Dichlorido(η<sup>4</sup>-cycloocta-1,5-diene)bis(triphenylphosphine)osmium(II)

Syntheses of osmium analogues of acceptor pincer ( CF 3 PCP)Ru-(II) systems are reported. Treatment of [Et 4 N] 2 OsCl 6 with CF 3 PCPH at 130 °C in ethanol in the presence of Et 3 N gave the coordinatively saturated anionic carbonyl complex HNEt 3 + [( CF 3 PCP)Os(CO)Cl 2 ] − , which subsequently may be converted to cis-( CF 3 PCP)Os(CO) 2 Cl or cis-( CF 3 PCP)Os(CO) 2 H by reaction with Me 3 SiOTf or (Et 3 Si) 2 (μ-H) + B(C 6 F 5 ) 4 −, respectively. ( CF 3 PCP)Os(cod)H was obtained in modest yields by thermolysis of Os(cod)(η 3 -2-methylallyl) 2 with CF 3 PCPH in neat cod under 3 atm of H 2 at 130 °C. The alkane dehydrogenation activity of ( CF 3 PCP)Os(cod)H was examined: under identical conditions to previously studied ( CF 3 PCP)Ru(cod)H (1:1 cyclooctane/tert-butylethylene, 200 °C), the initial turnover rate for cyclooctene production was 1520 h −1 , 75% the rate observed for the ruthenium analogue, but with significantly enhanced catalyst lifetime. Acceptorless cyclodecane dehydrogenation under reflux conditions gave 125 turnovers of cyclodecenes in one hour. Spectroscopic evidence on the nature of the catalyst resting state and catalyst thermal and air stability is presented.

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Acceptor Pincer Chemistry of Osmium: Catalytic Alkane Dehydrogenation by (^CF₃PCP)Os(cod)(H)

Gruver

Adams

Arulsamy

et al. 2013

Organometallics

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Substituent directed selectivity in anion recognition by a new class of simple osmium-pyrazole derived receptors

et al. 2016

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The present article deals with the structurally, spectroscopically and electrochemically characterised osmium-bipyridyl derived complexes [(bpy)2Os(II)(HL1)Cl]ClO4 [1]ClO4 and [(bpy)2Os(II)(HL2)Cl]ClO4 [2]ClO4 incorporating neutral and monodentate pyrazole derivatives (HL) with one free NH function (bpy = 2,2'-bipyridine, HL1 = pyrazole, HL2 = 3,5-dimethylpyrazole). The crystal structures of [1]ClO4 and [2]ClO4 reveal intramolecular hydrogen bonding interactions between the free NH proton of HL and the equatorially placed Cl(-) ligand (N-HCl) with donor-acceptor distances of 3.114(7) Å and 3.153(6) Å as well as intermolecular hydrogen bonding interactions between the NH proton and one of the oxygen atoms of ClO4(-) (N-HO) with donor-acceptor distances of 2.870(10) Å and 3.024(8) Å, respectively. The effect of hydrogen bonding interactions has translated into the less acidic nature of the NH proton of the coordinated HL with estimated pKa > 12. 1(+) and 2(+) exhibit reversible Os(II)/(III) and irreversible Os(III)/(IV) processes in CH3CN within ± 2.0 V versus SCE. The effect of 3,5-dimethyl substituted HL2 on 2(+) has been reflected in the appreciable lowering (40 mV) of the Os(II/III) potential, along with the further decrease in the acidity of the NH proton (pKa > 13.0) with regard to HL1 coordinated 1(+) (pKa: ∼ 12.3). The electronic spectral features of Os(ii) (1(+)/2(+)) and electrochemically generated Os(III) (1(2+)/2(2+)) derived complexes have been analysed by TD-DFT calculations. The efficacy of the 1(+) and 2(+) encompassing free NH proton towards the anion recognition process has been evaluated by different experimental investigations using a wide variety of anions. It however establishes that receptor 1(+) can recognise both F(-) and OAc(-) in acetonitrile solution, while 2(+) is exclusively selective for the F(-) ion.

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Dichlorido(η⁴-cycloocta-1,5-diene)bis(triphenylphosphine)osmium(II)

Cited by 2 publications

References 12 publications

Acceptor Pincer Chemistry of Osmium: Catalytic Alkane Dehydrogenation by (^CF₃PCP)Os(cod)(H)

Acceptor Pincer Chemistry of Osmium: Catalytic Alkane Dehydrogenation by (^CF₃PCP)Os(cod)(H)

Substituent directed selectivity in anion recognition by a new class of simple osmium-pyrazole derived receptors

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Dichlorido(η4-cycloocta-1,5-diene)bis(triphenylphosphine)osmium(II)

Cited by 2 publications

References 12 publications

Acceptor Pincer Chemistry of Osmium: Catalytic Alkane Dehydrogenation by (CF3PCP)Os(cod)(H)

Acceptor Pincer Chemistry of Osmium: Catalytic Alkane Dehydrogenation by (CF3PCP)Os(cod)(H)

Substituent directed selectivity in anion recognition by a new class of simple osmium-pyrazole derived receptors

Contact Info

Product

Resources

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Dichlorido(η⁴-cycloocta-1,5-diene)bis(triphenylphosphine)osmium(II)

Acceptor Pincer Chemistry of Osmium: Catalytic Alkane Dehydrogenation by (^CF₃PCP)Os(cod)(H)

Acceptor Pincer Chemistry of Osmium: Catalytic Alkane Dehydrogenation by (^CF₃PCP)Os(cod)(H)