A homologous series of alkaline earth phosphanides: syntheses, crystal structures, and unusual dynamic behavior of (THF)(n)M[P(CH(SiMe(3))(2))(C(6)H(4)-2-CH(2)NMe(2))](2) (M = Mg, Ca, Sr, Ba)

Lanthanide Mimicking by Magnesium for Oxazolidinone Synthesis

In the last decade, magnesium complexes have emerged as a viable alternative to transition-metal catalysts for the hydrofunctionalization of unsaturated bonds. However, their potential for advanced catalytic reactions has not been thoroughly investigated. To address this gap, we have developed a novel magnesium amide compound (3) using a PNP framework that is both bulky and flexible. Our research demonstrates that compound 3 can effectively catalyze the synthesis of biologically significant oxazolidinone derivatives. This synthesis involves a tandem reaction of hydroalkoxylation and cyclohydroamination of isocyanate using propargyl alcohol. Furthermore, we conducted comprehensive theoretical calculations to gain insights into the reaction mechanism. It is important to note that these types of transformations have not been reported for magnesium and would significantly enhance the catalytic portfolio of the 7th most abundant element.

Coordination of arenes and phosphines by charge separated alkaline earth cations

Generation of ‘naked’ β-diketiminato magnesium and calcium cations allows the isolation of benzene, toluene, 1,4-difluorobenzene and terminal phosphine adducts.

Diastereoselective synthesis of chiral aminophenolate magnesium complexes and their application in the stereoselective polymerization of rac-lactide and rac-β-butyrolactone

A series of magnesium silylamido complexes supported by chiral aminophenolate ligands were synthesized, and their catalytic behaviors toward the ring-opening polymerization of rac-lactide (LA) and rac-β-butyrolactone (BBL) were explored.

Synthesis, characterization and reactivity of potassium and barium complexes containing phosphane-borane stabilized methanides

The polymeric potassium complex [K{CH(PPh2BH3)2}]∞ (1) was prepared and used as a starting material for the syntheses of related N,N,N',N'-tetramethylethylenediamine (tmeda) and N,N,N',N',N''-pentamethyldiethylenetriamine (pmdta) ligated potassium derivatives [K{CH(PPh2BH3)2}(tmeda)2]∞ (2) and [K{CH(PPh2BH3)2}(pmdta)]2 (3). Salt metathesis reactions with [BaI2(thf)5] allowed the synthesis of the barium derivatives [BaI{CH(PPh2BH3)2}(thf)5] (5) and [Ba{CH(PPh2BH3)2}2(solv)2}] (solv = Et2O, thf) (6), which are more prone to subsequent reactions than the potassium derivatives. One of the resulting products, [Ba4O{CH(PPh2BH3)2}3{Ph2PCH(BH3)PPh2BH3}3] (7), which contains two different isomeric forms of the bis(borane) adduct of Ph2PCHPPh2, was isolated. The complexes were characterized by NMR techniques and single crystal X-ray diffraction measurements.

Alkali metal complexes of a naphthylamine-substituted phosphanide

The reaction between {(Me3Si)2CH}PCl2 and one equivalent of [C10H6-8-NMe2]Li, followed by in situ reduction with LiAlH4, gives the secondary phosphane {(Me3Si)2CH}(C10H6-8-NMe2)PH(1) in good yield as a colourless crystalline solid. Metalation of 1 with Bu(n)Li in diethyl ether gives the lithium phosphanide [{[{(Me3Si)2CH}(C10H6-8-NMe2)P]Li}2(OEt2)](2), which undergoes metathesis with either NaOBu(t) or KOBu(t) to give the heavier alkali metal derivatives [[{(Me3Si)2CH}(C10H6-8-NMe2)P]-Na(tmeda)](3) and [[{(Me3Si)2CH}(C10H6-8-NMe2)P]K(pmdeta)](4), after recrystallisation in the presence of the corresponding amine co-ligand [tmeda = N,N,N',N'-tetramethylethylenediamine, pmdeta = N,N,N',N",N"-pentamethyldiethylenetriamine]. Compounds 2-4 have been characterised by 1H, 13C{1H} and 31P{1H} NMR spectroscopy, elemental analyses and X-ray crystallography. Dinuclear 2 crystallises with the phosphanide ligands arranged in a head-to-head fashion and is subject to dynamic exchange in toluene solution; in contrast, compounds 3 and 4 crystallise as discrete monomers which exhibit no dynamic behaviour in solution. DFT calculations on the model compound [{[(Me)(C10H6-8-NMe2)P]Li},(OMe2)] (2a) indicate that the most stable head-to-head form is favoured by 15.0 kcal mol(-1) over the corresponding head-to-tail form.

Synthesis and Structure of a Molecular Barium Aminebis(phenolate) and Its Application as an Initiator for Ring-Opening Polymerization of Cyclic Esters

The synthesis and structural characterization of an unusual trinuclear barium aminebis(phenolate) complex are reported along with its application as an initiator for the ring-opening polymerization of epsilon-caprolactone and L-lactide.

The Solution Structures and Dynamics and the Solid-State Structures of Substituted Cyclopentadienyltitanium(IV) Trifluorides

Organotitanium fluorides (C5Me4R)TiF3 (R = H, Me, Et) sublimate with formation of crystalline dimers. From solution, we obtained crystals of dimers and tetramers. The tetramer [{(C5Me5)TiF3}4] irreversibly dissociates in the solid state to dimers (DeltaH = 8.33 kcal mol(-1)). The variable-temperature (1)H and (19)F NMR spectroscopy measurements of the toluene-d(8) solution of [{(C5Me5)TiF3}2] revealed at 202 K one monomeric, two dimeric (with C2h and Cs symmetry), two tetrameric (with D2 and C2v symmetry), and two trimeric (both C2 symmetry) molecules. With the increase in temperature and dilution of the solution, the composition of the solution shifts to the smaller molecules. The thermodynamic and activation parameters for the reversible dissociation of dimers to monomers in the solution are DeltaH = 9.2 kcal mol(-1), DeltaS = 24.2 cal mol(-1) K(-1), DeltaH(double dagger) = 12.2 kcal mol(-1), DeltaS(double dagger) = 9.7 cal mol(-1) K(-1). The dissociation path with a weakly double-bridged transition-state dimer was proposed. The thermodynamic parameters for the reversible dissociation of the C2v tetramer to the dimers in solution are DeltaH = 7.9 kcal mol(-1) and DeltaS = 26.8 cal mol(-1) K(-1). From both tetramers, the D2 molecule is 0.34(5) kcal mol(-1) lower in enthalpy and 6.5(5) cal mol(-1) K(-1) lower in entropy than the C2v molecule. The structures of both trimers were proposed. The low-temperature 19F NMR spectra of the CDCl3 solution of [{(C5Me5)TiF3}2] are consistent with equilibria of a monomer, two dimers (with C2h and Cs symmetry), and a trimer. The vapor pressure osmometric molecular mass determination of CDCl3 solution of [{(C5Me5)TiF3}2] at 302 K is consistent with the equilibrium of the dimer and the monomer.

Complexes of the Heavier Alkaline Earth Metals Ca, Sr, and Ba with O-Functionalized Phosphanide Ligands

Metathesis reactions between either SrI(2) or BaI(2) and 2 equiv of the potassium phosphanide [[(Me(3)Si)(2)CH]-(C(6)H(4)-2-OMe)P]K yield, after recrystallization, the complexes [[([Me(3)Si](2)CH)(C(6)H(4)-2-OMe)P](2)M(THF)(n)] [M = Sr, n = 2 (5); Ba, n = 3 (6)]. Similar metathesis reactions between MI(2) and 2 equiv of the more sterically demanding potassium phosphanide [[(Me(3)Si)(2)CH](C(6)H(3)-2-OMe-3-Me)P]K yield the chemically isostructural complexes [[([Me(3)Si](2)CH)(C(6)H(3)-2-OMe-3-Me)P](2)M(THF)(2)] [M = Ca (9), Sr (7), Ba (8)]. Compounds 5-9 have been characterized by multi-element NMR spectroscopy and X-ray crystallography. Complex 9 is thermally unstable and decomposes at room temperature to give the tertiary phosphane [(Me(3)Si)(2)CH](C(6)H(3)-2-OMe-3-Me)P(Me) and an unidentified Ca-containing product. Compounds 5 and 6 also decompose at elevated temperatures to give the corresponding tertiary phosphane [(Me(3)Si)(2)CH](C(6)H(4)-2-OMe)P(Me) and intractable metal-containing products. The decomposition of 5, 6, and 9 suggests that these compounds undergo an intramolecular methyl migration from the O atom in one phosphanide ligand to the P atom of an adjacent phosphanide ligand to give species containing dianionic alkoxo-phosphanide ligands.

Syntheses, Solid-State Structures, and Solution Studies by VT 31P NMR of [Zn{Se2P(OEt)2}2]∞ and [Zn2{Se2P(OiPr)2}4]

Complexes [Zn[Se(2)P(OEt)(2)](2)]( infinity ) (1) and [Zn(2)[Se(2)P(O(i)Pr)(2)](4)] (2) are prepared from the reaction of Zn(ClO(4))(2).6H(2)O and (NH(4))[Se(2)P(OR)(2)] (R = Et and (i)Pr) in a molar ratio of 1:2 in deoxygenated water at room temperature. Positive FAB mass spectra show m/z peaks at 968.8 (Zn(2)L(3)(+)) and 344.8 (ZnL(+)) for 1 and m/z at 1052.8 (Zn(2)L(3)(+)) for 2. (1)H NMR spectra exhibit chemical shifts at delta 1.43 and 4.23 ppm for 1 and 1.41 and 4.87 ppm for 2 due to Et and (i)Pr group of dsep ligands. While the solid-state structure of compound 1 is a one-dimensional polymer via symmetrically bridging dsep ligands, complex 2 in the crystalline state exists as a dimer. In both 1 and 2, zinc atoms are connected by two bridging dsep ligands with an additional chelating ligand at each zinc atom. The dsep ligands exhibit bimetallic biconnective (micro(2), eta(2)) and monometallic biconnective (eta(2)) coordination patterns. Thus, each zinc atom is coordinated by four selenium atoms from two bridging and one chelating dsep ligands and the geometry around zinc is distorted tetrahedral. The Zn-Se distances range between 2.422 and 2.524 A. From variable-temperature (31)P NMR studies it has been found that monomer and dimer of the complex are in equilibrium in solution via exchange of bridging and chelating ligands. However, at temperature above 40 degrees C the complex exists as a monomer and shows a very sharp peak while with lowering of the temperature the percentage of dimer increases gradually at the expense of monomer. Below -90 degrees C the complex exists as a dimer and two peaks are observed with equal intensities which are due to bridging and chelating ligands. (77)Se NMR spectra of both complexes at -30 degrees C exhibit three doublets due to the presence of monomer and dimer in solution.