Metallorganische Verbindungen der Lanthanoide, 89. Cyclooctatetraenyl‐Komplexe der frühen Übergangsmetalle und Lanthanoide, 6. (Cyclooctatetraenyl)[N,N′‐bis(trimethylsilyl)benzamidinato]‐und ‐[diphenylbis(trimethylsilylimido)phosphinato]‐Komplexe der Seltenen Erden; Röntgenstrukturanalyse von (C8H8)Tm[PhC(NSiMe3)2](THF), (C8H8)Lu[4‐MeOC6H4C(NSiMe3)2](THF) und (C8H8)Nd[P
Abstract:Metallorganische Verbindungen der Lanthanoide, 891' 1 Cyclooctatetraenyl-Komplexe der friihen Ubergangsmetalle und Lanthanoide, 6f21
(Cyclooctatetraenyl)[~,~'-bis(trimethylsilyl)benzamidinato]und -[diphenylbis( trimethylsilylimido)phosphinato]-Komplexeder Seltenen Erden; Rontgenstrukturanalyse von (CsHS)Tm[PhC(NSiMe3),](THF), ( CsHs)Lu[4-Me0 C6H4C( NSiMe3),] (THF) und ( C8Hs)Nd[Ph2P(NSiMe3)2 I( THF) Organometallic Compounds of the Lanthanoids. 89111. -Cyclooctatetraenyl Complexes of the Early Transition Metals… Show more
“…This is in good agreement with a recent detailed study describing the paramagnetic NMR analysis of substituted bis(cyclooctatetraenyl) lanthanide complexes . As expected, the 1 H NMR signals of the COT′′ ligands in the Pr complex 1 experience significant line‐broadening and a considerable paramagnetic shift to a higher field . The single resonance at δ = –6.77 ppm was assigned to the SiMe 3 protons, whereas the COT′′ ring protons gave rise to two broad singlets at δ = –10.15 and –14.15 ppm.…”
Five new lanthanide(III) sandwich and half‐sandwich complexes with bulky cyclooctatetraenyl ligands have been prepared and fully characterized, including single‐crystal X‐ray structure determination. The treatment of anhydrous lanthanide(III) chlorides, LnCl3 (Ln = Pr, Tb, Yb), with 2 equivalents of Li2COT′′ [COT′′ = 1,4‐bis(trimethylsilyl)cyclooctatetraene dianion] followed by crystallization in the presence of a coordinating solvent afforded the anionic sandwich complexes [Li(THF)4][Pr(COT′′)2] (1), [Li(DME)3][Tb(COT′′)2] (2; DME = 1,2‐dimethoxyethane), and [Li(TMEDA)2][Yb(COT′′)2] (3; TMEDA = N,N,N′,N′‐tetramethylethylenediamine). Attempted oxidation of 2 with silver iodide did not afford the neutral terbium(IV) sandwich complex [Tb(COT′′)2]. Instead, the tri(µ‐iodido)‐bridged dinuclear half‐sandwich complex [Li(DME)2][Tb2(µ‐I)3(COT′′)2] (4) was isolated in 72 % yield. In this complex, the Li(DME)2 fragment is attached to one of the µ‐iodido ligands. A closely related binuclear lutetium complex, [Li(DME)3][Lu2(µ‐Cl)3(COTbig)2]·DME (5), was obtained by using the “superbulky“ COTbig ligand [COTbig = 1,4‐bis(triphenylsilyl)cyclooctatetraenyl dianion]. In addition to the spectroscopic and structural characterization, the magnetic properties of the paramagnetic terbium(III) derivative 2 have been investigated and further complemented by ab initio computational methods. These results have been used to discuss the structural requirements for potential terbium(III) single‐ion magnets.
“…This is in good agreement with a recent detailed study describing the paramagnetic NMR analysis of substituted bis(cyclooctatetraenyl) lanthanide complexes . As expected, the 1 H NMR signals of the COT′′ ligands in the Pr complex 1 experience significant line‐broadening and a considerable paramagnetic shift to a higher field . The single resonance at δ = –6.77 ppm was assigned to the SiMe 3 protons, whereas the COT′′ ring protons gave rise to two broad singlets at δ = –10.15 and –14.15 ppm.…”
Five new lanthanide(III) sandwich and half‐sandwich complexes with bulky cyclooctatetraenyl ligands have been prepared and fully characterized, including single‐crystal X‐ray structure determination. The treatment of anhydrous lanthanide(III) chlorides, LnCl3 (Ln = Pr, Tb, Yb), with 2 equivalents of Li2COT′′ [COT′′ = 1,4‐bis(trimethylsilyl)cyclooctatetraene dianion] followed by crystallization in the presence of a coordinating solvent afforded the anionic sandwich complexes [Li(THF)4][Pr(COT′′)2] (1), [Li(DME)3][Tb(COT′′)2] (2; DME = 1,2‐dimethoxyethane), and [Li(TMEDA)2][Yb(COT′′)2] (3; TMEDA = N,N,N′,N′‐tetramethylethylenediamine). Attempted oxidation of 2 with silver iodide did not afford the neutral terbium(IV) sandwich complex [Tb(COT′′)2]. Instead, the tri(µ‐iodido)‐bridged dinuclear half‐sandwich complex [Li(DME)2][Tb2(µ‐I)3(COT′′)2] (4) was isolated in 72 % yield. In this complex, the Li(DME)2 fragment is attached to one of the µ‐iodido ligands. A closely related binuclear lutetium complex, [Li(DME)3][Lu2(µ‐Cl)3(COTbig)2]·DME (5), was obtained by using the “superbulky“ COTbig ligand [COTbig = 1,4‐bis(triphenylsilyl)cyclooctatetraenyl dianion]. In addition to the spectroscopic and structural characterization, the magnetic properties of the paramagnetic terbium(III) derivative 2 have been investigated and further complemented by ab initio computational methods. These results have been used to discuss the structural requirements for potential terbium(III) single‐ion magnets.
“…Mono(cyclooctatetraenyl)lanthanide complexes containing additional amidinate ligands have been reported many years ago by Schumann and Edelmann et al A series of complexes of the general formula (COT)Ln[ p -RC 6 H 4 C(NSiMe 3 ) 2 ](THF) (Ln = Y, Ce, Pr, Nd, Sm; R = H, OMe, CF 3 ) have been prepared and structurally characterized. The formation of mono(THF) solvates was observed throughout the series, independent of the ionic radius of the rare-earth metal used . More recently, the same basic structure was found for the mono(COT″) samarium amidinate complex (COT″)Sm( DIPP Form)(THF) ( DIPP Form = [HC(NAr) 2 ] − , Ar = 2,6-diisopropylphenyl) .…”
This paper gives a full account of the complex reaction
system LnCl3/(COT″)2– (COT″
= 1,4-bis(trimethylsilyl)cyclooctatetraenyl dianion). Four different
series of organolanthanide complexes of this bulky COT ligand have
been reported: (1) anionic sandwich complexes containing [Ln(COT″)2]− anions, (2) dimeric chloro-bridged mono(COT″)
complexes, (3) cluster-centered multidecker-sandwich complexes, and
(4) linear triple-decker sandwich complexes. In order to get a more
complete picture of the reaction system LnCl3/(COT″)2– and to examine possible steric effects exerted by
the COT″ ligand, four new rare-earth-metal COT″ complexes
have been prepared: [Li(DME)3][Ce(COT″)2] (1), [Li(THF)4][Nd(COT″)2] (2), [(COT″)Nd(μ-Cl)(THF)]2 (4), and (COT″)Yb(DIPPForm)(THF)
(5,; DIPPForm = [HC(NAr)2]−, Ar = 2,6-diisopropylphenyl). For comparison, the
COTTBS derivative [Li(DME)3][Ce(COTTBS)2] (3; COTTBS = 1,4-bis(tert-butyldimethylsilyl)cyclooctatetraenyl dianion) has
also been synthesized. It was found that the steric effect of either
COT″ or COTTBS on the molecular structures of the
anionic sandwich complexes 1–3 with
coplanar ring ligands is rather small. In (COT″)Yb(DIPPForm)(THF) (5), the combination of COT″ with
a sterically demanding formamidinate ligand in the coordination sphere
of Yb3+ still leaves room for THF coordination. For example,
in 4, the bulky COT″ leads to coordination of
only one THF per Ln in comparison to the parent chloro-bridged dimers
[(COT)Ln(μ-Cl)(THF)2]2. However, in the
dimeric chloro-bridged mono(COT″) complexes the presence of
COT″ reduces the number of coordinated THF molecules. Quite
surprisingly, an attempt to prepare the holmium analogue of the known
linear triple-decker sandwich complex (COT″)Nd(μ-η8:η8-COT″)Nd(COT″) led to formation
of the isomerized triple-decker (COT″)Ho[μ-η8:η8-C8H6(SiMe3)2-1,5]Ho(COT″) (6), as a result of
steric pressure-induced silyl group migration. All new complexes 1–6 have been structurally characterized
by X-ray diffraction.
“…Polydentate nitrogen ligands have been found to be highly suited to stabilize mono(cyclooctatetraene)lanthanide(III) complexes. These include silylated benzamidinate and diiminophosphinate anions as well as tridentate pyrazolylborate ligands. ,− Typical preparations are outlined in the eqs 77−79. …”
“…These include silylated benzamidinate and diiminophosphinate anions as well as tridentate pyrazolylborate ligands. 236,[245][246][247][248] Typical preparations are outlined in the eqs 77-79.The first "sandwich" complexes of the type (C 8 H 8 )-Ln[HB(pz) 3 ] had been synthesized earlier by Takats et al246 These compounds may either be unsolvated or can contain a coordinated THF molecule. Both series of complexes, (C 8 H 8 )Ln[HB(pz) 3 ] and (C 8 H 8 )Ln-[HB(3,5-Me 2 pz)…”
Over the years one major challenge has remained in organolanthanide chemistry: the synthesis of homoleptic alkyl and aryl complexes. The simplest organometallic compounds of the rare earths are the species LnR 2 or LnR 3 with the rare earth metals in their common oxidation states Ln 2+ and Ln 3+ which imply the coordination of only two or three ligands to the metal center. This is usually insufficient to meet the lanthanides' demands of steric saturation through high coordination numbers.Hence for a long time, only indirect evidence could be found for the existence of simple homoleptic organolanthanide compounds; the isolation and characterization of compounds belonging to this class were first achieved recently using pentafluorophenyl for Ln 2+ derivatives 12 and very bulky alkyl ligands for Ln 3+ species. [13][14][15] Especially for alkyls, very little structural data are available for compounds without any trimethylsilyl-substituted ligands which generally ensure higher stability. But nevertheless, due to the difficulties of their synthesis and their high reactivity alkyls and aryls still represent an interesting class of compounds. 16
Homoleptic σ-Alkyl ComplexesShortly after the synthesis of the first divalent solvent-free Ln alkyl, [(Me 3 Si) 3 C] 2 Yb, 17 the Eu analogue was prepared similarly by the reaction of EuI 2 and KC(SiMe 3 ) 3 in benzene. 18 It also features the bent structure displayed by the Yb complex but with a slightly smaller C-Eu-C angle (C-Eu-C ) 136°, C-Yb-C ) 137°) and longer Eu-C bonds (Eu-C ) 261 pm, Yb-C ) 249/250 pm). Salt metathesis was then again applied successfully to synthesize the first divalent Sm alkyl, Sm[C(SiMe 3 ) 2 (SiMe 2 OMe)] 2 (THF) Frank T. Edelmann was born in Hamburg, Germany, in 1954. He studied chemistry from 1974 to 1979 at the University of Hamburg, where he obtained his Diplom in 1979 and doctoral degree in 1983. His Ph.D. thesis entitled "The chemistry of the tricarbonyl(fulvene) chromium complexes" was carried out under the supervision of Prof. Ulrich Behrens. This was followed by two years (1983−1985) of postdoctoral research as a Feodor Lynen Fellow of the Alexander-von-Humboldt Foundation in the groups of Professors Josef Takats (
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