Photochemistry of some (η⁵-cyclopentadienyl)carbonylchloro complexes of molybdenum, tungsten, iron, and ruthenium in frozen gas matrices at ca. 12 K and in poly(vinyl chloride) films at ca. 12–298 K

Abstract

Infrared spectroscopic evidence including 13C0 substitution and energy-factored force-field fitting is presented to show that photolysis of [M (q5-C5H5) (CO),CI] complexes (M = Mo or W) in argon, methane, nitrogen, carbon monoxide, and 5% C, H, -CH, matrices at ca. 12 K yields ejection of CO and formation of the 16-electron species [M(q5-C5H5) (CO),CI] as the primary process. This process is reversible. In nitrogen and 5% C, H, -CH, matrices the [ M (q5-C5H5) (CO),CI] species react with N, and C2H4 to give cis-[ Mo(q5-C5H5) (CO),( N, ) CI] and cis-[ M (q5-C5H5) (CO),( C, H, ) CI] (M = Mo or W) respectively. In carbon monoxide matrices the ejection of CO is suppressed and the photolysis products are proposed to be the species [ M (q5-C5H5) (CO),] 'CI-(M = Mo or W), indicative of metal-chlorine bond heterolysis. Irradiation of [M(q5-C5H5) (CO),CI] complexes (M = Fe or Ru) in methane, nitrogen, and carbon monoxide matrices and in poly(viny1 chloride) films at ca. 12 K produced only the 16-electron species [M (q5-C5H5) (CO)CI] and CO indicating that dissociation, rather than cleavage of the metal-chlorine bond, is the principal reaction pathway. The primary process can be reversed thermally in the polymer films by virtue of their wider working temperature range (ca. 12-298 K). For the iron complex reversal occurred by ca. 60 K, whereas the ruthenium complex needed a higher temperature of annealing (ca. 80 K). The results of the low-temperature studies are discussed in relation to the thermal and photochemical reactions of complexes of Mo, W, Fe, and Ru in solution at ambient temperatures.f Non-S.I. unit employed: Torr x 133 Pa.

Ultraviolet photodissociation of gas-phase transition metal complexes: dicarbonylcyclopentadienyliodoiron(II)

“…to what extent the present conclusions will extrapolate to metal complexes that lack such a heavy atom. In this regard, we note an earlier photolysis study of CpFe(CO)2Cl in the wavelength range 290  λ  370 nm in a low temperature (12 K) matrix that identified loss of CO but no C-Cl bond fission 40 -an outcome that could be explained by invoking purely singlet state mediated photochemistry. The recent X-ray photoelectron spectroscopy study of the products formed in the λ = 266 nm photolysis of (gas phase) Fe(CO)5 also concluded that the loss of successive CO ligands occurs solely on singlet PESs, 18 Table 1 Threshold energies for forming selected product combinations defined relative to the singlet ground state of CpFe(CO)2I, calculated at the DFT/CAM-B3LYP/LANL2DZ level of theory.…”

Comparative photochemistry of ring-substituted half-sandwich tetracarbonylvanadium complexes in low-temperature matrices at ca. 12 K

“…The band shifts of ca. [40][41][42][43][44][45][46][47][48][49][50] cm'1 to lower wavenumbers are consistent with the observations for (tj5-C5H5)V(CO)3 (3b).22 It was not possible, however, even using high-energy UV irradiation (filter E, 290 < X < 370 and X > 550 nm; or filter F, 230 < X < 280 nm) to generate the corresponding dior monocarbonyl species Cp*V(CO)" ( = 1, 2) in the matrix. Interestingly, the bands of species la are shifted to higher wavenumbers.…”

Four-Legged Piano Stool Molybdenum(II) Compounds without Carbonyl Ligands. 4. Cyclopentadienylmolybdenum(II) Complexes with 16-Electron and 18-Electron Configurations

“…For instance, the CpMoX(CO) 2 (X ) Cl, CH 3 ) fragments are obtained by photolytic CO ejection from CpMoX(CO) 3 , but the primary photoproduct rapidly reacts with N 2 , C 2 H 4 , CO, and other sub- strates to afford saturated adducts. [40][41][42] Rare examples of stable 16-electron complexes are based on the general formula (Ring)MoXL 2 , where Ring is Cp or a substituted derivative, L is CO or phosphine, and X is an efficient π-donor group such as a phosphido or arsenido ligand. 20,[43][44][45] Consequently, all these complexes are effectively electronically saturated and are diamagnetic.…”

“…Half-sandwich 18-electron complexes of Mo(II) constitute a very extensive class of compounds. , Related complexes with a 16-electron configuration are rare, and most, especially when they contain one or more CO ligands, have only been observed as transients in chemical reactions. For instance, the CpMoX(CO) 2 (X = Cl, CH 3 ) fragments are obtained by photolytic CO ejection from CpMoX(CO) 3 , but the primary photoproduct rapidly reacts with N 2 , C 2 H 4 , CO, and other substrates to afford saturated adducts. − Rare examples of stable 16-electron complexes are based on the general formula (Ring)MoXL 2 , where Ring is Cp or a substituted derivative, L is CO or phosphine, and X is an efficient π-donor group such as a phosphido or arsenido ligand. 20,43-45 Consequently, all these complexes are effectively electronically saturated and are diamagnetic.…”