Heterobimetallic Lantern Complexes That Couple Antiferromagnetically through Noncovalent Pt···Pt Interactions

A series of Pt-based heterobimetallic lantern complexes of the form [PtM­(SAc)₄(OH₂)] (M = Co, <b>1</b>; Ni, <b>2</b>; Zn, <b>3</b>) were prepared using a facile, single-step procedure. These hydrated species were reacted with 3-nitropyridine (3-NO₂py) to prepare three additional lantern complexes, [PtM­(SAc)₄(3-NO₂py)] (M = Co, <b>4</b>; Ni, <b>5</b>; Zn, <b>6</b>), or alternatively dried in vacuo to the dehydrated species [PtM­(SAc)₄] (M = Co, <b>7</b>; Ni, <b>8</b>; Zn, <b>9)</b>. The Co- and Ni-containing species exhibit PtM bonding in solution and the solid state. In the structurally characterized compounds <b>1</b>–<b>6</b>, the lantern units form dimers in the solid state via a short Pt···Pt metallophilic interaction. Antiferromagnetic coupling between 3d metal ions in the solid state through noncovalent metallophilic interactions was observed for all the paramagnetic lantern complexes prepared, with <i>J</i>-coupling values of −12.7 cm^–1 (<b>1</b>), −50.8 cm^–1 (<b>2</b>), −6.0 cm^–1 (<b>4</b>), and −12.6 cm^–1 (<b>5</b>). The Zn complexes <b>3</b> and <b>6</b> also form solid-state dimers, indicating that the formation of short Pt···Pt interactions in these complexes is not predicated on the presence of a paramagnetic 3d metal ion. These contacts and the resultant antiferromagnetic coupling are also not unique to heterobimetallic lantern complexes with axially coordinated H₂O or the previously reported thiobenzoate supporting ligand

Heterobimetallic Lantern Complexes That Couple Antiferromagnetically through Noncovalent Pt···Pt Interactions

A series of Pt-based heterobimetallic lantern complexes of the form [PtM­(SAc)₄(OH₂)] (M = Co, <b>1</b>; Ni, <b>2</b>; Zn, <b>3</b>) were prepared using a facile, single-step procedure. These hydrated species were reacted with 3-nitropyridine (3-NO₂py) to prepare three additional lantern complexes, [PtM­(SAc)₄(3-NO₂py)] (M = Co, <b>4</b>; Ni, <b>5</b>; Zn, <b>6</b>), or alternatively dried in vacuo to the dehydrated species [PtM­(SAc)₄] (M = Co, <b>7</b>; Ni, <b>8</b>; Zn, <b>9)</b>. The Co- and Ni-containing species exhibit PtM bonding in solution and the solid state. In the structurally characterized compounds <b>1</b>–<b>6</b>, the lantern units form dimers in the solid state via a short Pt···Pt metallophilic interaction. Antiferromagnetic coupling between 3d metal ions in the solid state through noncovalent metallophilic interactions was observed for all the paramagnetic lantern complexes prepared, with <i>J</i>-coupling values of −12.7 cm^–1 (<b>1</b>), −50.8 cm^–1 (<b>2</b>), −6.0 cm^–1 (<b>4</b>), and −12.6 cm^–1 (<b>5</b>). The Zn complexes <b>3</b> and <b>6</b> also form solid-state dimers, indicating that the formation of short Pt···Pt interactions in these complexes is not predicated on the presence of a paramagnetic 3d metal ion. These contacts and the resultant antiferromagnetic coupling are also not unique to heterobimetallic lantern complexes with axially coordinated H₂O or the previously reported thiobenzoate supporting ligand

Spectroscopic and Theoretical Investigation of High-Spin Square-Planar and Trigonal Fe(II) Complexes Supported by Fluorinated Alkoxides

The electronic structures and spectroscopic behavior of three high-spin FeII complexes of fluorinated alkoxides were studied: square-planar {K(DME)2}2[Fe(pinF)2] (S) and quasi square-planar {K(C222)}2[Fe(pinF)2] (S′) and trigonal-planar {K(18C6)}[Fe(OC4F9)3] (T) where pinF = perfluoropinacolate and OC4F9 = tris-perfluoro-t-butoxide. The zero-field splitting (ZFS) and hyperfine structure parameters of the S = 2 ground states were determined using field-dependent 57Fe Mössbauer and high-field and -frequency electron paramagnetic resonance (HFEPR) spectroscopies. The spin Hamiltonian parameters were analyzed with crystal field theory and corroborated by density functional theory (DFT) and ab initio complete active space self-consistent field (CASSCF) calculations. Whereas the ZFS tensor of S has a small rhombicity, E/D = 0.082, and a positive D = 15.17 cm–1, T exhibits a negative D = −9.16 cm–1 and a large rhombicity, E/D = 0.246. Computational investigation of the structural factors suggests that the ground-state electronic configuration and geometry of T’s Fe site are determined by the interaction of [Fe(OC4F9)3]− with {K(18C6)}+. In contrast, two distinct countercations of S/S′ have a negligible influence on their [Fe(pinF)2]2– moieties. Instead, the distortions in S′ are likely induced by the chelate ring conformation change from δλ, observed for S, to the δδ conformation, determined for S′

Pt···Pt vs Pt···S Contacts Between Pt-Containing Heterobimetallic Lantern Complexes

A trio of Pt-based heterobimetallic lantern complexes of the form [(py)­PtM­(SAc)₄(py)] (M = Co, <b>1</b>; Ni, <b>2</b>; Zn, <b>3</b>) with unusual octahedral coordination of Pt­(II) was prepared from a reaction of [PtM­(SAc)₄] with excess pyridine. These dipyridine lantern complexes could be converted to monopyridine derivatives with gentle heat to give the series [PtM­(SAc)₄(py)] (M = Co, <b>4</b>; Ni, <b>5</b>; Zn, <b>6</b>). An additional family of the form [PtM­(SAc)₄(pyNH₂)] (M = Co, <b>7</b>; Ni, <b>8</b>; Zn, <b>9</b>) was synthesized from reaction of [PtM­(SAc)₄(OH₂)] or [PtM­(SAc)₄] with 4-aminopyridine. Dimethylsulfoxide and <i>N</i>,<i>N</i>-dimethylformamide were also determined to react with [PtM­(SAc)₄] (M = Co, Ni), respectively, to give [PtCo­(SAc)₄(DMSO)]­(DMSO), <b>10</b>, and [PtNi­(SAc)₄(DMF)]­(DMF), <b>11</b>. Structural and magnetic data for these compounds and those for two other previously published families, [PtM­(tba)₄(OH₂)] and [PtM­(SAc)₄(L)], L = OH₂, pyNO₂, are used to divide the structures among three distinct categories based on Pt···Pt and Pt···S distances. In general, the weaker donors H₂O and pyNO₂ seem to favor metallophilicity and antiferromagnetic coupling between 3d metal centers. When Pt···S interactions are favored over Pt···Pt ones, no coupling is observed and the p<i>K</i>_a of the pyridine donor correlates with the interlantern S···S distance. UV–vis–NIR electronic and ¹H NMR spectra provide complementary characterization as well

Room Temperature Stable Organocuprate Copper(III) Complex

The paramagnetic trigonal-planar copper complexes {K­(18C6)}­[Cu^II(OC­(CH₃)­(CF₃)₂)₃] (<b>2</b>) and K­[Cu^II(OC­(C₆H₅)­(CF₃)₂)₃] (<b>3</b>) have been prepared and characterized, including X-ray crystallography, in 61% and 3% yields, respectively. The latter complex does not form preferentially, because CuBr₂ and KOC­(C₆H₅)­(CF₃)₂)₃ also form the diamagnetic complexes {K­(18C6)}­[K₂{Cu^I(OC­(C₆H₅)­(CF₃)₂)₂}₃] (<b>4</b>) and {K­(18C6)}­[Cu^III(OC­(C₆H₄)­(CF₃)₂)₂] (<b>5</b>). These species were characterized by X-ray crystallography, UV–vis spectroscopy, ¹H, ¹³C­{¹H}, and ¹⁹F­{¹H} NMR spectroscopy, and elemental analysis. The unique organocuprate Cu­(III) species with {O₂C₂} coordination was formed by ortho metalation of two phenyl rings, resulting in <i>trans</i>-{O₂C₂} coordination of Cu­(III), and is stable at room temperature in the solid state and in dark solutions of THF

Room Temperature Stable Organocuprate Copper(III) Complex

The paramagnetic trigonal-planar copper complexes {K­(18C6)}­[Cu^II(OC­(CH₃)­(CF₃)₂)₃] (<b>2</b>) and K­[Cu^II(OC­(C₆H₅)­(CF₃)₂)₃] (<b>3</b>) have been prepared and characterized, including X-ray crystallography, in 61% and 3% yields, respectively. The latter complex does not form preferentially, because CuBr₂ and KOC­(C₆H₅)­(CF₃)₂)₃ also form the diamagnetic complexes {K­(18C6)}­[K₂{Cu^I(OC­(C₆H₅)­(CF₃)₂)₂}₃] (<b>4</b>) and {K­(18C6)}­[Cu^III(OC­(C₆H₄)­(CF₃)₂)₂] (<b>5</b>). These species were characterized by X-ray crystallography, UV–vis spectroscopy, ¹H, ¹³C­{¹H}, and ¹⁹F­{¹H} NMR spectroscopy, and elemental analysis. The unique organocuprate Cu­(III) species with {O₂C₂} coordination was formed by ortho metalation of two phenyl rings, resulting in <i>trans</i>-{O₂C₂} coordination of Cu­(III), and is stable at room temperature in the solid state and in dark solutions of THF

Pt···Pt vs Pt···S Contacts Between Pt-Containing Heterobimetallic Lantern Complexes

A trio of Pt-based heterobimetallic lantern complexes of the form [(py)­PtM­(SAc)₄(py)] (M = Co, <b>1</b>; Ni, <b>2</b>; Zn, <b>3</b>) with unusual octahedral coordination of Pt­(II) was prepared from a reaction of [PtM­(SAc)₄] with excess pyridine. These dipyridine lantern complexes could be converted to monopyridine derivatives with gentle heat to give the series [PtM­(SAc)₄(py)] (M = Co, <b>4</b>; Ni, <b>5</b>; Zn, <b>6</b>). An additional family of the form [PtM­(SAc)₄(pyNH₂)] (M = Co, <b>7</b>; Ni, <b>8</b>; Zn, <b>9</b>) was synthesized from reaction of [PtM­(SAc)₄(OH₂)] or [PtM­(SAc)₄] with 4-aminopyridine. Dimethylsulfoxide and <i>N</i>,<i>N</i>-dimethylformamide were also determined to react with [PtM­(SAc)₄] (M = Co, Ni), respectively, to give [PtCo­(SAc)₄(DMSO)]­(DMSO), <b>10</b>, and [PtNi­(SAc)₄(DMF)]­(DMF), <b>11</b>. Structural and magnetic data for these compounds and those for two other previously published families, [PtM­(tba)₄(OH₂)] and [PtM­(SAc)₄(L)], L = OH₂, pyNO₂, are used to divide the structures among three distinct categories based on Pt···Pt and Pt···S distances. In general, the weaker donors H₂O and pyNO₂ seem to favor metallophilicity and antiferromagnetic coupling between 3d metal centers. When Pt···S interactions are favored over Pt···Pt ones, no coupling is observed and the p<i>K</i>_a of the pyridine donor correlates with the interlantern S···S distance. UV–vis–NIR electronic and ¹H NMR spectra provide complementary characterization as well

Structural and Electronic Properties of Old and New A₂[M(pin^F)₂] Complexes

Seven new homoleptic complexes of the form A₂[M­(pin^F)₂] have been synthesized with the dodecafluoropinacolate (pin^F)^2– ligand, namely (Me₄N)₂[Fe­(pin^F)₂], <b>1</b>; (Me₄N)₂[Co­(pin^F)₂], <b>2</b>; (ⁿBu₄N)₂[Co­(pin^F)₂], <b>3</b>; {K­(DME)₂}₂[Ni­(pin^F)₂], <b>4</b>; (Me₄N)₂[Ni­(pin^F)₂], <b>5</b>; {K­(DME)₂}₂[Cu­(pin^F)₂], <b>7</b>; and (Me₄N)₂[Cu­(pin^F)₂], <b>8</b>. In addition, the previously reported complexes K₂[Cu­(pin^F)₂], <b>6</b>, and K₂[Zn­(pin^F)₂], <b>9</b>, are characterized in much greater detail in this work. These nine compounds have been characterized by UV–vis spectroscopy, cyclic voltammetry, elemental analysis, and for paramagnetic compounds, Evans method magnetic susceptibility. Single-crystal X-ray crystallographic data were obtained for all complexes except <b>5</b>. The crystallographic data show a square-planar geometry about the metal center in all Fe (<b>1</b>), Ni (<b>4</b>), and Cu (<b>6</b>, <b>7</b>, <b>8</b>) complexes independent of countercation. The Co species exhibit square-planar (<b>3</b>) or distorted square-planar geometries (<b>2</b>), and the Zn species (<b>9</b>) is tetrahedral. No evidence for solvent binding to any Cu or Zn complex was observed. Solvent binding in Ni can be tuned by the countercation, whereas in Co only strongly donating Lewis solvents bind independent of the countercation. Indirect evidence (diffuse reflectance spectra and conductivity data) suggest that <b>5</b> is not a square-planar compound, unlike <b>4</b> or the literature K₂[Ni­(pin^F)₂]. Cyclic voltammetry studies reveal reversible redox couples for Ni­(III)/Ni­(II) in <b>5</b> and for Cu­(III)/Cu­(II) in <b>8</b> but quasi-reversible couples for the Fe­(III)/Fe­(II) couple in <b>1</b> and the Co­(III)/Co­(II) couple in <b>2</b>. Perfluorination of the pinacolate ligand results in an increase in the central C–C bond length due to steric clashes between CF₃ groups, relative to perhydropinacolate complexes. Both types of pinacolate complexes exhibit O–C–C–O torsion angles around 40°. Together, these data demonstrate that perfluorination of the pinacolate ligand makes possible highly unusual and coordinatively unsaturated high-spin metal centers with ready thermodynamic access to rare oxidation states such as Ni­(III) and Cu­(III)

Thiocyanate-Ligated Heterobimetallic {PtM} Lantern Complexes Including a Ferromagnetically Coupled 1D Coordination Polymer

A series of heterobimetallic lantern complexes with the central unit {PtM­(SAc)₄(NCS)} have been prepared and thoroughly characterized. The {Na­(15C5)}­[PtM­(SAc)₄(NCS)] series, <b>1</b> (Co), <b>2</b> (Ni), <b>3</b> (Zn), are discrete compounds in the solid state, whereas the {Na­(12C4)₂)}­[PtM­(SAc)₄(NCS)] series, <b>4</b> (Co), <b>5</b> (Ni), <b>6</b> (Zn), and <b>7</b> (Mn), are ion-separated species. Compound <b>7</b> is the first {PtMn} lantern of any bridging ligand (carboxylate, amide, etc.). Monomeric <b>1</b>–<b>7</b> have M²⁺, necessitating counter cations that have been prepared as {(15C5)­Na}⁺ and {(12C4)₂Na}⁺ variants, none of which form extended structures. In contrast, neutral [PtCr­(tba)₄(NCS)]_∞ <b>8</b> forms a coordination polymer of {PtCr}⁺ units linked by (NCS)⁻ in a zigzag chain. All eight compounds have been thoroughly characterized and analyzed in comparison to a previously reported family of compounds. Crystal structures are presented for compounds <b>1</b>–<b>6</b> and <b>8</b>, and solution magnetic susceptibility measurements are presented for compounds <b>1</b>, <b>2</b>, <b>4</b>, <b>5</b>, and <b>7</b>. Further structural analysis of dimerized {PtM} units reinforces the empirical observation that greater charge density along the Pt-M vector leads to more Pt···Pt interactions in the solid state. Four structural classes, one new, of {MPt}···{PtM} units are presented. Solid state magnetic characterization of <b>8</b> reveals a ferromagnetic interaction in the {PtCr­(NCS)} chain between the Cr centers of <i>J</i>/<i>k</i>_B = 1.7(4) K

Pt–Mg, Pt–Ca, and Pt–Zn Lantern Complexes and Metal-Only Donor–Acceptor Interactions

Pt-based heterobimetallic lantern complexes of the form [PtM­(SOCR)₄(L)] have been shown previously to form intermolecular metallophilic interactions and engage in antiferromagnetic coupling between lanterns having M atoms with open shell configurations. In order to understand better the influence of the carboxylate bridge and terminal ligand on the electronic structure, as well as the metal–metal interactions within each lantern unit, a series of diamagnetic lantern complexes, [PtMg­(SAc)₄(OH₂)] (<b>1</b>), [PtMg­(tba)₄(OH₂)] (<b>2</b>), [PtCa­(tba)₄(OH₂)] (<b>3</b>), [PtZn­(tba)₄(OH₂)] (<b>4</b>), and a mononuclear control (Ph₄P)₂[Pt­(SAc)₄] (<b>5</b>) have been synthesized. Crystallographic data show close Pt–M contacts enforced by the lantern structure in each dinuclear case. ¹⁹⁵Pt-NMR spectroscopy of <b>1</b>–<b>4</b>, (Ph₄P)₂[Pt­(SAc)₄] (<b>5</b>), and several previously reported lanterns revealed a strong chemical shift dependence on the identity of the second metal (M), mild influence by the thiocarboxylate ligand (SOCR; R = CH₃ (thioacetate, SAc), C₆H₅ (thiobenzoate, tba)), and modest influence from the terminal ligand (L). Fluorescence spectroscopy has provided evidence for a Pt···Zn metallophilic interaction in [PtZn­(SAc)₄(OH₂)], and computational studies demonstrate significant dative character. In all of <b>1</b>–<b>4</b>, the short Pt–M distances suggest that metal-only Lewis donor (Pt)–Lewis acceptor (M) interactions could be present. DFT and NBO calculations, however, show that only the Zn examples have appreciable covalent character, whereas the Mg and Ca complexes are much more ionic