Paul J. Roberts

Phosphorus-based 1,3-dipoles as three-electron one-carbon ligands: x-ray structure of μ-[phenyl(dicyclohexylphosphonio)ethenidyl]-μ-(diphenylphosphido)hexacarbonyldiiron, Fe2(CO)6[CC(PCy2H)Ph](PPh2)

Abstract The synthesis of μ-[phenyl(dicyclohexylphosphonio)ethenidyl]-μ-(diphenylphosphido)hexacarbonyldiiron, Fe2(CO)6[CC(PCy2H)Ph](PPh2) via nucleophilic attack by dicyclohexylphosphine at the β-carbon atom of the σπ-acetylide in Fe2(CO)6(CCPh)(PPh2) is described. This complex, which contains a one-carbon 3-electron bridging ligand has been characterised by microanalysis, infrared, mass, Mossbauer and 31P NMR spectroscopy and by a single crystal X-ray structure determination. Crystals are monoclinic, space group P21/c with a 10.932(3), b 8.983(2), c 38.644(6) A, β 94.48(2)°. With four molecules per unit cell and a formula weight of 764.4, the calculated density of 1.342 g cm−3 agrees with the measured value of 1.34 g cm−3. The structure was solved by heavy atom methods and refined by least squares techniques with iron and phosphorus atoms having anisotropic thermal parameters, to R and Rw values of 0.068 and 0.075 respectively. In the binuclear molecule an ironiron bond of length 2.550(2) A is bridged by a diphenylphosphido group and the carbon atom of an unusual dipolar ligand Cy2(H)P+C(Ph)C−. In the bridging one-carbon-3-electron ligand the coordinated carbon atom is trigonal and the atoms P(1), C(8), C(31), C(7) are virtually coplanar. Structural parameters are compared with those of other complexes containing bridging one-carbon, 3-electron and two-carbon, 3-electron ligands. Nucleophilic attack by phosphorus and nitrogen nucleophiles on σπ-acetylides appears to be a general route to these ligands.

Gas-phase reactions on platinum. Synthesis and crystal structure of anti- tetramantane, a large diamondoid fragment

anti-Tetramantane, a C22H28 hydrocarbon having the regular topology of the diamondoid lattice, has been synthesised by a double homologation of diamantane, the key step involving a ring expansion–cyclisation reaction of a polycyclic diene in hydrogen in the gas phase on a platinum-silica catalyst; the structure has been established by an X-ray crystal analysis.

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.

The absolute configuration of (+)-isocamphenilanic acid by X-ray analysis and of (–)-camphene

The absolute configuration of (+)-isocamphenilanic acid (3,3-dimethylnorbornane-exo-2-carboxylic acid)(2; R = OH) has been defined by an X-ray crystallographic examination of the p-bromophenacyl ester. Degradation of this (+)-acid by the Cope procedure proceeds by normal cis-elimination to furnish (–)-camphene, but is in conflict with the reported chemical conversion of (–)-camphene into (–)-camphene into (–)-isocamphenilanic acid.

Crystal and molecular structure of trans,trans-tetrabenzo[a,c,g,i]cyclododecene

The title compound crystallizes in space group C2/c with a= 16·810(5), b= 16·694(5), c= 13·835(4)A, β= 98·41(2)°. The structure was solved by direct methods from diffractometer data and was refined to R 0·060 for 2416 independent, observed reflexions. The structure consists of two independent molecules lying in different orientations on crystallographic two-fold axes. This implies that the free molecule has D2(222) symmetry. The molecular geometry in the crystal structure is discussed in terms of distortion from this symmetry.