Reactivity of Diimido Complexes of Moybdenum and Tungsten towards Lithium Derivatives of Diphosphanes and Triphosphanes

Iron(II) Complexes of P3 -Chain Ligands: Structural Diversity

Iron(II) complexes containing ligands with a R2 P-P-PR2 unit were synthesized by metathesis reactions. With R=tBu, a mixture of two isomers is formed; in one of them, the terminal phosphorus binds to the Fe center (ylidic structure), while in the other one, the central P atom is linked to Fe. Starting from differently functionalized parent triphosphanes and corresponding functionalized Fe complexes, the ratio of isomers does not change. The outcome of the reaction and therefore the binding modes of the triphosphane ligands in the resulting compounds can be influenced by the size of the substituents. In the case of R=iPr a chelate complex is formed (both terminal P atoms are linked to the Fe center). Applying the mixed-substituted triphosphane, the ylidic structure of the resulting complex is preferred. The new compounds were characterized by NMR spectroscopy in solution and single-crystal X-ray diffraction in solid-state. The synthetic work was supported by DFT calculations.

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.

The new diphosphanylphosphido complexes of tungsten(vi) and molybdenum(vi). Their synthesis, structures and properties

We report on the reactivity of R2P-P(Li)-PR'2 (R = tBu, iPr, R' = NEt2, iPr) towards diimido complexes [(dippN)2MCl2·dme] (M = Mo, W and dipp = 2,6-iPr2C6H3). A series of new complexes with diphosphanylphosphido ligands R2P-P-PR'2 were isolated. The solid-state structures of [(dippN)2M(Cl)(1,2-η-iPr2P-P-PiPr2)] (2Mo and 2W) and [(dippN)2M(Cl){1,2-η-tBu2P-P-P(NEt2)2}] (3Mo and 3W) were established by single-crystal X-ray diffraction analysis and indicate a side-on geometry of the R2P-P-PR'2 moiety. 3W and 3Mo are the first triphosphorus complexes with the amido ligand NEt2 on the P atom. [(dippN)2M(Cl)(1,2-η-tBu2P-P-PtBu2)] (1Mo and 1W) and 3Mo and 3W display similar side-on geometry in solution and in the solid state. By contrast, 2Mo and 2W reveal a dynamic behavior in solution. For the first time, the reactivity of diphosphanylphosphido complexes towards different nucleophiles was studied. The complexes react with the phosphorus nucleophile Ph2PLi, yielding phosphanylphosphinidene complexes [(dippN)2M(Cl)(η2-P-PR2)]- Li+ (M = Mo, W) together with related diphosphanes R'2P-PPh2. Carbon nucleophile MeLi does not yield [(dippN)2M(Cl)(η2-P-PR2)]- Li+ but substitutes a Cl ligand at the metal center. Moreover, we compare the coordination of the R2P-P-PR'2 moiety to different metal centers based on DFT methods.

Symmetrical and unsymmetrical diphosphanes with diversified alkyl, aryl, and amino substituents

Synthesis, classification, and analysis of the structural, electronic and spectroscopic properties of a series of novel diphosphanes with diversified substituents.

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

This work describes a series of iron(II) phosphanylphosphido complexes. These compounds were obtained by reacting lithiated diphosphanes R₂PP(SiMe₃)Li (R = t-Bu, i-Pr) with an iron(II) β-diketiminate complex, [LFe(μ₂-Cl)₂Li(DME)₂] (1), where DME = 1,2-dimethoxyethane and L = Dippnacnac (β-diketiminate). While the reaction of 1 with t-Bu₂PP(SiMe₃)Li yields [LFe(η¹-Me₃SiPP-t-Bu₂)] (2), that of 1 with equimolar amounts of i-Pr₂PP(SiMe₃)Li, in DME, leads to [LFe(η²-i-Pr₂PPSiMe₃)] (3). In contrast, the reaction of 1 with (i-Pr₂N)₂PP(SiMe₃)Li provides not an iron-containing complex but 1-[(diisopropylamino)phosphine]-2,4-bis(diisopropylamino)-3-(trimethylsilyl)tetraphosphetane (4). The structures of 2-4 were determined using diffractometry. Thus, 2 exhibits a three-coordinate iron site and 3 a four-coordinate iron site. The increase in the coordination number is induced by the change from an anticlinal to a synclinal conformation of the phoshpanylphosphido ligands. The electronic structures of 2 and 3 were assessed through a combined field-dependent ⁵⁷Fe Mössbauer and high-frequency and -field electron paramagnetic resonance spectroscopic investigation in conjunction with analysis of their magnetic susceptibility and magnetization data. These studies revealed two high-spin iron(II) sites with S = 2 ground states that have different properties. While 2 exhibits a zero-field splitting described by a positive D parameter (D = +17.4 cm^-1; E/D = 0.11) for 3, this parameter is negative [D = -25(5) cm^-1; E/D = 0.15(5)]. Density functional theory (DFT) and time-dependent DFT (TDDFT) calculations provide insights into the origin of these differences and allow us to rationalize the fine and hyperfine structure parameters of 2 and 3. Thus, for 2, the spin-orbit coupling mixes a z²-type ground state with two low-lying {xz/yz} orbital states. These interactions lead to an easy plane of magnetization, which is essentially parallel to the plane defined by the N-Fe-N atoms. For 3, we find a yz-type ground state that is strongly mixed with a low-lying z²-type orbital state. In this case, the spin-orbit interaction leads to a partial unquenching of the orbital momentum along the x axis, that is, to an easy axis of magnetization oriented roughly along the Fe-P bond of the phosphido moiety.

Reactions of Lithiated Diphosphanes R2P-P(SiMe3)Li (R = tBu and iPr) with [MeNacnacTiCl2·THF] and [MeNacnacTiCl3]. Formation and Structure of TitaniumIII and TitaniumIV β-Diketiminato Complexes Bearing the Side-on Phosphanylphosphido and Phosphanylphosphinidene Functionalities

β-Diketiminate complexes of Ti^III-containing phosphanylphosphido ligands [^MeNacnacTi(Cl){η²-P(SiMe₃)-PR₂}] (^MeNacnac^- = [Ar]NC(Me)CHC(Me)N[Ar]; Ar = 2,6-iPr₂C₆H₃) were prepared by reactions of [^MeNacnacTiCl₂·THF] with lithium derivatives of diphosphanes R₂P-P(SiMe₃)Li (R = tBu, iPr) in toluene solutions. Surprisingly, reactions of [^MeNacnacTiCl₂·THF] with R₂P-P(SiMe₃)Li in THF solutions led to Ti^IV complexes containing phosphanylphosphinidene ligands [^MeNacnacTi(Cl)(η²-P-PtBu₂)] via an autoredox path involving a migration of a nitrene NAr from the Nacnac skeleton to the Ti centers. Solid-state structures of [^MeNacnacTi(Cl){η²-P(SiMe₃)-PtBu₂}] (1a) and [^MeNacnacTi(Cl)(η²-P-PtBu₂)] (two isomers 2a1, 2a2) together with [^MeNacnacTi(Cl){η²-P(SiMe₃)-PiPr₂}] (1b) and [^MeNacnacTi(Cl)(η²-P-PiPr₂)] (2b) were established by the single-crystal X-ray diffraction and display clearly side-on geometry of the (Me₃Si)P-PR₂ and P-PR₂ moieties in the solid state. Phosphanylphosphinidene complexes [^MeNacnacTi(Cl)(η²-P-PR₂)] indicate that the ³¹P NMR resonances of phosphinidene P atoms appear at a very low field in solution and in the solid state.

The reactivity of 1,1-dichloro-2,2-di-tert-butyldiphosphane towards lithiated metal carbonyls: a new entry to phosphanylphosphinidene dimers

Reactions of [Cp*(OC)₃M]Li (Cp* = C₅Me₅, M = Mo, W) towards t-Bu₂P–PCl₂ lead to the formation of phosphanylphosphinidene dimers [Cp*(OC)₃M(η²-t-Bu₂P–P)]₂ in fairly good yields.

An investigation on the chemistry of the R2P = P ligand: reactions of a phosphanylphosphinidene complex of tungsten(VI) with electrophilic reagents

The nucleophilic properties of the title compound [(2,6-i-Pr2C6H3N)2(Cl)W(η(2)-t-Bu2P = P)]Li·3DME (1) were investigated in reactions with selected electrophilic reagents such as MeI, M(CO)5THF (M = Cr, Mo, W), AlCl3, and GaCl3. Methylation of 1 by MeI yields phosphanylphosphido complexes [(2,6-i-Pr2C6H3N)2W(X)(1,2-η-t-Bu2P = P-CH3)] (X = Cl, I) (2-Cl/2-I) with the formation of a new P-C bond. Moreover, 1 reacts with electrophilic compounds [(OC)5M·THF] (M = Cr, Mo, W) to yield a series of novel dinuclear phosphanylphosphinidene complexes [(2,6-i-Pr2C6H3N)2(Cl)W(1,2-η-t-Bu2P = P-M(CO)5)]Li·3DME (3, 4, 5) with very long P-M distances. Adducts [(2,6-i-Pr2C6H3N)2(Cl)W(1,2-η-t-Bu2P = P-MCl3)]Li·3DME (6, 7) formed by reaction of 1 with GaCl3 and AlCl3 are labile and dissociate into 1 and MCl3 (M = Ga, Al). The outcomes of reactions were monitored by (31)P-NMR spectroscopy. Furthermore, the structures of the isolated complexes 2-Cl/2-I, 3, 4, and [(2,6-i-Pr2C6H3N)2(Cl)W(1,2-η-t-Bu2P = P-W(t-Bu2PH)(CO)3COLi·2DME] (5-P) were confirmed unambiguously by X-ray diffraction studies.

Reactivity of Phosphanylphosphinidene Complex of Tungsten(VI) toward Phosphines: A New Method of Synthesis of catena-Polyphosphorus Ligands

The reactivity of an anionic phosphanylphosphinidene complex of tungsten(VI), [(2,6-i-Pr2C6H3N)2(Cl)W(η(2)-t-Bu2P═P)]Li·3DME toward PMe3, halogenophosphines, and iodine was investigated. Reaction of the starting complex with Me3P led to formation of a new neutral phosphanylphosphinidene complex, [(2,6-i-Pr2C6H3N)2(Me3P)W(η(2)-t-Bu2P═P)]. Reactions with halogenophosphines yielded new catena-phosphorus complexes. From reaction with Ph2PCl and Ph2PBr, a complex with an anionic triphosphorus ligand t-Bu2P-P((-))-PPh2 was isolated. The main product of reaction with PhPCl2 was a tungsten(VI) complex with a pentaphosphorus ligand, t-Bu2P-P((-))-P(Ph)-P((-))-P-t-Bu2. Iodine reacted with the starting complex as an electrophile under splitting of the P-P bond in the t-Bu2P═P unit to yield [(1,2-η-t-Bu2P-P-P-t-Bu2)W(2,6-i-Pr2C6H3N)2Cl], t-Bu2PI, and phosphorus polymers. The molecular structures of the isolated products in the solid state and in solution were established by single crystal X-ray diffraction and NMR spectroscopy.