Dirhodium(II) Compounds with Bridging Thienylphosphines: Studies on Reversible P,C/P,S Coordination

Monocyclometalated compound [Rh₂{(C₈H₄S)P(C₈H₅S)₂}(CH₃CO₂H)₂(O₂CCH₃)₃] ( 1 a ) and bis‐cyclometalated compound [Rh₂{(C₈H₄S)P(C₈H₅S)₂}₂(CH₃CO₂H)₂(O₂CCH₃)₂] ( 2 a ) have been isolated from the reaction of dirhodium tetraacetate and tris(2‐benzo[b]thienyl)phosphine ( 2 BTP ) using low acidic solutions. By contrast, in pure acetic acid the reaction of Rh₂(O₂CCH₃)₄ with 2 BTP and tris(2‐thienyl)phosphine ( 2 TP ), followed by replacement of the axial acetate ligands by chlorides, led to [Rh₂{(2‐C₈H₅ S )P(2‐C₈H₅S)₂}₂Cl₂(O₂CCH₃)₂] ( 3 b ) and [Rh₂{(2‐C₄H₃ S )P(C₄H₃S)₂}₂Cl₂(O₂CCH₃)₂] ( 5 b ), respectively. These new dirhodium(II) compounds possess equatorial bridging ligands in a phosphorous–sulfur (P,S) coordination mode. The reversible switching between the P,C and P,S bonding mode of the phosphine has been studied in the monocyclometalated [Rh₂{(C₄H₂S)P(C₄H₃S)₂}(CH₃CO₂H)₂(O₂CCH₃)₃] ( 6 a ), which was selectively transformed into compound [Rh₂{(2‐C₄H₃ S )P(C₄H₃S)₂}(CF₃SO₃)(CH₃CO₂H)(O₂CCH₃)₃] ( 7 c ) in triflic acid media. Remarkably, compound 7 c reverts to the starting compound 6 a upon treatment with sodium acetate. Theoretical DFT calculations for both the P,C/P,S rearrangement and the base‐promoted reversion have been performed to explain the experimental findings. Data suggest the P,C/P,S rearrangement occurs by means of a “concerted protonation–demetalation mechanism” followed by η² coordination of the thienyl ring and subsequent isomerization to the S‐η¹‐coordination mode. In the reversion reaction, the base coordinated at the axial position would promote a concerted metalation–deprotonation mechanism.     

Phosphinophosphiniden-Phosphorane tBu2P?P = P(R)tBu2 aus Li(THF)2[η2-(tBu2P)2P] und Alkylhalogeniden

The Phosphinophosphinidene-phosphoranes ^tBu₂P? P = P(R)^tBu₂ from Li(THF)₂[η²-(^tBu₂P)₂P] and Alkyl Halides We report the formation of ^tBu₂P? P = P(R)^tBu₂ a and (^tBu₂)₂PR b (with R = Me, Et, ⁿPr, ⁱPr, ⁿBu, PhCH₂, H₂C = CH? CH₂ and CF₃) reactions of Li(THF)₂[η²-(^tBu₂P)₂P] 2 with MeCl, MeI, EtCl, EtBr, ⁿPrCl, ⁿPrBr, ⁱPrCl, ⁿBuBr, PhCH₂Cl, H₂C = CH? CH₂Cl or CF₃Br. In THF solutions the ylidic compounds a predominate, whereas in pentane the corresponding triphosphanes b are preferrably formed. With ClCH₂? CH = CH₂ only b is produced; CF₃Br however yields both ^tBu₂P? P = P(Br)^tBu₂ and ^tBu₂P? P = P(CF₃)^tBu₂, but no b . The ratio of a:b is influenced by the reaction temperature, too. The compounds ^tBu₂P? P = P(Et)^tBu₂ 4a and (^tBu₂P)₂PEt 4 b , e. g., are produced in a ratio of 4:3 at ?70°C in THF, and 1:1 at 20°C; whereas 1:1 is obtained at ?70°C in pentane, and 1:2 at 20°C. Neither ^tBuCl nor H₂C = CHCl react with 2 . The compounds a decompose thermally or under UV irradiation forming ^tBu₂PR and the cyclophosphanes (^tBu₂P)_nP_n.     

Synthese und Kristallstruktur der Spiro-Verbindung [(i-Pr)2P(S)NSiMe3]2SnCl2

Synthesis and Crystal Structure of the Spirocycle [(i-Pr)₂P(S)NSiMe₃]₂SnCl₂ The reaction of (i-Pr)₂P(S)N(SiMe₃)₂ ( 1 ) with SnCl₄ in 2:1 ratio yields under elimination of ClSiMe₃ the four-membered spirocycle [(i-Pr)₂P(S)NSiMe₃]₂SnCl₂ ( 2 ). The molecular structure of 2 was investigated by an X-ray structure analysis. Compound 2 crystallises in the monoclinic space group P2₁, Z = 2, a = 938.1(1), b = 1 424.1(2), c = 1 207.2(1) pm, β = 110.59(1)°, R = 2.05% for 4 102 reflexions. Compound 2 is a spirocycle with two Sn? N? P? S-rings joined at tin. The two rings are in cis-position.     

Electrodeposition mechanism of Ni?Mo?P alloy in the solution of ammoniac citrate

The induced codeposition mechanism of Mo, P and Ni from the solution of ammoniac citrate was studied by means of steady-state polarization, AC impedance and X-ray Photoelectron Spectroscopy (XPS). The result of electrochemical measurements proved that [NiCit(NHs)₂]- is the electro-active species of nickel, though nickel ions exist mainly as [NiCit(NH₃)₃]^? in ammoniac citrate. XPS experiments proved the existence of tetravalent molybdenum corresponding to MoO₂ on the surface of mme deposits. The intermediate product, MoO₂, WM probably reduced to Mo in the alloy deposit by atomic hydrogen adsorbed on the induced metal nickel. The reduction of H₂PO^?₂ occurs through two distinctive steps with PH₃ an an intermediate, which subsequently reacts with atomic hydrogen to form P in the alloy deposit. The electrodeposition mechanism was proposed in this paper.     

[iPr2P]2P?SiMe3 und [iPr2P]2PLi – Synthese und Reaktionen Struktur des [iPr2P]2P?P[PiPr2]2

[iPr₂P]₂P? SiMe₃ and [iPr₂P]₂PLi – Synthesis and Reactions Structure of [iPr₂P]₂P? P[PiPr₂]₂ [iPr₂P]₂P? SiMe₃ 1 and [iPr₂P]₂PLi 2 were prepared to investigate the influence of the bulky alkyl groups on formation and properties of the ylides R₂P? P?P(X)R₂ (R = iPr, tBu; X = Br, Me) in reactions of 1 with CBr₄ and of 2 with 1,2-dibromoethane or MeCl, resp. Compared to the iPr groups the tBu groups favour the formation of ylides. With CBr₄ 1 forms iPr₂P? P?P(Br)iPr₂ 5 just as a minor product which decomposes already below ?30°C. With 1,2-dibromoethane 2 yields only traces of 5 but [iPr₂P]P? P[P(iPr)₂]₂ 7 as main product. With MeCl 2 gives iPrP? P?P(Me)iPr₂ 9 and [iPr₂P]₂PMe 10 in a molar ratio of 1:1. 9 is considerably more stable than 5. 7 crystallizes triclinic in the space group P1 (No. 2) with a = 10.813 Å, b = 11.967 Å, c = 15.362 Å, α = 67.90°, β = 71.36°, γ = 64.11° and two formula units in the unit cell.     

Optimization of electroless Ni?P coatings based on multiple roughness characteristics

This paper presents an experimental study of roughness characteristics of electroless Ni? P coatings. Optimization of coating process parameters is done with multiple surface roughness characteristics based on Taguchi method coupled with grey relational analysis. Experiments are carried out by utilizing the combination of process parameters based on L₂₇ Taguchi orthogonal design with three process parameters, viz. bath temperature, concentration of nickel source solution and concentration of reducing agent. Results show that concentration of the reducing agent and its interaction with concentration of the nickel source solution have significant influence in controlling the roughness characteristics of electroless Ni? P coating. Grey‐based Taguchi method is found to optimize the coating parameters fairly well. The surface morphology and composition of coatings are also studied with the help of scanning electron microscopy, energy dispersed X‐ray analysis and X‐ray diffraction analysis. No significant change in nickel and phosphorous content of coatings occurs with annealing. The Ni? P deposit is nanocrystalline in the as‐plated condition, and upon heat treatment at 400 °C it produces Ni₅P₂, Ni₂P, and NiP₂ as major compound constituents. Copyright © 2008 John Wiley & Sons, Ltd.     

Die Kristallstruktur des Tetrakis(di-tert.-butylphosphino)diphosphans. [(tBu)2P]2P?P[P(tBu)2]2

The Crystal Structure of Tetrakis(di-tert.-butylphosphino)diphosphane [(tBu)₂P]₂P? P[P(tBu)₂]₂ [(tBu)₂P]₂P? P[P(tBu)₂]₂ 1 obtained at ?20°C from a solution of (tBu)₂P? P=P(Br)tBu₂ forms yellow crystals (regular hexagons). 1 crystallizes monoclinic in the space group C2/c with a = 2145.6pm, b = 1137pm, c = 1696.1pm, β = 110.075° and Z = 4 formula units in the elementary cell. Due to high steric load the bond angles at the tertiary P atoms with δ = 115.7° are significantly larger than those at the primary P atoms with δ = 108.6°.     

Reaktionen des tBu(Me3Si)P?P(Li)?P(tBu)2 mit CH3Cl und 1,2-Dibromethan

Reactions of tBu(Me₃Si)P? P(Li)? P(tBu)₂ with CH₃Cl and 1,2-Dibromoethane tBu(Me₃Si)P? P(Li)? P(tBu)₂ · 0.95 THF 1 with CH₃Cl (?70°C) yields tBu(Me₃Si)P? P = P(Me)(tBu)₂ 2 at ?70°C, with 1,2-Dibromoethane tBu(Me₃Si)P? PBr? P(tBu)₂ 3 (main product) and tBu(Me₃Si)P? P?P(Br)tBu₂ 4. 3 eliminates Me₃SiBr yielding the cyclotetraphosphane {tBuP? P[P(tBu)₂]}₂ 5 .     

A Panel of Cytochrome P450 BM3 Variants to Produce Drug Metabolites and Diversify Lead Compounds

Herein we demonstrate that a small panel of variants of cytochrome P450 BM3 from Bacillus megaterium covers the breadth of reactivity of human P450s by producing 12 of 13 mammalian metabolites for two marketed drugs, verapamil and astemizole, and one research compound. The most active enzymes support preparation of individual metabolites for preclinical bioactivity and toxicology evaluations. Underscoring their potential utility in drug lead diversification, engineered P450 BM3 variants also produce novel metabolites by catalyzing reactions at carbon centers beyond those targeted by animal and human P450s. Production of a specific metabolite can be improved by directed evolution of the enzyme catalyst. Some variants are more active on the more hydrophobic parent drug than on its metabolites, which limits production of multiply‐hydroxylated species, a preference that appears to depend on the evolutionary history of the P450 variant.     

Die Bildung von [(tBu)2P]2P?P[P(tBu)2]2 aus LiP[P(tBu)2]2 und 1,2-Dibromethan. Die Thermolyse von tBu2P?PP(Br)tBu2

[(tBu)₂P]₂P? P[P(tBu)₂]₂ from LiP[P(tBu)₂]₂ and 1,2-Dibromomethane. Pyrolysis of tBu₂P? P?P(Br)tBu₂ All products of the reaction of [tBu₂P]₂PLi 1 with 1,2-dibromoethane 2 were investigated. Already at ?70°C tBu₂P? P?P(Br)tBu₂ 3 as main product and [tBu₂P]₂PBr 4 are formed. Only with an excess of 1 also [tBu₂P]P? P[P(tBu)₂]₂ 5 is obtained. Warming of a pure solution of 3 in toluene from ?70°C to ?30°C leads to 4 , and at 20°C tBu₂PBr and the cyclophosphanes P₄[P(tBu)₂]₄ and P₃[P(tBu)₂]₃ are observed. 5 does not result from 3 , it's rather a byproduct from the reaction of 1 with 4 . Also the ylide 3 and 1 yields 5 .     

Zur Bildung und Struktur der Phosphinophosphiniden-phosphorane tBu2P?PP(Me)tBu2 1, tBu(Me3Si)P?PP(Me)tBu2 2 und tBu2P?PP(Br)tBu2 3

Synthesis and Structure of Phosphinophosphinidene-phosphoranes tBu₂P? P?P(Me)tBu₂ 1, tBu(Me₃Si)P? P?P(Me)tBu₂ 2, and tBu₂P? P?P(Br)tBu₂ 3 A new method for the synthesis of 1 and 2 (Formulae see ?Inhaltsübersicht”?) is reported based on the reaction of 5 with substitution reagents (Me₂SO₄ or CH₃Cl). The results of the X-ray structure determination of 1 and 2 are given and compared with those of 3 . While in 3 one P? P distance corresponds to a double bond and the other P? P distance to a single bond (difference 12.5 pm) the differences of the P? P distances in 1 and 2 are much smaller: 5.28 pm in 1 , 4.68 pm in 2 . Both 1 and 2 crystallize monoclinic in the space group P2₁/n (Z = 4). 2 additionally contains two disordered molecules of the solvent pentane in the unit cell. Parameters of 1 : a = 884.32(8) pm, b = 1 924.67(25) pm, c = 1 277.07(13) pm, β = 100.816(8)°, and of 2 : a = 1 101.93(12) pm, b = 1 712.46(18) pm, c = 1 395.81(12) pm, β = 111.159(7)°, all data collected at 143 K. The skeleton of the three P atoms is bent (PPP angle 100.95° for 1 , 100.29° for 2 and 105.77° for 3 ). Ab initio SCF calculations are used to discuss the bonding situation in the molecular skeleton of the three P atoms of 1 and 3 . The results show a significant contribution of the ionic structure R₂P? P(^?)? P(⁺)(X)R₂. The structure with (partially) charged P atoms is stabilized by bulky polarizable groups R (as tBu) as compared to the fully covalent structure R₂P? P(X)? PR₂.     

tBu2P?PP(X)tBu2-Ylide (X = Cl,Br, I) durch Halogenierung von [tBu2P]2P?SiMe3

tBu₂P? P?P(X)tBu₂ Ylides (X = Cl, Br, I) by Halogenation of [tBu₂P]₂P? SiMe₃ [tBu₂P]₂P? SiMe₃ 1 with halogenating agents as Br₂, I₂, Br-succinimide, CCl₄, CBr₄, CI₄ or C₂Cl₆ via cleavage of the Si? P bond in 1 produces the ylides tBu₂P? P?P(X)tBu₂ (X = Cl, Br, I). This proceeds independent from the formerly known pathway – [tBu₂P]₂PLi + 1,2-dibromoethane – and shows that the Li-phosphide must not be present as a necessary requirement for the formation of ylides.     

对氯硝基苯吸附在银纳米粒子上的偶联反应

表面增强拉曼光谱(SERS)具有极高的检测灵敏度, 通过检测吸附分子的SERS信号, 可以获得表面吸附分子的结构以及可能发生的反应. 在拉曼激发光源的辐射下, 在碱性溶液中, 银纳米粒子表面吸附的对氯硝基苯(PCNB)的SERS光谱与其固体的常规拉曼光谱相比, 出现异常SERS谱. 通过采用密度泛函理论(DFT)计算, 对PCNB以及可能的偶联产物p,p''-二氯偶氮苯(DCAB)进行理论分析以及谱峰归属, 发现这些异常峰来自其偶联产物DCAB的偶氮C－N＝N－C基团的基频振动.     

Komplexchemie P-reicher Phosphane und Silylphosphane. XIV. Phosphinophosphiniden tBu2P?P als Ligand in den Pt-Komplexen [η2-{tBu2P?P}Pt(PPh3)2] und [η2-{tBu2P?P}Pt(PEtPh2)2]

Coordination Chemistry of P-rich Phosphanes and Silylphasphanes. XIV. The Phosphinophosphinidene ^tBu₂P? P as a Ligand in the Pt Complexes [η²-{^tBu₂P? P}Pt(PPh₃)₂] and [η²-{^tBu₂P? P}Pt(PEtPh₂)₂] [η²-{^tBu₂P? P}Pt(PPh₃)₂ 1 and [η²-{^tBu₂P? P}Pt(PEtPh₂)₂] 2 are the first complex compounds of ^tBu₂P? P 5 . They are formed in the reaction of ^tBu₂P? P ? P(Me)^tBu₂ 3 with [η²-{H₂C ? CH₂}Pt(PPh₃)₂] 6 or [η²-{H₂C ? CH₂}Pt(PEtPh₂)₂] 7 , respectively. Compound 1 is less stable than 2 and reacts on to [η²-{^tBu₂P? P} Pt(PPh₃)(P^tBu₂Me)] 10 with the coincidently formed ^tBu₂PMe. The molecular structures of 1 and 2 were derived from their ¹H and ³¹P-NMR spectra, 2 was additionally characterized by a X ray structure determination. 2 crystallizes in the monoclinic space group P2₁/n with a = 1222.36(7) pm, b = 1770.7(1) pm, c = 1729.7(1) pm, β = 108.653(6)°.     

The Reaction Activity of Aromatic Carbonyl Compounds with Diphenylphosphine Oxide Studied by 31P NMR

Abstract

A series of α-hydroxyphosphine oxides were prepared by the reactions of diphenylphosphine oxide and aromatic carbonyl compounds and characterized by ¹H NMR, ¹³C NMR, ³¹P NMR, FT-IR, ESI-MS, and HR-MS spectra. The reaction rates and experimental conditions of aromatic aldehydes and aromatic ketones were obviously different due to the activity of their carbonyls. The different substituents of the aromatic aldehydes affected the reaction rate too, and the quantitative reactivity of their substituent conformed to the Hammett equation. The results were confirmed by ³¹P NMR spectroscopy.