium precursors, led to the ate complex [KSr(C 3 H 5 ) 3 ] regardless of the stoichiometry 61. The THF adduct [KSr(C 3 H 5 ) 3 (thf) 3 ] forms a coordination polymer in the solid state, with the allyl ligands showing μ 2 ‐η 3 :η 3 coordination modes.…”

Strukturell definierte Allylverbindungen der Hauptgruppenmetalle: Koordination und Reaktivität

“…57a Ebenso liegen im verbrückenden μ 2 ‐η 3 :η 3 ‐Koordinationsmodus ( E ) nur M‐C Allyl ‐Bindungen mit π‐Charakter vor. E führt zu cyclischen Oligomeren42 sowie ein‐43 oder zweidimensionalen61 Koordinationspolymeren im Festkörper. Für beide Bindungsmodi, D und E , werden delokalisierte π‐Elektronen im Allylliganden beobachtet.…”

“…Kürzlich wurde die Herstellung von [Sr(C 3 H 5 ) 2 ] über eine andere Syntheseroute, nämlich die Reaktion von [K(C 3 H 5 )] mit verschiedenen Strontiumvorstufen, neuerlich untersucht. Dies führte unabhängig von der eingestellten Stöchiometrie zum At‐Komplex [KSr(C 3 H 5 ) 3 ] 61. Das THF‐Addukt [KSr(C 3 H 5 ) 3 (thf) 3 ] liegt im Festkörper als Koordinationspolymer vor, in dem die Allylliganden μ 2 ‐η 3 :η 3 ‐Bindungsmodi aufweisen.…”