Jeffery F. Sawyer

Charge-transfer interactions in the square-planar chalcogen cations, M42+: preparation and crystal structures of the compounds (Se42+)-(Sb2F42+)(Sb2F5+)(SbF6–)5, (Se42+)(AlCl4–)2, and (Te42+)(SbF6–)2

The solid-state structures of the compounds (1)(Se42+)(Sb2F42+)(Sb2F5+)(SbF6–)5, (2)(Te42+)(SbF6–)2, and (3)(Se42+)(AlCl4–)2 are reported. The first compound was initially isolated from the reaction of a 1:3 sulphurselenium alloy with a SbF5–SO2 solution and the second by the reaction of a mixture of tellurium and germanium, with a SbF5–SO2 solution. They have also been prepared by the direct oxidation of Se and Te with SbF5 in SO2. Crystals of (1) are monoclinic, space group P21/c, with a= 15.739(3), b= 13.498(2), c= 17.040(4)A, β= 92.26(2)°, and Z= 4. The dark red plates of (2) are triclinic, space group A, with a= 5.700(2), b= 16.252(6). c= 8.076(2)A, α= 100.56(3), β= 102.67(3), γ= 97.47(3)°, and Z= 2. Compound (3) is orthorhombic, space group Pbam, with a= 13.245(3), b= 13.223(3), c= 9.266(2)A, and Z= 4. The structures of compounds (1) and (2) have been solved by direct methods and compound (3) by a Patterson function. They were refined by least squares to final agreement indices of R= 0.052 (R′= 0.062). 0.051 (0.064), and 0.042 (0.046) for 3 634, 709, and 912 observed reflections respectively. In these three compounds, the approximately square-planar chalcogen cations Se42+ and Te42+ were found to have crystallographic inversion symmetry with average Se–Se and Te–Te distances of 2.260(4)(1), 2.688(3)(2), and 2.286(2)A(3). These values are close to the distances observed in the other examples of these cations. The packing of these and other examples of the Ma42+ cations, the anion–cation charge-transfer interactions, and the stereochemistry of the fluorine contacts to the antimony(III) atoms in the Sb2F42+ and Sb2F5+ ions and related species are discussed.

The synthesis and structural characterization of the η1; η3-allyl bridged bimetallic complexes [η3-2-(η5-Cp)(OC)(PR3)-Fe-allyl Pt(PPh3)2]PF6 (PR3 = PPh2H, PPh2Me)

The cationic complex [η5-Cp(OC)(η2-allene)Fe(PPh2H)]PF6 reacts with Pt-(C2H4)(PPh3)2 via C2H4 substitution (rather than oxidative addition of the PH bond) to give [η3-(2-η5-Cp(OC)(PR3)Fe-allyl)Pt(PPh3)2]PF6 PR3 = PPh2H the structure of which has been determined by a single crystal X-ray diffraction study of its dimethylphenylphosphine analog [Pr3 = PMe2Ph]. Crystal data: [C53H50FeOP3 Pt+] [PF6−]·2[C6H6] is triclinic, space group P1 with a 13.504(2), b 14.044(6), c 17.759(4) A, α 98.05(2), β 108.59(1), γ 104.44(2)°, U 3002(3) A3, Z = 2, Dx 1.49 Mg m−3, λ(Mo-Kα) 0.71069 A, μ 27.6 cm−1, F(000) = 1356, T 298 K, R = 0.0527 (Rw = 0.0575) for 7731 observed (I > 3σ(I) reflections. The compound contains an ordered η2-η1-Fe, η3-Pt allyl moiety with PtC distances of 2.151(9) and 2.165(8) A to the terminal atoms and 2.272(7) A to the central atom; the FeC distance is 1.967(7) A. The plane of the allyl group is canted at an angle of 122.5° with respect to the PtP2 plane. The Pt…Fe separation is 3.794(1) A.

X-Ray crystal and multinuclear n.m.r. study of FXeN(SO2F)2; the first example of a xenon–nitrogen bond

An X-ray crystallographic study has shown that FXeN(SO2F)2 contains an Xe–N bond, representing the first definitive proof for its existence; solution 15N and 129Xe n.m.r. studies of 15N-enriched FXeN(SO2F)2 also demonstrate that this bond is present in solution.

Observation of bridged–terminal hydrido equilibria in a series of iron–platinum bimetallic complexes

Oxidative addition of Fe(CO)4PR2H to Pt(C2H4)(PR′3)2 gives an equilibrium mixture of (OC)3Fe(µ-PR2)(µ-H)Pt(PR′3)2 and (OC)3(H)F[graphic omitted]t(PR′3)2, the first system in which an equilibration between bridge and terminal hydride bonding modes can be observed.

Bridged ring a steroids: total synthesis of (±)-14β-hydroxy-1β,4β-methano-5β,8α,9β-androstane-7,17-dione

A modification of the Torgov steroid synthesis in which a vinyl methyl ether group in ring B stabilizes the critical cationic intermediate has been used to synthesize the title compound (15), whose structure has been confirmed by X-ray crystallographic analysis.

Metal-assisted CO labilization and intramolecular hydride transfer reactions in heterobimetallic µ-phosphido–hydrido carbonyl complexes

The oxidative addition of the P–H bond of (OC)5M(PPh2H)(M = Cr, Mo, W) to zerovalent platinum complexes initially forms heterobimetallic µ-phosphido terminal hydrido complexes which readily rearrange via bridging carbonyl and platinum–terminal carbonyl intermediates to give the µ-phosphido-µ-hydrido complexes (OC)4M(µ-PPh2)(µ-H)Pt(PR3)2.

Bridge vs. terminal protonation of isostructural Mo–Pt and W–Pt heterobimetallic compounds

Protonation of the complexes cp(OC)2[graphic omitted](CO)(PPh3)(cp = cyclopentadienyl) exhibits an M-dependent site selectivity, with protonation occurring at the metal–metal bond for M = Mo to give [cp(OC)2Mo(µ-PPh2)(µ-H)-Pt(CO)PPh3]+ whilst for M = W protonation occurs directly at he tungsten to give a terminal hydrido cation [cp-(OC)2H[graphic omitted](CO)PPh3]+.

Total syntheses of (±)-α-biotol, (±)-β-biotol, and (±)-4-epi-α-biotol

Total syntheses of (±)-α-biotol, (±)-β-biotol, and (±)-4-epi-α-biotol from dimethyl 3-hydroxy-6-oxo-4,4,exo-8-trimethyl-cis-bicyclo[3.3.0]oct-2-ene-1,2-dicarboxylate are reported.

Unusual hydrogen transfer pathways in a Re–Pt heterobimetallic system

The cation cis-[cp(OC)(ON)Re(µ-Pcy2)PtH(PPh3)2]+{obtained from the oxidative addition of [cp(OC)(ON)RePcy2H]+ to Pt(C2H4)(PPh3)2; cp = cyclopentadienyl, cy = cyclohexyl}, undergoes a base-catalysed proton transfer accompanied by Co loss to give a terminal rhenium–hydrido cation [cp(ON)H[graphic omitted](PPh3)2]+ as the kinetically formed product, which in the presence of halide ions (other than F–) isomerizes to the thermodynamically preferred product [cp(ON)Re(µ-Pcy2)(µ-H)Pt(PPh3)2]+.

Synthesis and site-selective protonation of MoPt and WPt bimetallic complexes

The reaction of [M(cp)(CO)3(PPh3H)]PF61(M = Mo or W, cp =η-C5H5) with [Pt(C2H4)(PPh3)2] proceeds rapidly with a 1 : 2 (M : Pt) stoichiometry to give [(OC)2(cp)[graphic omitted]t(CO)(PPh3)]4 and [PtH(PPh3)3]PF65. However, using an initial 1 : 1 stoichiometry the final product is [(OC)2(cp)M(µ-H)(µ-PPh2)Pt(PPh2)2]PF68. The mechanisms of these reactions are shown to involve deprotonation of 1 to give [(OC)3M(cp)(PPh2)]2 followed by reaction of the latter with [Pt(C2H4)(PPh3)2] and subsequent transfer of CO from M to Pt to give 4. Protonation of 4 with HBF4 is metal (M) dependent and proceeds to give [(OC)2(cp)Mo(µ-H)(µ-PPh2)Pt(CO)(PPh3)]BF412a with M = Mo but for M = W the major product is [(OC)2H(cp)[graphic omitted]t(CO)(PPh3)]BF413b. Variable-temperature 1H NMR studies show that the terminal hydride cation of 13b is rapidly equilibrating with a small amount of the hydride-bridged isomeric cation [(OC)2(cp)W(µ-H)(µ-PPh2)Pt(CO)(PPh3)]+. Complex 4 reacts with PPh3(60 °C) and 1,2-bis(diphenylphosphino)ethane (dppe) at 20 °C to give [(OC)2(cp)[graphic omitted]t(PPh3)2]9 and [(OC)2(cp)[graphic omitted]t(dppe)]10. On bubbling CO through a solution of 9(20 °C) complex 4 is rapidly regenerated. Reaction of 4 with HCl gives [(OC)2(cp)M(µ-H)(µ-PPh2)PtCl(PPh3)]15. The molecular structure of [(OC)2(cp)[graphic omitted]t(CO)(PPh3)]4b has been determined by single-crystal X-ray diffraction.