Caesar V. Senoff

Nucleophilic substitution by arenethiolates at the carbene carbon of pentacarbonyl(methoxymethylcarbene)-metal(o) complexes (metal = Cr, Mo, or W)

The phenylthiocarbene complexes, [(CO)5MC(CH3)(SPh)] (M = Cr, Mo, or W) have been prepared in good yield by the reaction of [(CO)5MC(CH3)(OCH3)] (M = Cr, Mo, or W) with NaSPh in benzene/methanol in the presence of HCl. A series of para-substituted phenylthiocarbene complexes of tungsten. [(CO)5WC(CH3)SC6H4Y)], (Y = p-Br, p-F, p-H, p-CH3, p-OCH3 or p-OH) have also been prepared by the reaction of the appropriate arenethiolate ion with [(CO)5WC(CH3)(OCH3)]. Poor nucleophiles such as p-nitrobenzenethiolate and pentafluorobenzenethiolate did not react with [(CO)5WC(CH3)(OCH3) to form the corresponding phenylthiocarbene complex. A mechanism accounting for the formation of these phenylthiocarbene complexes is proposed. The complexes have been characterized by their infrared, electronic, mass, 1H NMR, and 13C NMR spectra. These spectroscopic data have been used to establish the structure of these complexes in solution and indicate that the phenyl ring bonded to sulfur is probably not coplanar with the “carbene” plane.

Metal-olefin complexes: Synthesis and molecular structure of trans-chloro(ethylene)bis(triphenylphosphine)iridium(I), IrCI(C2H4)(PPh3)2

Abstract The complex, trans-IrCl(C2H4)(PPh3)2 has been isolated and its structure in the solid state determined by single-crystal X-ray diffraction. The crystals are monoclinic P21/c, with a = 12.334(2), b = 22.957(4), c = 14.039(2) A, β = 125.54(1)°, Z = 4. The structure was solved by the heavy-atom method and refined by least-squares techniques to an R value of 0.032 for 4006 reflections. The molecule has a trans-square planar configuration. The coordinated ethylene is π-bonded to the iridium atom and is essentially perpendicular to the P2IrCl plane with a very short CC distance of 1.375(10) A. The olefin exerts a negligible trans-influence on the IrCl bond. Principal bond lengths are: IrCl, 2.371(2); IrP, 2.318(3), 2.312(3); IrC(1), 2.123(8); IrC(2), 2.112(8) A.

The molecular dynamics of fluxional organometallic molecules in the solid state: tetracarbonylbis(cyclooctatetraene)triruthenium(0)

Abstract The “wide line” NMR spectrum of tetracarbonylbis(cyclooctatetraene)triruthenium(0) is markedly temperature dependent, indicating that the cyclooctatetraene rings are reorienting in the solide state. An energy of activation of 5.15 kcal/mol for ring rearrangement is found from T 1 measurements. A comparison of the experimental second moment, 0.72 G 2 at 304 K, with theoretical second moments calculated for several different modes of reorientation supports a rearrangement process through a series of 1,2 shifts. The results are discussed in relation to the known crystal structure data for the complex.

Transmission of electronic effects in trans-hydrido-(arenethiolato)bis(triphenylphosphine)platinum(II) complexes

Abstract A series of para -substituted benzenethiols have been shown to react with Pt(Ph 3 P) 3 or Pt(Ph 3 P) 4 to form trans -[PtH(SC 6 H 4 Y)(Ph 3 P) 2 ] where Y = NO 2 , Br, Cl, F, H, CH 3 , CH 3 O, or NH 2 . Good correlations have been obtained when v (PtH) or J (PtH) is plotted against the Hammett substituent parameter,σ p . These linear correlations are discussed in terms of electron density changes at platinum due to the mesomeric and inductive effects of the para -substituent. The electronic spectra of this series of complexes have been examined in benzene and are characterized by a charge transfer band which has been assigned to an L → M electron transfer process.

A triply bridged dimeric iridium(III) hydride: μ-chlorodi-μ-(phenylthio)di{hydridobis(triphenylphosphine)iridium(III)} perchlorate, [(Ph3P)2(H)Ir(SPh2ClIr(H)(PPh3)2]ClO4 · 3(CH3)2CO

Abstract The dimeric iridium(III) hydride, [IrHCl(SPh)(PPh 3 ) 2 ] 2 has been shown to react with silver perchlorate in acetone to produce the triply bridged dimeric species, [(Ph 3 P) 2 (H)Ir(Sph) 2 ClIr(H)(PPh 3 ) 2 ClO 4 · 3(CH 3 ) 2 CO, whose structure has been determined by single-crystal X-ray crystallography.

Tris(2-aminoethyl)amine complexes of palladium(II)

Abstract The syntheses of a series of complexes of the type, [PdX(tren)] Y where tren = N(CH2CH2NH2)3, X = Cl, BPh−4 are described and their physico-chemical proBPH4 are described and their physico-chemical properties compared with the trenMe6 analogues where trenMe6 = N(CH2CH2N(CH3)2)3. The available data suggest that these complexes are four coordinate in the solid state but exist in solution as an equilibrium involving five and four coordinate species. In the presence of ClO−4 ion, [Pd(NCS)(tren)]+ forms [Pd(NCS)(trenH)](ClO4)2 where trenH = N(CH2CH2NH2)2(CH2CH2NH+3. The complex having X = NCS undergoes an N → S isomerization when the anion is changed from SCN− to BPh−4.