1,3-Diphosphacyclobutene Cobalt Complexes

The synthesis and characterization of rare 1,3-diphosphacyclobutene transition-metal complexes is described. Reactions of the cobalt-hydride complex [Co(P₂C₂tBu₂)₂H] ( G ) with nBuLi, tBuLi, or PhLi afforded [Li(solv)_x{Co(η³-P₂C₂tBu₂HR)(η⁴-P₂C₂tBu₂)}] ( 1 : R=nBu, (solv)_x=(Et₂O)₂; 2 : R=tBu, (solv)_x=(thf)₂; 3 : R=Ph, (solv)_x=(Et₂O)(thf)₂), with an η³-coordinated 1,3-diphosphacyclobutene ligand as a result of organyl-anion attack at one of the phosphorus atoms of the bis(1,3-diphosphacyclobutadiene) backbone. In contrast to the reactions with PhLi, the aryl-magnesium compounds p-tolyl magnesium chloride and p-fluorophenyl magnesium bromide deprotonate [Co(P₂C₂tBu₂)₂H] to give the magnesium salt [Mg(MeCN)₆][Co(η⁴-P₂C₂tBu₂)₂]₂ ( 4 ), which contains a bis(1,3-diphosphacyclobutadiene)-cobaltate anion. The [Co(η⁴-P₂C₂tBu₂)₂]⁻ anions are well separated from the octahedral [Mg(MeCN)₆]²⁺ cation in the molecular structure of 4 . Compound 1 reacts with Me₃SiCl to give neutral [Co(η³-P₂C₂tBu₂HnBu)(η⁴-P₂C₂tBu₂SiMe₃)] ( 5 , 52 % yield) with an SiMe₃ group attached to one of the P atoms of the previously unfunctionalized backbone.     

Organometallic complexes in ascidian embryonic development: II. Effects on different stages and larvae

The effects of the organometallic compounds Bu₂Sn-D -(?;)sorbitol, Bu₂Sn-D -(+)glucose, Bu₂Sn-D -(?)fructose and Bu₂Sn-D -(+)glyceraldehyde were tested in vivo on different stages of Ascidian development, larval movement and metamorphosis. Organotin(IV) complexes are organometallic compounds widely used as industrial biocides, antifouling agents and agricultural fungicides and are toxic to a range of organisms. Two-cell stage embryos, if incubated for one hour in the organotin (IV) solutions, stopped the cleavage, which was restored when they were transferred into normal sea water. The gastrula stage was seriously affected in 10^?4mol dm^?3 solutions of the above-mentioned complexes: 85% of the embryos were anomalous neurulae with open neural folds, 5% were twisted larvae. The gastrulae, when incubated for 1 h in 10^?5mol dm^?3 solutions, developed twisted larvae in ovular envelopes and immobile larvae with twisted tails. Larvae treated with 10^?4mol dm^?3 and 10^?5 mol dm^?3 Bu₂Sn-D -(?)sorbitol, Bu₂Sn-D -(+)glucose and Bu₂Sn-D -(+)glyceraldehyde solutions stopped swimming, did not metamorphose and afterwards underwent cytolysis. An initial hyperactivity of circular movements, followed by immobility, was observed in the larvae incubated in Bu₂Sn-D -(?;)fructose.     

Reaktionen des [η2-{P–PtBu2}Pt(PPh3)2] und [η2-{P–PtBu2}Pt(dppe)] mit Metallcarbonylen. Bildung von [η2-{(CO)5M · PPtBu2}Pt(PPh3)2] (M = Cr,W) und [η2-{(CO)5Cr · PPtBu2}Pt(dppe)]

Coordination Chemistry of P-rich Phosphanes and Silylphosphanes. XVI [1] Reactions of [g²-{P–P^tBu₂}Pt(PPh₃)₂] and [g²-{P–P^tBu₂}Pt(dppe)] with Metal Carbonyls. Formation of [g²-{(CO)₅M · PP^tBu₂}Pt(PPh₃)₂] (M = Cr, W) and [g²-{(CO)₅Cr · PP^tBu₂}Pt(dppe)] [η²-{P–P^tBu₂}Pt(PPh₃)₂] 4 reacts with M(CO)₅ · THF (M = Cr, W) by adding the M(CO)₅ group to the phosphinophosphinidene ligand yielding [η²-{(CO)₅Cr · PP^tBu₂}Pt(PPh₃)₂] 1 , or [η²-{(CO)₅W · PP^tBu₂}Pt(PPh₃)₂] 2 , respectively. Similarly, [η²-{P–P^tBu₂}Pt(dppe)] 5 yields [η²-{(CO)₅Cr · PP^tBu₂}Pt(dppe)] 3 . Compounds 1 , 2 and 3 are characterized by their ¹H- and ³¹P-NMR spectra, for 2 and 3 also crystal structure determinations were performed. 2 crystallizes in the monoclinic space group P2₁/n (no. 14) with a = 1422.7(1) pm, b = 1509.3(1) pm, c = 2262.4(2) pm, β = 103.669(9)°. 3 crystallizes in the triclinic space group P1 (no. 2) with a = 1064.55(9) pm, b = 1149.9(1) pm, c = 1693.2(1) pm, α = 88.020(8)°, β = 72.524(7)°, γ = 85.850(8)°.     

Bildung und Struktur des iso-Tetraphosphans P(PtBu2)3: ein Molekül mit einem planaren,dreibindigen P-Atom

Formation and Structure of the iso -Tetraphosphane P(P^tBu₂)₃: a Molecule with a Planar Three-coordinated P Atom The iso-tetraphosphane P(P^tBu₂)₃ ( 1 ) was obtained by irradiating ^tBu₂P–P=P(Me)^tBu₂ ( 3 ). 1 forms hexagonal crystals (space group P6₃/m) with a = 1005,63(8), c = 1621,4(2) pm, Z = 2. The P(P^tBu₂)₃ molecules are arranged in a hexagonally close packed lattice. The four P atoms in each molecule are coplanar with P–P bond distances 219.08(4) pm and P–P–P angles 120°. The observed planar geometry is in accordance with ab initio calculations.     

Reactions of tBu2P–PLi–PtBu2 with [(Et3P)2MCl2] (M = Ni,Pd, Pt). Synthesis and Properties of [(1,2‐η‐tBu2P=P–PtBu2)M(PEt3)Cl] (M=Ni,Pd)

^tBu₂P–PLi–P^tBu₂·2THF reacts with [cis‐(Et₃P)₂MCl₂] (M = Ni, Pd) yielding [(1,2‐η‐^tBu₂P=P–P^tBu₂)Ni(PEt₃)Cl] and [(1,2‐η‐^tBu₂P=P–P^tBu2)Pd(PEt₃)Cl], respectively. ^tBu₂P– PLi–P^tBu₂ undergoes an oxidation process and the ^tBu₂P–P–P^tBu₂ ligand adopts in the products the structure of a side‐on bonded 1,1‐di‐tert‐butyl‐2‐(di‐tert‐butylphosphino)diphosphenium cation with a short P–P bond. Surprisingly, the reaction of ^tBu₂P–PLi–P^tBu₂·2THF with [cis‐(Et₃P)₂PtCl₂] does not yield [(1,2‐η‐^tBu₂P=P–P^tBu₂)Pt(PEt₃)Cl].     

Kristallstrukturen,spektroskopische Charakterisierung und Normalkoordinatenanalyse von (n‐Bu4N)2[M(ECN)4] (M = Pd,Pt; E = S,Se)

Crystal Structures, Spectroscopic Analysis, and Normal Coordinate Analysis of ( n ‐Bu₄N)₂[M(ECN)₄] (M = Pd, Pt; E = S, Se) The reaction of (NH₄)₂[PdCl₄] or K₂[PtCl₄] with KSCN or KSeCN in aqueous solutions yields the complex anions [Pd(SCN)₄]^2–, [Pt(SCN)₄]^2– and [Pt(SeCN)₄]^2–, which are converted into (n‐Bu₄N) salts with (n‐Bu₄N)HSO₄. (n‐Bu₄N)₂[Pd(SeCN)₄] is formed by treatment of (n‐Bu₄N)₂[PdCl₄] with (n‐Bu₄N)SeCN in acetone. X‐ray structure determinations on single crystals of (n‐Bu₄N)₂[Pd(SCN)₄] (monoclinic, space group P2₁/n, a = 13.088(3), b = 12.481(2), c = 13.574(3) Å, β = 91.494(15)°, Z = 2), (n‐Bu₄N)₂[Pd(SeCN)₄] (monoclinic, space group P2₁/n, a = 13.171(2), b = 12.644(2), c = 13.560(2) Å, β = 91.430(11)°, Z = 2) and (n‐Bu₄N)₂[Pt(SeCN)₄] (monoclinic, space group P2₁/n, a = 13.167(2), b = 12.641(1), c = 13.563(2) Å, β = 91.516(18)°, Z = 2) reveal, that the compounds crystallize isotypically and the complex anions are centrosymmetric and approximate planar. In the Raman spectra the metal ligand stretching modes of (n‐Bu₄N)₂[Pd(SCN)₄] ( 1 ) and (n‐Bu₄N)₂[Pt(SCN)₄] ( 3 ) are observed in the range of 260–303 cm^–1 and of (n‐Bu₄N)₂[Pd(SeCN)₄] ( 2 ) and (n‐Bu₄N)₂[Pt(SeCN)₄] ( 4 ) in the range of 171–195 cm^–1. The IR and Raman spectra are assigned by normal coordinate analysis using the molecular parameters of the X‐ray determination. The valence force constants are f_d(PdS) = 1.17, f_d(PdSe) = 1.17, f_d(PtS) = 1.44 and f_d(PtSe) = 1.42 mdyn/Å. The ⁷⁷Se NMR resonances are 23 for 2 , –3 for 4 and the ¹⁹⁵Pt NMR resonances 549 for 3 and 130 ppm for 4 .     

Synthesis and Chloride Affinity of Sterically Demanding Ditopic Lithium Bis(pyrazol‐1‐yl)borates

The synthesis and full characterization of the sterically demanding ditopic lithium bis(pyrazol‐1‐yl)borates Li₂[p‐C₆H₄(B(Ph)pz^R₂)₂] is reported (pz^R = 3‐phenylpyrazol‐1‐yl ( 3 ^Ph), 3‐t‐butylpyrazol‐1‐yl ( 3 ^tBu)). Compound 3 ^Ph crystallizes from THF as THF‐adduct 3 ^Ph(THF)₄ which features a straight conformation with a long Li···Li distance of 12.68(1) Å. Compound 3 ^tBu was found to function as efficient and selective scavenger of chloride ions. In the presence of LiCl it forms anionic complexes [ 3 ^tBuCl]⁻ with a central Li‐Cl‐Li core (Li···Li = 3.75(1) Å).     

Structural features of the formation of La1?xCaxFeO3?δ (0 ≤x ≤ 0.7) hetero valent solid solutions

A synthesis method with the use of polymer-salt compositions (calcination temperature 800°C) provides the preparation of various solid solutions of a La_1−x Ca _x FeO_3−δ series in the 0≤ x≤ 0.7 range, which belong to the perovskite structure type. A morphotropic phase transition occurs from the orthorhombic perovskite modification (0≤ x ≤ 0.4) to the cubic one (0.5 ≤ x≤ 0.7). A growing number of microdistortions in the perovskite structure and the formation of a microblock structure in the morphotropic phase transition region are observed with increasing degree of calcium substitution for lanthanum. Calcination of solid solutions with x = 0.6 and 0.7 at temperatures above 1000°C in the air or under conditions of reduced oxygen partial pressure (laboratory vacuum of 10⁻³ Torr) results in the formation of a nanostructured state with coherently grown blocks of perovskite and Grenier phase, which is due to irreversible oxygen loss.     

Heterodinukleare Komplexe: Synthese und Kristallstrukturen von [RuRh(μ‐CO)(CO)4(μ‐PtBu2)(tBu2PH)], [RuRh(μ‐CO)(CO)3(μ‐PtBu2)(μ‐Ph2PCH2PPh2)] und [CoRh(CO)4(μ‐H)(μ‐PtBu2)(tBu2PH)]

Heterobinuclear Complexes: Synthesis and X‐ray Crystal Structures of [RuRh(μ‐CO)(CO)₄(μ‐P^tBu₂)(^tBu₂PH)], [RuRh(μ‐CO)(CO)₃(μ‐P^tBu₂)(μ‐Ph₂PCH₂PPh₂)], and [CoRh(CO)₄(μ‐H)(μ‐P^tBu₂)(^tBu₂PH)] [Ru₃Rh(CO)₇(μ₃‐H)(μ‐P^tBu₂)₂(^tBu₂PH)(μ‐Cl)₂] ( 2 ) yields by cluster degradation under CO pressure as main product the heterobinuclear complex [RuRh(μ‐CO)(CO)₄(μ‐P^tBu₂)(^tBu₂PH)] ( 4 ). The compound crystallizes in the orthorhombic space group Pcab with a = 15.6802(15), b = 28.953(3), c = 11.8419(19) Å and V = 5376.2(11) ų. The reaction of 4 with dppm (Ph₂PCH₂PPh₂) in THF at room temperature affords in good yields [RuRh(μ‐CO)(CO)₃(μ‐P^tBu₂)(μ‐dppm)] ( 7 ). 7 crystallizes in the triclinic space group P 1 with a = 9.7503(19), b = 13.399(3), c = 15.823(3) Å and V = 1854.6 ų. Moreover single crystals of [CoRh(CO)₄(μ‐H)(μ‐P^tBu₂)(^tBu₂PH)] ( 9 ) could be obtained and the single‐crystal X‐ray structure analysis revealed that 9 crystallizes in the monoclinic space group P2₁/a with a = 11.611(2), b = 13.333(2), c = 18.186(3) Å and V = 2693.0(8) ų.     

FT-EPR Spectroscopic Study of Silicophosphate Glasses Derived from Gels

(100-x) mole% SiO₂-x mole% P₂O₅-glasses withx=1–9 have been prepared by the sol-gel process using tetraethylorthosilicate and triethylphosphate as precursors. The gels were fired at various temperatures up to 950°C and then exposed to γ-ray irradiation to induce paramagnetic centers. CW-EPR and FT-EPR Spectroscopies were employed at temperatures between 4 and 300 K in order to determine the resulting structures. The dried gels exhibited four types of O ₂ ⁻ -ions trapped in pores of different sizes. The gels fired atT=670°C exhibited theE’ ₁-center and non-bridging oxygen as a results of the fracture of the Si-O-Si bonds. At higher temperatures, the spectra of the POHC, POHC ^b ,E’, and CH ₃ ⁻ -centers have been detected that are a function ofx andT.     

Electric properties of solid solutions based on strontium tantalate with perovskite-type structure. Protonic conductivity

Conductivity of the Sr_{6 − 2x} Ta_{2 + 2x} O_{11 + 3x} (0 ≤ x ≤ 0.33) solid solutions with the cryolite structure was studied in the atmosphere with a high content of water vapors under temperature and oxygen activity variation in the gas phase. Appearance of the protonic conductivity component was proved at the temperatures below 700°C. It was found that protonic conductivity increases at a decrease in parameter x in the composition series, which is due to an increase of both the concentration of protonic defects formed in the structure and of their mobility. In the case of compositions with x < 0.15 at the temperatures below 550°C, the protonic transport becomes predominant.     

[Co4P2(PtBu2)2(CO)8] und [{Co(CO)3}2P4tBu4] aus Co2(CO)8 und tBu2P–P=P(Me)tBu2

Coordination Chemistry of P‐rich Phosphanes and Silylphosphanes. XIX. [Co₄P₂(P^tBu₂)₂(CO)₈] and [{Co(CO)₃}₂P₄^tBu₄] from Co₂(CO)₈ and ^tBu₂P–P=P(Me)^tBu₂ Co₂(CO)₈ reacts with ^tBu₂P–P=P(Me)^tBu₂ yielding the compounds [Co₄P₂(P^tBu₂)₂(CO)₈] ( 1 ) and [{η^2tBu₂P=P–P=P^tBu₂}{Co(CO)₃}₂] ( 2 a ) cis, ( 2 b ) trans. In 1 , four Co and two P atoms form a tetragonal bipyramid, in which two adjacent Co atoms are μ₂‐bridged by ^tBu₂P groups. Additionally, two CO groups are linked to each Co atom. In 2 a and 2 b , each of the Co(CO)₃ units is η²‐coordinated to the terminal P₂ units resulting in the cis‐ and trans‐configurations 2 a and 2 b . 1 crystallizes in the orthorhombic space group Pnnm (No. 58) with a = 879,41(5), b = 1199,11(8), c = 1773,65(11) pm. 2 a crystallizes in the monoclinic space group P2₁/n (No. 14) with a = 875,97(5), b = 1625,36(11), c = 2117,86(12) pm, β = 91,714(7)°. 2 b crystallizes in the triclinic space group P 1 (No. 2) with a = 812,00(10), b = 843,40(10), c = 1179,3(2) pm, α = 100,92(2)°, β = 102,31(2)°, γ = 102,25(2)°.     

Manganese-Mediated Formic Acid Dehydrogenation

A robust and rapid manganese formic acid (FA) dehydrogenation catalyst is reported. The manganese is supported by the recently developed, hybrid backbone chelate ligand ^tBuPNNOP (^tBuPNNOP=2,6-(di-tert-butylphosphinito)(di-tert-butylphosphinamine)pyridine) ( 1 ) and the catalyst is readily prepared with MnBrCO₅ to form [(^tBuPNNOP)Mn(CO)₂][Br] ( 2 ). Dehydrohalogenation of 2 generated the neutral five coordinate complex (^tBuPNNOP)Mn(CO)₂ ( 3 ). Dehydrogenation of FA by 2 and 3 was found to be highly efficient, exhibiting turnover frequencies (TOFs) exceeding 8500 h⁻¹, rivaling many noble metal systems. The parent chelate, ^tBuPONOP (^tBuPONOP=2,6-bis(di-tert-butylphosphinito)pyridine) or ^tBuPNNNP (^tBuPNNNP=2,6-bis (di-tert-butylphosphinamine)pyridine), coordination complexes of Mn were synthesized, respectively affording [(^tBuPONOP)Mn(CO)₂][Br] ( 4 ) and [(^tBuPNNNP)Mn(CO)₂][Br] ( 5 ). FA dehydrogenation with the hybrid-ligand supported 2 exhibits superior catalysis to 4 and 5 .     

Two Rare-Earth Molecular Ferroelectrics with High Curie Temperatures,Large Spontaneous Polarization,Switchable Second Harmonic Generation Effects,and Strong Photoluminescence

Smart multifunctional molecular ferroelectrics bearing high Curie temperatures and diverse excellent physical properties, such as second harmonic generation (SHG) responses, luminescence, and semiconductivity, among others, have significant applications but have seldom been documented. Herein, the rare-earth metals Nd and Pr are introduced into a simple molecular system (nBu₄N )₃[M(NO₃)_x(SCN)_y] (nBu₄N₌tetrabutyl ammonium, M=rare-earth metal, nBu=CH₃CH₂CH₂CH₂), and two new multifunctional molecular ferroelectrics are obtained: (nBu₄N )₃[Nd(NO₃)₄(SCN)₂] ( 1 ) and (nBu₄N )₃[Pr(NO₃)₄(SCN)₂] ( 2 ). Their distinct heat and dielectric anomaly dependence on temperature verifies that compounds 1 and 2 experience high-temperature para-ferroelectric phase transitions at 408 and 413 K, respectively. Strikingly, both molecular ferroelectrics possess large spontaneous polarization with P_s values of 9.05 and 8.50 μC cm⁻², respectively, and are further characterized by the appearance of multiple intersecting non-180° domains and polarization switching behavior. In particular, compounds 1 and 2 show good stability with only a small decrease in SHG intensity after switching cycles, suggesting that they have great potential for application in nonlinear optical (NLO) switches. Simultaneously, the rare-earth compounds 1 and 2 present bright yellow–red and bright green fluorescence, respectively, at room temperature.     

Ionic mobility in β-PbF<Subscript>2</Subscript> doped by yttrium and lanthanum fluorides

NMR (¹⁹F, ²⁰⁷Pb) and impedance spectroscopy methods are used to investigate the ionic mobility and conductivity in solid solutions of (1 ? x)PbF₂ ? xMF₃ (where M is Y³⁺ and La³⁺) at 0.05 ≤ x ≤ 0.1. The factors determining the form of ionic movement in these systems and its energy in a range of temperatures from 170 K to 500 K are considered and analyzed. It is found that the solid solutions studied can be related to the class of superionic conductors: their σ value is 2·10^?3 ? 5·10^?3 S/cm at temperatures above 470 K, and the activation energy does not exceed 0.52–0.58 eV.     

Host/Guest Simulation of Fluorescent Probes Adsorbed into Low‐Density Polyethylene, 1. Excimer Formation of 1,3‐Di(1‐pyrenyl)propane

Molecular dynamics and Rotational Isomer State/Monte Carlo techniques with a Dreiding 1.01 Force Field are employed to study the excimer formation of isolated 1,3‐di(1‐pyrenyl)propane and the probe adsorbed into a low‐density polyethylene (LDPE) matrix model. The probability of formation of each molecular conformer at several temperatures was calculated using these theoretical techniques. Conformational statistical analysis of the four torsion angles (ϕ₁, ϕ₂, θ₁, θ₂) of Py3MPy showed that the angles —C—C^ar— (ϕ₁, ϕ₂) present two states c ^± = ±90°; and the angles —C—C— (θ₁, θ₂), the three trans states = 180°, g ^± = ±60°. The correlation of θ₁–θ₂ torsion angles showed that the most probable pairs were g⁺g^– and g^–g⁺ for the excimer‐like specimens, although these angles are distorted because of interactions with the polymer matrix. The temperature dependence of the excimer‐formation probability revealed that this process was thermodynamically controlled in the isolated case. When the probe was adsorbed into the LDPE matrix, the excimer formation process was reversed at T = 375 K. At T >  375 K, the behavior was similar to the isolated case but, at T < 375 K, excimer formation probability increased with temperature as found experimentally by steady‐state fluorescence spectroscopy. This temperature was coincident with the onset of the LDPE melting process, determined experimentally by thermal analysis.     

Lanthanide(II) Complexes of the Dihydrotriazinido Ligand [N{C(Ph)=N}2C(tBu)Ph]−

The potassium dihydrotriazinide K(L^Ph,tBu) ( 1 ) was obtained by a metal exchange route from [Li(L^Ph,tBu)(THF)₃] and KOtBu (L^Ph,tBu = [N{C(Ph)=N}₂C(tBu)Ph]). Reaction of 1 with 1 or 0.5 equivalents of SmI₂(thf)₂ yielded the monosubstituted Sm^II complex [Sm(L^Ph,tBu)I(THF)₄] ( 2 ) or the disubstituted [Sm(L^Ph,tBu)₂(THF)₂] ( 3 ), respectively. Attempted synthesis of a heteroleptic Sm^II amido‐alkyl complex by the reaction of 2 with KCH₂Ph produced compound 3 due to ligand redistribution. The Yb^II bis(dihydrotriazinide) [Yb(L^Ph,tBu)₂(THF)₂] ( 4 ) was isolated from the 1:1 reaction of YbI₂(THF)₂ and 1 . Molecular structures of the crystalline compounds 2 , 3· 2C₆H₆ and 4· PhMe were determined by X‐ray crystallography.     

Tris(tert-butyl)phosphine selenide,the missing link in tris(tert-butyl)­phosphine chalcogenide structures tBu3P=X (X = O,S, Se,Te)

In tris(tert-butyl)­phosphine selenide, C₁₂H₂₇PSe, all the methyl ligands are disordered over two sites in the ratio 70/30. The mol­ecule displays crystallographic C₃ symmetry. The bond angles at the P atom are distorted tetrahedral [C—P—C 110.02 (5)° and Se=P—C 108.91 (5)°]. The P—C and P=Se bond lengths are 1.908 (1) and 2.1326 (6) Å, respectively. A comparison of the structural data of the complete series of tris(tert-butyl)­phosphine chalcogenides (^tBu₃PO, ^tBu₃PS, ^tBu₃PSe and ^tBu₃PTe) with the corresponding data of other phosphine chalcogenides substituted by smaller organic groups shows the great influence of the bulky tert-butyl ligands.     

Synthesis,characterization and in-vitro antitumour activity of dibutyltin carboxylates involving the perfluorophenyl moiety: Crystal structure of the dimeric bis[(4-fluoro- and pentafluoro-benzoato)di-n-butyltin] oxides

Crystal structure determinations of {[(F₅C₆COO)Bu₂Sn]₂O}₂ and {[(4-F-C₆H₄COO)-Bu₂Sn]₂O}₂ show that the structures are similar and feature central Bu₄Sn₂O₂ units with two Bu₂Sn groups connected by bridging oxygen atoms. Each pair of exo- and endo-cyclic tin atoms is linked by an almost symmetrically bridging carboxylate group, with the two remaining groups attached to the exocyclic tin atom only. Crystals of {[(F₅C₆COO)Bu₂Sn]₂O}₂ are triclinic, space group P1, with unit cell dimensions a = 12.425(3) Å, b = 13.090(5) Å, c = 11.697(3) Å, α = 95.31(3)°, β = 93.28(2)°, γ = 113.01(2)°, V = 1734(1) ų, Z = 1. Crystals of {[(4-F-C₆H₄COO)Bu₂Sn]₂O}₂, are also triclinic, space group PI, a = 12.599(6) Å, b= 25.359(4) Å, c = 11.480(4) Å, α = 91.44(3)°, β = 114.77(3)°, γ=97.43(3)°, V=3289(2) ų, Z=2. The structures were refined to final R= 0.046, R_w = 0.046 for 4312 reflections with I≥ 3.0 σ(l) for {[(F₅C₆COO)Bu₂Sn]₂O}₂ and R=0.061, R_w=0.068 for 4112 reflections with l≥3.0 σ(l for {[(4-F-C₆H₄COO)Bu₂Sn]₂O}₂.     

Review: Chemistry of the phosphinophosphinidene tBu2P?P,a novel π‐electron ligand

In reactions with transition metal compounds, ^tBu₂P? P?P(X)^tBu₂ (X = Br, Me) acts mainly as a precursor of the ^tBu₂P? P ligand, whereas ^tBu(Me₃Si)P? P?P(Me)^tBu₂ acts as a precursor of the (Me₃Si)P?P^tBu ligand. Up to now, only Pt(0) d¹⁰ ML₂ metal centres were found to be able to stabilize the ^tBu₂P? P group in ‘pure form’ by means of η²‐coordination (side on). Several compounds of the [{η² ? ^tBu₂P? P}Pt(PR₃)₂] type were sufficiently stable to be isolated and characterized; however, not all of them gave single crystals suitable for X‐ray structure determinations. The X‐ray structures of these compounds and of [{µ ? (1,2:2 ? η ? ^tBu₂P? P)Pt(PR₃)₂} {M(CO)₅}] strongly suggest the ethene‐like form of 1,1‐di‐tert‐butyldiphosphene in these complexes. Such a form is also in agreement with RI DFT calculations with SVP basis for free ^tBu₂P? P. However, in trapping experiments with cyclic olefins and cyclic dienes ^tBu₂P? P exhibits, to some extent, electrophilic ‘singlet carbene’ properties. Copyright © 2002 John Wiley & Sons, Ltd.