Michael T. Gamer

Pentanuclear Dysprosium Hydroxy Cluster Showing Single-Molecule-Magnet Behavior

A pentanuclear dysprosium hydroxy cluster of composition [Dy 5(mu 4-OH)(mu 3-OH) 4(mu-eta (2)-Ph 2acac) 4(eta (2)-Ph 2acac) 6] ( 1; Ph 2acac = dibenzoylmethanide) was prepared starting from [DyCl 3.6H 2O] and dibenzoylmethane. Both static (dc) and dynamic (ac) magnetic properties of 1 have been studied. Below 3 K, the appearance of slow relaxation of the magnetization typical for single-molecule magnets is seen, even if no hysteresis effects on the M vs H data are observed above 1.8 K.

[{(η5-C5Me5)2Sm}4P8]: A Molecular Polyphosphide of the Rare-Earth Elements

[{(eta(5)-C(5)Me(5))(2)Sm}(4)P(8)], a molecular polyphosphide of the rare-earth elements having a realgar core structure, was synthesized by a one-electron redox reaction of divalent samarocen and white phosphorus.

Homoleptic Lanthanide Complexes of Chelating Bis(phosphanyl)amides: Synthesis, Structure, and Ring‐Opening Polymerization of Lactones

Treatment of the bis(phosphanyl)amide (Ph2P)2NH with KH in boiling THF followed by crystallization from THF/n-pentane leads to [K(thf)n][N(PPh2)2] (n = 1.25, 1.5). Reaction of [K(thf)n][N(PPh2)2] with anhydrous yttrium or lanthanide trichlorides in a 3:1 molar ratio afforded homoleptic bis(phosphanyl)amide complexes [Ln[N(PPh2)2]3] (Ln = Y, Er) as large crystals in good yields. [Ln[N(PPh2)2]3] can also be obtained by reaction of the homoleptic bis(trimethylsilyl)amides of Group 3 metals and lanthanides [Ln[N(SiMe3)2]3] (Ln = Y, La, Nd) with three equivalents of (Ph2P)2NH in boiling toluene. The single-crystal X-ray structures of these complexes always show eta 2 coordination of the ligand. Dynamic behavior of the ligand is observed in solution and is caused by rapid exchange of the two different phosphorus atoms. [Ln[N(PPh2)2]3] was used as catalyst for the polymerization of epsilon-caprolactone. Significant differences in terms of correlation of theoretical and experimental molecular weights as well as polydispersities were observed depending on the nature of Ln. On the basis of the crystal structure of the heteroleptic complex [Lu[N(PPh2)2]3(thf)], we suggest that in the initiation step of epsilon-caprolactone polymerization the lactone adds to the lanthanide atom to form a sevenfold coordination sphere around the central atom.

Mixed‐Metal Lanthanide–Iron Triple‐Decker Complexes with a cyclo‐P5 Building Block

Tripleand multidecker sandwich complexes have been discussed in the last decades for their unique electrical and magnetic properties. The organic spacer between the metals may facilitate intermetallic electronic communication, which has a high potential for molecular electronics. A number of one-dimensional organometallic sandwich molecular wires (SMWs) have been extensively studied. Thus, the multilayer vanadium–arene (Ar) organometallic complexes [Vn(Ar)m], which can be produced in a molecular beam by laser vaporization, are a class of one-dimensional molecular magnets. Ferrocene-based molecular wires have been synthesized in the gas phase and characterized by mass spectroscopy. It was calculated that these compounds have half-metallic properties with 100 % negative spin polarization near the Fermi level in the ground state. In contrast to this investigation in the gas phase, studies on related organometallic tripleand multidecker sandwich complexes containing f-block elements (lanthanides or actinides) in condensed phase remain rare; studies were mostly on the cyclooctatetraene ligand and its derivatives. The only rare-earth-element triple-decker complex with heterocycles is the low-valent scandium 1,3,5-triphosphabenzene complex [{(hP3C2tBu2)Sc}2(m-h 6 :h-P3C3tBu3)], which was obtained by cocondensation of scandium vaporized in an electron beam with an excess of the phosphaalkyne tBuC P. Apart from organometallic compounds, tripleand multidecker sandwich complexes of the 4f elements consisting of “salen” type Schiff base ligands, phthalocyanines, and porphyrins have been extensively studied because these compounds exhibit tunable spectroscopic, electronic, and redox properties, and different extents of intramolecular p–p interactions. Despite these promising physical properties further investigations on 4f elements based tripleand multidecker sandwich complexes are obviously hampered by the limited variety of ligands that have been attached to the metal centers to date. Based on these considerations, we present herein mixed d/f-block-metal triple-decker complexes with a purely inorganic all-phosphorus middle deck. In contrast to d-block chemistry, where purely inorganic ring systems of Group 15 elements such as P5 and P6, [9] As5, [9c] and Sb5 [10] are well-established, there is no analogy with the fblock elements to date. On the other hand, it was shown only recently that rare-earth elements can stabilize highly reactive main-group species such as N2 3 . Although some heavier Group 15–lanthanide compounds, such as phosphides (Ln PR2), [12] arsenides (Ln AsR2), 13] stibides (Ln Sb3), and bismutides (Ln Bi Bi Ln) are known, the first molecular polyphosphide of the rare-earth elements, [(Cp*2Sm)4P8] (Cp* = h-C5Me5), was recently synthesized. [16] The structure of the complex is very rare and can be described as a realgartype P8 4 ligand trapped in a cage of four samarocenes. As no triple-decker sandwich complex of the rare-earth elements with a polyphosphide middle-deck bridging the metal centers is known, we focused our interest on the cyclo-P5 ligand. The structure and properties of this ligand are very similar to the well-known cyclopentadienyl anion (Scheme 1) and could therefore have many possible coordination modes.

Cyclopentadienyl complexes of yttrium and the lanthanides with bis(phosphinimino)methanides

Abstract Metallocenes of yttrium and the lanthanides with bis(phosphinimino)methanides in the coordination sphere are reported. Reaction of [{CH(PPh2NSiMe3)2-κ2N,N′,κC}LnCl2]2 (Ln=Y, Sm, Er) with Na(C5H5) in a 1:4 molar ratio in THF afforded the corresponding metallocenes [(η5-C5H5)2Ln{CH(PPh2NSiMe3)2-κ2N,N′,κC}]. The structures of these new compounds were investigated in solution and in the solid state. Single crystal X-ray structures show that both imine groups and the methine carbon are bound to the lanthanide atom.

Di‐ and Trinuclear Gold Complexes of Diphenylphosphinoethyl‐Functionalised Imidazolium Salts and their N‐Heterocyclic Carbenes: Synthesis and Photophysical Properties

Diphenylphosphinoethyl-functionalised imidazolium salts and their silver-carbene complexes were used to synthesise a series of di- and trinuclear gold complexes through ligand exchange and transmetallation, respectively. Besides a few positively charged macrocyclic compounds with different anions (both with and without activation of the carbene function), we were able to obtain neutral polynuclear complexes by varying the gold precursor. The synthesised gold complexes show a variety of photophysical properties, including bright white photoluminescence at ambient temperature.

Slow magnetic relaxation in four square-based pyramidal dysprosium hydroxo clusters ligated by chiral amino acid anions – a comparative study

The synthesis and characterization of three chiral and one achiral amino acid anion ligated dysprosium hydroxo clusters [Dy5(OH)5(α-AA)4(Ph2acac)6] (α-AA = d-PhGly, l-Pro, l-Trp, Ph2Gly; Ph2acac = dibenzoylmethanide) are reported. The solid state structures were determined using single crystal X-ray diffraction and show that five Dy(iii) ions are arranged in a square-based pyramidal geometry with NO7-donor-sets for the basal and O8-donor-sets for the apical Dy atom. Both static (dc) and dynamic (ac) magnetic properties were investigated for all four compounds and show a slow relaxation of magnetization, indicative of single molecule magnet (SMM) behaviour below 10 K in all cases. The similar SMM behaviour observed for all four compounds suggests that the very similar coordination geometries seen for the dysprosium atoms in all members of this family, which are independent of the amino acid ligand used, play a decisive role in steering the contribution of the single ion anisotropies to the observed magnetic relaxation.

Reaction of Cp2ZrCl2 with Inorganic Amides

The reactions of [η5-Cp2ZrCl2] (Cp = η5-C5H5) with [K(THF)n][N(PPh2)2] (n = 1.25—1.5) and K[CH(PPh2NSiMe3)2] are reported. The first reaction led to the monoamido complex [η5-Cp2Zr(Cl)N(PPh2)2] in which the {(Ph2P)2N}— ligand — via a phosphorous and the nitrogen atom — is coordinated to the zirconium atom in a chelating (η2) fashion. Reaction of the potassium methanide compound, K{CH(PPh2NSiMe3)2} with zirconocene dichloride yield the carbene-like mono cyclopentadienyl complex [η5-CpZr(Cl){C(PPh2NSiMe3)2}]. The complex is formed by a salt metathesis and concomitant a cyclopentadiene extrusion. Reaktionen von Cp2ZrCl2 mit anorganischen Amiden Es wird uber die Reaktion von [η5-Cp2ZrCl2] (Cp = η5-C5H5) mit [K(THF)n][N(PPh2)2] (n = 1.25—1.5) bzw. K[CH(PPh2NSiMe3)2] berichtet. Durch die erste Reaktion wird der Monoamido-Komplex [η5-Cp2Zr(Cl)N(PPh2)2] erhalten, in dem der {(Ph2P)2N}—-Ligand chelatisierend (η2), d.h. uber ein Phosphor- und das Stickstoffatom an das Zirkoniumatom gebunden ist. Die Reaktion der Kaliummethanidverbindung K{CH(PPh2NSiMe3)2} mit Zirkonocendichlorid ergibt den carbenartigen Monocyclopentadienylkomplex [η5-CpZr(Cl){C(PPh2NSiMe3)2}]. Der Komplex wird durch eine Salzmetathese bei gleichzeitiger Cyclopentadienabspaltung generiert.

Intramolecular phosphorus-phosphorus bond formation within a Co2P4 core.

The reduction of [(Cp‴Co)2(μ,η(2:2)-P2)2] (Cp‴ = 1,2,4-tBu3C5H2) with the samarocenes, [(C5Me4R)2Sm(THF)n] (R = Me or n-propyl), gives [(Cp‴Co)2P4Sm(C5Me4R)2]. This is the first example of an intramolecular P-P coupling in a polyphosphide complex upon reduction of the transition metal. The formation of the P-P bond is not a result of the direct reduction of the phosphorus atoms but is induced by a rearrangement of the positive charges between the metal atoms.

Realgar as a building block for lanthanide clusters: encapsulation of a copper cluster by a lanthanide cluster.

The reactions of the divalent lanthanide metallocenes [Cp*2Ln(thf)2] (Cp* = η(5)-C5Me5; Ln = Sm, Yb) with realgar (As4S4) gave the open cage tetrametallic complex [(Cp*2Sm)(Cp*Sm)3AsS3(Cp*AsS2)2(thf)3] (1) or the trimetallic cage compound [(Cp*Yb)3As2S4(Cp*AsS2)(thf)2] (2), respectively, by reductive cleavage of the inorganic cage. As result of a Cp* transfer, the novel Cp*AsS2(2-) anion is formed. Moreover, the As2S4(4-) anion, which is bound in 2, is observed for the first time in coordination chemistry. Closed cage compounds are formed by either using bulkier ligands or a different As/S cage. The reaction of [Cp‴2Sm] (Cp‴ = (1,2,4-(t-Bu)3C5H2)) with As4S4 and the reaction of [Cp*2Yb(thf)2] with dimorphite (As4S3) gave the closed 11-vertex cage clusters [(Cp‴Sm)3(AsS3)2] (3) and [(Cp*Yb)3(AsS3)2] (4), respectively. The reaction of 3 with [CuMes] resulted in the formation of the Sm/S/Cu cluster [(Cp‴Sm(thf))4Cu4S6] (5), in which the Sm atoms encapsulate a classical Cu4S6(8-) cluster core. This is the first transition metal chalcogenide cluster encapsulated by f-elements. Alternatively, the endohedral cluster can thus be described as [Cu4@{(Cp‴Sm(thf))4S6}], in which a Cu4 tetrahedron is encapsulated by the samarium sulfido cluster {(Cp‴Sm(thf))4S6}.