s-Block metal complexes of a bulky, donor-functionalized allyl ligand

Abstract

Crystallographic and NMR spectroscopic studies on allyl complexes of lithium, potassium and magnesium containing an O-donor functionality are described.

Alkali Metal Complexes of Silyl‐Substituted ansa‐(Tris)allyl Ligands: Metal‐, Co‐Ligand‐ and Substituent‐Dependent Stereochemistry

“…[40] The asymmetric allyl coordination in 8 is likely to arise from steric clashes between the three pmdeta ligands, and may indicate partial delocalization of the formal negative charges within the allyl anions as has previously been observed in intramolecularly solvated alkalimetal allyl compounds. [24][25][26][27]30,41] Indeed, it is notable that the allylic carbon-carbon bonds in 8 are unequal in length, with C(2)-C(3) and C(3)-C(4) being 1.382(7) and 1.426(7) Å, C(17)-C(18) and C(18)-C(19) being 1.367(7) and 1.424 (7), and C(32)-C(33) and C(33)-C(34) being 1.379 (7) 3 form, revealing that these two configurations are very close in energy. Consequently, it is possible that environment effects may play a role in determining the preference of one stereochemistry over the other.…”

Complexes with Sterically Bulky Allyl Ligands: Insights into Structure and Bonding

“…[19] Support for this conclusion is found in a related lithium complex formed from the tetrahydrofurfuryl-substituted derivative of the AЈ ligand ( Figure 2). [33] The dimeric complex has Li1-O1 and Li2-O2 bond lengths that are indistinguishable at 1.87 Å, and the C-C allyl bonds are slightly more delocalized (∆ = 0.052 Å) than in {Li [1,1Ј,3- Figure 3). [42] The π-bonded allyl ligands are at an angle of 60-62°from the major chain axes, and the Li-C distances range from 2.16 Å to 2.35 Å.…”

“…The reaction of Li[AЈ] with tetrahydrofurfuryl tosylate produces [4-(tetrahydrofuran-2-yl)but-1-ene-1,3-diyl]bis(trimethylsilane) (Scheme 6); it can subsequently be deprotonated with alkyllithium reagents or MgBu 2 to produce new metal complexes. [33] Scheme 6. Synthesis of a thf-functionalized allyl ligand.…”

“…The potassium salt of the AЈ anion, for example, has been crystallized as DME and thf solvates, {K[AЈ](dme)} ϱ [45] and {K[(AЈ)(thf) 3/2 ]} ϱ , [29] and also as the base-free complex, {K[AЈ]} ϱ . [19] The tetrahydrofurfuryl-substituted derivative of the AЈ anion has been crystallized as its potassium salt, [33] and the dimethylsilyl ansa-bis(silylcyclohexenyl)-dipotassium complex {K 2 [(η 3 -C 6 H 4 SiMe 3 -6) 2 SiMe 2 ]-(thf) 3 } ϱ has been isolated as a thf solvate. [32] All five compounds are coordination polymers with potassium ions linked by bridging π-allyl ligands.…”

Symmetric Assembly of a Sterically Encumbered Allyl Complex: Mechanochemical and Solution Synthesis of the Tris(allyl)beryllate, K[BeA′3] (A′ = 1,3-(SiMe3)2C3H3)

“…Density functional theory (DFT) calculations suggested that a base-free Be(C3H3E2)2 (E = H, SiH3) complex would be more slightly more stable with delocalized, π-type allyls than with monodentate, sigmabonded ligands (Scheme 1). If so, beryllium allyls would join those of magnesium, in which monodentate allyl ligands are uniformly found in complexes that are ether-solvated [12], but that in the absence of ethers, cation-π interactions with the metal can create "slipped-π" bonding [13]. Scheme 1.…”