Steering of Configuration by (2‐Phosphanyl)phenolato Ligands in Trimethylphosphane Iron Complexes

(Diphenylphosphanyl)phenols C₆H₃(1‐OH)(2‐PPh₂)(4‐R¹)(6‐R²), abbreviated as (P^∧OH), oxidatively add to Fe(PMe₃)₄ affording hydridoiron(II) compounds fac‐FeH(P^∧O)(PMe₃)₃ ( 1 : R¹=R²=H; 2 : R¹=Me, R²=H; 3 : R¹=OMe, R²=H; 4 : R¹=Me, R²=CMe₃; 5 : R¹=R²=CMe₃) with high stereoselectivity. (2‐diphenylphosphanyl)thiophenol (P^∧SH) reacts accordingly forming fac‐FeH(P^∧S)(PMe₃)₃ ( 9 ). Complete assignment of ¹H, ¹³C, and ³¹P signals is achieved by 2D heteronuclear shift correlations. 4,6‐Di‐tert‐butyl‐(2‐diphenylphosphanyl)phenol reacts with FeI(Me)(PMe₃)₄ to form FeI(P^∧O)(PMe₃)₂ ( 6 ). 4 , 5 and 9 under 1 bar of CO are converted to monocarbonyl derivatives FeH(P^∧X)(CO)(PMe₃)₂ ( 7 , 8 : X = O; 10 : X = S) which in solution form mixtures of two isomers A and B . 4 and 5 react with their parent phosphanylphenols, respectively, to give diamagnetic complexes Fe(P^∧O)₂(PMe₃) ( 11 , 12 ) which dissociate trimethylphosphane to give paramagnetic compounds Fe(P^∧O)₂. The same phosphanylphenols react with FeCl₃ to afford racemic mixtures of complexes Fe(P^∧O)₃ ( 13 , 14 ). Structural data were also obtained from single crystals of compounds 1 , 5 , and 11 .     

Dampfdruckmessungen und Protonenresonanzuntersuchung an Hydriden der intermetallischen Phasen Ti2(Ni,Co) und Ti2(Ni,Fe)

NMR and hydrogen equilibrium pressure measurements were performed on hydrides of the intermetallic compounds Ti₂(Ni, Co) and Ti₂(Ni, Fe). The following values of enthalpy H and entropy S for the formation of the hydrides of the intermetallic phases Ti₂Co and Ti₂Ni were found: H(Ti₂CoH _y )=–47.6 kJ/mol H₂, H(Ti₂NiH _y )=–53.7 kJ/mol H₂; S(Ti₂CoH _y )=–119.8 J/(K·mol H₂), S(Ti₂NiH _y )=–127.5 J/(K·mol H₂). By substitution of Ni or Co by Fe, the values of H and S of the corresponding quaternary hydrides become less negative. An interpretation of the experimental results is tried by the model ofShaltiel and coworkers.Proton diffusion was investigated in a series of the intermetallic hydrides Ti₂(Ni, Co)H _x and Ti₂(Ni, Fe)H _x . The diffusion rate is lowered by increased Ni/Fe substitution. Substitution of Ni by Co scarcely effects the hopping process. The activation energies were found to be smaller for the Ti₂Ni-hydrides compared with the Ti₂Co-hydrides.

Herrn Prof. Dr.H. Nowotny zum 70. Geburtstag gewidmet.     

Preparation of Hydride‐Ethylene Complexes of Osmium

Ethylene complexes [OsH(η²‐CH₂=CH₂)L₄]Y ( 1 , 2 ) [L = PPh(OEt)₂, P(OEt)₃; Y = OTf, BPh₄] were prepared by reacting the dihydride OsH₂L₄ first with methyl triflate CH₃OTf and then with ethylene (1 atm). Alternatively, the compound [OsH(η²‐CH₂=CH₂){PPh(OEt)₂}₄]OTf was prepared by allowing the dinitrogen derivative [OsH(N₂){PPh(OEt)₂}₄]OTf to react with ethylene. Acrylonitrile CH₂=C(H)CN reacts with OsH(OTf)L₄ [L = P(OEt)₃] to give the complex [OsH{κ¹‐NCC(H)=CH₂}{P(OEt)₃}₄]BPh₄ ( 3 ). The complexes were characterized spectroscopically (IR and ¹H, ¹³C, ³¹P NMR) and by X‐ray crystal structure determination of the [OsH(η²‐CH₂=CH₂){PPh(OEt)₂}₄]BPh₄ derivative.     

Anionic Magnesium and Calcium Hydrides: Transforming CO into Unsaturated Disilyl Ethers

The synthesis, characterisation and reactivity of two isostructural anionic magnesium and calcium complexes is reported. By X-ray and neutron diffraction techniques, the anionic hydrides are shown to exist as dimers, held together by a range of interactions between the two anions and two bridging potassium cations. Unlike the vast proportion of previously reported dimeric group 2 hydrides, which have hydrides that bridge two group 2 centres, here the hydrides are shown to be “terminal”, but stabilised by interactions with the potassium cations. Both anionic hydrides were found to insert and couple CO under mild reaction conditions to give the corresponding group 2 cis-ethenediolate complexes. These cis-ethenediolate complexes were found to undergo salt elimination reactions with silyl chlorides, allowing access to small unsaturated disilyl ethers with a high percentage of their mass originating from the C₁ source CO.     

Abstandsvergleich M–H/M–D aus Röntgen‐ und Neutronenbeugungsdaten am Beispiel von Na3Rh(H/D)6

Comparison of the Distances M–H/M–D from X‐Ray and Powder Neutron Scattering Data on the Example of Na₃Rh(H/D)₆ Mixtures of NaNH₂, NaN₃ and Rh heated to 600 °C in autoclaves for salt melts show no indication of formation of ternary nitrides, but unexpectedly single crystals of a ternary hydride, Na₃RhH₆, were obtained. These crystals were isolated by washing the reaction product with liquid ammonia at room temperature. During this procedure metallic sodium – formed by decomposition of both the amide and the azide at elevated temperatures – is removed. X‐ray diffraction measurements on single crystals of Na₃RhH₆ allowed to even refine the displacement parameters of the hydrogen atoms and to compare the obtained results with data from powder neutron scattering of Na₃RhD₆ published by Bronger, Gehlen and Auffermann [1]. Only little differences are found between the lattice parameters, atomic positions and, noteworthy, the resulting distances Rh–H and Rh–D, respectively.     

Vinamidin‐stabilisierte Alane

Vinamidine Stabilised Alanes The alane complexes (C₅H₇N₂R₂)AlH₂ ( 2 ) (R = Me, ⁱPr, Ph) are obtained from the vinamidines C₅H₈N₂R₂ ( 1 ) and Me₃N · AlH₃ as reactive solids in good yields. Excess hydride reagent affords the formation of perhydrogenated ring systems from which {(C₁₁H₂₄N₂)Al₂H₄}₂ ( 6 ) could be prepared in a preparative scale. The X‐ray structures of (C₅H₇N₂Me₂)AlH₂ ( 2 a ) and (C₅H₇N₂ⁱPr₂)AlH₂ ( 2 b ) exhibit the expected near planar ring geometries. In 6 , two units of (C₁₁H₂₄N₂)Al₂H₄ ( 5 ) are connected via hydrogen bridges to form a central planar Al₂H₂ core.     

Catalytic Enantioselective Reduction of Ketones by a Chiral Gallium Complex and Catecholborane

A catalytically active version of Noyori's famous BINAL reagent Li[AlH(OEt)(BINOL dianion)] is formed by the combination of LiGaH₄, monothiobinaphthol (MTB), and catecholborane. With this mixture unsymmetrical ketones can be reduced in high enantioselectively. Un=unsaturated unit; R=alkyl.     

X-Ray Structural Analysis of a Novel Lithium Hydride/Lithium tert-Butoxide Superaggregate: Li33H17(OtBu)16

Extraordinary solubility in hydrocarbons is exhibited by the novel superaggregate Li₃₃H₁₇(OtBu)₁₆, which crystallizes from photolyzed solutions of lithium tert-butoxide and tert-butyllithium (ROLi:RLi≥7:3). The structure of the compound (the framework of Li, H, and O atoms without tBu groups is shown on the right) resembles a disrupted lithium hydride lattice with an inner hydride-rich core and an outer shell of lipophilic tert-butoxide groups.     

Characterization of a New Tetranuclear Cluster of Palladium, [Pd4(dppm)4(H)]—

The recently discovered and characterized [Pd₄(dppm)₄(H)]²⁺ cluster catalyst ( 1 ; dppm = Ph₂PCH₂PPh₂), slowly evolves in the presence of the reducing tetraphenylborate anion, to generate a new diamagnetic cluster [Pd₄(dppm)₄(H)]⁺ ( 2 ). The evolution of this starting material 1 , has been monitored using NMR (¹H and ³¹P), UV‐vis and ESR spectroscopy. This new 56‐electron Pd cluster has been characterized from X‐ray crystallography, and consists of a cyclic species exhibiting an approximate puckered square structure. The Pd₂ bond distances are 2.7367(10) and 2.7495(11)Å and indicate the presence of weak bonding. The diagonal Pd···Pd separations are 3.646(10) and 3.590(10)Å indicating that the square is relatively symmetric. Such a structure is unprecedented for “Pd_x(dppm)_x” species. Although not formally observed from the X‐ray data, the hydride is assumed to be fluxional as found in 1 . The cyclic voltammogram for 2 exhibits an irreversible reduction wave at —1.65V vs SCE which is greater than that found for 1 , and corroborates the lower oxidation state for Pd (+1/2). The Pd‐H bonding scheme and MO symmetry for a model cluster where the hydride has been placed at the center of the Pd₄ frame, have been addressed qualitatively using the EHMO model. These calculations demonstrate clearly that the Pd‐H bonding is strong.     

用氢化物—原子荧光法测定水处理剂中微量铅

对氢化物－原子荧光法测定水处理剂聚合氯化铝和硫酸铝中铅的测定介质、测定条件及干扰元素进行了探讨,拟定了简便,快速,准确测定两种水处理剂中微量铅的方法。在测定条件下,方法的线性范围为０￣５０ｎｇ·ｍｌ＾－１,检出限为０．４ｎｇ·ｍｌ＾－１,回收率在９０％￣１１０％之间。