8.4.5. Nitromercuration Reactions 3878 9. Hydroamination of Alkenes and Alkynes under Microwave Irradiation 3878 * To whom correspondence should be addressed. Phone: +49 241 8

Hydroamination: direct addition of amines to alkenes and alkynes.

5. Hydrosilylation 3862 5.1. Alkene Hydrosilylation 3863 5.2. Ketone Hydrosilylation 3865 6. Alkene Hydrogenation 3866 7. Aldol-, Mannich-, and Michael-Type Reactions 3867 7.1. Enantioand Diastereoselective Conversions 3867 7.2. Remarks on Stereoselective Induction 3869 8. Miscellaneous Conversions 3869 9. Analogies between Yb2+ and Ca2+ Chemistry 3871 10. Conclusions and Perspectives 3872 11. References 3873

From limestone to catalysis: application of calcium compounds as homogeneous catalysts.

For decades, the organometallic chemistry of the rare earth elements was largely dominated by the cyclopentadienyl ligand and its ring-substituted derivatives. A hot topic in current organolanthanide chemistry is the search for alternative ligand sets which are able to satisfy the coordination requirements of the large lanthanide cations. Among the most successful approaches in this field is the use of amidinate ligands of the general type [RC(NR')(2)](-) (R = H, alkyl, aryl; R' = alkyl, cycloalkyl, aryl, SiMe(3)) which can be regarded as steric cyclopentadienyl equivalents. Closely related are the guanidinate anions of the general type [R(2)NC(NR')(2)](-) (R = alkyl, SiMe(3); R' = alkyl, cycloalkyl, aryl, SiMe(3)). Two amidinate or guanidinate ligands can coordinate to a lanthanide ion to form a metallocene-like coordination environment which allows the isolation and characterization of stable though very reactive amide, alkyl, and hydride species. Mono- and trisubstituted lanthanide amidinate and guanidinate complexes are also readily available. Various rare earth amidinates and guanidinates have turned out to be very efficient homogeneous catalysts e.g. for ring-opening polymerization reactions. Moreover, certain alkyl-substituted lanthanide tris(amidinates) and tris(guanidinates) were found to be highly volatile and could thus be promising precursors for ALD (= Atomic Layer Deposition) and MOCVD (= Metal-Organic Chemical Vapor Deposition) processes in materials science and nanotechnology. This tutorial review covers the success story of lanthanide amidinates and guanidinates and their transition from mere laboratory curiosities to efficient homogeneous catalysts as well as ALD and MOCVD precursors.

Lanthanide amidinates and guanidinates: from laboratory curiosities to efficient homogeneous catalysts and precursors for rare-earth oxide thin films

A series of homoleptic metal amidinates of the general type [M(R-R'AMD)(n)](x) (R = (i)Pr, (t)Bu, R' = Me, (t)Bu) has been prepared and structurally characterized for the transition metals Ti, V, Mn, Fe, Co, Ni, Cu, Ag, and La. In oxidation state 3, monomeric structures were found for the metals Ti(III), V(III), and La(III). Bridging structures were observed for the metals in oxidation state 1. Cu(I) and Ag(I) are held in bridged dimers, and Ag(I) also formed a trimer that cocrystallized with the dimer. Metals in oxidation state 2 occurred in either monomeric or dimeric form. Metals with smaller ionic radii (Co, Ni) were monomeric. Larger metals (Fe, Mn) gave monomeric structures only with the bulkier tert-butyl-substituted amidinates, while the less bulky isopropyl-substituted amidinates formed dimers. The new compounds were found to have properties well-suited for use as precursors for atomic layer deposition (ALD) of thin films. They have high volatility, high thermal stability, and high and properly self-limited reactivity with molecular hydrogen, depositing pure metals, or water vapor, depositing metal oxides.

/pdf/synthesis-and-characterization-of-volatile-thermally-stable-2z9jll17rq.pdf

Synthesis and Characterization of Volatile, Thermally Stable, Reactive Transition Metal Amidinates

Cationic organometallic complexes of scandium, yttrium, and the lanthanoids.

ion upon treatment with B(C6F5)3 in THF to generate the cationic species [(MAC)Y(CH2SiMe3)][B(C6F5)3(CH2SiMe3)]. However, this salt was found to be highly unstable and could not be isolated as a pure material.97 Fryzuk et al. have developed a remarkable organoyttrium chemistry around the phosphorus-containing macrocycle syn-{P2N2} ({P2N2} ) [PhP(CH2SiMe2NSiMe2CH2)2PPh]). The starting material was the chloride-bridged dimer [{P2N2}Y(μ-Cl)]2, which can be prepared in 95% yield by the reaction of synLi2(THF){P2N2} with YCl3(THF)3 in THF solution. Straightforward metathesis using the very bulky alkyllithium reagent LiCH(SiMe3)2 according to eq 29 (methyl groups on Si omitted for clarity) afforded the monomeric yttrium alkyl species {P2N2}YCH(SiMe3)2 in 92% yield. Use of the less sterically hindered alkyl moiety CH2SiMe3 followed by addition of THF resulted in formation of the THF adduct {P2N2}YCH2SiMe3(THF), whereas the THF-free compound could only be isolated as a highly reactive oily material.98 A quite remarkable samarium alkyl complex of complicated molecular structure was reported by Gambarotta et al.99 Samarium diiodide acted as reducing agent in the reaction with (phenylenebis(3,5-tBu4-salicylidene)iminato)sodium, (3,5tBu4salophen)Na2(THF)3, to give dimeric [Sm2(SBSB)(THF)3]‚2toluene (SB-SB ) C-C bonded 3,5tBu4salophen dimer). The new ligand resulted from the reductive coupling of two imino functional groups of two 3,5-tBu4salophenSm units. Subsequent treatment with MeLi resulted in a novel oxo-bridged dimer (24), featuring alkylation of both samarium atoms and arising from cleavage of the C-C bond connecting the two units, as well as complete reduction of the imine groups of the salophen ligands and THF deoxygenation. In the formula drawing depicted here the bridging phenylene rings are omitted for clarity.99 Carbene complexes of the lanthanide elements have first become available through the use of the stable Arduengo-type carbenes.100,101 Organolanthanide derivatives are readily accessible by adding the heterocyclic carbene ligands to various diand trivalent rare earth complexes such as decamethylsamarocene. Cyclopentadienyl-free derivatives have been obtained by reacting 1,3,4,5-tetramethylimidazol-2-ylidene with the tris(2,2,6,6-tetramethylheptane-3,5-dionato) complexes of yttrium and europium, Ln(THD)3 (Ln ) Y, Eu). The two carbene complexes 25 were isolated as white solids in quantitative yield. The europium complex was structurally characterized by X-ray analysis. Despite the differences in the ionic radii of the two metals 7-coordinate monocarbene adducts are formed in both cases. With 266.3(4) pm the Eu-C distance in (1,3,4,5-tetramethylimidazol-2-ylidene)Eu(THD)3 is comparable to Pr(III)-C and Sm(III)-C distances reported for some isonitrile complexes.102,103 In the 13C NMR spectrum of the yttrium complex the resonance for the former carbene carbon is at δ 199.38 (cf. δ 214 for the free carbene ligand) and shows a 13C-89Y coupling of 33 Hz which indicates that the Y-C bond does not dissociate rapidly on the NMR time scale.101 The bulkier 1,3-diisopropyl-4,5dimethylimidazol-2-ylidene (iPr-Carb) has been used to synthesize a mixed carbene-THF alkyl Lu(CH2SiMe3)3(THF)(Pr-Carb) (26).22d Due to its higher steric demand, the carbene ligand occupies an equatorial position (Lu-C(Carb) ) 249 pm). Somewhat related to the carbene complexes is a highly unusual monomeric samarium bis(iminophosphoranyl) chelate complex which has been reported by Cavell et al.104 Addition of H2C(Ph2PdNSiMe3)2 to a toluene solution of samarium tris(dicyclohexylamide) afforded bright yellow [κ-C,N,N′-C(Ph2Pd NSiMe3)2]Sm(NCy2)(THF) (27). The core of the molecule consists of two nearly planar, fused fourmembered rings with a Sm-C shared edge. With 246.7(4) pm the Sm-C bond length is considerably shorter (10%) than the average samarium-carbon distances, indicating that 27 can be formulated as a carbene complex. Non-Cyclopentadienyl Organolanthanide Complexes Chemical Reviews, 2002, Vol. 102, No. 6 1865

Synthesis and structural chemistry of non-cyclopentadienyl organolanthanide complexes.

SmCl3 reacts with Me3SiCH2Li in THF yielding Sm(CH2SiMe3)3(THF)3 (1). The single crystal X-ray structural analyses of 1, Er(CH2SiMe3)3(THF)2 (2), Yb(CH2SiMe3)3(THF)2 (3), and Lu(CH2SiMe3)3(THF)2 (4) show the Sm atom in a fac-octahedral coordination and the heavier lanthanides Er, Yb, and Lu trigonal bipyramidally coordinated with the three alkyl ligands in equatorial and two THF molecules in axial positions.



Metallorganische Verbindungen der Lanthanoide. 157 [1] Die Molekulstruktur von Tris(trimethylsilylmethyl)samarium, -erbium, -ytterbium und -lutetium



SmCl3 reagiert mit Me3SiCH2Li in THF unter Bildung von Sm(CH2SiMe3)3(THF)3 (1). Die Einkristall rontgenstrukturanalysen von 1, Er(CH2SiMe3)3(THF)2 (2), Yb(CH2SiMe3)3(THF)2 (3) und Lu(CH2SiMe3)3(THF)2 (4) zeigen das Sm Atom fac-oktaedrisch und die schweren Lanthanoide Er, Yb und Lu trigonal bipyramidal koordiniert mit den drei Alkylliganden in aquatorialer und zwei THF Molekulen in axialer Position.

Organometallic Compounds of the Lanthanides. 157 [1] The Molecular Structure of Tris(trimethylsilylmethyl)samarium, ‐erbium, ‐ytterbium, and ‐lutetium

Ln(CH2SiMe3)3(THF)2 react with 1,3-di-iso-propyl-4,5-dimethylimidazol-2-ylidene (ImMe2iPr2) yielding Ln(CH2SiMe3)3(THF)(ImMe2iPr2) (1, Ln = Er and 2, Ln = Lu). Reaction of 1 and 2 with an excess of ImMe2iPr2 results in the formation of the heteroleptic alkyllanthanide complexes Ln(CH2SiMe3)3(ImMe2iPr2)2 (3, Ln = Er) and (4, Ln = Lu). The molecular structures of 1, 2, and 4 show a distorded trigonal bipyramidal arrangement around the lanthanide centers with two alkyl ligands and one carbene in the equatorial positions.

Organometallic Compounds of the Lanthanides. 181 Alkyllanthanide Carbene Complexes

The reactions of PhCH2SiMe3 (1), PhCH2SiMe2tBu (2), PhCH2SiMe2Ph (3), 3,5-Me2C6H3CH2SiMe3 (4), and 3,5-Me2C6H3CH2SiMe2tBu (5) with nBuLi in tetramethylethylenediamine (tmeda) afford the corresponding lithium complexes [Li(tmeda)][CHRSiMe2R′] (R, R′ = Ph, Me (6), Ph, tBu (7), Ph, Ph (8), 3,5-Me2C6H3, Me (9), and 3,5-Me2C6H3, tBu (10)), respectively. The new compounds 5, 7, 8, 9 and 10 have been characterized by 1H and 13C NMR spectroscopy, compounds 7, 8 and 9 also by X-ray structure analysis.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1002/zaac.200800312

Synthesis and Structural Characterization of Some Novel Trialkylsilyl‐substituted Lithium Benzyl Complexes [Li(tmeda)][CHRSiMe2R′] (R = Ph, 3,5‐Me2C6H3; R′ = Me, tBu, Ph)

PrCl3, NdCl3, SmCl3, ErCl3, and LuCl3 react with three mole equivalents of [Li(tmeda)][CHPhSiMe3] (1), [Li(tmeda)][CHPhSiMe2tBu] (2), [Li(tmeda)][CHPhSiMe2Ph] (3), and [Li(tmeda)][CH(C6H3Me2-3,5)SiMe2tBu] (4) forming the ate complexes [Li(tmeda)2][Ln(CHPhSiMe3)3Cl] (Ln = Pr (5a), Nd (6a), Sm (7a)), [Li(tmeda)2][Ln(CHPhSiMe2tBu)3Cl] (Ln = Pr (5b), Nd (6b), Sm (7b)), [Li(tmeda)2][Pr(CHPhSiMe2Ph)3Cl] (5c), and [Li(tmeda)2][Ln(CH(C6H3Me2-3,5)SiMe2tBu)3Cl] (Ln = Er (8d), Lu (9d)). {[Li(tmeda)]2[Nd(CHPhSiMe3)Cl4]}2 (10) and {[Li(tmeda)][Nd(CHPhSiMe3)Cl3(THF)]}2 (11) crystallize from concentrated ethereal solutions of 6a after addition of pentane. 4 reacts with two equivalents of ErCl3 and LuCl3 yielding [Li(tmeda)]2(μ-Cl)3Ln(CHPhSiMe2tBu)2 (Ln = Er (12), Lu (13)). Compounds 7a,b, 9d, and 13 have been characterized by 1H and 9d and 13 also by 13C NMR spectroscopy, compounds 6b, 7a, 8d, 9d, 10, 11, 12, and 13 by X-ray structure analysis.

Organometallic Compounds of the Lanthanides. 183 Lanthanide Benzyl Complexes of the Type [Li(tmeda)2][Ln(CHRSiMe2R′)3Cl] (Ln = Pr, Nd, Sm, Er, Lu; R = Ph, 3,5‐Me2C6H3; R′ = Me, tBu, Ph) and [Li(tmeda)]2(μ‐Cl)3Ln(CHPhSiMe2tBu)2 (Ln = Er, Lu)

Dominique M. M. Freckmann

Papers

Synthesis and structural chemistry of non-cyclopentadienyl organolanthanide complexes.

Organometallic Compounds of the Lanthanides. 157 [1] The Molecular Structure of Tris(trimethylsilylmethyl)samarium, ‐erbium, ‐ytterbium, and ‐lutetium

Organometallic Compounds of the Lanthanides. 181 Alkyllanthanide Carbene Complexes

Synthesis and Structural Characterization of Some Novel Trialkylsilyl‐substituted Lithium Benzyl Complexes [Li(tmeda)][CHRSiMe2R′] (R = Ph, 3,5‐Me2C6H3; R′ = Me, tBu, Ph)

Organometallic Compounds of the Lanthanides. 183 Lanthanide Benzyl Complexes of the Type [Li(tmeda)2][Ln(CHRSiMe2R′)3Cl] (Ln = Pr, Nd, Sm, Er, Lu; R = Ph, 3,5‐Me2C6H3; R′ = Me, tBu, Ph) and [Li(tmeda)]2(μ‐Cl)3Ln(CHPhSiMe2tBu)2 (Ln = Er, Lu)