A thermal route to stereospecifically CO labelled group VIB metal pentacarbonyl amine derivatives

A method for the synthesis of stereospecifically, equatorially labelled cis-M(CO)₄(¹³CO)(amine) derivatives where M = Cr, Mo, and W has been developed involves ¹³CO substitution into the vacant coordination site created by the facile dissociation of an amine ligand from cis-M(CO)₄(amine)₂ derivatives. The mechanistic implications of this extremely stereoselective reaction are discussed.     

A mass spectral study of intramolecular rearrangements in cis-M(CO)4(13CO)piperidine (M = Cr,W) derivatives

Low voltage mass spectra of cis-M(CO)₄(¹³CO)piperidine (M = Cr,W) show the initial loss of CO to proceed with complete scrabling of the label between axial and equatorial sites.     

Tetracarbonyl group 6 complexes containing secondary and tertiary phosphines

The mixed ligand tetracarbonyl derivatives, cis-M(CO)₄(PPh₂H)(PPh₃) (M  Cr, Mo, W) and cis-W(CO)₄(PPh₂H)(L) (L  PEt₃, PEt₂Ph, PEtPh₂) have been prepared from the reaction of M(CO)₅PPh₂H with L in THF in the presence of potassium t-butoxide. These reactions are accompanied in most instances by the formation of [W(CO)₅PPh₂]⁻, [(OC)₅M(μ-PPh₂)M(CO)₅]⁻, [(OC)₅M(μ-PPh₂)-M(CO)₄(PPh₂H)]⁻, [(OC)₄M(μ-PPh₂)₂M(CO)₄]²⁻, (OC)₄M(μ-PPh₂)₂M(CO)₄, and cis-M(CO)₄(PPh₂H)₂.     

Stereochemically nonrigid six-coordinate metal carbonyl complexes : IV. A 13C NMR investigation of cis-M(CO)4X2 and M′(CO)5X derivatives (M = Fe,Ru, Os; M′ = Mn,Re; X = H,I)

The ¹³C NMR spectra of cis-M(CO)₄X₂ and M′(CO)₅X (M = Fe, Ru, Os; M′ = Mn, Re; X = H, I) and cis·Os(CO)₄Me₂ are reported. Variable temperature spectra demonstrated the stereochemical nonrigidity of cis-Fe(CO)₄H₂ and the stereochemical rigidity of the rest. The carbonyl averaging process in cis-Fe(CO)₄H₂ occurs without ligand dissociation. Improved syntheses of some of these derivatives are also given.     

Bidentate amines as bridges between M(CO)2Cl (M = Rh OR Ir) units

The preparation and characterization by elemental analysis, electronic and infrared spectroscopy are reported for the monomeric complexes cis-(amine)-M(CO)₂Cl (M = Ir or Rh, amine = 1,8-naphthyridine or pyridazine; M = Ir, amine = o-phenylenediamine) and the binuclear species (1,8-naphthyridine)Rh₂(CO)₄Cl₂, (1,8-naphthyridine)IrRh(CO)₄Cl₂, (pyrazine)Rh₂(CO)₄Cl₂ and (1,3-di-4-pyridylpropane)Rh₂(CO)₄Cl₂.     

Kinetics and mechanism of ligand substitution reactions in [cis-M(CO)4(amine)(EPh3)] complexes (M = Mo,W; amine = pyridine,piperidine; E = As,Sb)

Group 6 metal carbonyls [cis-M(CO)₄(amine)(EPh₃)] (M = Mo, W; amine = piperidine (pip), pyridine (py); E = As, Sb) have been prepared and characterized. These complexes react thermally in chlorobenzene solutions with phosphine or phosphite ligands (= L) to give cis- and trans-M(CO)₄(L)(EPh₃) products. Kinetics of amine substitution by L in these complexes, under pseudo-first-order conditions, indicate that these reactions proceed by a rate law that is first-order in concentration of the metal complex. Rate constants and activation parameters for these reactions have been determined and are discussed. Competition studies for the [M(CO)₄(EPh₃)] intermediates show that these intermediates are highly reactive and react almost indiscriminately with various incoming nucleophiles with slight preference for more basic ones.     

Reactions of M2Cl4(PR3)4 (M  Mo and W) with carbon monoxide

The reactions of M₂Cl₄(PR₃)₄ derivatives (M  Mo, W and PR₃  PEt₃, PBu₃ⁿ) with CO at atmospheric pressure in toluene at 70°C to afford M(CO)₃(PR₃)₂Cl₂ and trans-M(CO)₄(PR₃)₂ are reported.     

Influence de la nature du solvant sur le comportement photochimique de complexes trans- ET cis-[PtCl2(éthylène)(amine)]

Nature of the solvent plays a major role in the photochemical behaviour of cis- and trans-[PtCl₂(ethylene)(amine)] complexes. Dimeric compounds [Pt₂Cl₄-(amine)₂] are obtained on irradiation of these complexes in chloroform or diethyl ether. A non-stereospecific reaction of photosubstitution is observed in nitrile solvents. When methanol, dimethoxyethane or dimethylformamide are used as solvents, cis and trans complexes have a quite different photochemical behaviour, but in all of the cases, a photodegradation leading to ionic species [PtCl₃(ethylene)]^? H⁺ amine and [PtCl₃(amine)]^? H⁺ amine is the main reaction.     

Reactions of cis-[dicarbonylbis(1,2-bis(dimethylphosphino)ethane)metal] compounds of chromium and molybdenum with organic electron acceptors; Tetracyanoethene, 1,2,4,5-tetracyanobenzene and 1,3,5-trinitrobenzene

Reaction between cis-[Mo(CO)₂(dmpe)₂] (dmpe =Me₂PCH₂CH₂PMe₂) and organic π-acids tetracyanoethene (TCNE), 1,2,4,5-tetracyanobenzene (TCNB) and 1,3,5-trinitrobenzene (TNB) proceeds via electron transfer from the metal complex, which is oxidised to the 17-electron trans-[Mo(CO)₂(dmpe)₂]⁺ ion, to the organic acceptor which is reduced to the radical anion. The final products of the reactions are characterised ascis-[Mo{C₂(CN)₃} (CO)₂(dmpe)₂] [CN], cis-[Mo{C₆H₂(CN)₄} (CO)₂(dmpe)₂] [C₆H₂(CN)₄]₈ and [Mo(CO)₂(dmpe)₂ · 2 C₆H₃(NO₂)₃] by analysis and spectroscopic (IR, NMR, ESR) measurements which are compared with those of cis-[MoX(CO)₂(dmpe)₂]X (X = Cl, Br, I) and fac, fac-[Mo₂Cl₄(CO)₄(dmpe)₃]. The reaction of cis-[Cr(CO)₂(dmpe)₂] with TCNE gives trans-[Cr(CO)₂(dmpe)₂]⁺ [TCNE]^? only.     

Zur kenntnis der chemie der metallcarbonyle und der cyanokomplexe in flüssigem ammoniak : XXXIII. Über die darstellung neuer carbamoylcarbonyl-komplexe aus bekannten und neuen kationischen carbonylverbindungen des mangans und rheniums

The covalent carbamoyl carbonyl compounds Re(CO)₅COHN₂, cis-M(CO)₄(L)CONH₂, M(CO)₃(L)₂CONH₂ and M(CO)₃(D)CONH₂ (M = Mn, Re; L = PPh₃, PEt₃; D = bipy, phen) are formed by reactions of the cationic complexes [Re(CO)₆]⁺, [M(CO)₅L]⁺, [M(CO)₄L₂]⁺ and [M(CO)₄D]⁺ (M = Mn, Re; L = PPh₃, PEt₃; D = bipy, phen) with liquid NH₃ with concomitant deprotonation: [M(CO)_6?nL_n]⁺ + 2 NH₃ → M(CO)_5?nL_nCONH₂ + NH₄⁺ (n = 0, 1, 2) and [M(CO)₄D]⁺ + 2 NH₃ → M(CO)₃(D)CONH₂ + NH₄⁺ The stability of the above-mentioned carbamoyl carbonyl complexes increases from the penta- to the tetra- to the tri-carbonyl derivatives. In all cases the rhenium compounds are much more stable than the corresponding manganese complexes. Whereas the carbamoyl compound Re(CO)₄(PEt₃)CONH₂ can be isolated by reaction of [Re(CO)₅PEt₃]⁺ with NH₃, the corresponding manganese complex undergoes Hofmann degradation of amides even at ?70°C to form HMn(CO)₄PEt₃ and NH₄NCO. The IR and some mass and ¹H NMR spectra of the new hexacoordinated carbamoyl carbonyl complexes are discussed and the reactions of these compounds with liquid NH₃, HCl and CH₃OH are described.     

Synthesis of octahedral carbonyl complexes of manganese(I) with SCN or CN ligands. Crystal structure of fac-[SCNMn(CO)3(dppm)]

The complexes fac-[XMn(CO)₃(dppm)], cis,cis-[XMn(CO)₂(dppm)(P(OPh)₃)] and trans-[XMn(CO)(dppm)₂] with X = SCN or CN have been prepared from the corresponding bromocarbonyls and the salts AgX or KX, or, in the case of the di- and mono-carbonyls, from fac-[XMn(CO)₃(dppm)] with X = SCN or CN by thermal or photochemical CO substitution by the ligands P(OPh)₃ or dppm. The structure of fac-[SCNMn(CO)₃(dppm)] has been determined by X-ray diffraction. The crystals are monoclinic, space group P2₁/n, and the structure has been refined to R = 0.058 for 4123 reflexions measured in the range 2 ⩽ θ ⩽ 30 at room temperature. The cis,cis-[NCMn(CO)₂(dppm)(P(OPh)₃)] complex can be oxidized and subsequently reduced to the isomer trans-[NCMn(CO)₂(dppm)(P(OPh)₃)]. All the neutral cyanide complexes react readily with MeI and KPF₆ to give the corresponding methylisocyanide derivatives [Mn(CO)₂(dppm)(P(OPh)₃)(CNMe)]PF₆ and [Mn(CO)(dppm)₂(CNMe)]PF₆. The stereochemistries of the compounds is discussed in relation to the ³¹P NMR spectra.     

Synthesis, characterization, and coordination chemistry of two new tartaric acid-derived bis(phosphite) ligands

The syntheses of two chiral bis(phosphite) ligands with tartaric acid-derived backbones: 1 (from dimethyl tartrate) and 2 (from dipyrollidene tartramide), three complexes of 1: cis-Mo(CO)₄(1), cis-PtCl₂(1), and cis-PdCl₂(1) and two complexes of 2: cis-Mo(CO)₄(2) and cis-PdCl₂(2) are described. Each ligand and complex has been fully characterized by ¹H, ¹³C, and ³¹P NMR spectroscopy, and the coordination ³¹P NMR chemical shifts have been compared to those observed for complexes of related ligands. The X-ray crystal structures of each of the metal complexes have also been determined. The X-ray crystal structures indicate that the conformation of the seven-membered chelate ring varies depending on the substituents on the tartrate backbone. However, the conformations of the seven-membered rings do not change when the metal center is changed or when the coordination environment around the metal center is changed.     

The nature of the lowest excited state and photosubstitution reactivity of tetracarbonyl-1,10-phenanthrolinetungsten(0) and related complexes

Absorption and emission spectral studies of M(CO)₄L complexes (M = Cr Mo, W; L = 2,2′-bipyridine, 1,10-phenanthroline, 5-CH₃-, 5-Cl-, 5-Br-, 5-NO₂-1,10-phenanthroline) have been carried out and reveal that the lowest excited state in every case is charge-transfer (CT) in character, M→ CT in absorption, and in no case do the ligand field (LF) excited states cross below the CT state. Minimum energies of the LF states have been established by the spectroscopic study of cis-bis(pyridine)- and cis-bis(aliphatic amine)-tetracarbonylmetal(0) complexes which all have LF lowest excited states for M = Mo, W. For the M(CO)₄L complexes emission is detectable for M = Mo or W and occurs in the range 14.40-15.66 kK with lifetimes of 7.9-13.3 μsec and quantum yields of 0.02–0.09 all in EPA solution at 77 K. For the bis-pyridine and -aliphatic amine complexes emission occurs only from the W complexes and is of the order of 3.0–4.0 kK higher in energy than for the M(CO)₄L complexes. Photosubstitution of pyridine is efficient in cis-W(CO)₄(py)₂ (py = pyridine): Φ_436nm = 0.23; Φ_405nm = 0.27; and Φ_366nm = 0.23. The M(CO)₄L complexes have strongly wavelength dependent, but modest, quantum yields for CO substitution and show that the lowest CT state is unreactive. Typical values for CO substitution for M = W and L = 1,10-phenanthroline are: Φ_436nm = 1.6 × 10^?4; Φ_405nm = 1.2 × 10^?3; Φ_366nm = 9.2 × 10^?3; and Φ_313nm = 2.2 × 10^?2.     

Rhodium- and iridium-manganese carbonyl complexes containing bridging Ph2PCH2PPh2 ligands

Treatment of mer,cis-[MnCl(CO)₂(dppm-PP′)(dppm-P)] with [Rh₂Cl₂(CO)₄] in the presence of CO and PF₆⁻ gives [Cl(OC)₂Mn(μ-dppm)₂Rh(CO)₂]PF₆ which might have a bridging chloride ligand. Similar treatment of mer,cis-[MnBr(CO)₂(dppm-PP')(dppm-P)] gave [Br(OC)₂Mn(μ-dppm)₂Rh(CO)₂]PF₆ which ³¹P-{¹H} NMR spectroscopy showed to be a mixture of two closely related species. Treatment of mer,cis-[MnCl(CO)₂(dppm-PP') (dppm-P)] with [Rh₂Cl₂(CO)₄] at −30°C probably gave [Cl(OC)₂Mn(μ-dppm)₂ Rh(CO)₂]Cl but this decomposes above 0°C: the corresponding dibromide was made similarly and is somewhat more stable than the dichloride. Treatment of mer,cis-[MnX(CO)₂(dppm-PP')(dppm-P)] (X = Cl or Br) with [IrCl(CO)₂(p-toluidine)] and CO-PF₆⁻ gave [X(OC)₂Mn(μ-dppm)₂Ir(CO)₂]PF₆. Neutral complexes of type [X(OC)₂Mn (μ-dppm)₂Ir(CO)X'] (X and X' = Cl or Br) are very labile and rapidly decompose to give [Ir(CO)(dppm-PP')₂]⁺ and other (unidentified) products. Treatment of mer,cis-[MnX-(CO)₂(dppm-PP')(dppm-P)] with [RhH(CO)(PPh₃)₃] gave [X(OC)Mn(μ-dppm)₂(μ-H)(μ-CO)Rh(CO)] (X = Cl or Br). These heterobimetallic compounds generally showed broad ¹³P-{¹H} resonances for the P nuclei bonded to Mn at ca 20°C due to some coupling with the ⁵⁵Mn nucleus (I = 100% abundant), but at −30°C these resonances sharpened up due to more rapid quadrupolar relaxation at the lower temperature. NMR and IR data are given.     

Tertiary phosphine complexes of cyclopentadienylmolybdenum carbonyl halides. Stereoselective syntheses and isomer separations

Pure cis and trans isomers of CpMo(CO)₂(L)X (Cp = η⁵-C₅H₅, L = PPh₃ or PBu₃, X = Br, or I) have been separated by chromatography and characterized by infrared and proton NMR spectroscopy. The reactions of trans-CpMo(CO)₂(L)CH₃ with HgX₂ (X = Cl, Br, I, SCN) afford cis-CpMo(CO)₂(L)X in high yield. Both linkage isomers are obtained in the reaction with Hg(SCN)₂, L = PPh₃. The mercuric halides react with CpMo(CO)₂(L)COCH₃ to form the metalmetal bonded derivatives trans-CpMo(CO)₂(L)HgX. Reactions of CpMo(CO)₂(L)CH₃ or CpMo(CO)₂(L)COCH₃ with bromine or iodine yield the halide complexes CpMo(CO)₂(L)X (X = Br and I, respectively), the product mixtures containing high proportions of the trans isomers.     

Phosphorus(III)-Nitrogen-Sulphur Compounds: Synthesis and Metal Complexes

Abstract

The preparation and X-ray structure (M=Mo) of complexes of the type M(CO)₅(Ph₂PNSO) (M=Cr,Mo) are described. These complexes are used in the synthesis of homo- and hetero-dinuclear complexes of Ph₂PNSNPPh₂. A ³¹P DNMR study of these dinuclear complexes indicates a cis, trans → trans, cis isomerization in solution. The preparation and X-ray structure (M=Cr) of the mononuclear complexes, cis-M(CO)₄(P(Ph)₂NSN(Ph)₂P), (M=Cr,Mo) are also described.     

Bridging versus chelating diphosphine in clusters: Isomers of Os3(CO)10(diphosphine)

Isomers of Os₃(CO)₁₀(diphosphine) (diphosphine = Ph₂P(CH₂)_nPPh₂; n = 2 (dppe), n = 3 (dppp), and n = 4 (dppb)) have been prepared in which the diphosphine is chelating (1,1-isomer) or bridging (1,2-isomer), respectively, by displacing butadiene or acetonitrile from the complexes Os₃(CO)₁₀(cis- or trans-C₄H₆) or Os₃(CO)₁₀(MeCN)₂. Ph₂PCH₂PPh₂ (dppm) gives only the known bridging (1,2-isomer) whichever starting material is used. Structures have been established by infrared, ³¹P and ¹³C NMR methods.     

Neutral and cationic dicarbonyl complexes of manganese (I) with diphosphines

The reaction of BrMn(CO)₅ with dppm in refluxing toluene gives the neutral compunds cis-cis-BrMn(CO)₂(dppm)₂ which has been shown by ³¹P NMR spectroscopy to have one dppm monodentate and the other bidendate. This complex reacts with TIPF₆ in dichloromethane solution to give the salt cis-[Mn(CO)₂-(dppm)₂]PF₆ or, if the reaction is carried out in the presence of CO, the salt mer-[Mn(CO)₃(dppm)₂]PF₆ which also has one monodentate dppm (by ³¹P NMR). The cationic complex cis-[Mn(CO)₂(dppm)₂]⁺ isomerizes to the transisomer when irradiated with UV light, while heating of the latter gives back the cis-isomer. The perchlorate salts of the cation cis-[Mn(CO)₂(dppm)₂⁺ can be prepared by reacting fac-O₃ClOMn(CO)₃(dppm) withdppm in refluxing toluene, and trans-[Mn(CO)₂(diphos)(diphos)′]⁺, diphos or diphos′ being dppm or dppe, by treating the fac-O₃ClMn(CO)₃(diphos) with dppm or dppe under UV irradiation.     

Platinum-promoted cyclization reactions of amino olefins : II. Regio- and stereoselectivity in the cyclization reactions of C-methyl substituted pent-4-enylamines

The compounds 1-, 2- and 3-methylpent-4 enylamine cyclize, in a reaction medium containing [PtCl₄]^2-, to the corresponding cis- and trans-dimethylpyrrolidines showing marked regio and stereoselectivity effects. The following cyclization reactions are also reported: a) that of hex-4-enylamine which gives a mixture of 2-ethylpyrrolidine and 2-methylpiperidine, b) that of 2,2-dimethylpent-4-enylamine which produces 2,4,4-trimethylpyrrolidine and c) that of 2,2-dimethylhex-4-enylamine which results in the formation of 2-ethyl-4,4-dimethylpyrrolidine and 2-methyl-5,5-dimethylpiperidine.The X-ray crystal structures of trans-[PtCl₂(amine)(Et₃P)] (amine = cis-2, 4-dimethylpyrrolidine and cis-2,3-dimethylpyrrolidine) are reported.     

Organometallic chemistry in a conventional microwave oven: the facile synthesis of group 6 carbonyl complexes

Syntheses proceeding by reflux may be improved, accelerated and simplified, by carrying out the reaction in a modified conventional microwave oven. To demonstrate the potential of this method, the synthesis of over 20 group 6 organometallic compounds is reported. Hexacarbonyls, most notably Mo(CO)₆, react with a range of mono, and bi, and tridentate ligands in a modified conventional microwave oven. They generally proceed without an inert atmosphere, yields are high and reaction times are short. For example, cis-[Mo(CO)₄(dppe)] is prepared in >95% yield in 20 min. Reaction of Mo(CO)₆ with dicyclopentadiene affords a simple one-step synthesis of [CpMo(CO)₃]₂ in >90% yield, which reacts further with alkynes in toluene to produce dimetallatetrahedrane derivatives, [Cp₂Mo₂(CO)₄(μ-RC₂R)]; presumably via the in situ formation of air-sensitive [CpMo(CO)₂]₂. Dimolybdenum tetra-acetate is also prepared in 48% yield in 45 min, however, this reaction requires an inert atmosphere. While W(CO)₆ reacts rapidly with amines to give cis diamine adducts in high yields, direct reactions with phosphines are not so clean. Bis(phosphine) complexes are, however, cleanly formed when a small amount of piperidine is added to the reaction mixture, presumably via the bis(piperidine) complex cis-[W(CO)₄(pip)₂]. Reactions with Cr(CO)₆ generally require an inert atmosphere and proceed less cleanly, although the important synthon [Cr(CO)₅Cl][NEt₄] was prepared in 30 min (74% yield), while [(η⁶-C₆H₅OMe)Cr(CO)₃] can be prepared in 45% after 4 h.