Synthetic, Structural, and Spectroscopic Characterization of a Novel Family of High-Spin Iron(II) [(β-Diketiminate)(phosphanylphosphido)] Complexes

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'.

A Comprehensive Experimental and Theoretical Study on the [{(η5-C5H5)2Zr[P(µ-PNEt2)2P(NEt2)2P]}]2O Crystalline System

The structure of tetraphosphetane zirconium complex C₅₂H₁₀₀N₈OP₁₀Zr₂1 was determined by single crystal X-ray diffraction analysis. The crystal belongs to the monoclinic system, space group P21/c, with a = 19.6452(14), b = 17.8701(12), c = 20.7963(14)Å, α = γ = 90°, β = 112.953(7)°, V = 6722.7(8)Å3, Z = 4. The electronic structure of the organometallic complex has been characterized within the framework of Quantum Chemical Topology. The topology of the Electron Localization Function (ELF) and the electron density according to the Quantum Theory of Atoms in Molecules (QTAIM) show no covalent bonds involving the Zr atom, but rather dative, coordinate interactions between the metal and the ligands. This is the first reported case of a Zr complex stabilized by an oxide anion, anionic cyclopentadienyl ligands and rare tetraphosphetane anions.

Experimental and theoretical investigation of the reactivity of [(BDI*)Ti(Cl){η2-P(SiMe3)-PiPr2}] towards selected ketones

In this work, we report a new type of reactivity of [(BDI*)Ti(Cl){η2-P(SiMe3)-PiPr2}] (1) towards ketones (BDI* = 2,6-diisopropylphenyl-β-methyldiketiminate ligand). In the reaction of 1 with acetone, cyclopentanone or cyclohexanone, a ketone moiety is inserted into Ti-Pphosphanyl or Ti-Pphosphido bonds to form complexes with a new C-P-P moiety, providing [(BDI*)Ti(Cl){η2-P(SiMe3)-PiPr2-C(Me)2O}] (2a), [(BDI*)Ti(Cl){η2-OC(Me)2P(SiMe3)-PiPr2}] (2b), [(BDI*)Ti(Cl){η2-P(SiMe3)-P(iPr)2-{C(CH2)4}O}] (3a), and [(BDI*)Ti(Cl){η2-P(SiMe3)-P(iPr)2-{C(CH2)5}O}] (4a). Starting complex 1 reacts with cyclohexanone, yielding a monocrystalline complex [{(ArN[double bond, length as m-dash]C(Me)CHC(Me)[double bond, length as m-dash]NAr)C(CH2)5O}Ti(Cl){PiPr2-P(SiMe3)C(CH2)5O}] (4d) with the insertion of two ketone molecules. Interestingly, we found that monoinserted complexes 2a and 3a may be oxidized via a reaction with AgCl, leading to elimination of the -SiMe3 group and oxidation of the titanium atom. This reaction led us to isolate the Ti(iv) complex [(BDI*)Ti(Cl){η2-P-P(iPr)2-{C(CH2)5}O}] (5) in crystalline form. To identify the kinds of products that may be formed and determine which products are the most energetically favoured ones, we conducted a thermodynamic DFT study of 1 towards acetone, cyclopentanone and cyclohexanone. Structures 2a, 2b, 3a, 3e, 4a, 4d, and 5 were characterized by X-ray crystallography, and complex 5 was also identified by NMR spectroscopy.

Solvent Impact on the Diversity of Products in the Reaction of Lithium Diphenylphosphide and a Ti(III) Complex Supported by a tBu2P-P(SiMe3) Ligand

We present two important trends in the reactivity of the titanium complex [^MeNacNacTi(Cl){η²-P(SiMe₃)-PtBu₂}] (^MeNacNac^- = [Ar]NC(Me)CHC(Me)N[Ar]; Ar = 2,6-iPr₂Ph) with nucleophilic reagents RLi (R = Ph₂P, tBuO, (Me₃Si)₂N, and tBu₂N) depending on the reaction medium. Reaction in nonpolar solvent (toluene) leads to three main products: via an autoredox process and nucleophilic substitution at the Ti-atom to afford the Ti(IV) complex [^MeNacNacTi(R){η²-P-PtBu₂}] (1 for R = PPh₂), via the elimination of Me₃SiR to afford Ti(III) complex [^MeNacNacTi(Cl){η²-P-PtBu₂}]^-[Li(12-crown-4)₂]⁺ (2), and via 2e^- reduction process to afford new ionic complex [{ArNC(Me)CHC(Me)}Ti═NAr{η¹-P(SiMe₃)-PtBu₂}]^-[Li(12-crown-4)₂]⁺ (3). Quite differently, the complex [^MeNacNacTi(Cl){η²-P(SiMe₃)-PtBu₂}] reacts with Ph₂PLi in THF, unexpectedly yielding two new, four-coordinate Ti(IV) imido complexes 4a [{ArNC(Me)═CHC(H)(Me)-P(PtBu₂)}Ti═NAr(Cl)]^-[Li(12-crown-4)₂]⁺·(toluene)₂ and 4b [{ArNC(CH₂)CH═C(Me)-P(PtBu₂)}Ti═NAr(Cl)]^-[Li(12-crown-4)₂]⁺·(Et₂O). Complex 2 dissolved in THF converts to 4a and 4b. 1, 2, 3, 4a, and 4b were characterized by X-ray diffraction. 1, 4a, and 4b were also fully characterized by multinuclear NMR spectroscopy.

Diphosphination of CO2 and CS2 mediated by frustrated Lewis pairs – catalytic route to phosphanyl derivatives of formic and dithioformic acid

The first example of CO₂ diphosphination is described.

Reactions of (Ph)tBuP-P(SiMe3)Li·3THF with [(PNP)TiCl2] and [MeNacNacTiCl2·THF]: synthesis of first PNP titanium(iv) complex with the phosphanylphosphinidene ligand [(PNP)Ti(Cl){η2-P-P(Ph)tBu}]

Herein, the lithium derivative of diphosphane, (Ph)tBuP-P(SiMe3)Li (1), is isolated for the first time and investigated in reactions with β-diketiminate (MeNacnac- = [Ar]NC(Me)CHC(Me)N[Ar]; Ar = 2,6-iPr2C6H3) and PNP-pincer (PNP = N[2-PiPr2-4-methylphenyl]2) Ti(iii) complexes. The β-diketiminate titanium(iii) complex containing the phosphanylphosphido ligand [MeNacNacTi(Cl){η2-P(SiMe3)-P(Ph)tBu}] (2) is prepared via the reaction of [MeNacNacTiCl2·THF] with (Ph)tBuP-P(SiMe3)Li in toluene solution with good yield and purity. The corresponding titanium(iv) complex involving the phosphanylphosphinidene ligand [MeNacNacTi(Cl){η2-P-P(Ph)tBu}] (3) is synthesized via the oxidation of complex (2) with [iBu3PAgCl]4. Interestingly, an analogous PNP titanium(iv) complex, [(PNP)Ti(Cl){η2-P-P(Ph)tBu}] (4), is obtained in the reaction of [(PNP)TiCl2] with (Ph)tBuP-P(SiMe3)Li in toluene solution and a 1 : 1 molar ratio instead of the expected titanium(iii) complex with the phosphanylphosphido ligand. The solid-state structures of (Ph)tBuP-P(SiMe3)Li·3THF (1), [MeNacNacTi(Cl){η2-P(SiMe3)-P(Ph)tBu}] (2), [MeNacNacTi(Cl){η2-P-P(Ph)tBu}] (3) and [(PNP)Ti(Cl){η2-P-P(Ph)tBu}] (4) are determined by single-crystal X-ray diffraction, which reveals that in all obtained complexes, both the phosphanylphosphinidene (Ph)tBuP-P and phosphanylphosphido (Ph)tBuP-P(SiMe3) ligands are bidentate-coordinated to the metal center.