Wasif Hussain

A convenient synthesis of 1,2-bis(dichlorophosphino)ethane, 1,2-bis(dimethylphosphino)ethane and 1,2-bis(diethylphosphino)ethane

Abstract A simple synthesis of 1,2-bis(dimethylphosphino)ethane, 1,2-bis(diethyl-phosphino)ethane, and 1,2-bis(dicyclohexylphosphino)ethane is reported. The method involves the synthesis of 1,2-bis(dichlorophosphino)ethane using a procedure patented by Toy and Uhing; the halide is allowed to react with the appropriate Grignard reagent to give the required tetraalkyldiphosphine. The phosphines produced in this way are moderately sensitive to air but not spontaneously inflammable as previously reported.

Diazoalkane complexes and related compounds from reactions of dinitrogen complexes of tungsten and molybdenum with gem-di-bromides, and from condensation of hydrazido(2–)-complexes with aldehydes

The reactions of trans-[W(N2)2(Ph2PCH2CH2PPh2)2] with gem-dibromides lead to new diazoalkane complexes. These do not react with protonic acids, but the unique diazoalkane carbons are attacked by nucleophiles, such as LiMe, to yield diazenido-complexes, some of which cannnot be obtained by conventional means. Other nucleophiles, such as ButO–, cleave the nitrogen–carbon bond. The reactions of trans-[Mo(N2)2(Ph2PCH2CH2PPh2)2] with gem-dibromides are more complex, and diazoalkane complexes are, at best, minor products.

ELECTROCHEMICAL SYNTHESIS AND STRUCTURAL CHARACTERISATION OF TRANSITION METAL COMPLEXES WITH 2,6-BIS(1-SALICYLOYLHYDRAZONOETHYL)PYRIDINE, H4DAPS

Neutral manganese, cobalt and nickel complexes of the pentadentate hydrazone 2,6-bis(1-salicyloylhydrazonoethyl)pyridine (H4daps) have been prepared by means of electrochemical syntheses. They have been characterised by elemental analyses, IR spectroscopy, fast atom bombardment mass spectrometry (FAB) and magnetic susceptibility measurements. The molecular structures of [Mn(H2daps)(py)2] 1, [Co(H2daps)(py)2] 2, [Ni2(H2daps)2]·CH2Cl23, and [Ni2(H2daps)2(py)2]·CH2Cl24 have been determined by X-ray diffraction. Depending on the nature of the metal ion, the dianionic [H2daps]2– ligand shows different co-ordination modes in these complexes: 1 and 2 are mononuclear with the metal atom in a pentagonal bipyramidal environment, 3 and 4 are binuclear with a helicate structure in which the nickel atoms attain octahedral co-ordination.

A diazomethane complex of tungsten

Abstract Methylene bromide reacts with [W(N2)2 (Ph2PCH2CH2PPh2)2] in benzene solution, under tungsten filament light irradiation, to yield [WBr(N2CH2)(Ph2PCH2CH2PPh2)2] Br which containsdiazomethane as a ligand

Syntheses and molecular structures of the tridentate phosphine ligand 2-[Ph2P(CH2)3NCH]C6H4OH (HL) and its rhenium(V) complex [ReOCl2L]·0.25CH2Cl2

The tridentate ligand 2-[Ph2P(CH2)3NCH]C6H4OH (HL), which contains both ‘hard’ and ‘soft’ potential donor atoms, has been synthesized. Single-crystal X-ray diffraction studies show that, in the solid state, this ligand adopts a structure in which the oxygen and nitrogen atoms are linked by an intramolecular hydrogen bond. The reaction of this material with [ReOCl4]– to form [ReOCl2L] leads to the replacement of the proton in this hydrogen bond by rhenium(V), and the folding of the trimethylene chain to bring the phosphorus atom [Re–P 2.442(5)A] into a position which allows the ligand to bind facially to the {ReO}3+ moiety through all three donor atoms. The co-ordination site trans to the ReO oxygen [Re–O = 1.711 (13)A] is occupied by the phenolic oxygen [Re–O = 1.965(13)A] and the rhenium atom has a distorted octahedral co-ordination environment.

Reactions of trans-bis[1,2-bis(diphenylphosphino)ethane]bis(dinitrogen)-tungsten and -molybdenum with α-ω-dibromides, Br(CH2)nBr (n= 2–12)

The reactions of trans-[M(N2)2(Ph2PCH2CH2PPh2)2](M = Mo or W) with Br(CH2)nBr under irradiation in benzene solution yield products which are a function of n. For n= 3, complexes containing the group N2(CH2)3Br are formed. For n= 4 or 5, complexes with rings N(CH2)n are formed and for n= 6–12 two series of complexes, containing either N2(CH2)nN2 or N2(CH2)nBr are isolated. Members of the two series may be isolated as diazenido-complexes [MBr{N2(CH2)nBr}(Ph2PCH2CH2PPh2)2] or [{µ-N2(CH2)nN2}{MBr(Ph2PCH2CH2PPh2)2}2] respectively, both of which can be protonated reversibly to hydrazido(2–)-forms.

The protonation of molybdenum and tungsten bis(diphosphine)bis(dinitrogen) complexes: the crystal and molecular structure of bis[1,2-bis(diethylphosphino)ethane]bromo[hydrazido(2–)]tungsten bromide–methanol (2/1)

The reactions of [M(N2)2(L–L)2][M = Mo or W; L–L = diphosphine = Et2PCH2CH2PEt2(depe) or (4-MeOC6H4)2PCH2CH2P(C6H4OMe-4)2(dmppe)] with acids HX (X = Cl or Br) yield various products. Those containing nitrogen include [MHX(NNH2)(L–L)2]2+, and [MX(NNH2)(L–L)2]+, but the course of the reaction is also solvent dependent. The crystal structure of the complex [WBr(NNH2)(Et2PCH2CH2PEt2)2]Br·0.5MeOH is described.

A possible bis(carbon dioxide) adduct of molybdenum(0)

SummaryReaction of CO2 with [Mo(N2)2Ph2PCH2CH2PPh2] in PhMe at room temperature produces a material which analyses for [Mo(CO2)2(Ph2PCH2CH2PPh2)2], and which may be a bis(carbon dioxide) complex.The recent description(1) of a CO2 complex of molybdenum, namely [Mo(CO2)2(PMe3)4], prompts us to report a homologous compound [Mo(CO2)2(Ph2PCH2CH2PPh2)2], which we isolated from the reaction of CO2 and [Mo(N2)2(Ph2PCH2CH2PPh2)2] at room temperature under tungsten-filament irradiation. The similar reaction in PhMe at reflux produces [Mo(CO)2(Ph2PCH2CH2PPh2)2](2).The yellow crystalline compound was isolated as a THF solvate inca. 75% yield and is air-stable. The i.r. spectrum contains a strong band in the 1695–1710 cm−1 region, associated with the CO2, which compares with the 1670 cm−1 band reported(1) for [Mo(CO2)2(PMe3)4] and a band at 1760 cm−1 found for [Mo(CO2)2(PMe2Ph)4](3).The diamagnetic compound has not yet provided crystals suitable for x-ray analysis. Consequently, we were not able to determine whether this is a genuine CO2 complex or whether the two CO2 molecules have combined head-to-tail, as found for [Ir(C2O4)Cl(PMe3)3](4). The31P {1H} n.m.r. spectrum shows a pair of asymmetric doublets centred atca. 108 and 78 p.p.m. downfield from (MeO)3P. This suggests that the phosphoruses are no longer equivalent. The13C {1H n.m.r. spectrum has a broad resonance at 27.1 p.p.m. downfield from TMS, which may arise from the bound CO2 in whatever form it may be.Reactions with acids and oxidising agents did not give conclusive results. Thus treatment with Br2 (4 moles) in C6H6 yields CO (1 mole) and CO2 (1 mole); H2SO4 and HCl in C6H6 produced CO2 (1 mole), as does neat CCl4. The most convincing experiment was the reaction with MeNC, which was carried out in THF under reflux in a closed system. Two moles of CO2 were evolved, and the complex product was the known material(5) [Mo(CNMe)2(Ph2PCH2CH2PPh2)2], formed in quantitative yield.We think that this material is probably a bis(carbon dioxide) complex, its stability arising from the lack of dissociation of the two diphosphine ligands, but we cannot exclude the possibility of head-to-tail ring(4). We observed no reactions with CO, H2, MeBr or P(O2CH2)3CMe, but Ph2PCH2CH2PPh2 in C6H6 under reflux produces CO2 (1 mole).Carbon dioxide in THF under irradiation reacts only slowly with [W(N2)2(PMe2Ph)4] and [W(N2)2(Ph2PCH2PPh2)2]; no products have been identified.

Diazoalkane complexes of molybdenum and tungsten via hydrazido(2–) complexes

The reaction of [Mo(N2)2(depe)2](depe = Et2PCH2CH2PEt2) with MeBr affords [MoBr(NNMe2)(depe)2]Br, whereas EtBr yields both [MoBr(NNEt)(depe)2] and [MoBr(NNEt2)(depe)2]Br. Condensation of acetaldehyde with [MBr(NNH2)(depe)2]+(M = Mo or W) gives the diazoalkane complexes [MBr(NNCHMe)(depe)2]+ which can be used to synthesize alkyldiazenido-compounds by reaction with Li[AlH4].

The preparation and properties of some diphosphines R2PCH2CH2PR2(R = alkyl or aryl) and of their rhenium(I) dinitrogen derivatives

The synthesis of a range of diphosphines R2PCH2CH2PR2 from Cl2PCH2CH2PCl2 is described. The properties of a series of complexes [ReCl(N2)(R2PCH2CH2PR2)2] derived from them are discussed. The relationship between the values of E½ox and ν(N2) for the complexes suggests that electron-withdrawing substituents on the diphosphine upset the usual balance of σ and π effects in rhenium–dinitrogen bonding.