Organometallic and Metal-amide Precursors for Transition Metal and Lanthanide Cluster Complexes with Interesting Electronic an Magnetic Properties

Abstract

This project exploited the Brönsted basicity of the organometallic/metal-amide compounds,MnCp2 and Ln[N(SiMe3)2]3·LiCl(THF)3 (Ln = Gd, Tb and Dy) in attempts to synthesizepolymetallic cluster compounds via deprotonation of X-H (X = N or S) bond containing proligands.The chemical, electronic and magnetic properties of the resulting compounds werestudied with a variety of methods.The reaction of Ln[N(SiMe3)2]3·LiCl(THF)3 (Ln = Gd, Tb and Dy) with EtSH yieldsa series of [{Ln(N(SiMe3)2)(μ2-SEt)2}4(μ3-SEt)][Li(THF)4] "Ln4" squares in which theterbium and dysprosium analogues show SMM behaviour in zero field, with the dysprosiumanalogue displaying a fast relaxation process which can be "switched off" by the applicationof a 2000 Oe external field.Reactions of MnCp2 with Me3SiNP(NHR)3 (R = nPr, Cy, tBu) afforded a series ofcompounds; [CpMn{Me3SiN=P(NHnPr)2(μ-NnPr)}]2, [Mn{Me3SiN=P(NHCy)2(NCy)}2]and [CpMn{Me3SiN=P(NHtBu)2(NtBu)}]. Q-band EPR studies of these complexes revealthat altering the R group attached to the ligand causes a variation in coordination geometryaround the manganese centers and as such alters the electronic properties of the manganesecentres present in each complex.In order to avoid the synthesis of potentially unstable organometallic/metal-amideprecursors, one pot synthetic methodologies were developed to allow the isolation a series ofμ8-oxo centred Li7M cubes [MLi7(μ8-O)(μ-hpp)6]+ (M = Co, Mn and Zn). Addition ofstiochiometric amounts of water to the initial reaction mixture produced the Li7M cubes inhigh yields.Extension of the one pot synthetic strategy to the use of DyCl3 and YbCl3 inreactions with Li-TMP (TMP = 2,2,6,6-tetramethylpipiridine) afforded the lanthanidedimers [Ln(TMP)2(μ-OEt)]2 (Ln = Dy and Yb) in which the EtO- ligands were formed via insitu ether cleavage and the dysprosium analogue shows SMM behaviour under a 7000Oeapplied field.

Date of Award	31 Dec 2012
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Richard Layfield (Supervisor) & Richard Winpenny (Supervisor)