Broad-band irradiation (λmax = 350 nm) of FvRu2(CO)4 (1, Fv = η5:η5-bicyclopentadienyl) resulted in rapid isomerization to colorless (μ2-η1:η5-cyclopentadienyl)2Ru2(CO)4 (2) in a novel process involving a formal dinuclear oxidative addition to a C−C bond. The product reverted to 1 upon heating in solution or in the solid state, under the latter conditions with an enthalpy change of −29.8 (1.5) kcal mol-1. Mechanistic studies with a mixture of 1 and 1-d8 revealed the absence of label scrambling, pointing to intramolecular pathways. The quantum yield (0.15) was unaffected by the presence of CCl4, and no chlorination products were observed under these conditions. Irradiation of solutions of 1 or 2 with 300 nm light provided Fv(μ2-η1:η5-cyclopentadienyl)2Ru4(CO)6 (6) or, in the presence of alkynes, the adducts FvRu2(CO)3(RCCR) (8−10, R = H, C6H5, CO2CH3). Heating 1 and PR3 (R = CH2CH3, CH3, or OCH3) yielded FvRu2(CO)3(PR3) (12−14), in which a fluxional process occurs characterized by intramolecular terminal t...

Photochemistry of (Fulvalene)tetracarbonyldiruthenium and Its Derivatives: Efficient Light Energy Storage Devices

Monosubstituted cyclopentadienyl half-sandwich transition metal complexes

The success of tris(pyrazolyl)borates has inspired the development of new scorpionate ligands that are based on other donor groups. These include borate ligands with thioimidazolyl, selenoimidazolyl, phosphine and N-heterocyclic carbene donors, ligands that provide a facial array of [S3], [Se3], [P3], and [C3] donors, respectively. These ligands are all more strongly donating than the tris(pyrazolyl)borates, with tris(carbene)borate ligands having the greatest donor strength. Despite the design similarities, strongly donating scorpionates differ in their topology and flexibility, donor properties and degradation pathways. The structural and electronic properties of these ligands are contrasted and related to their chemistry, particularly that of the transition metals. Bidentate congeners of all these ligands are also known and are briefly covered. The ability of strongly donating scorpionate ligands to stabilize metal ligand multiple bonds in late transition metal complexes is also briefly discussed.

Strongly donating scorpionate ligands

This paper introduces a sterically encumbered, strong-field tris(diisopropylphosphino)borate ligand, [PhBPiPr3] ([PhBP^(iPr)_(3)] = [PhB(CH_2P^iPr_2)_3]^-, to probe aspects of its conformational and electronic characteristics within a host of complexes. To this end, the Tl(I) complex, [PhBP^iPr_3]Tl (1), was synthesized and characterized in the solid-state by X-ray diffraction analysis. This precursor proves to be an effective transmetallating agent, as evidenced by its reaction with the divalent halides FeCl_2 and CoX_2 (X = Cl, I) to produce the monomeric, 4-coordinate, high-spin derivatives [PhBP^iPr_3]FeCl_2 and [PhBP^iPr_3]CoX (X = Cl_3, I_4) in good yield. Complexes 2−4 were each characterized by X-ray diffraction analysis and shown to be monomeric in the solid-state. For conformational and electronic comparison within a system exhibiting higher than 4-coordination, the 16-electron ruthenium complexes {[PhBP^iPr_3]Ru(μ-Cl)}_2 (5) and {[PhBP_3]Ru(μ-Cl)}_2 (6) were prepared and characterized ([PhBP_3] = [PhB(CH_2PPh_2)_3]^-. The chloride complexes 2 and 3 reacted with excess CO to afford the divalent, monocarbonyl adducts [PhBP^iPr_3]FeCl(CO) (7) and [PhBP^iPr_3]CoCl(CO) (8), respectively. Reaction of 4 with excess CO resulted in the monovalent, dicarbonyl product [PhBP^iPr_3]CoI(CO)_2 (9). Complexes 5 and 6 also bound CO readily, providing the octahedral, 18-electron complexes [PhBP^iPr_3]RuCl(CO)_2 (10) and [PhBP_3]RuCl(CO)_2 (11), respectively. Dimers 5 and 6 were broken up by reaction with trimethylphosphine to produce the mono-PMe_3 adducts [PhBP^iPr_3]RuCl(PMe_3) (12) and [PhBP3]RuCl(PMe3) (13). Stoichiometric oxidation of 3 with dioxygen provided the 4-electron oxidation product [PhB(CH_2P(O)^iPr_2)_2(CH_2P^iPr_2)]CoCl (14), while exposure of 3 to excess oxygen results in the 6-electron oxidation product [PhB(CH_2P(O)^iPr_2)_3]CoCl (15). Complexes 2 and 4 were characterized via cyclic voltammetry to compare their redox behavior to their [PhBP_3] analogues. Complex 4 was also studied by SQUID magnetization and EPR spectroscopy to confirm its high-spin assignment, providing an interesting contrast to its previously described low-spin relative, [PhBP_3]CoI. The difference in spin states observed for these two systems reflects the conformational rigidity of the [PhBPiPr3] ligand by comparison to [PhBP_3], leaving the former less able to accommodate a JT-distorted electronic ground state.

The Strong-Field Tripodal Phosphine Donor, [PhB(CH2PiPr2)3]-, Provides Access to Electronically and Coordinatively Unsaturated Transition Metal Complexes

H.J. Lyons

Papers

A new type of isomerism in some phosphine and phosphite derivatives of the metal carbonyls

Kinetics of substitution reactions of cyclopentadienyl metal carbonyl halides

Solvent and structural effects in substitution reactions of metal carbonyl halides

Isomerie von phosphin‐ und phosphit‐derivaten von metallcarbonylen

Einfluesse von loesungsmittel und struktur auf die substitutionsrk. von metallcarbonylhalogeniden