Reactivity of Bulky Formamidinatosamarium(II or III) Complexes with CO and CS Bonds

The preparation of a new heterobimetallic samarium­(II) formamidinate complex and selected reactions of samarium­(II) complexes and one samarium­(III) formamidinate complex with benzophenone or CS₂ are discussed. Treatment of the tris­(formamidinato)­samarium­(III) complex [Sm­(DippForm)₃] <b>1</b> (DippForm = <i>N</i>,<i>N</i>′-bis­(2,6-diisopropylphenyl)­formamidinate, (CH­(NC₆H₃-^<i>i</i>Pr₂-2,6)₂) with potassium graphite in toluene yielded the dark brown heterobimetallic formamidinatosamarium­(II)/potassium complex [KSm­(DippForm)₃]_<i>n</i> <b>2</b>. Divalent <b>2</b>, a Lewis base solvent free homoleptic species, differs significantly from the related heteroleptic formamidinatosamarium­(II) complex [Sm­(DippForm)₂(thf)₂] <b>3</b> with respect to its constitution, structure, and reactivity toward benzophenone. While <b>2</b> reacts giving complex <b>1</b>, the reaction of <b>3</b> with benzophenone generates the highly unusual [Sm­(DippForm)₂(thf)­{μ-OC­(Ph)(C₆H₅)­C­(Ph)₂O}­Sm­(DippForm)₂] (C₆H₅ = 1,4-cyclohexadiene-3-yl-6-ylidene) <b>4</b>. The formation of <b>4</b> highlights a rare C–C coupling between a carbonyl carbon and the carbon at the para position of a phenyl group of the OCPh₂ fragment. An analogous reaction of [Yb­(DippForm)₂(thf)₂] gives an isostructural complex <b>4Yb</b>. <b>3</b> reacts with carbon disulfide forming a light green dinuclear formamidinatosamarium­(III) complex [{Sm­(DippForm)₂(thf)}₂(μ-η²(C,S):κ­(S′,S″)-SCSCS₂)] <b>5</b> through an unusual C–S coupling induced by an amidinatolanthanoid species giving the thioformylcarbonotrithioate ligand. The trivalent organometallic [Sm­(DippForm)₂(CCPh)­(thf)] complex activates the CO bond of benzophenone by an insertion reaction, forming the light yellow [Sm­(DippForm)₂{OC­(Ph)₂C₂Ph}­(thf)] <b>6</b> as a major product and light yellow unsolvated [Sm­(DippForm)₂{OC­(Ph)₂C₂Ph}] <b>7</b> as a minor product. Molecular structures of complexes (<b>2</b>, <b>4</b>–<b>7</b>) show that κ­(<i>N</i>,<i>N</i>′) bonding between a DippForm and samarium atom exists in all compounds, but in <b>2</b>, DippForm also bridges K and Sm by 1κ­(N):2κ­(N′) bonding and two 2,6-diisopropylphenyl groups are η⁶-bonded to potassium

Rare-Earth Metalation of Calix[4]pyrrole/Calix[4]arene Free of Alkali-Metal Companions

The redox transmetalation/protolysis (RTP) reactions of ytterbium or neodymium metal with calix[4]­H₄ (5,11,17,23-tetra-<i>tert</i>-butylcalix­[4]­arene-25,26,27,28-tetrol) in the presence of bis­(pentafluorophenyl)mercury under ultrasonication yielded [Ln^III(calix­[4]­H)­(thf)]₂ (<b>1</b>, Ln = Yb; <b>2</b>, Ln = Nd). The characterization of both <b>1</b> and <b>2</b>, including an X-ray single-crystal structural determination for <b>2</b>, suggests triple deprotonation of the macrocyclic ligand on metalation. The related RTP reaction of H₄N₄Et₈ (<i>meso</i>-octaethylcalix­[4]­pyrrole) with ytterbium metal and Hg­(C₆F₅)₂ at ambient temperature, however, resulted in quadruple deprotonation and afforded the ytterbium­(II) calix[4]­pyrrolide complex [Yb₂(N₄Et₈)­(thf)₄] (<b>3</b>) in good yield. Subsequent oxidation of <b>3</b> by dioxygen generated the novel tetranuclear ytterbium­(III) complex [Yb₄(μ-O)₂(N₄Et₈)₂(thf)₂] (<b>4</b>). The structures of the ytterbium­(II) complex <b>3</b> and the ytterbium­(III) complex <b>4</b> incorporate endo <b>(3)</b> and endo/exo (<b>4</b>) pyrrolide sandwich and half-sandwich units, respectively, with metal centers η¹ bound by nitrogen and η⁵ bonded by pyrrolide rings. The RTP reaction of lanthanum metal using diphenylmercury in place of bis­(pentafluorophenyl)mercury gave the triply deprotonated and N-confused pyrrolide (with an alkyl substituent of one pyrrolide ring migrated to a β-position) macrocyclic complex [La₂(HN₃N′Et₈)₂] (<b>5</b>). The triple deprotonation of the macrocyclic ligand H₄N₄Et₈ was also achieved through its reaction with 3 molar equiv of potassium metal, giving colorless crystals of [{K₃(HN₄Et₈)­(thf)­(PhMe)₂}_n] (<b>6</b>). However, an attempt to isolate the corresponding partially deprotonated calix[4]­pyrrolide ytterbium­(III) complex through the metathesis reaction of potassium precursor <b>6</b> with ytterbium triiodide was unsuccessful

Rare-Earth Metalation of Calix[4]pyrrole/Calix[4]arene Free of Alkali-Metal Companions

The redox transmetalation/protolysis (RTP) reactions of ytterbium or neodymium metal with calix[4]­H₄ (5,11,17,23-tetra-<i>tert</i>-butylcalix­[4]­arene-25,26,27,28-tetrol) in the presence of bis­(pentafluorophenyl)mercury under ultrasonication yielded [Ln^III(calix­[4]­H)­(thf)]₂ (<b>1</b>, Ln = Yb; <b>2</b>, Ln = Nd). The characterization of both <b>1</b> and <b>2</b>, including an X-ray single-crystal structural determination for <b>2</b>, suggests triple deprotonation of the macrocyclic ligand on metalation. The related RTP reaction of H₄N₄Et₈ (<i>meso</i>-octaethylcalix­[4]­pyrrole) with ytterbium metal and Hg­(C₆F₅)₂ at ambient temperature, however, resulted in quadruple deprotonation and afforded the ytterbium­(II) calix[4]­pyrrolide complex [Yb₂(N₄Et₈)­(thf)₄] (<b>3</b>) in good yield. Subsequent oxidation of <b>3</b> by dioxygen generated the novel tetranuclear ytterbium­(III) complex [Yb₄(μ-O)₂(N₄Et₈)₂(thf)₂] (<b>4</b>). The structures of the ytterbium­(II) complex <b>3</b> and the ytterbium­(III) complex <b>4</b> incorporate endo <b>(3)</b> and endo/exo (<b>4</b>) pyrrolide sandwich and half-sandwich units, respectively, with metal centers η¹ bound by nitrogen and η⁵ bonded by pyrrolide rings. The RTP reaction of lanthanum metal using diphenylmercury in place of bis­(pentafluorophenyl)mercury gave the triply deprotonated and N-confused pyrrolide (with an alkyl substituent of one pyrrolide ring migrated to a β-position) macrocyclic complex [La₂(HN₃N′Et₈)₂] (<b>5</b>). The triple deprotonation of the macrocyclic ligand H₄N₄Et₈ was also achieved through its reaction with 3 molar equiv of potassium metal, giving colorless crystals of [{K₃(HN₄Et₈)­(thf)­(PhMe)₂}_n] (<b>6</b>). However, an attempt to isolate the corresponding partially deprotonated calix[4]­pyrrolide ytterbium­(III) complex through the metathesis reaction of potassium precursor <b>6</b> with ytterbium triiodide was unsuccessful

Rare-Earth Metalation of Calix[4]pyrrole/Calix[4]arene Free of Alkali-Metal Companions

The redox transmetalation/protolysis (RTP) reactions of ytterbium or neodymium metal with calix[4]­H₄ (5,11,17,23-tetra-<i>tert</i>-butylcalix­[4]­arene-25,26,27,28-tetrol) in the presence of bis­(pentafluorophenyl)mercury under ultrasonication yielded [Ln^III(calix­[4]­H)­(thf)]₂ (<b>1</b>, Ln = Yb; <b>2</b>, Ln = Nd). The characterization of both <b>1</b> and <b>2</b>, including an X-ray single-crystal structural determination for <b>2</b>, suggests triple deprotonation of the macrocyclic ligand on metalation. The related RTP reaction of H₄N₄Et₈ (<i>meso</i>-octaethylcalix­[4]­pyrrole) with ytterbium metal and Hg­(C₆F₅)₂ at ambient temperature, however, resulted in quadruple deprotonation and afforded the ytterbium­(II) calix[4]­pyrrolide complex [Yb₂(N₄Et₈)­(thf)₄] (<b>3</b>) in good yield. Subsequent oxidation of <b>3</b> by dioxygen generated the novel tetranuclear ytterbium­(III) complex [Yb₄(μ-O)₂(N₄Et₈)₂(thf)₂] (<b>4</b>). The structures of the ytterbium­(II) complex <b>3</b> and the ytterbium­(III) complex <b>4</b> incorporate endo <b>(3)</b> and endo/exo (<b>4</b>) pyrrolide sandwich and half-sandwich units, respectively, with metal centers η¹ bound by nitrogen and η⁵ bonded by pyrrolide rings. The RTP reaction of lanthanum metal using diphenylmercury in place of bis­(pentafluorophenyl)mercury gave the triply deprotonated and N-confused pyrrolide (with an alkyl substituent of one pyrrolide ring migrated to a β-position) macrocyclic complex [La₂(HN₃N′Et₈)₂] (<b>5</b>). The triple deprotonation of the macrocyclic ligand H₄N₄Et₈ was also achieved through its reaction with 3 molar equiv of potassium metal, giving colorless crystals of [{K₃(HN₄Et₈)­(thf)­(PhMe)₂}_n] (<b>6</b>). However, an attempt to isolate the corresponding partially deprotonated calix[4]­pyrrolide ytterbium­(III) complex through the metathesis reaction of potassium precursor <b>6</b> with ytterbium triiodide was unsuccessful

Rare-Earth Metalation of Calix[4]pyrrole/Calix[4]arene Free of Alkali-Metal Companions

The redox transmetalation/protolysis (RTP) reactions of ytterbium or neodymium metal with calix[4]­H₄ (5,11,17,23-tetra-<i>tert</i>-butylcalix­[4]­arene-25,26,27,28-tetrol) in the presence of bis­(pentafluorophenyl)mercury under ultrasonication yielded [Ln^III(calix­[4]­H)­(thf)]₂ (<b>1</b>, Ln = Yb; <b>2</b>, Ln = Nd). The characterization of both <b>1</b> and <b>2</b>, including an X-ray single-crystal structural determination for <b>2</b>, suggests triple deprotonation of the macrocyclic ligand on metalation. The related RTP reaction of H₄N₄Et₈ (<i>meso</i>-octaethylcalix­[4]­pyrrole) with ytterbium metal and Hg­(C₆F₅)₂ at ambient temperature, however, resulted in quadruple deprotonation and afforded the ytterbium­(II) calix[4]­pyrrolide complex [Yb₂(N₄Et₈)­(thf)₄] (<b>3</b>) in good yield. Subsequent oxidation of <b>3</b> by dioxygen generated the novel tetranuclear ytterbium­(III) complex [Yb₄(μ-O)₂(N₄Et₈)₂(thf)₂] (<b>4</b>). The structures of the ytterbium­(II) complex <b>3</b> and the ytterbium­(III) complex <b>4</b> incorporate endo <b>(3)</b> and endo/exo (<b>4</b>) pyrrolide sandwich and half-sandwich units, respectively, with metal centers η¹ bound by nitrogen and η⁵ bonded by pyrrolide rings. The RTP reaction of lanthanum metal using diphenylmercury in place of bis­(pentafluorophenyl)mercury gave the triply deprotonated and N-confused pyrrolide (with an alkyl substituent of one pyrrolide ring migrated to a β-position) macrocyclic complex [La₂(HN₃N′Et₈)₂] (<b>5</b>). The triple deprotonation of the macrocyclic ligand H₄N₄Et₈ was also achieved through its reaction with 3 molar equiv of potassium metal, giving colorless crystals of [{K₃(HN₄Et₈)­(thf)­(PhMe)₂}_n] (<b>6</b>). However, an attempt to isolate the corresponding partially deprotonated calix[4]­pyrrolide ytterbium­(III) complex through the metathesis reaction of potassium precursor <b>6</b> with ytterbium triiodide was unsuccessful

Synthesis and Structure of New Lanthanoid Carbonate “Lanthaballs”

New insights into the synthesis of high-nuclearity polycarbonatolanthanoid complexes have been obtained from a detailed investigation of the preparative methods that initially yielded the so-called “lanthaballs” [Ln₁₃(ccnm)₆(CO₃)₁₄(H₂O)₆(phen)₁₈] Cl₃(CO₃)·25H₂O [<b>α-1Ln</b>; Ln = La, Ce, Pr; phen = 1,10-phenanthroline; ccnm = carbamoylcyanonitrosomethanide]. From this investigation, we have isolated a new pseudopolymorph of the cerium analogue of the lanthaball, [Ce₁₃(ccnm)₆(CO₃)₁₄(H₂O)₆(phen)₁₈]·Cl₃·CO₃ (<b>β-1Ce</b>). This new pseudopolymorph arose from a preparation in which fixation of atmospheric carbon dioxide generated the carbonate, and the ccnm ligand was formed in situ by the nucleophilic addition of water to dicyanonitrosomethanide. From a reaction of cerium­(III) nitrate, instead of the previously used chloride salt, with (Et₄N)­(ccnm), phen, and NaHCO₃ in aqueous methanol, the new complex Na­[Ce₁₃(ccnm)₆(CO₃)₁₄(H₂O)₆(phen)₁₈]­(NO₃)₆·20H₂O (<b>2Ce</b>) crystallized. A variant of this reaction in which sodium carbonate was initially added to Ce­(NO₃)₃, followed by phen and (Et₄N)­(ccnm), also gave <b>2Ce</b>. However, an analogous preparation with (Me₄N)­(ccnm) gave a mixture of crystals of <b>2Ce</b> and the coordination polymer [CeNa­(ccnm)₄(phen)₃]·MeOH (<b>3</b>), which were manually separated. The use of cerium­(III) acetate in place of cerium nitrate in the initial preparation did not give a high-nuclearity complex but a new coordination polymer, [Ce­(ccnm)­(OAc)₂(phen)] (<b>4</b>). The first lanthaball to incorporate neodymium, namely, [Nd₁₃(ccnm)₄(CO₃)₁₄(NO₃)₄(H₂O)₇(phen)₁₅]­(NO₃)₃·10H₂O (<b>5Nd</b>), was isolated from a preparation similar to that of the second method used for <b>2Ce</b>, and its magnetic properties showed an antiferromagnetic interaction. The identity of all products was established by X-ray crystallography

Anion–Anion Interactions in the Crystal Packing of Functionalized Methanide Anions: An Experimental and Computational Study

Examination of the crystal structures of (Me₄N)­(dcnm) (<b>1</b>), (Me₄N)­(dcnom) (<b>2</b>), and (Me₄N)­(nbdm) (<b>3</b>) [dcnm = dicyanonitrosomethanide, dcnom = dicyanonitromethanide, nbdm = nitroso-<i>N</i>,<i>N</i>-bis­(dicyanomethanide)] reveals the anions pack in an unusual columnar array, with distances between the planar species suggestive of π–π stacking. This columar packing motif is not observed in the crystal structures of (Me₄N)­(ccnm) (<b>4</b>) and (Me₄N)­(ccnom) (<b>6</b>) (ccnm = carbamoylcyanonitrosomethanide, ccnom = carbamoylcyanonitromethanide), in which hydrogen bonding between anions is the dominant supramolecular interaction. Ab initio calculations performed at the HF and MP2 levels of theory on ionic clusters of varying size further explored the nature and strength of anionic interactions observed in crystal structures. The first syntheses of the nbdm and ccnom anions are also reported

A Modern Twist to a Classic Synthetic Route: Ph₃Bi-Based Redox Transmetalation Protolysis (RTP) for the Preparation of Barium Metalorganic Species

This paper reports advances in redox transmetalation/protolysis (RTP) utilizing the readily available Ph₃Bi for the synthesis of a series of barium metal-organic species. On the basis of easily available starting materials, an easy one-pot procedure, and workup, we have obtained BaL₂ compounds (L = bis­(trimethyl­silyl)­amide, phenyl­(trimethyl­silyl)­amide, penta­methyl­cyclo­penta­dienide, fluorenide, 2,6-di-isopropylphenolate, and 3,5-diphenyl­pyrazolate) quantitatively by sonication of an excess of barium metal with triphenyl­bismuth and HL in per­deutero­tetra­hydrofuran, as established by NMR measurements. Rates of conversion are affected by both p<i>K</i>_a and bulk of HL. Competition occurs from direct reaction of Ba with HL, thereby enhancing the overall conversion, the effect being pronounced for the less bulky and more acidic ligands. Overall, the method significantly adds to the synthetic armory for barium metal-organic/​organometallic compounds

C–H Bond Activation and Isoprene Polymerization by Rare-Earth-Metal Tetramethylaluminate Complexes Bearing Formamidinato N‑Ancillary Ligands

The bimetallic formamidinate complexes Ln­(Form)­(AlMe₄)₂ (Ln = Y, Form (ArNCHNAr) = EtForm (Ar = 2,6-Et₂C₆H₃), MesForm (Ar = 2,4,6-Me₃C₆H₂), DippForm (Ar = 2,6-<i>i</i>Pr₂C₆H₃), <i>t</i>BuForm (Ar = 2-<i>t</i>BuC₆H₄); Ln = La, Form = DippForm, <i>t</i>BuForm) were obtained in high yield by protonolysis reactions between formamidines (FormH) and homoleptic rare-earth-metal tetramethylaluminates Ln­(AlMe₄)₃. Y­(Form)­(AlMe₄)₂ (Form = EtForm, DippForm) were also prepared by treatment of Y­(Form)­[N­(SiHMe₂)₂]₂(thf) with trimethylaluminum after the former were prepared by the protonolysis of Y­[N­(SiHMe₂)₂]₃(thf)₂ complexes with EtFormH or DippFormH. The monomeric six-coordinate complexes Ln­(Form)­(AlMe₄)₂ (Ln = Y, Form = EtForm, MesForm, DippForm, <i>t</i>BuForm; Ln = La, Form = DippForm, <i>t</i>BuForm) show similar molecular structures with distorted-octahedral geometry and bidentate (N,N′) Form and AlMe₄ ligands. The complex [La­(EtFormAlMe₃)­(AlMe₄)₂]­(C₇H₈)_1.5 from a protonolysis reaction between La­(AlMe₄)₃ and EtFormH has the EtForm ligand adopting a configuration in which one nitrogen and one aryl substituent are coordinated to the eight-coordinate lanthanum center in an η¹(N):η⁶(arene) manner. From the reaction of La­(AlMe₄)₃ with MesFormH, C–H bond activation of an <i>o</i>-methyl group of the mesityl moiety occurred, yielding [La­{η¹(N):η⁶(Ar)-Me₂CH₂FormAlMe₃}­(AlMe₃)­(AlMe₄)]­[La­(Me₂CH₂FormAlMe₃)­(AlMe₃)­(AlMe₄)]­(C₆H₁₄)_1.5 (Me₂CH₂Form = MesForm-H­(<i>o</i>-Me)), in which two linkage isomers of Me₂CH₂Form were observed. Investigations were carried out on the compounds [Ln­(Form)­(AlMe₄)₂] (Ln = Y, La; Form = EtForm, DippForm) as precatalysts activated by [Ph₃C]­[B­(C₆F₅)₄] or [PhNMe₂H]­[B­(C₆F₅)₄] in isoprene polymerization. While the lanthanum complexes showed narrower molecular weight distributions (PDI < 1.2), a stereodirecting role was evidenced for the cocatalysts (trityl borate, maximum 87% trans-1,4-selectivity; anilinium borate, maximum 82% cis-1,4-selectivity)

Structure, Magnetic Behavior, and Anisotropy of Homoleptic Trinuclear Lanthanoid 8‑Quinolinolate Complexes

Three complexes of the form [Ln^III₃(OQ)₉] (Ln = Gd, Tb, Dy; OQ = 8-quinolinolate) have been synthesized and their magnetic properties studied. The trinuclear complexes adopt V-shaped geometries with three bridging 8-quinolinolate oxygen atoms between the central and peripheral eight-coordinate metal atoms. The magnetic properties of these three complexes differ greatly. Variable-temperature direct-current (dc) magnetic susceptibility measurements reveal that the gadolinium and terbium complexes display weak antiferromagnetic nearest-neighbor magnetic exchange interactions. This was quantified in the isotropic gadolinium case with an exchangecoupling parameter of <i>J</i> = −0.068(2) cm^–1. The dysprosium compound displays weak ferromagnetic exchange. Variable-frequency and -temperature alternating-current magnetic susceptibility measurements on the anisotropic cases reveal that the dysprosium complex displays single-molecule-magnet behavior, in zero dc field, with two distinct relaxation modes of differing time scales within the same molecule. Analysis of the data revealed anisotropy barriers of <i>U</i>_eff = 92 and 48 K for the two processes. The terbium complex, on the other hand, displays no such behavior in zero dc field, but upon application of a static dc field, slow magnetic relaxation can be observed. Ab initio and electrostatic calculations were used in an attempt to explain the origin of the experimentally observed slow relaxation of the magnetization for the dysprosium complex