Lewis acid enhanced axial ligation of [Mo2]4+ complexes

Thiolate-Thione Redox-Active Ligand with a Six-Membered Chelate Ring via Template Condensation and Its Pt(II) Complexes

A new template condensation reaction has been discovered in a mixture of Pt(II), thiobenzamide, and base. Four complexes of the general form [Pt(ctaPh^R)₂], R = CH₃ (1a), H (1b), F (1c), Cl (1d), cta = condensed thioamide, have been prepared under similar conditions and thoroughly characterized by ¹H NMR and UV-vis-NIR spectroscopy, (spectro)electrochemistry, elemental analysis, and single-crystal X-ray diffraction. The ligand is redox active and can be reduced from the initial monoanion to a dianionic and then trianionic state. Chemical reduction of 1a with [Cp₂Co] yielded [Cp₂Co]₂[Pt(ctaPh^CH3)₂], [Cp₂Co]₂[1a], which has been similarly characterized with the addition of EPR spectroscopy and SQUID magnetization. The singly reduced form containing [1a]^1-, (nBu₄N)[Pt(ctaPh^CH3)₂], has been generated in situ and characterized by UV-vis and EPR spectroscopies. DFT studies of 1b, [1b]^1-, and [1b]^2- confirm the location of additional electrons in exclusively ligand-based orbitals. A detailed analysis of this redox-active ligand, with emphasis on the characteristics that favor noninnocent behavior in six-membered chelate rings, is included.

Structural diversity in copper(I) iodide complexes with 6-thioxopiperidin-2-one, piperidine-2,6-di-thione and isoindoline-1,3-di-thione ligands

Copper(I) iodide complexes are well known for displaying a diverse array of structural features even when only small changes in ligand design are made. This structural diversity is well displayed by five copper(I) iodide compounds reported here with closely related piperidine-2,6-di-thione (SNS), isoindoline-1,3-di-thione (SNS6), and 6-thioxopiperidin-2-one (SNO) ligands: di-μ-iodido-bis-[(aceto-nitrile-κN)(6-sulfanylidenepiperidin-2-one-κS)copper(I)], [Cu2I2(CH3CN)2(C5H7NOS)2] (I), bis-(aceto-nitrile-κN)tetra-μ3-iodido-bis-(6-sulfanylidenepiperidin-2-one-κS)-tetra-hedro-tetra-copper(I), [Cu4I4(CH3CN)4(C5H7NOS)4] (II), catena-poly[[(μ-6-sulfanylidenepiperidin-2-one-κ2 O:S)copper(I)]-μ3-iodido], [CuI(C5H7NOS)] n (III), poly[[(piperidine-2,6-di-thione-κS)copper(I)]-μ3-iodido], [CuI(C5H7NS2)] n (IV), and poly[[(μ-isoindoline-1,3-di-thione-κ2 S:S)copper(I)]-μ3-iodido], [CuI(C8H5NS2)] n (V). Compounds I and II crystallize as discrete dimeric and tetra-meric complexes, whereas III, IV, and V crystallize as polymeric two-dimensional sheets. To the best of our knowledge, compound III is the first instance of an extended hexa-gonal [Cu3I3] structure that is not supported by bridging ligands. Structures I, II, and IV display weak to moderately strong Cu⋯Cu cuprophilic inter-actions [Cu⋯Cu inter-nuclear distances range between 2.5803 (10) and 2.8485 (14) Å]. All structures except III display weak hydrogen-bonding inter-actions between the N-H of the ligand and the μ2 and μ3-I- atoms. Structure III contains classical N-H⋯O inter-actions between the SNO ligands that connect the mol-ecules in a three-dimensional framework. Complex V features π-π stacking inter-actions between the aryl rings of the SNS6 ligands within the same polymeric sheet. In structure IV, there were three partially occupied solvent mol-ecules of di-chloro-methane and one partially occupied mol-ecule of aceto-nitrile present in the asymmetric unit. The SQUEEZE routine [Spek (2015 ▸). Acta Cryst. C71, 9-18] was used to correct the diffraction data for diffuse scattering effects and to identify the solvent mol-ecules. The given chemical formula and other crystal data do not take into account the solvent mol-ecules.

Structure and magnetic properties of a novel heteroheptanuclear metal string complex [Ni3Ru2Ni2(μ7-teptra)4(NCS)2](PF6)

We report the synthesis of a novel heteroheptanuclear metal string complex (HMSC) [Ni₃Ru₂Ni₂(μ₇-teptra)₄(NCS)₂](PF₆) 1 supported by tetra-pyridyl-tri-amine (H₃teptra) ligands. We employed X-ray diffraction and other spectroscopic techniques to characterize the complex. The observed remarkably short Ru-Ru distance of 2.2499(3) Å for 1 is indicative of a unique metal-metal interaction in the mixed-valence [Ru₂]⁵⁺ (S = 3/2) unit. The complex exhibits a relatively high magnetic moment value of 4.55 B.M. at 4 K, which increases rapidly to 6.00 B.M. at 30 K and remains at 6.11 B.M. from 50 to 300 K as shown by SQUID measurements, indicating a high spin (S≥ 3/2) system which is further supported by the analyses of EPR spectra at low temperatures. These magnetic behaviors can be ascribed to the result of spin-exchange interactions among multi-spin centers.

Nonhelical heterometallic [Mo2M(npo)4(NCS)2] string complexes (M = Fe, Co, Ni) with high single-molecule conductance

Nonhelical metal strings, [MoMoM(npo)₄(NCS)₂], exhibited better overlaps of d_x2−y2 between neighbouring metal centres, stronger MoMo bonds, and superior single-molecule conductance.

Electrochemical and structural investigation of the interactions between naphthalene diimides and metal cations

Cyclic voltammetry and X-ray diffraction studies reveal the strength and nature of the interactions between Li⁺/Mg²⁺ and reduced naphthalene diimides.

K3[Mo2(SNO5)4Cl]3[Mo2(SNO5)4]: the first example of a heterometallic extended metal atom node (HEMAN)

We present the synthesis, structure, and electrochemistry of K₃[Mo₂(SNO5)₄Cl]₃[Mo₂(SNO5)₄] (1, HSNO5 = monothiosuccinimide), the first example of a heterometallic extended metal atom node (HEMAN).

Metal-only Lewis pairs between group 10 metals and Tl(i) or Ag(i): insights into the electronic consequences of Z-type ligand binding

Complexes bearing electron rich transition metal centers, especially those displaying coordinative unsaturation, are well-suited to form reverse-dative σ-interactions with Lewis acids. Herein we demonstrate the generality of zerovalent, group 10 m-terphenyl isocyanide complexes to form reverse-dative σ-interactions to Tl(i) and Ag(i) centers. Structural and spectroscopic investigations of these metal-only Lewis pairs (MOLPs) has allowed insight into the electronic consequences of Lewis-acid ligation within the primary coordination sphere of a transition metal center. Treatment of the bis-isocyanide complex, Pt(CNArDipp2)2 (ArDipp2 = 2,6-(2,6-(i-Pr)2C6H3)2C6H3) with TlOTf (OTf = [O3SCF3]-) yields the Pt/Tl MOLP [TlPt(CNArDipp2)2]OTf (1). 1H NMR and IR spectroscopic studies on 1, and its Pd congener [TlPd(CNArDipp2)2]OTf (2), demonstrate that the M → Tl interaction is labile in solution. However, treatment of complexes 1 and 2 with Na[BArF4] (ArF = 3,5-(CF3)2C6H3) produces [TlPt(CNArDipp2)2]BArF4 (3) and [TlPd(CNArDipp2)2]BArF4 (4), in which Tl(i) binding is shown to be static by IR spectroscopy and, in the case of 3, 195Pt NMR spectroscopy as well. This result provides strong evidence that the M → Tl linkages can be attributed primarily to σ-donation from the group 10 metal to Tl, as loss of ionic stabilization of Tl by the triflate anion is compensated for by increasing the degree of M → Tl σ-donation. In addition, X-ray Absorption Near-Edge Spectroscopy (XANES) on the Pd/Tl and Ni/Tl MOLPs, [TlPd(CNArDipp2)2]OTf (2) and [TlNi(CNArMes2)3]OTf, respectively, is used to illustrate that the formation of a reverse-dative σ-interaction with Tl(i) does not alter the spectroscopic oxidation state of the group 10 metal. Also reported is the ability of M(CNArDipp2)2 (M = Pt, Pd) to form MOLPs with Ag(i), yielding the complexes [AgM(CNArDipp2)2]OTf (5, M = Pt; 6, M = Pd). As was determined for the Tl-containing MOLPs 1-4, it is shown that the spectroscopic oxidation states of the group 10 metal in 5 and 6 are essentially unchanged compared to the zerovalent precursors M(CNArDipp2)2. However, in the case of 5 and 6, the formation of a dative M → Ag σ-bonding interaction facilitates the binding of Lewis bases to the group 10 metal trans to Ag, illustrating the potential of acceptor fragments to open up new coordination sites on transition metal complexes without formal, two-electron oxidation.

Electronic tuning of Mo2(thioamidate)4 complexes through π-system substituents and cis/trans isomerism

We report an exploration of the coordination chemistry of a systematic series of cyclic thioamidate ligands with the quadruply-bonded Mo2(4+) core. In addition to the S and N donor atoms that bind to Mo, the ligands utilized in this study have an additional O or S atom in conjugation with the thioamidate π system. The preparation of four new Mo2 complexes is described, and these compounds are characterized by X-ray crystallography, NMR and UV-vis spectroscopy, electrochemistry, and DFT calculations. These complexes provide a means to interrogate the electronics of Mo2(thioamidate)4 systems. Notably, we describe the first two examples of Mo2(thioamidate)4 complexes in their cis-2,2-regioisomer. By varying the π-system substituent and regioisomerism of these compounds, the electronics of the dimolybdenum core is shown to be altered with varying degrees of effect. Cyclic voltammetry results show that changing the π-system substituent from O to S results in an increase in the Mo2(4+/5+) oxidation potential by 170 mV. Changing the arrangement of ligands around the dimolybdenum core from trans-2,2 to cis-2,2 slightly weakens the metal-ligand bonds, raising the oxidation potential by a more modest 30-100 mV. MO diagrams of each compound derived from DFT calculations support these conclusions as well; the identity of the π-system substituent alters the δ-δ* (HOMO-LUMO) gap by up to 0.4 eV, whereas regioisomerism yields smaller changes in the electronic structure.

Facile synthesis of heterotrimetallic metal-string complex [NiCoRh(dpa)4Cl2] through direct metal replacement

This communication provides a practical strategy for the synthesis of heterotrimetallic extended metal atom chains with supported dpa(-) ligands. The transformation of the CoCoRh to a NiCoRh trinuclear complex can be achieved by direct metallic replacement. Furthermore, the first (CoRh)(4+) metal-metal bond is described here.