Photochemistry of the Clusters Os3(CO)10(L) (L = 2,2'-Bipyridine, 2,2'-Bipyrimidine, 2,3-Dipyrid-2-ylpyrazine, 2,3-Dipyrid-2-ylbenzoquinoxaline). Reversible Opening of an Os-Os Bond with Formation of a Zwitterion

Abstract

Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. [6312][6313][6314][6315][6316][6317][6318] Photochemistry of the Clusters OS~(CO)~O(L) (L = 2,2'-Bipyridine, 2,2'-Bipyrimidine, 2,3-Dipyrid-2-ylpyrazine, 2,3-Dipyrid-2-ylbenzoquinoxaline). The complexes OS~(CO)IO(L) (L = 2,2'-bipyridine (bpy), 2,2'-bipyrimidine (bpym), 2,3-dipyrid-2-ylpyraine (dpp), and 2,3-dipyrid-2-ylbenzoquinoxaline (dpb)) were synthesized, and their low-energy Os -L (MLCT) transitions were characterized with resonance Raman spectroscopy. Continuous wave excitation into the MLCT transitions does not lead to product formation. However, rapid-scan IR and nano-and picosecond time-resolved absorption spectra show the formation of a transient species (for L = bpy, bpym, and dpp) which reacts back to give the parent complex. In toluene the transient has a lifetime of less than 10 ns and is assigned to an MLCT state of the cluster. In coordinating solvents a different transient species is observed with a lifetime that strongly depends

Unprecedented Coordination of 4,4′,5,5′-Tetramethyl-2,2′-biphosphinine Doubly Bridging over an Open Triosmium Core

“…[1][2][3] In comparison with σN,σNЈ-chelated 2,2Ј-bipyridine, its aromatic phosphorus derivative 4,4Ј,5,5Ј-tetramethyl-2,2Ј-biphosphinine (tmbp) binds as a fairly strong π-acceptor ligand in a variety of mononuclear complexes, and better stabilizes low oxidation states of the metal in the M(σP,σPЈ-tmbp) chelate ring. Such ligands include 4,4Ј-di-R-2,2Јbipyridine and pyridine-2-carbaldehyde-NЈ-R-imine (R ϭ alkyl).…”

Unprecedented Coordination of 4,4′,5,5′-Tetramethyl-2,2′-biphosphinine Doubly Bridging over an Open Triosmium Core

“…The corresponding electronic transition exhibits negligible solvatochromism, [9] in contrast to the lowest-energy electronic transition of [Os 3 (CO) 10 (bpy)], which possesses a dominant metal(core)-to-ligand charge transfer character. [1,10] The involved frontier orbitals of 1 probably have a dominant contribution from the tmbp ligand. [8] This may explain the observed inherent photostability of 1, as no specific metal-ligand or metal-metal bonds are significantly weakened upon visible excitation.…”

“…Such ligands include 4,4Ј-di-R-2,2Ј-bipyridine and pyridine-2-carbaldehyde-NЈ-R-imine (R ϭ alkyl). [1][2][3] In comparison with σN,σNЈ-chelated 2,2Ј-bipyridine, its aromatic phosphorus derivative 4,4Ј,5,5Ј-tetramethyl-2,2Ј-biphosphinine (tmbp) binds as a fairly strong π-acceptor ligand in a variety of mononuclear complexes, and better stabilizes low oxidation states of the metal in the M(σP,σPЈ-tmbp) chelate ring. [4,5] In addition, it may bind as a cyclophosphahexatriene with localized double bonds, for example in [Mn 2 (CO) 6 (tmbp)] where it chelates to one Mn(CO) 3 moiety through the P lone pairs and to the other metal centre through the internal PϭC bonds.…”

Bonding and Redox Properties of [Os3(CO)9(tmbp)(L)] (tmbp=4,4′,5,5′-tetramethyl-2,2′-biphosphinine; L=CO, PPh3) Clusters with an Unprecedented Electron-Deficient Metallic Core and Doubly Bridging Biphosphinine Dianion

“…Pure 2 was obtained as a purple powder in 85 % yield. 1 Crystallography: Crystal data and details of the structure determination of cluster 2 are presented in Table 9. Crystals of 2 ¥ C 6 H 12 were grown by heating a solution of the complex in cyclohexane for five days at 80 8C.…”

“…ÀOs(CO) 4 ÀOs (CO) 2 (a-diimine .À )]. [1,2] Electrochemical reduction of [Os 3 (CO) 10 (a-diimine)] initially gives the radical anions [Os 3 (CO) 10 (a-diimine .À )], which are thermally unstable and convert to various anionic open-triangle products in a series of chemical and electron-transfer steps. [3,4] In both the biradical photoproducts and the radical anions there is an unpaired electron localized on the reducible a-diimine ligand.…”