4 research outputs found
Inhibition of Alkali Metal Reduction of 1-Adamantanol by London Dispersion Effects
A series of alkali metal 1-adamantoxide (OAd1) complexes of formula [M(OAd1)(HOAd1)2], where M=Li, Na or K, were synthesised by reduction of 1-adamantanol with excess of the alkali metal. The syntheses indicated that only one out of every three HOAd1 molecules was reduced. An X-ray diffraction study of the sodium derivative shows that the complex features two unreduced HOAd1 donors as well as the reduced alkoxide (OAd1), with the Ad1 fragments clustered together on the same side of the NaO3 plane, contrary to steric considerations. This is the first example of an alkali metal reduction of an alcohol that is inhibited from completion due to the formation of the [M(OAd1)(HOAd1)2] complexes, stabilized by London dispersion effects. NMR spectroscopic studies revealed similar structures for the lithium and potassium derivatives. Computational analyses indicate that decisive London dispersion effects in the molecular structure are a consequence of the many CâHâ
â
â
HâC interactions between the OAd1 groups.Peer reviewe
Two-coordinate, non-linear vanadium(II) and chromium(II) complexes of the silylamide ligand âN(SiMePhâ)â:characterization and confirmation of orbitally quenched magnetic moments in complexes with sub-dâľ electron configurations
Abstract
The two-coordinate metal amide complexes V{N(SiMePhâ)â}â (1) and Cr{N(SiMeâPh)â}â (2) were synthesized by reaction of two equivalents of LiN(SiMePhâ)â with VIâ(THF)â or CrClâ(THF)â in n-hexane. Their crystal structures showed that they have bent coordination, N-V-N = 137.0(4)°, N-Cr-N = 139.19(5)°, at the metals. The vanadium complex (1) displayed no tendency to isomerize as previously observed for some V(II) amido complexes. Curie fits of SQUID magnetic measurements afforded magnetic moments of 3.36 (1) and 4.68 (2) ÎźB, consistent with high-spin configurations. These values are lower than the spin-only values of 3.88 and 4.90 ÎźB expected for dÂł and dâ´ complexes, suggesting a significant unquenched orbital angular momentum contribution to the overall moment, which is lower as a result of the positive spin-orbit coupling constants
Molecular Complexes Featuring Unsupported Dispersion-Enhanced AluminumâCopper and GalliumâCopper Bonds
The reaction of the copper(I) β-diketiminate copper complex {(Cu(BDIMes))2(Îź-C6H6)} (BDIMes = N,Nâ˛-bis(2,4,6-trimethylphenyl)pentane-2,4-diiminate) with the low-valent group 13 metal β-diketiminates M(BDIDip) (M = Al or Ga; BDIDip = N,Nâ˛-bis(2,6-diisopropylphenyl)pentane-2,4-diiminate) in toluene afforded the complexes {(BDIMes)CuAl(BDIDip)} and {(BDIMes)CuGa(BDIDip)}. These feature unsupported copperâaluminum or copperâgallium bonds with short metalâmetal distances, CuâAl = 2.3010(6) Ă
and CuâGa = 2.2916(5) Ă
. Density functional theory (DFT) calculations showed that approximately half of the calculated association enthalpies can be attributed to London dispersion forces.peerReviewe