Structure and Magnetization Dynamics of Dy−Fe and Dy−Ru Bonded Complexes

Abstract

We present an investigation of isostructural complexes that feature unsupported direct bonds between a formally trivalent lanthanide ion (Dy3+) and either a first‐row (Fe) or a second‐row (Ru) transition metal (TM) ion. The sterically rigid, yet not too bulky ligand PyCp22− (PyCp22−=[2,6‐(CH2C5H3)2C5H3N]2−) facilitates the isolation and characterization of PyCp2Dy−FeCp(CO)2 (1; d(Dy–Fe)=2.884(2) Å) and PyCp2Dy−RuCp(CO)2 (2; d(Dy–Ru)=2.9508(5) Å). Computational and spectroscopic studies suggest strong TM→Dy bonding interactions. Both complexes exhibit field‐induced slow magnetic relaxation with effectively identical energy barriers to magnetization reversal. However, in going from Dy−Fe to Dy−Ru bonding, we observed faster magnetic relaxation at a given temperature and larger direct and Raman coefficients, which could be due to differences in the bonding and/or spin–phonon coupling contributions to magnetic relaxation.

An 'Intermetallic' Molecular Nanomagnet with the Lanthanide Coordinated Only by Transition Metals

“…Other intramolecular contacts of Er III involve Cp ligands with the shortest ErC distances in the 2.829(8)-3.056(13) Å range -well beyond typical coordination bonds of lanthanide complexes. The Er-Re distances in ErRe3 (2.9004(5), 2.9124(5) and 2.9172(5) Å) are similar to those reported for [Sm III (Re I Cp2)3], [La III (Re I Cp2)3] and [Lu III (Re I Cp2)3] 32 as well as other molecular compounds with unsupported rare earthtransition metal bonds 34,38 and the intermetallic SmCo5 with Sm-Co distances of 2.888 Å. 1 The comparison of the Re-Cp distances in ErRe3 and the [Cp2ReH] starting material (SCXRD structural analysis of [Cp2ReH] was performed as part of this study Table S1; CCDC 2027573) confirms the change of the valence state of the Re centers upon coordination to Er III .…”

“…37 The concept of unsupported bonds between the lanthanide and the transition metal was first introduced and explored by Kempe et al 32,34 Later, it was proposed by Rinehart and Long 15 as a possible strategy towards molecular nanomagnets and put to use by Nippe et al reporting MNMs with unsupported direct bonds between the dysprosium ion and 4d (Fe) or 4d (Ru) transition metal ions. 38 However, the magnetic memory effect (magnetic hysteresis) has not been observed, most probably due to the unfavorable ligand field geometry 38 or the unfortunate choice of the rare-earth metal. 32 Noteworthy, the introduction of p-block heavy metals directly into the coordination sphere of the lanthanide was also pursued resulting in interesting examples of MNMs.…”

Heterometallic Clusters with Multiple Rare Earth Metal–Transition Metal Bonding

“…Since the first RE–TM bond in (C 5 H 5 ) 2 Y­(THF)­Re 2 H 7 (PMe 2 Ph) 4 was structurally characterized by Evans and co-workers in 1990, many chemists have studied this important and fundamental field. Representative examples include complexes with RE–Re (RE = Y, La, Sm, Yb, Lu), − RE–Fe (RE = Nd, Yb, Sc, Y, Lu, La, Dy, Ce), − Sm–Co, RE–Ni (RE = Sc, Y, La, Lu), − RE–Pd (RE = Nd, Sc), − and RE–Pt (RE = Sc, Y, Lu) , bonds. In addition, some examples with metal–metal bonds between RE and main-group metals have also been reported. − However, notwithstanding these important discoveries, bimetallic species with a RE–Rh bond are rare and to the best of our knowledge the heterometallic complexes with multiple RE–Rh bonds are unknown.…”

Molecular Complexes Featuring Unsupported Dispersion-Enhanced Aluminum–Copper and Gallium–Copper Bonds

“…However, most of the examples presented to date use bridging ligands to support the metal–metal bonds, or such bonds are formed as part of a cluster species. − Some examples include heteroatom (e.g., μ-hydrido) bridges between the metal centers, as seen in the complexes {Cu­(BDI Ar )­(H)­Au­(IPr)} (BDI Ar = N , N ′-bis­(pentafluorophenyl)­pentane-2,4-diiminate; IPr = 1,3-diisopropyl­phenyl­imidazol-2-ylidene) and {Zr­(H)­(Cp) 2 (H) 2 M­(BDI Dip )} (M = Zn, Mg, Al; Cp = cyclopentadienyl; BDI Dip = N , N ′-bis­(2,6-diisopropylphenyl)­pentane-2,4-diiminate). , Recent examples of heterobimetallic complexes with metal–metal bonds include the two-coordinate Mn(0) species {Mn­(L)­(Mg­(BDI Mes ))} (L = N­(C 6 H 2 {C­(H)­Ph 2 } 2 i Pr-2,6,4)­(Si i Pr 3 ); BDI Mes = N , N ′-bis­(2,4,6-trimethylphenyl)­pentane-2,4-diiminate), as well as the palladium complex, {Pd­(H) 3 (Mg­(BDI Dip ) 3 } . Other examples include unsupported Fe–Mn or Fe–Cr bond formation stabilized by bulky terphenyl ligands, as well as Dy–Fe and Dy–Ru bonds featuring Cp-based ligands for single molecule magnet applications …”

“…21 Other examples include unsupported Fe−Mn or Fe−Cr bond formation stabilized by bulky terphenyl ligands, 22 as well as Dy−Fe and Dy−Ru bonds featuring Cp-based ligands for single molecule magnet applications. 23 A theme that has attracted increased attention is the use of low-valent p-block compounds as "ligands" in heterometallic species to form metal−metal bonds. 24−26 Group 13 based metal(I) ligands in particular have generated interest as synthons for metal−metal bonded compounds.…”