Some recent developments in the chemistry of multiply bonded dimetal complexes that contain the intramolecular bridging phosphine ligands R2P(CH2)nPR2

Recent synthetic and structural studies on multiply bonded complexes of stoichiometry M₂X₄[μ-R₂P(CH₂)_nPR₂]₂ (M = Mo, W or Re; X = Cl, Br or I; R = Me, Et or Ph; n = 1 or 2), the ditungsten(III) hydride W₂(μ-H)(μ-Cl)Cl₄(μ-dppm)₂ (dppm = Ph₂PCH₂PPh₂), Re₂Cl₄(μ-dmpm)₃ (dmpm = Me₂PCH₂PMe₂), and M₂(μ-Cl)₂ Cl₄(μ-R₂PCH₂PR₂)₂ (R = Me or Ph) are surveyed. The first examples of multiply bonded complexes that contain the Ph₂PCH  CHPPh₂ ligand (abbreviated dppee) are described, viz. the α- and β-isomers of M₂X₄(dppee)₂ (M = Mo or Re, X = Cl or Br). The reactions of Re₂X₄(dppm)₂ (X = Cl or Br) with RNC, RCN and CO ligands that yield complexes in which a metal-metal multiple bond is preserved are reviewed.     

Synthesis and structural characterization of [PhE(BNMe2)2]2 (E = P or As): Six-Membered P2B4 and As2B4 Rings with Unusual Structures

The reaction of either Li₂PPh or Li₂AsPh with the diborane(4) derivative B₂(NMe₂)₂Br₂ affords the compounds [PhP(BNMe₂)₂]₂ ( 1 ) or [PhAs(BNMe₂)₂]₂ ( 2 ) in good yield. Both 1 and 2 have cyclic structures featuring non-planar P₂B₄ or As₂B₄ six-membered rings which have chair configurations. Although all four borons in each ring have planar coordination, the two phosphorus or arsenic centers have different degrees of pyramidalization. Bond distances within the rings indicate that the B? B, B? P or B? As bonds are single, whereas the exo-B? N bond lengths are consistent with significant π-bonding. The ring structures of 1 and 2 are in sharp contrast to the related boron-nitrogen species (t-BuN)₂N₄Me₄ which has a nido-N₂B₄ framework. The attempted synthesis of the nitrogen analogue of 1 or 2 by using a similar approach did not result in the isolation of [PhN(BNMe₂)₂]₂, instead the tetramino diborane(4) species [B(NMe₂)NHPh]₂ ( 3 ), which has a structure similar to other tetramine diborane(4) compounds, was isolated.     

Titanocene and zirconocene dichloride derivatives with hydroxylic reagents

The reaction of Cp₂TiCl₂ (Cp = C₅H₅) with ethanol in the presence of Et₃N in acetonitrile yields the derivatives CpTiCl(OEt)₂ or CpTiCl₂(OEt). Similar reactions of Cp₂MCl₂ (M = Ti or Zr) with glycols (GH₂ = 1,2-propanediol, 2,3-butanediol, pinacol or hexylene glycol) or fluoro-β-diketones (KeH = hexafluoroacetylacetone(hfa), benzoyltrifluoroacetone (bta) or 2-thenoyltrifluoroacetone (tta)) gave CpMCl(G) or CpMCl(Ke)₂.     

Reaktionen von π-Organokomplexen des Nickels mit tertiären Phosphanen

Reactions of π-Organonickel Complexes with Tertiary Phosphanes In a hexane solution Ni(C₅H₅)₂ reacts with PBu₃ or Ph₂PBu forming the nickel(O) complexes Ni(PBu3)₄ or Ni(Ph₂PBu)₄ (A). Under the same conditions only one cyclopentadienyl ligand is substituted by PhPBu₂ and the nickel(I) compound (C₅H₅)Ni (PhPBu₂)₂ (B) is obtained. Products of the reactions between B and α,α′-dipyridyl, hydrogen chlorid in ether, or Ni(PhPBu₂),Cl₂ are Ni(dipy)₂, [PhPHBu₂]₂[NiCl₄], or (C₅H₅) Ni(PhPBu₂)₂Cl. By the reaction with HgCl₂ a cyclopentadienyl compound of an unknown structur is formed. The compound Ni(PhPBu₂)₄ which is analogous to A is synthesized by the reduction of bis(acety1acetonato)-nickel with Et₂AlOEt in the presence of PhPBu₂ or by the reaction of bis (cyclooctadiene-1,5)-nickel with PhPBu₂.     

Organometallic chemistry of chiral diphosphazane ligands: Synthesis and structural characterisation

The diphosphazane ligands of the type, (C₂₀H₁₂O₂)PN(R)P(E)Y₂ (R = CHMe₂ or (S)-*CHMePh; E = lone pair or S; Y₂ = O₂C₂₀H₁₂ or Y = OC₆H₅ or OC₆H₄Me-4 or OC₆H₄OMe-4 or OC₆H₄Bu^t-4 or C₆H₅) bearing axially chiral 1,1'-binaphthyl-2,2′-dioxy moiety have been synthesised. The structure and absolute configuration of a diastereomeric palladium complex, [PdCl₂{ηsu2}-((O₂C₂₀H₁₂)PN((S)-*CHMePh)PPh₂] has been determined by X-ray crystallography. The reactions of [CpRu(PPh₃)₂Cl] with various symmetrical and unsymmetrical diphosphazanes of the type, X₂PN(R)PYY′ (R = CHMe₂ or (S)-*CHMePh; X = C₆H₅ or X₂ = O₂C₂₀H₁₂; Y=Y′= C₆H₅ or Y = C₆H₅, Y′ = OC₆H₄Me-4 or OC₆H₃Me₂-3,5 or N₂C₃HMe₂-3,5) yield several diastereomeric neutral or cationic half-sandwich ruthenium complexes which contain a stereogenic metal center. In one case, the absolute configuration of a trichiral ruthenium complex, viz. [Cp*Ruη₂-Ph₂PN((S)-*CHMePh)*PPh (N₂C₃HMe₂-3,5)Cl] is established by X-ray diffraction. The reactions of Ru₃(CO)₁₂ with the diphosphazanes (C₂₀H₁₂O₂)PN(R)PY₂ (R = CHMe₂orMe; Y₂=O₂C₂₀H₁₂or Y= OC₆H₅ or OC₆H₄Me-4 or OC₆H₄OMe-4 or OC₆H₄Bu^t-4 or C₆H₅) yield the triruthenium clusters [Ru₃(CO)₁₀{η-(O₂C₂₀H₁₂)PN(R)PY₂}], in which the diphosphazane ligand bridges two metal centres. Palladium allyl chemistry of some of these chiral ligands has been investigated. The structures of isomeric η³-allyl palladium complexes, [Pd(η³-l,3-R′₂-C₃H₃){η²-(rac)-(0₂C₂₀H₁₂)PN(CHMe₂)PY₂}](PF₆) (R′ = Me or Ph; Y = C₆H₅ or OC₆H₅) have been elucidated by high field two-dimensional NMR spectroscopic and X-ray crystallographic studies.     

The formation of alkyne and alkynyl complexes by reaction of 1-alkynes with trans-[M(N2)2(PH2PCH2CH2PPh2)2] (M  Mo OR W) and with [Mo(Ph2PCH2PPh2)3]: X-ray structure of trans-[Mo(CCPh)2(PH2PCH2CH2PPh2)2]

Reaction of RCCH (R  Ph, CO₂Meor CO₂Et) with trans-[M(N₂)₂(dppe)₂] (M  Mo or W; dppe  Ph₂PCH₂CH₂PPh₂) or [Mo(dppm)₃] (dppm  Ph₂PCH₂PPh₂) gives the alkyne complexes [M(RCCH)₂(diphos)₂] (diphos  dppe, M  Mo, R = Ph; dihpos  dppm, M  Mo, R  Ph or CO₂Me) and the alkynyl complexes trans-[M(cCR)₂(dppe)₂], [MH₂(CCR)₂ (dppe)₂] (M  Mo or W. R  Ph, CO₂Me or CO₂Et) and cis-[WH(CCCO₂Me)(dppe)₂]: the X-ray structure of trans-[Mo(CCPh)₂(dppe)₂] is reported.     

Protonation of a series of diphosphazane- and diphosphine-bridged derivatives of iron and ruthenium: dependence of the nature of the hydride ligand on the metal and the bridging diphosphorus ligand

Protonation of the dinuclear compounds [M₂(μ-CO)(CO)₄(μ-R₂PYPR₂)₂] by HBF₄ or HPF₆ leads to the formation of crystalline cationic hydrido products [M₂H(CO)₅(μ-R₂PYPR₂)₂]X and [M₂(μ-H)(μ-CO)(CO)₄(μ-R₂PYPR₂)₂]X (X = BF₄ or PF₆) in which the hydride ligand is terminal for M = Ru, Y = N(Et) and R = OMe or OPrⁱ and bridging for M = Fe, Y = CH₂ and R = Me or Ph, for M = Fe, Y = N(Et) and R = OMe, OEt, OPrⁱ or OPh and for M = Ru, Y = CH₂ and R = Ph; the fluxional behaviour of [Ru₂H(CO)₅{μ-(RO)₂PN(Et)P(OR)₂}₂]⁺ (R = Me or Prⁱ) in solution is described.     

Epoxidation of phosphinoyl alkenes with hydrogen peroxide

The epoxidation of alkenylphosphorus compounds with hydrogen peroxide was systematically studied, revealing that while alkenylphosphine oxides failed to produce the corresponding epoxides, alkenylphosphonates, or phosphinates having a phenyl group at α-position reacted with H₂O₂/K₂CO₃ or alkenylphosphonic acids or phosphinic acids having an aliphatic group at α- or β-positions reacted with H₂O₂/Na₂WO₄/Et₃N to produce high yields of the corresponding epoxides.     

An efficient one-pot synthesis of 2,5-disubstituted thiophenes from 1-propynylamines or allenic amines and thiocarbonyl compounds

Metallation of the ynamine CH₃CCNEt₂ or the allenic amines H₂CCCHNR₂ (R = CH₃ or C₂H₅) with Schlosser's reagent BuLi · t-BuOK, followed by reaction with a thiocarbonyl compound XCSSCH₃ (X = Me₂N, Et₂N, CH₃S, t-Bu, O-t-Bu, Ph or 2-thienyl) and then addition of water, gives 2,5-disubstituted thiophenes (with Me₂N or Et₂N and X as substituents) in good yields.     

Thermal and X-ray diffraction investigations of some lanthanum(III) and neodymium(III) oxide-alkali persulfate binary systems

Different molar ratios of La₂O₃ or Nd₂O₃:Na₂/K₂S₂O₈ have been prepared, and the results of their TG and DTA investigations, under an atmosphere of static air, are reported. The effects of either La₂O₃ or Nd₂O₃ on the thermal decomposition of the persulfates from ambient to 1050°C, using a derivatograph, have been studied. It has been found that La₂O₃ lowers the initial decomposition temperatures of these alkali persulfates through catalytic activity. Nd₂O₃ shows little or no catalytic effect and therefore it acts as an insulator. Intermediate and final products are identified by X-ray diffraction analysis. The stoichiometric molar ratios of the solid state reactions are 1:3::R₂O₃:M₂S₂O₈. (R = La or Nd. M = Na or K), which give double salts of formulae: NaLa(So₄)₂, KLa(SO₄)₂, NaNd(SO₄)₂, and KNd(SO₄)₂. No sulfates or oxysulfates of lanthanum or neodymium have been identified.     

1-Organyl-2-azasilatran-3-ones

New 1-organyl-2-azasilatran-3-ones have been synthesized via the reaction of trifunctional silanes RSiX₃ (R = Et, Pr, Ph, CH₂=CH, or ClCH₂; X = Cl or Me₂N) with N,N-bis(2-hydroxyethyl)glycinamides (HOCH₂CH₂)₂NCH₂C(O)NHR (R = H or Me) and their N′,O-trimethylsilyl derivatives. The obtained products can be hydrolyzed to give the corresponding organylsilanetriols. Lithiation of 1-methyl- and 1-phenyl-2-azasilatran-3-ones with n-butyllithium or their reduction with lithium aluminum hydride leads to the products of splitting of the atrane backbone RSiBu₃ and RSiH₃ (R = Me or Ph), respectively.     

Synthesis of transition-metal Lewis acid adducts of trans-[ReCl(CNR)(Ph2PCH2CH2PPh2)2] (R = alkyl). A chemical and a quantum-chemical study of electrophilic β-addition to ligating isocyanide

Treatment of trans-[ReCl(CNR)(dppe)₂] (R = Me or Bu^t, dppe = Ph₂PCH₂CH₂ PPh₂) with CoCl₂(THF)_1.5, [ReOCl₃(PPh₃)₂] or [WCl₄L₂] (L = PPh₃ or PEtPh₂) affords the dinuclear adducts [ReCl(CN(M)R)(dppe)₂] (M = CoCl₂(THF), ReOCl₃(PPh₃) or WCl₄L, respectively) (formed via electrophilic β-addition of the electron-acceptor molecules to the isocyanide ligands), which undergo dissociation oxidation (for M = CoCl₂(THF) or ReOCl₃(PPh₃)). These reactions are considered in the light of results of extended Hückel calculations.     

Beryllium Halide Complexes Incorporating Neutral or Anionic Ligands: Potential Precursors for Beryllium Chemistry

Reactions of the beryllium dihalide complexes [BeX₂(OEt₂)₂] (X=Br or I) with N,N,N′,N′‐tetramethylethylenediamine (TMEDA), a series of diazabutadienes, or bis(diphenylphosphino)methylene (DPPM) have yielded the chelated complexes, [BeX₂(TMEDA)], [BeX₂{(RN=CH)₂}] (R=tBu, mesityl (Mes), 2,6‐diethylphenyl (Dep) or 2,6‐diisopropylphenyl (Dip)), and the non‐chelated system, [BeI₂(κ¹‐P‐DPPM)₂]. Reactions of lithium or potassium salts of a variety of β‐diketiminates have given both three‐coordinate complexes, [{HC(RCNAr)₂}BeX] (R=H or Me; Ar=Mes, Dep or Dip; X=Br or I); and four‐coordinate systems, [{HC(MeCNPh)₂}BeBr(OEt₂)] and [{HC(MeCNDip)(MeCNC₂H₄NMe₂}BeI]. Alkali metal salts of ketiminate, guanidinate, boryl/phosphinosilyl amide, or terphenyl ligands, lead to dimeric [{BeI{μ‐[(OCMe)(DipNCMe)]CH}}₂], and monomeric [{iPr₂NC(NMes)₂}BeI(OEt₂)], [κ²‐N,P‐{(HCNDip)₂B}(PPh₂SiMe₂)NBeI(OEt₂)] and [{C₆H₃Ph₂‐2,6}BeBr(OEt₂)], respectively. Compound [{HC(MeCNPh)₂}BeBr(OEt₂)] undergoes a Schlenk redistribution reaction in solution, affording the homoleptic complex, [{HC(MeCNPh)₂}₂Be]. The majority of the prepared complexes have been characterized by X‐ray crystallography and multi‐nuclear NMR spectroscopy. The structures and stability of the complexes are discussed, as is their potential for use as precursors in poorly developed low oxidation state beryllium chemistry.     

pp Homoconjugation in organic radicals

ESR data for various radicals of type R₂?CR₂X, when R is H or alkyl, and X is either Cl, Br or I, or PR₂ and AsR₂, are discussed in terms of pp homoconjugation. For the β-halogen radicals, the small size of the anisotropic coupling provides some evidence for this effect, but for the β-PR₂ and β-AsR₂ radicals, the greatly enhanced isotropic coupling to ³¹P or ⁷⁵As compared with those for the corresponding cation-radicals, R₂?CR₂PR⁺₃ or R₂?CR₂AsR⁺₃, is taken as good evidence for homoconjugation.     

Stabilisation of [Fe2(CO)9] and [Ru2(CO)9] bu substitution with bridging diphosphorus ligands

Reaction of [Fe₂(CO)₉] with a half molar amount of R₂PYPR₂ (Y = CH₂, R = Ph, Me, OMe or OPrⁱ; Y = N(Et), R = OPh, OMe or OCH₂; Y = N(Me), R = OPrⁱ or OEt) leads to the ready formation of a product which on irradiation with ultraviolet light rapidly decarbonylates to the heptacarbonyl derivative [Fe₂(μ-CO)(CO)₆{μ-R₂PYPR₂}]. Treatment of the latter with a slight excess of the appropriate ligand results, under photochemical conditions, in the formation of the dinuclear pentacarbonyl complex [Fe₂(μ-CO)(C))₄{μ-R₂PYPR₂}₂] but under thermal conditions in the formation of the mononuclear species [Fe(CO)₃{R₂PYPR₂}]. Reaction of [Ru₃(CO)₁₂] with an equimolar amount of (RO)₂PN(R′)P(OR)₂ (R′ = Me, R = Prⁱ or Et; R′ = Et, R = Ph or Me) under either thermal or photochemical conditions produces [Ru₃(CO)₁₀{μ-(RO)₂PN(OR)₂}] which reacts further with excess (RO)₂PN(R′)P(OR)₂ on irradiation with ultraviolet light to afford the dinuclear compound [Ru₂(μ-CO)(CO₄{μ-(RO)₂PN(R′)P(OR)₂}₂]. The molecular structure of [Ru₂(μ-CO)(CO)₄{μ-(MeO)₂PN(Et)P(OMe)₂}₂], which has been determined by X-ray crystallography, is described.     

Mono- and bis-alkoxides of tris(3,5-dimethylpyrazolyl)borato molybdenum and tungsten nitrosyls

The complexes [ML^*(NO)Cl(OR)] {L^* = HB(3,5-Me₂C₃HN₂)₃; M= Mo, R = CH₂CH₂X, X = Cl, OMe or OEt; (CH₂)_nOH, n = 2, 5, 6; M = W, R = CH₂CH₂X, X = Cl, OMe or OEt; (CH₂)_nOH, n = 2–6; CH₂(CF₂)₃CH₂OH; CHMeCH₂CMe₂OH} and [ML^*(NO)(OR)₂] {M = Mo, R = CH₂CH₂X, X = Cl, OMe or OEt; (CH₂)_nOH, n = 2–6; M = W,R = CH₂CH₂X, X= Cl, OMe or OEt; (CH₂)_nOH, n = 2,4–6; CH₂(CF₂)₃CH₂OH} have been prepared from [ML^*(NO)Cl₂] and the appropriate alcohol in the presence of NEt₃ or NaCO₃, and have been characterized by IR, ¹H NMR and mass spectroscopy.     

Cobalt(II) and nickel(II) complexes with 4-amino-6-methyl-5-oxo-3-phenylamino-1,2,4-triazine

Summary Cobalt(II) and nickel(II) complexes of 4-amino-6-methyl-5-oxo-3-phenylamino-1,2,4-triazine (ATAZ), MX₂(ATAZ)₂ · 2 H₂O (M = Co or Ni; X = Cl, Br, I or NCS), have been isolated. The electronic spectra, magnetic moments and i.r. spectra of the compounds have been studied.Pseudo-octahedral environments are proposed for the complexes: [MX₂(ATAZ)₂]. 2 H₂O (M = Ni or Co; X = Cl or Br) and [CoI₂(ATAZ)₂(H₂O)₂], and apseudo-tetrahedral structure for [NiX₂(ATAZ)₂] · 2 H₂O (X = I or NCS) and [Co(NCS)₂-(ATAZ)₂] · 2 H,O. However, [CoX₂(ATAZ)₂]. 2 H₂O (X = Cl or Br) give acetone solutions containing tetrahedral cobalt(II).     

Organothallium compounds : XVII. Halogenobis(polyfluorophenyl)thallium(III) complexes

The preparations, stabilities and structures of the complexes R₂TlX and R₂ LTlX (R = C₆F₅, p-HC₆F₄, or o-HC₆F₄; X = Br or Cl; L = Ph₃PO, 2,2′-bipyridyl (bpy) or Ph₃P) have been examined or (R = C₆ F₅) reinvestigated. The derivatives R₂TlX are monomeric in acetone, from which the complex (p-HC₆F₄)₂ Me₂COTIBr has been isolated. In this solvent, the complexes R₂LTlX (L = Ph₃PO, bpy, or Ph₃P) undergo partial dissociation by loss of L. When L = bpy, there is also slight ionization into R₂LTl⁺ and R₂TlX^?₂. The acceptor properties of R₂TlX compounds towards uncharged ligands decrease R = C₆F₅ ? p-HC₆F₄ > o-HC₆F₄ > Ph. Dimeric behaviour is observed for R₂TIX compounds in benzene, whilst R₂LTlX (L = Ph₃PO or bpy) derivatives show slight but significant association. In the solid state, R₂TlX compounds are considered to be polymeric with five coordinate thallium, and R₂LTlX derivatives to be dimeric with five (L = Ph₃PO) or six (L = bpy) coordinate thallium by contrast with four coordinate dimeric and four or five coordinate monomeric structures previously proposed for the respective pentafluorophenyl derivatives. Halogen bridging is unsymmetrical for R = C₆F₅ or p-HC₆F₄, but may be more symmetrical for R = o-HC₆F₄ when L = Ph₃PO or bpy. Reported structural data for the complexes (C₆F₅)LTlX (L = Ph₃AsO, Ph₃P, Ph₃As, or 1,10-phenanthroline; X = Br or Cl) and (C₆F₅)₂TlCl^?₂ are reinterpreted and the proposed structures revised.     

Synthesis of divalent aryloxy- and diorganoamido-lanthanides from bis(pentafluorophenyl)lanthanide(II) complexes

The complexes M(OR)₂(thf)₃ (M = Yb or Eu, R = 2,6-Bu^t₂-4-MeC₆H₂; M = Yb, R = 2,4,6-Bu^t₃C₆H₂ or 2,6-Bu^t₂C₆H₃; thf = tetrahydrofuran) and M(NR₂)₂(thf)₄ (M = Yb or Eu, R₂N = carbazol-9-yl; M = Yb, R₂N = 2-phenylindol-1-yl) have been prepared by reactions of (C₆F₅)₂M (M = Yb or Eu) with substituted phenols, carbazole, or 2-phenylindole.     

Coordination chemistry of poly(1-pyrazolyl)alkanes,part IV. Copper(II) complexes of bis- and tris-(1-pyrazolyl)methane

Summary The reactions of some copper(II) salts with bis(1-pyrazolyl)methane, H₂Cbpz, bis(3,5-dimethylpyrazolyl)methane, H₂Cbdmpz, and tris(1-pyrazolyl)methane, HCtpz give the following solid complexes: CuLX₂ · nH₂O (L=H₂Cbpz, H₂Cbdmpz or HCtpz; X=Cl^–, Br^–, NO ₃ ^– , OAc^–, or 1/2 SO ₄ ^2– and n=0, 1, 3 or 5) and CuL₂X₂ · nH₂O (L=HCtpz, X= C^–, Br^–, NO ₃ ^– or ClO ₄ ^– and n=0 or 2). The complexes have been characterised by elemental analysis, visible and i.r. spectral measurements.The reactions of Cu(HCtpz)X₂ · nH₂O (X=Cl^– or Br^–) with acetylacetonate (acac^–), dialkyldithiocarbamate (S₂CNMe ₂ ^– , S₂CNEt ₂ ^– ) or poly(1-pyrazolyl)borate (H₂Bbpz^–, HBtpz^–) in aqueous solutions lead to the displacement of HCtpz and the subsequent formation of neutral [Cu(acac)₂], [Cu(S₂CNR₂)₂], [Cu(H₂Bbpz)₂] and Cu(HBtpz)₂ while the reaction with oxalate ion, C₂O ₄ ^2– yields a stable neutral solid compound, [Cu(HCtpz)(C₂O₄)].