Infrared spectroscopic study of the photochemical substitution and oxidative addition reactions of (.eta.5-C5R5)M(CO)4 compounds of group 5 metals: characterization of the products of reaction with nitrogen, hydrogen and HSiEt3-xClx and the kinetic investigation of (.eta.5-C5R5)M(CO)3 intermediates

Formation and reactivity of organometallic alkane complexes

“…The second order rate constants for the reaction of a series of n-heptane complexes with CO (k CO ) are shown in Table 1. The reactivity of the organometallic alkane complexes studied has been found to decrease on going both across and down Groups V-VII [49,51,56,57].…”

“…[59]. allowed for systematic investigations into the electronic and steric factors affecting the stability of transition metal alkane complexes [49][50][51][52]. The reactivity of the organometallic alkane complex to ligand substitution is measured and the second order rate constant (k 2 ) for this reaction, determined by measuring the pseudo-first order rate as a function of CO concentration, can be used as a measure of the relative stability of the alkane complex, Scheme 2 [53,54].…”

Time-resolved infrared (TRIR) study on the formation and reactivity of organometallic methane and ethane complexes in room temperature solution

“…Time-resolved infrared (TRIR) spectroscopy has proved to be a powerful tool for the study of metal carbonyl alkane complexes. Their reactivity decreases on going both across and down groups 5,6, and 7 (10)(11)(12), and these observations led to the identification of a very long-lived alkane complex, Re(Cp)(CO) 2 (nheptane) (Cp ϭ 5 OC 5 H 5 ), which has a lifetime of Ϸ25 ms at room temperature (13). The relative stability of Re(Cp)(CO) 2 (alkane) complexes allowed Re(Cp)(CO) 2 (C 5 H 10 ) to be observed at 180 K by NMR spectroscopy (14), and subsequent NMR studies have been carried out to determine the binding modes of a series of related alkanes to the Re(CpЈ)(CO) 2 moiety (15,16).…”

“…Metal-alkane binding enthalpies have been determined by photoacoustic calorimetry (PAC) and TRIR spectroscopy for a range of group 6 [M(CO) 5 (heptane)] and group 7 [M(Cp)(CO) 2 (heptane)] complexes in solution, and these are found to range between 40 and 57 kJ⅐mol Ϫ1 (10,(20)(21)(22)(23)(24). Gas-phase TRIR studies have demonstrated that the shorter n-alkane species have progressively lower binding energies to the metal, with CH 4 being the most weakly bound (25).…”

Open shell organometallics: a general analysis of their electronic structure and reactivity

“…This result is unusual because the two substrates are isoelectronic and isosteric and add with very similar rates to most other 16-electron organometallic fragments, e.g. CpM(CO) 3 (M = V, Nb, Ta), [49] though these are probably solvated species in the hydrocarbon or noble gas matrices in which they are photogenerated. A slightly faster CO addition (less than one order of magnitude) can be understood on the basis of HammondÕs principle since the newly formed M-CO bond is stronger than the corresponding M-N 2 bond.…”