Trans Group VI metal dicarbonyls. Stereochemical control by seven-coordinate intermediates

Abstract

Notes tadiene and trimethylenemethane are similar.However, the fact that the weighted average of the C Is binding energies of the trimethylenemethane ligand is actually slightly less than the C Is binding energy of the butadiene ligand suggests slightly greater back-bonding to trimethylenemethane than to butadiene. This interpretation is consistent with the fact that the Fe 2p3/2, carbonyl C Is, and O Is binding energies are higher (by 0.30, 0.14, and 0.07 eV, respectively) in the trimethylenemethane complex than in the butadiene complex. Indeed, even infrared C-0 stretching frequencies indicate more back-bonding to the trimethyleneemethane ligand than to the butadiene ligand.22

Investigation of isomerism rates and mechanism of some 17- and 18-electron substituted carbonyl complexes of chromium, molybdenum, and tungsten using double potential step chronoamperometry

“…Finally, we believe his interpretation of the George and Siebold NMR data5 is incorrect with respect to mechanistic conclusions. These NMR data, together with the rate constants measured recently by Wreford,20 have been obtained in the absence of supporting electrolyte, and as a result, the rate of isomerization appears to be much slower. Apparently medium effects (ionic strength) are extremely critical and invalid comparisons of data have been made by Elson.…”

Interconversion of cis-trans isomers in MX(CO)2(unsymmetric, bidentate phosphine)2

“…Caled for C18H40IO2P4Ta: C, 30.01: , 5.60. Found: C,30.13; H, 5.96. TaI(CO)2(dmdppe)2 (6). 4 (583 mg, 0.852 mmol) and 216 mg of I2 (0.852 mmol) were reacted as in the preparation of 1 to yield, after crystallization from benzene-heptane, orange crystals of 6: IR (THF solution) vCo 1834 (vs), 1763 (s) cm"1; mass spectrum m/e 776 (12C221H48127I160231P4181Ta)+, 748 (P -CO)+, 720 (P -2CO)+.…”