Static and dynamic stereochemistry of hexaethylbenzene and of its tricarbonylchromium, tricarbonylmolybdenum, and dicarbonyl(triphenylphosphine)chromium complexes

Tricarbonyl(η6-trimethylphenylsilane)molybdenum

“…Selected bond lengths and angles are given in Table 2. The Mo--C(carbonyl) [average 1.958 (6) ,~] and C--O [average 1.148 (7) ,~] distances are similar to those found for other arene)(CO)3] complexes (Koshland, Myers & Chesick, 1977;Iverson, Junter, Blount, Damewood & Mislow 1981;Braga & Grepionl 1990;Biirgi, Raselli, Braga & Grepioni, 1992). The Mo atom is situated 1.908 (3) A above the centre of the planar arene ring, which compares with 1.908 ,~ in [Mo(zrMes) (Koshland, Myers & Chesick, 1977) (Braga & Grepioni, 1990)].…”

“…In general, they show dynamic stereochemistry both in solution and in the solid state (Wagner & Hanson, 1987). Variation in the arene ring substituents leads to different conformations of the tricarbonyl moiety with respect to the arene ring (i. e. staggered or eclipsed) (Koshland, Myers & Chesick, 1977;Hossain & van der Helm, 1978;Iverson, Junter, Blount, Damewood & Mislow, 1981;Alyea, Ferguson & Somogyvari, 1983;Kerschner, Torres, Fanwick, Rothwell & Huffman, 1989;Braga & Grepioni, 1990;B/irgi, Raselli, Braga & Grepioni, 1992). As a preliminary to multinuclear NMR spectroscopic studies on such molybdenumcarbonyl complexes, we have investigated the structure of [Mo(CO)3(r/6-C6HsSiMe3)], (1); the results are reported herein.…”

Monoclinic and triclinic forms of [1,2-bis(diphenylphosphino)propane](η6-methyldiphenylphosphine)(methyldiphenylphosphine)molybdenum(0) benzene solvate

“…All these Mo-C distances are significantly shorter than examples where the r/6 ring is trans to carbonyl ligands. Typical Mo-C distances in the latter compounds are 2.35-2.38 A (Alyea, Ferguson & Somogyvari, 1983;Hossain & van der Helm, 1978;Iverson, Hunter, Blount, Damewood & Mislow, 1981;Koshland, Myers & Chesick, 1977).…”

Restricted rotation about arene–oxygen bonds in some 1,3-di-tert-butyl-2-methoxyarenedicarbonylphosphorus(III)chromium compounds

“…There remains the anomaly of the steric considerations discussed above: we are unable to explain why our series should show the opposite behaviour to those in the literature. Significantly though, the AG* values for all of our complexes and for Mislow's hexaethylbenzene complex (9) were close to 50 kJ mol-'. The McGlinchey work (10) produced a AGS of about this size, too, and it seems possible that all of these cases involve restricted rotation of the side chain in the complexed arene.…”