Mo Angle Research Articles

Substitution of chloride in [PtCl 2(dppe)] by the chiral anionic ligand [Mo(CO) 5(PPhH)] − : Synthesis and X-ray structure of [Pt(μ-PPhH) 2{Mo(CO) 5} 2(dppe)] and a 31P{ 1H} NMR analysis of its isomeric products and fluxionality

Reaction of the chiral anionic ligand [Mo(CO) 5(PPhH)] − with [PtCl 2(L-L)] affords the neutral trimetallic monophosphido bridged complexes [Pt(μ-PPhH) 2{Mo-(CO) 5} 2(L-L)] (L-L = dppe, Ph 2PCH 2CH 2PPh 2, 2; dpae, Ph 2AsCH 2CH 2AsPh 2, 3; dppe′, cis-Ph 2PCH=CHPPh 2, 4). Compounds 2–4 are the first examples of heterometallic complexes that contain two chiral primary phosphido bridges existing as pairs of diastereoisomers. [Pt(μ-PPhH) 2{Mo(CO) 5} 2(dppe)] ( 2) has been characterized spectroscopically and by a single-crystal X-ray analysis. The molecular structure of 2 can be considered either as Mo 2Pt phosphido-bridged trimer or a square-planar Pt II complex bonded to one chelating dppe and two anionic phosphine ligands. The latter PtP 4 description successfully accounts for the line broadening observed in the 31P{ 1H} NMR spectra of 2–4, which can be understood in terms of the existence of several interconverting rotameric forms arising from restricted rotation about the Pt-phosphido bond. The PtPMo angles of 122.1(1) and 123.5(1)° are some of the largest ever to be reported for phosphido-bridged heterometallics, reflecting the long PtMo separations [4.349(2) and 4.320(2) Å] and the electronic and structural flexibility of the phosphido bridge. The PtMo compound [Pt(μ-PPhH) 2{Mo-(CO) 4} (dppe)] (5), comprised of one neutral and one dianionic chelate ligand, was prepared from [Li] 2[Mo(CO) 5(PPhH) 2] and [PtCl 2(dppe)] and was shown to contain a conformationally rigid PtP 4 structure with characteristically sharp 31P resonances. The 31P{ 1H} NMR spectrum of 5 is rich with information analysing as two overlapping AA′XX′ spin systems together with their AA′XX′M (M = 195Pt) counterparts. The values of 2 J(P-P) and 1J( 195 Pt-P) are significantly lower for PPhH{Mo(CO) 5}− than dppe, a difference that cannot be accounted for solely on the basis of bond length variations. Meso-[Pt(μ-PPhH) 2{Mo(CO) 5} 2(dppe)] ( 2) is thermodynamically unstable, undergoing a rapid intramolecular elimination of [Mo(CO) 6] to generate [Pt(μ-PPhH) 2{Mo(CO) 4} (dppe)] (5), while its racemic diastereoisomer, that which was observed in the crystal, decomposes to unidentified phosphorus-containing products.

Novel oxo-bridged dinuclear molybdenum(II) complexes: reaction of [MO 2(O 32CCH 3) 2(CH 3CN) 6](BF 4) 2with aromatic isocyanides. X-Ray crystal structures of [Mo 2(μ-O)(RN 10](BF 4) 2 (R = 2,6-Me 2C 6H 3) and [Mo(= O)F(RNC) 4](BF 4) (R = 2,4,6-Me 3C 6H 2)

Treatment of the dinuclear molybdenum complex [Mo 2(O 2CCH 3) 2(CH 3CN) 6](BF 4) 2 with aromatic isocyanides (RNC) gave an oxo-bridged dinuclear molybdenum(II) complex, [Mo 2(μ-O)(RNC) 10](BF 4) 2 ( 1), and a mononuclear molybdenum(IV) complex, [Mo(= O)F(RNC) 4]BF 4( 2) (R = 2,6-dimethylphenyl (Xyl) or 2,4,6-trimethylphenyl (Mes)), which were characterized by IR, electronic, 1H and 19F NMR spectroscopy and X-ray crystallographic analyses. Complex 1a (R = Xyl) crystallizes in the triclinic form, space group P 1 , with a = 13.431(5) A ̊ , b = 15.548(7) A ̊ , c = 12.616(5) A ̊ , α = 111.74(3)°, β = 92.80(3)°, γ = 101.80(3)° and Z = 1 (R = 0.060 and R w = 0.054 for 2818 independent reflections with I >3 σ( I)) Complex 2b (R = Mes) crystallizes in the triclinic form, space group P 1 , with a = 14.317(4) A ̊ , b = 16.16(1) A ̊ , c = 8.968(8) A ̊ , α = 100.31(4)°, β = 97.54(2)°, γ = 91.69(4)° and Z = 2 (R = 0.059 and R w = 0.059 for 2225 independent reflections with I >3 σ( l)) Complex 1 consists of two molybdenum atoms bridged linearly by an oxygen atom. Each molybdenum atom is octahedrally coordinated by five isocyanides and an oxygen atom. Two equatorial planes, Mo(RNC) 4, mutually adopt an eclipsed form. The MoO bond length is 1.876(2) Å and the MoOMo angle is constrained to 180°. Complex 2 has a distorted octahedral geometry, in which molybdenum atom is occupied by four isocyanides, O and F atoms.

A comparison of the solid-state structures of four crystallographically independent molecules of bis(pentamethylcyclopentadienyl)dioxodimolybdenum(VI) oxide, [Cp*MoO 2] 2O

Two previously undisclosed polymorphs of [Cp*MoO 2] 2O have been crystallographically characterized: 1: monoclinic, P2 1/ n, a 8.145(4), b 9.193(3), c 15.263(5) Å, β 93.61 (3)°, V 1140.9(8) Å 3, Z = 2, R( F) = 4.78%; II, monoclinic, P2 1/ n, a 9.434(3), b 16.872(5), c 14.157(4) Å, β 97.19 (2)°, V 2235.7 (12) Å 3, Z = 4, R( F = 4.39%. A third polymorph ( III, Z = 6) has recently been reported in two independent accounts [J.W. Faller and Y. Ma, J. Organomet. Chem., 340 (1980) 59; P. Leoni, M. Pasquali, L. Salsini, C. di Burgno. D. Braga and P. Sabatino, J. Chem. Soc., Dalton Trans., (1989) 155]. The existence of three polymorphs with four independent molecules containing six crystallographically independent, but chemically identical, Cp*Mo groups creates an unusual opportunity to examine the ranges of intramolecular bond parameters. Such knowledge is essential to a discussion of the extent to which intermolecular (crystal packing) factors affect these parameters. The MgOMo angle is found to vary from strict linearity (in 1 and II) to 172.7(3)° (in II). The range of terminal MoO distances exceeds the entire ranges seen in all previously known Mo(VI) structures containing MoO bonds.

Studies on the structure of the paramagnetic μ-oxo dimer of molybdenum(V) in hydrochloric acid solutions by exafs

X-ray absorption spectra for molybdenum(V) in hydrochloric acid solutions were measured and their XANES and EXAFS were analysed. The μ-oxo dimer of Mo v was detected in 4.5–6.0 M HCl solutions. The Mo: in the dimer is 2.94–3.06 Å and the Mo ;OMo angle is ca 104–111°.

High oxidation state organometallics. Pentamethylcyclopentadienyloxo-molybdenum(VI) and -tungsten(VI) complexes

The preparation, isolation, and characterization of [(η 5-C 5Me 5)MoO 2] 2O ( 1) and (η 5-C 5Me 5)MoO 2Cl ( 2) and their tungsten analogues ( 1′ and 2′) are described. A substantial improvement in stability, ease of preparation, and ease of separation from other reaction products are observed for these Cp * complexes compared to their cyclopentadienyl counterparts. The binuclear pentaoxo compound, 1, crystallizes in the monoclinic space group P2 1 c with one and a half molecules in the asymmetric unit, Z = 6, a 21.265(7), b 9.237(3), c 17.669(5) Å, β 101.78(3)°, and V 3398(4) Å 3. Anisotropic refinement of the molybdenum and isotropic refinement of the non-metal atoms with no hydrogen atoms included converged to the residuals R 1 = 0.075, R 2 = 0.088. Two independent μ-oxo complexes are represented in the cell: one is centrosymmetric having the bridging oxygen on a special position: and the other nearly centrosymmetric having a MoOMo angle of 177.9(5)°. Grignard addition to 2′ yields the air-stable alkyl, (η 5-C 5Me 5)WO 2CH 2SiMe 3.

Crystal and molecular structure of 1,1,1,1-tetracarbonyl-2,2-bis(η-cyclopentadienyl-bis(µ-diphenylphosphido)-molybdenumzirconium, [(cp)2Zr(µ-PPh2)2-Mo(CO)4

The compound [(cp)2Zr(µ-PPh2)2Mo(CO)4](1), where cp =η-C5H5, has been prepared and characterised by a single-crystal X-ray diffraction study. The crystals are monoclinic, space group P21/c, Z= 4, with a= 17.506(9), b= 14.607(8), c= 14.887(11)Å, and β= 104.0(1)°. 3 715 Independent reflections above background have been measured on a diffractometer and the structure refined to R 0.069. The discrete molecules have approximate C2v symmetry. The µ-PPh2 groups bridge symmetrically across the (cp)2Zr and Mo(CO)4 moieties forming an approximately planar four-membered ring [Zr–P–Mo–P–], with the basic geometries about zirconium being tetrahedral and about molybdenum octahedral. The Zr ⋯ Mo distance of 3.290(1)Å signifies the presence of a single donor–acceptor bond Mo0→ ZrIV thereby conferring a formal 18-electron closed-shell electronic configuration upon both metal centres. Dimensions of the bridge are Zr–P 2.61 8(3) and 2.631 (3), Mo–P 2.543(3) and 2.536(3)Å, P–Zr–P 98.5(1), and P–Mo–P 103.1(1)°. The Zr–P–Mo angles are 79.2(1) and 79.1(1)°.

The reactions of acetone and of diacetone alcohol with [Mo{HB(3,5-Me2C3HN2)3}(NO)I2]. The formation of [Mo{HB(3,5-Me2C3HN2)3}(NO)I(OEt)] and the structures of [{Mo[HB(3,5-Me2C3HN2)3](NO)I}2O] and a bicyclic salt [C6H3Me5N2(OH)][I½(I3)½

The complex [Mo{HB(Me2pz)3}(NO)I2](Me2pz = 3,5-dimethylpyrazolyl) reacted with boiling acetone and with diacetone alcohol (4-hydroxy-4-methyl-2-pentanone) over several days, giving low yields of the salt of the cation [C6H3Me5N2(OH)]+, [{Mo[HB(Me2pz)3](NO)I}2O], and [Mo{HB(Me2pz)3}(NO)I(OEt)]. The structure of an iodide salt of the organic cation, and of the bimetallic species have been determined crystallographically. The organic salt is a bicyclic species derived by fusion of a C3 fragment (possibly derived from diacetone alcohol) across the N–N bond of 3,5-dimethylpyrazole. The bimetallic species can be described as two distorted, eclipsed octahedra sharing the bridging O atom, where the Mo–O distances are 1.86 and 1.93 A, and the Mo–O–Mo angle is 171°. Possible routes to the formation of these compounds are discussed.

Crystal and molecular structure of pyridinium di-?-oxo-bis(oxodichloroaquomolybdate(V)) monohydrate, (pyh)2[Mo2O4Cl4(H2O)2] � H2O

The crystal and molecular structure of pyridinium di-μ-oxo-bis(oxodichloroaquomolybdate(V)) monohydrate has been determined from MoKα diffractometer data. The compound crystallizes in the monoclinic space groupP21/m witha = 7.544(1),b= 17.046(3),c = 7.894(1) A, β = 106.00(1) ° andZ = 2. The structure was solved by the heavy-atom technique and refined by full-matrix least-squares method toR = 0.046, using 1800 reflections for whichF> 4σ(F). Molybdenum atoms are linked by the double oxygen bridge with an Mo—O distance of 1.943(4) A and an Mo—O—Mo angle of 83.4(2) °. The Mo—Mo distance is 2.584(1) A, indicating direct Mo—Mo bonding. The pyridinium and [Mo2O4C14(H2O)2]2- ions are hydrogen bonded through N—H ... O bonds. The N ... O contact is 2.656(8) A.