Cumulative subject index: Vol. 126(1977)–150(1978)

1,3-Cyclooctadiene reacts with trimethylaluminum and potassium according to the equation 4K + 4Al(CH₃)₃ + 2C₈H₁₂

3K[Al(CH₃)₄]+K[(C₈H₁₂)₂Al] to give potassium bis(3,8-cis-cyclooctenyl) aluminate. The compound can be described as a bicyclo derivative of cyclooctene formed by the 1,4 addition to 1,3-cyclooctadiene. The structure of the complex was determined from 4500 unique data measured by single crystal X-ray diffractometer techniques. Full matrix least squares refinement gave final agreement factors of R₁ = 0.043 (observed data) and R₂ = 0.045 (all data) in the monoclinic space group P2₁/c (a = 9.658(6), b = 12.220(8) and c = 14.150(9)Å; β = 113.85(1)°; V = 1527.43 Å; Z = 4 for ?_calc = 1.23 g cm^?3).     

Cumulative author index: Vol. 126(1977)–150(1978)

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, Mössbauer 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) Å, 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 R_w values of 0.068 and 0.075 respectively. In the binuclear molecule an ironiron bond of length 2.550(2) Å 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.