Solid-state structure and reactivity in solution. 7. Flash photolytic studies of tetracarbonyltungsten(0) intermediates containing five- and six-membered chelating rings coordinating through sulfur

Octahedral metal carbonyls. 63. Chelate ring displacement of DTHp from cis-(DTHp)W(CO)4 by Lewis bases (DTHp = 2,2,6,6-tetramethyl-3,5-dithiaheptane, Lewis base = L (phosphine, phosphite))

“…Activation parameters for chelate ring closure in cis-[(solv)(?71-DTHp)W(CO)4] intermediates in both BB and DCE were determined from data taken over a temperature range of 10-45 °C. Enthalpies of activation for desolvation (DCE, 5.6 (5) kcal/mol; BB,6.4 (3) kcal/mol) are significantly smaller than is that (13.0 (4) kcal/mol) for loss of CB from di-[(CB)(P(0-;-Pr)3)W(CO)4], a process that has been found to be dissociative in nature.1 Moreover, that study showed that CB dissociates more rapidly from that complex than does either BB or DCE, suggestive of W-BB and W-DCE bonding being stronger than that of W-CB.1 The enthalpies of activation reported here are also smaller than the n-hept-Cr bond strength (ca. 10 kcal/mol; n-hept (18) It has been shown, in general, that flash photolysis of cis-(L)(L')M-(CO)4 complexes (L, L' = a Lewis base coordinating through N, P, or S) affords both the cis and trans five-coordinate species; the trans isomer reacts much more slowly than does the cis.…”

“…bAH_9* = 31.3 (5) kcal/mol; ASV = 21.6 (16) cal/(deg mol). c AH = -0.4 (9) kcal/mol; AS = 0.8 (30) cal/(deg mol).…”

Chelate ring closing and opening behavior in cyclopentadienyl cobalt(III) complexes with pendant nitrogen functional group

“…Since the rate constant k 1 describes the rupture of the chelated Co-N bond and the formation of a solvated reaction intermediate, the smallest k 1 value found for 3c implies that the metal-nitrogen bond in 3c is the most difficult one to rupture. The rate of chelate ring closing in coordinatively unsaturated metal complex is known as an ultrafast process and depends on the forming ring size [59][60][61][62]. The solvated ring opened reaction intermediate I S depicted in Scheme 2 are expected to be nearly identical in electronic property of the metal in spite of the different functional groups in their side chains.…”