PMe2Ph Ligand Research Articles

Polyhedral osmaborane chemistry: the platination of [4,4,4-(CO)(PPh3)2-nido-4-OsB5H9] and the isolation, nuclear magnetic resonance properties, and molecular structures of two seven-vertex nido-type dimetallaheptaboranes [(CO)(PPh3)2HOs(PMe2Ph)ClPtB5H7] and [(CO)(PPh3)(PPh2)Os(PPh3)PtB5H7Ph

Reaction of the nido six-vertex osmaborane [(CO)(PPh3)2OsB5H9]1 with base followed by [PtCl2(PMe2Ph)2] yields (34%) the air-stable lemon-yellow seven-vertex osmaplatinaborane [(CO)(PPh3)2[graphic omitted]tB5H7]2 which retains the approximate structure of the nido six-vertex osmaborane 1, but which has three basal atoms (BBOs) co-ordinated trihapto to a {PtCl(PMe2Ph)} moiety, with the platinum and osmium atoms linked by a two-electron hydrogen bridge. The overall seven-vertex structure resembles that of a regular triangulated dodecahedron that has a five-connected vertex missing. It is geometrically and electronically nido. Treatment of this species with base, or thermolysis at 140°C, gives a small yield (3%) of the related species [(CO)(PPh3)([graphic omitted]tB5H7Ph]3. This is formally derived from 2via PPh3⇌ PMe2Ph ligand exchange plus the elimination of HCl, and has a similar nido-type seven-vertex osmaplatinaheptaborane cluster geometry. Now however there is a direct osmium–platinum bond, the metals are also linked by a four-electron {PPh2} bridge, and a migrant phenyl group is bound to a basal boron atom on the nido-{OsB5} subcluster. The compounds have been investigated by NMR spectroscopy, the results of which suggest that a number of other (minor) products from the reactions may also be interesting platinaosmaboranes. Crystals of 2 are monoclinic, space group P21/n, with a= 1.5397(3), b= 1.8489(3), c= 1.7189(3) nm, β= 92.568(13)° and Z= 4. Crystals of 3 are triclinic, space group P(no. 2), with a= 1.4491(7), b= 1.7730(4), c= 1.0763(3) nm, α= 82.08(2), β= 102.71(3), γ= 105.42(4)° and Z= 2.

Reactions of the co-ordinatively unsaturated µ3-alkylidyne cluster [WFe2(µ3-CC6H4Me-4)(µ-H)(µ-PPh2)(CO)6(η-C5H5)] with PMe2Ph

Treatment of the co-ordinatively unsaturated complex [WFe2H (µ3-CR)(µ- PPh2)(CO)6(η-C5H5)](3b; R = C6H4Me-4) with 1 equivalent of PMe2Ph at 20 °C affords the thermally unstable kinetic derivative [WFe2(µ3-CR)(µ-H)(µ-PPh2)(CO)6(PMe2Ph)(η-C5H5)](4). N.m.r. spectroscopy reveals that at –40 °C compound (4) exists as an equilibrium mixture of two isomers [(4a) : (4b)= 4:3]. The core structures of all the PMe2Ph derivatives described have features in common, and consist of a WFe2 triangle of metal atoms which is capped by a µ3-CR moiety. One W–Fe bond is bridged by a µ-PPh2ligand and the W atom carries a CO ligand and a cyclopentadienyl ring. In addition, for (4a) and (4b), the Fe–Fe bond is bridged by an hydride ligand and the iron atom remote from the µ-PPh2 group carries three terminal CO ligands. The Fe atom which is ligated by the µ-PPh2 group carries two CO ligands and the PMe2Ph ligand. In isomer (4a) one of the latter CO ligands is pseudo trans to the µ-PPh2 group, whereas the PMe2Ph ligand adopts this site in (4b). At ambient temperature rotation of the Fe(CO)2(PMe2Ph) group leads to interconversion of (4a) and (4b), but at this temperature (4) also isomerises to the thermodynamically favoured isomer [WFe2(µ3-CR)(µ-H)(µ-PPh2)(µ-CO)(CO)5(PMe2Ph)(η-C5H5)](5). In compound (5) the hydride ligand bridges a W–Fe bond and the Fe–Fe bond is bridged by a CO ligand. The iron atom ligated by the µ-PPh2 group carries two terminal CO ligands, whilst the remaining iron centre now carries the PMe2Ph ligand and two terminal CO ligands. Thermal decarbonylation of (5) gives two new co-ordinatively unsaturated isomers [WFe2H(µ3-CR)(µ-PPh2)(CO)5(PMe2Ph)(η-C5H5)](7) and (8) which do not interconvert at room temperature. The structure of (7) is closely related to that of compound (4) except that an FeH(CO)(PMe2Ph) group is now ligated by the µ-PPh2 ligand. The structure of (8) is similarly related to that of (5), but the Fe–Fe bond is no longer bridged by a CO ligand and the hydride occupies a terminal site on the Fe atom remote from the µ-PPh2 group. Compound (7) does not react with CO, but (8) with CO readily gives the saturated precursor (5). Compounds (7) and (8) do not react with PMe5Ph at ambient temperatures but both react with this ligand in refluxing toluene to give good yields of the co-ordinatively unsaturated bis-PMe2Ph complex [WFe2H(µ3-CR)(µ-PPh2)(CO)4(PMe2Ph)2(η-C5H5)](9). In compound (9) the iron centre remote from the µ-PPh2 group carries two CO ligands and a PMe2Ph ligand, whilst an FeH (CO)(PMe2Ph) group is ligated by the µ-PPh2 ligand.

Reaction of [FeCo(CO)7(µ-CHCRH)](R = H or Ph) with dimethylphenylphosphine. Synthesis and structure of [FeCo(CO)4(µ-CO)-(PMe2Ph)2(µ-CHCH2)], an electronically unbalanced iron–cobalt complex

The reaction of [FeCo(CO)7(µ-CHCRH)](R = H or Ph) with PMe2Ph leads to complexes [FeCo(CO)6(PMe2Ph)(µ-CHCPhH)] and [FeCo(CO)5(PMe2Ph)2(µ-CHCRH)]. The disubstituted compounds contain two PMe2Ph ligands linked to iron and two bridging ligands, carbonyl and vinyl. The structure of [FeCo(CO)4(µ-CO)(PMe2Ph)2(µ-CHCH2)] has been solved by X-ray diffraction methods.

The reactions of (η 5-C 5H 5)NiO(s) 3(μ-H) 3(CO) 9 with group V donor ligands. Spectroscopic characterization of the disubstituted derivatives, and crystal structure of (η 5-C 5H 5)NiO(s) 3(μ-H) 3(CO) 7(PMe 2Ph) 2

The complex (η 5-C 5H 5NiO(s) 3(μ-H) 3(CO) 9 ( 1 reacts with phosphines in the presence of Me 3NO to give monosubsituted derivatives, the main products, along with smaller amounts of disubstituted derivatives. The IR and NMR spectroscopic characterizations of two representative disubstituted derivatives are described. The crystal structure of (η 5-C 5H 5)NiO(s)(μ-H) 3(CO) 7(PMe 2Ph) 2 has been determined by X-ray diffraction. The crystals are monoclinic, space group P2 1/ a with Z = 4 in a unit cell of dimensions a 18.198(8), b 20.865(8), c 8.656(5) Å, β 99.67(2)°. The structure was solved by direct and Fourier methods and refined by full-matrix least-squares to R = 0.061 for 3139 observed reflections. The structure can be regarded as derived from that of 1 (which has a tetrahedral NiO(s) core with three hydride hydrogen atoms bridging the OsOs edges, a cyclopentadienyl group coordinated to the Ni atom,and nine terminal carbonyls bound to the Os atoms, three for each Os atom) by replacing two axial carbonyls by two PMe 2Ph ligands.

NMR coalescence effects resulting from stereochemical non-rigidity and halide exchange in octahedral rhodium(III) and iridium(III) tertiary phosphine complexes

The PMe 2Ph ligands in the aquo-cations mer- [MCl 2(H 2O)(PMe 2Ph) 3][ClO 4] rapidly exchange on the NMR time-scale giving coalescence in the 1H and 31P NMR spectra. Dissociation of the H 2O ligand which is trans to PMe 2Ph leads to a five- coordinate intermediate. This intermediate (M = Rh) is believed to be involved in the rapid reaction of [RhCl 2(H 2O)(PMe 2Ph) 3] [ClO 4] with mer- [RhCl 3(PMe 2Ph) 3] by a chloride transfer mechanism leading to total exchange of the PMe 2Ph ligands.

ChemInform Abstract: CONSECUTIVE SUBSTITUTION IN, AND REDUCTION OF, η‐ALLYL MOLYBDENUM(II) COMPLEXES, AND A STUDY OF LIGAND EXCHANGE IN A MOLYBDENUM(0) PRODUCT

AbstractDie Reaktion der nach einer modifizierten Literaturmethode dargestellten Verbindungen (I) mit den Phosphinen PMe2Ph oder PMePhg verläuft in zwei Stufen.

Consecutive substitution in, and reduction of, η-allyl molybdenum(II) complexes, and a study of ligand exchange in a molybdenum(0) product

Reactions of the allyl and 2-methylallyl complexes[Mo(CO)2Cl(η-C3H4R)(NCMe)2](R = H or Me) with ligands L = PMe2Ph or PMePh2 involve initial substitution to give [Mo(CO)2Cl(η-C3H4R)L2] followed by reduction to cis-[Mo(CO)2L4] or [Mo(CO)2(NCMe)(PMePh2)3]. The reduction, which is first order in the concentrations of both molybdenum complex and L, is thought to involve initial nucleophilic attack on the allyl ligand. Two of the PMe2Ph ligands in cis-[Mo(CO)2(PMe2Ph)4], believed to be the mutually cis pair, undergo rapid dissociative exchange with free PMe2Ph in solution at high temperatures: the exchange occurs without scramblig the cis pair of ligands with the trans pair. In the absence of free PMe2Ph, slow decomposition at 353 K yields specifically the mer isomer of [Mo(CO)3(PMe2Ph)3]. It is shown that this is the expected result if the labile Mo–P bonds are those to the cis pair of PMe2Ph ligands.

Interconversion of methyl and acetyl complexes and isomerization of acetyl complexes of ruthenium(II)

Complexes [Ru(CO)2X(Me)L2][(I), where X = Cl, Br, or I, and L = PMe2Ph or AsMe2Ph] react extremely rapidly with ligands L′(L′= CO, PMe2Ph, and several other ligands with phosphorus donor atoms, and AsMe2Ph) to form products [Ru(CO)X(COMe)L2L′], (II). The reactions involve initial intramolecular combination of methyl and carbonyl ligands followed by attack by L′trans to the newly formed acetyl ligand, which has a strong trans-directing effect. The trans-labilizing influence of the acetyl ligand makes the Ru–L′ bond in (II) extremely labile, and hence the reactions are easily reversed, regenerating (I). In many instances the products (II) undergo a slower rearrangement to a different isomer, (III), indicating that the stereochemistry of the initial reaction is kinetically controlled. The final position of equilibrium between (II) and (III) varies widely with the nature of X and L′: increases in either the size or the π-accepting ability of L′ favour (II), whereas an increase in the size of the halide ligand favours (III). Reconversion of isomer (III) of the complexes [Ru(CO)X(COMe)L2L′] into the methyl complexes (I), which may be either direct or via(II), is much slower than that of (II) into (I).

Cationic ruthenium systems. Part 2. Synthesis, characterization, and X-ray structure of hydridopentakis(dimethylphenylphosphine)-ruthenium(II) hexafluorophosphate: a discussion of the effects of steric strains on the reactivity of the complex

The complex [RuH(PMe2Ph)5][PF6] has been prepared by treatment of a methanolic solution of [RuH(cod)(NH2-NMe2)3][PF6](cod = cyclo-ocata-1,5-diene) with PMe2Ph under argon and has been characterized by microanalytical, i.r., and 1H n.m.r. data and by a three-dimensional X-ray structure determination. The colourless crystals of [RuH(PMe2Ph)5][PF6], M= 938, are orthorhombic, space group P212121, a= 21.55(3), b= 19.08(3), c= 10.38(2)A, U= 4 269 A3, Dm= 1.48, Dc= 1.46 g cm–3, Z= 4. The structure has been solved by the heavyatom method and refined by least squares to R 0.061 for 1 954 observed reflections collected on a diffractometer using graphite-monochromatized Mo-Kα radiation. The co-ordination about the ruthenium is distorted octahedral. The length of the bond to the phosphine trans to the hydride ligand (Ru–P 2.48 A) is significantly longer than those to the other four phosphine ligands (mean Ru–P 2.40 ± 0.01 A). There is considerable strain within the cation caused by non-bonded repulsions between the methyl and phenyl groups on different phosphine ligands. A discussion of the build-up of steric strain in co-ordination complexes containing PMe2Ph ligands is presented.

Isomerism in carbonyldihalogenotris(phosphine)ruthenium(II) complexes: photochemical and thermal rearrangements

Four isomers of the complexes [Ru(CO)Cl2(PMe2Ph)2L′][(I), (II), (IV), and (VI); L′= P(OMe)3 or PPh(OMe)2] can be isolated and characterized. Isomer (II) is obtained, directly or indirectly, by heating any of the otherthree isomers, but irradiation of (II) leads specificallyto isomer (I). A separate equilibrium exists between (I) and (VI). Isomers (I) and (II) of complexes [Ru(CO)X2(PMe2Ph)3](X = Cl, Br, or I) can be similarly interconverted. Kinetic study of the rearrangement (I)→(II) for [Ru(CO)Cl2(PMe2Ph)3] indicates that the initial step involves loss of a PMe2Ph ligand: the five-co-ordinate intermediate obtained can either react directly with PMe2Ph to form isomer (II) or rearrange prior to reaction with PMe2Ph. Evidence of the lability of the bonds to both types of phosphorus ligand in the various isomers of the complexes [Ru(CO)Cl2(PMe2Ph)2L′][L′= P(OMe)3 or PPh(OMe)2] suggests that mechanisms involving initial dissociation of a phosphorus ligand may also be involved in their interconversions.

Nuclear magnetic resonance studies on metal complexes. Part IX. A 31P-INDOR investigation of IrCl3(PMe2Ph)(Ph2PCH2CH2PPh2) and related complexes

The complexes IrCl2X(PMe2Ph)(Ph2PCH2CH2PPh2)(X = NO3, NO2, N3, NCO, –NCS, Cl, Br, I, pyridine, or CO), IrCl3(AsMe2Ph)(Ph2PCH2CH2PPh2), and IrCl3(PMe2Ph)(Ph2AsCH2CH2AsPh2) have been synthesised. The relative signs of the coupling constants, 2J(P–CH3), 4J(P–lr–P-CH3)(trans), and 2J(P–lr–P)(trans) and the 31P chemical shifts have been measured using the methyl resonance pattern of the PMe2Ph or AsMe2Ph ligand and 31P-INDOR. I.r. and electronic absorption spectral data are also reported and discussed.