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The ate complex (thf)LiCe[N(SiHMe2)2]4 reacts readily with 2–4 equiv. 1,1,3,3‐N,N,N′,N′‐tetramethylguanidine (HTMG) via a tandem protonolysis/HTMG monoinsertion/HNMe2 elimination reaction, affording [Ce{N(SiHMe2)2}2(μ‐LTMG)]2 [LTMG = N=C(NMe2)N=C(NMe2)2]. Reaction of (thf)LiCe[N(SiHMe2)2] with 1 equiv. HTMG gave a silylamido/guanidine mono‐exchange, leading to the isolation of the dimeric compound [Ce{N(SiHMe2)2}2(μ‐TMG)]2, which could be converted further into [Ce{N(SiHMe2)2}2(μ‐LTMG)]2 by addition of another equiv. of HTMG. The mechanism of formation of complex [Ce{N(SiHMe2)2}2(μ‐LTMG)]2 are discussed. [ABSTRACT FROM AUTHOR]

Trinuclear rare-earth metal methylidene complexes with a Ln3(μ3-CH2)(μ3-Me)(μ2-Me)3 structural motif were synthesized by applying three protocols. Polymeric [LuMe3]n (1-Lu) reacts with the sterically demanding amine H[NSiMe3(Ar)] (Ar = C6H3iPr2-2,6) in tetrahydrofuran via methane elimination to afford isolable monomeric [NSiMe3(Ar)]LuMe2(thf)2 (4-Lu). The formation of trinuclear rare-earth metal tetramethyl methylidene complexes [NSiMe3(Ar)]3Ln3(μ3-CH2)(μ3-Me)(μ2-Me)3(thf)3 (7-Ln; Ln = Y, Ho, Lu) via reaction of [LnMe3]n (1-Ln; Ln = Y, Ho, Lu) with H[NSiMe3(Ar)] is proposed to occur via an “intermediate” species of the type [NSiMe3(Ar)]LnMe2(thf)x and subsequent C−H bond activation. Applying Lappert's concept of Lewis base-induced methylaluminate cleavage, compounds [NSiMe3(Ar)]Ln(AlMe4)2 (5-Ln; Ln = Y, La, Nd, Ho) were converted into methylidene complexes 7-Ln (Ln = Y, Nd, Ho) in the presence of tetrahydrofuran. Similarly, tetramethylgallate complex [NSiMe3(Ar)]Y(GaMe4)2 (6-Y) could be employed as a synthesis precursor for 7-Y. The molecular composition of complexes 4-Ln, 5-Ln, 6-Y and 7-Ln was confirmed by elemental analyses, FTIR spectroscopy, 1H and 13C NMR spectroscopy (except for holmium derivatives) and single-crystal X-ray diffraction. The Tebbe-like reactivity of methylidene complex 7-Nd with 9-fluorenone was assessed affording oxo complex [NSiMe3(Ar)]3Nd3(μ3-O)(μ2-Me)4(thf)3 (8-Nd). The synthesis of 5-Ln yielded [NSiMe3(Ar)]2Ln(AlMe4) (9-Ln; Ln = La, Nd) as minor side-products, which could be obtained in moderate yields when homoleptic Ln(AlMe4)3 were treated with two equivalents of K[NSiMe3(Ar)]. [ABSTRACT FROM AUTHOR]

The reaction of monomeric [(Tp tBu,Me)LuMe2] (Tp tBu,Me=tris(3-Me-5- tBu-pyrazolyl)borate) with primary aliphatic amines H2NR (R= tBu, Ad=adamantyl) led to lutetium methyl primary amide complexes [(Tp tBu,Me)LuMe(NHR)], the solid-state structures of which were determined by XRD analyses. The mixed methyl/tetramethylaluminate compounds [(Tp tBu,Me)LnMe({μ2-Me}AlMe3)] (Ln=Y, Ho) reacted selectively and in high yield with H2NR, according to methane elimination, to afford heterobimetallic complexes: [(Tp tBu,Me)Ln({μ2-Me}AlMe2)(μ2-NR)] (Ln=Y, Ho). X-ray structure analyses revealed that the monomeric alkylaluminum-supported imide complexes were isostructural, featuring bridging methyl and imido ligands. Deeper insight into the fluxional behavior in solution was gained by 1H and 13C NMR spectroscopic studies at variable temperatures and 1H-89Y HSQC NMR spectroscopy. Treatment of [(Tp tBu,Me)LnMe(AlMe4)] with H2N tBu gave dimethyl compounds [(Tp tBu,Me)LnMe2] as minor side products for the mid-sized metals yttrium and holmium and in high yield for the smaller lutetium. Preparative-scale amounts of complexes [(Tp tBu,Me)LnMe2] (Ln=Y, Ho, Lu) were made accessible through aluminate cleavage of [(Tp tBu,Me)LnMe(AlMe4)] with N, N, N′, N′-tetramethylethylenediamine (tmeda). The solid-state structures of [(Tp tBu,Me)HoMe(AlMe4)] and [(Tp tBu,Me)HoMe2] were analyzed by XRD. [ABSTRACT FROM AUTHOR]

Trivalent Eu[N(SiHMe2)2]3(THF)2 can easily be synthesized by applying a routine salt metathesis protocol (EuCl3(THF)2 and 3 equiv. of Li[N(SiHMe2)2] in n-hexane) which crystallizes isotypically to its analogues of the rare-earth metal series (space group P21/c). Transsilylamination of Eu[N(SiMe3)2]2(THF)2 with a slight excess of HN(SiHMe2)2 in n-hexane-THF yields the divalent trinuclear compound Eu{[μ-N(SiHMe2)2]2Eu-[N(SiHMe2)2](THF)}2, the solid-state structure of which differs significantly from the samarium and ytterbium analogues by showing three unique molecules in the asymmetric unit of which one is related to the two others by an inversion. Using crude Eu[N(SiMe3)2]3 in transsilylamination reactions with HN(SiHMe2)2 in n-hexane afforded n-hexane-insoluble trivalent ate complexes {MEu[N(SiHMe2)2]4}n (M = Na, K) depending on the synthesis conditions of Eu[N(SiMe3)2]3. Performing the transsilylamination of Eu[N(SiMe3)2]3 with a large excess of HN(SiHMe2)2 at elevated temperatures gave reproducibly the donor-free, mixedvalent, trinuclear compound EuII{[μ-N(SiHMe2)2]EuIII[N(SiHMe2)2]3}2 in good yield. [ABSTRACT FROM AUTHOR]

Trivalent Eu[N(SiHMe2)2]3(THF)2 can easily be synthesized by applying a routine salt metathesis protocol (EuCl3(THF)2 and 3 equiv. of Li[N(SiHMe2)2] in n-hexane) which crystallizes isotypically to its analogues of the rare-earth metal series (space group P21/c). Transsilylamination of Eu[N(SiMe3)2]2(THF)2 with a slight excess of HN(SiHMe2)2 in n-hexane-THF yields the divalent trinuclear compound Eu{[μ-N(SiHMe2)2]2Eu-[N(SiHMe2)2](THF)}2, the solid-state structure of which differs significantly from the samarium and ytterbium analogues by showing three unique molecules in the asymmetric unit of which one is related to the two others by an inversion. Using crude Eu[N(SiMe3)2]3 in transsilylamination reactions with HN(SiHMe2)2 in n-hexane afforded n-hexane-insoluble trivalent ate complexes {MEu[N(SiHMe2)2]4}n (M = Na, K) depending on the synthesis conditions of Eu[N(SiMe3)2]3. Performing the transsilylamination of Eu[N(SiMe3)2]3 with a large excess of HN(SiHMe2)2 at elevated temperatures gave reproducibly the donor-free, mixedvalent, trinuclear compound EuII{[μ-N(SiHMe2)2]EuIII[N(SiHMe2)2]3}2 in good yield. [ABSTRACT FROM AUTHOR]

Treatment of boryllithium (THF)2Li[B(NDippCH)2] (Dipp = 2,6-diisopropylphenyl) with various amounts of AlMe3 or GaMe3 leads to the formation of inter group 13 compounds. Equimolar reactions result in ate complexes of the type (THF)nLi(Me3M)[B(NDippCH)2] (M = Al, Ga) with discrete (n = 2, 3) or eight-membered ring structures (n = 1). We reported previously that use of excessive amounts of group 13 metal methyl compounds can result in four-coordinate THF-adducts (THF)(Me2M)[B(NDippCH)2] or unsolvated complexes {(Me2M)[B(NDippCH)2]}x (M = Al, x = 2; M = Ga, x = 1) via separation of LiMMe4. Polymeric [(THF)Li(Et3Al){B(NDippCH)2}]n is formed when boryllithium is reacted with an equimolar amount of AlEt3. The discrete THF-adduct (THF)Et2Al[B(NDippCH)2] can be isolated when using a boryllithium/AlEt3 ratio of 1 : 5. The reaction of THF-adduct (THF)Me2Ga[B(NDippCH)2] with La(AlMe4)3 affords the heterogallate complex La[(Me3Ga){B(NDippCH)2}]3, according to a donor-assisted tetramethylaluminate/alkylgallate exchange. The obtained complexes feature rare examples of crystallographically characterized noncluster compounds with unsupported B-Al and B-Ga contacts. [ABSTRACT FROM AUTHOR]

Bis(dimethylsih/l)amide and bis(dimethylphenylsilyl)amide complexes of the divalent transition metals chromium, manganese, and cobalt were synthesized. Dimeric, donor-free {Mn[N(SiHMe2)2]2}**2 could be obtained via two different pathways, a salt metathesis route (utilizing MnCl2(thf)1.5 and LiN(SiHMe2)2) and a transsilylamination protocol (utilizing Mn[N(SiMe3)2]2(thf) and HN(SiHMe2)2). Addition of 1,1,3,3-tetramethylethylendiamine (tmeda) to {Mn[N(SiHMe2)2]2}2 yielded the monomeric adduct Mn[N(SiHMe2)2]2(tmeda). The syntheses of Cr[N(SiHMe2)2]2(tmeda), Co[N(SiMe3)2][N-(SiHMe2)2](tmeda), and Co[N(SiHMe2)2]2(tmeda) were achieved by transsilylamination from Cr[N(SiMe3)2]2(tmeda) and {Co[N(SiMe3)2]2}2(µ-tmeda), respectively. Bis(dimethylphenylsilyl)amide complexes Mn[N(SiMe2Ph)2]2, Cr[N(SiMe2Ph)2]2, and Co[N(SiMe2Ph)2]2(thf) were obtained via salt metathesis employing MCl2(thf)x (M = Cr, Mn, Co) with equimolar amounts of LiN(SiMe2Ph)2 in n-hexane. Treatment of CrCl2 with LiN(SiMe2Ph)2 in thf gave Cr[N(SiMe2Ph)2]2(thf)2, featuring an almost square planar trans-coordination. All complexes were examined by elemental analyses, DRIFT and UV--vis spectroscopy, as well as X-ray structure analysis, paying particular attention to secondary M--SiH β-agostic and M---?(???n?) interactions. Magnetic moments were determined by Evans' method. [ABSTRACT FROM AUTHOR]

The μ2-imide complexes [Ln(AlMe4)(μ2-Nmes*)]x(mes* = C6H2tBu3-2,4,6) (Ln = Y, La,Nd, Lu) are synthesized from homoleptic heterobimetallic complexesLn(AlMe4)3utilizing two distinct protocols:reaction with 2,4,6-tri-tert-butylaniline in hexanevia methane elimination or with potassium (2,4,6-tri-tert-butylphenyl)amide in toluene according to a salt metathesis–protonolysistandem reaction. Complexes [Ln(AlMe4)(μ2-Nmes*)]2(Ln = Y, Nd, Lu) revealed isomorphous solid-statestructures, featuring an asymmetrically bridged Ln2N2core with very short Ln–N distances (2.071(1)–2.155(3)Å). In the solid-state structure of the lanthanum derivativesimilar dimeric subunits assemble as La4Al4oligomersthrough μ2-η1:η2-bridging tetramethylaluminato moieties. [La(AlMe4)(μ2-Nmes*)]4displays La---arene interactions (2.702(6)Å) that are considerably shorter than the La(μ-CH3)aluminatobond lengths. [ABSTRACT FROM AUTHOR]

Homoleptic tetramethylaluminates Ln(AlMe 4 ) 3 react with KTp t Bu,Me (Tp t Bu,Me = tris(3- t Bu-5-Me-pyrazolyl)borato) to yield rare-earth-metal methylidene complexes (Tp t Bu,Me )Ln(μ 3 -CH 2 )[(μ-Me)AlMe 2 ] 2 (Ln = La, Ce, Nd). The lanthanum reaction is prone to additional C-H- and B-N-bond activation, affording coproducts La[HB(pz Me, t Bu )(pz CMe2,Me ) 2 ][(μ-CH 2 )(μ-Me)AlMe 2 ] 2 and [La(μ-pz t Bu,Me )(AlMe 4 ) 2 ] 2 (pz t Bu,Me = 3- t Bu-5-Me-pyrazolato). The protonolysis reaction of Ln(AlMe 4 ) 3 and Hpz t Bu,Me provides more efficient access to [Ln(μ-pz t Bu,Me )(AlMe 4 ) 2 ] 2 (Ln = La, Nd). Treatment of Ln(AlMe 4 ) 3 with KTp Me,Me led to methylidene complexes (Tp Me,Me )Ln(μ 3 -CH 2 )[(μ-Me)AlMe 2 ] 2 (Ln = Nd, Sm) or bis(tetramethylaluminate) complexes (Tp Me,Me )Ln(AlMe 4 ) 2 (Ln = Y, Lu). The neodymium reaction generated methine derivative (Tp Me,Me )Nd[(μ 4 -CH)(AlMe 2 ) 2 (μ-pz ,Me,Me )][(μ-Me)AlMe 2 ] as a minor coproduct. The reaction of Ln(GaMe 4 ) 3 (Ln = Y, La, Ce, Nd, Sm, Ho) with HTp t Bu,Me gave methylidene complexes (Tp t Bu,Me )Ln(μ 3 -CH 2 )[(μ-Me)GaMe 2 ] 2 (Ln = La, Ce, Nd, Sm) and alkyl complexes (Tp t Bu,Me )LnMe[(μ-Me)GaMe 3 ] (Ln = Y, Ho), while competing B-N bond activation reactions produced GaMe 2 [BH(Me)(μ-pz t Bu,Me ) 2 ] and (Tp t Bu,Me )Ln(η 2 -pz t Bu,Me )[(μ-Me)GaMe 3 ] (Ln = Y, Ho). The steric impact of the Tp R,Me ligands was examined by cone angle calculations. Rare-earth-metal methylidene complexes (Tp t Bu,Me )Ln(μ 3 -CH 2 )[(μ-Me)EMe 2 ] 2 (E = Al, Ga) successfully promote carbonyl methylenation reactions upon addition of ketone.

In patients with implants next to natural teeth, clinicians often observe a change in the interproximal space. Although there may have been good proximal contact when the implant crown was inserted, this may have dissolved later. A gap appears to occur in 1/3 to 2/3 of the cases examined, with the mesial side usually being affected. This is mainly explained by the mesial drift of the teeth, while the implant is immobile as an "ankylosed unit".

Trinuclear rare-earth metal methylidene complexes with a Ln3(μ3-CH2)(μ3-Me)(μ2-Me)3 structural motif were synthesized by applying three protocols. Polymeric [LuMe3]n (1-Lu) reacts with the sterically demanding amine H[NSiMe3(Ar)] (Ar = C6H3iPr2-2,6) in tetrahydrofuran via methane elimination to afford isolable monomeric [NSiMe3(Ar)]LuMe2(thf)2 (4-Lu). The formation of trinuclear rare-earth metal tetramethyl methylidene complexes [NSiMe3(Ar)]3Ln3(μ3-CH2)(μ3-Me)(μ2-Me)3(thf)3 (7-Ln; Ln = Y, Ho, Lu) via reaction of [LnMe3]n (1-Ln; Ln = Y, Ho, Lu) with H[NSiMe3(Ar)] is proposed to occur via an "intermediate" species of the type [NSiMe3(Ar)]LnMe2(thf)x and subsequent C-H bond activation. Applying Lappert's concept of Lewis base-induced methylaluminate cleavage, compounds [NSiMe3(Ar)]Ln(AlMe4)2 (5-Ln; Ln = Y, La, Nd, Ho) were converted into methylidene complexes 7-Ln (Ln = Y, Nd, Ho) in the presence of tetrahydrofuran. Similarly, tetramethylgallate complex [NSiMe3(Ar)]Y(GaMe4)2 (6-Y) could be employed as a synthesis precursor for 7-Y. The molecular composition of complexes 4-Ln, 5-Ln, 6-Y and 7-Ln was confirmed by elemental analyses, FTIR spectroscopy, (1)H and (13)C NMR spectroscopy (except for holmium derivatives) and single-crystal X-ray diffraction. The Tebbe-like reactivity of methylidene complex 7-Nd with 9-fluorenone was assessed affording oxo complex [NSiMe3(Ar)]3Nd3(μ3-O)(μ2-Me)4(thf)3 (8-Nd). The synthesis of 5-Ln yielded [NSiMe3(Ar)]2Ln(AlMe4) (9-Ln; Ln = La, Nd) as minor side-products, which could be obtained in moderate yields when homoleptic Ln(AlMe4)3 were treated with two equivalents of K[NSiMe3(Ar)].

The reaction of monomeric [(Tp(tBu,Me) )LuMe2 ] (Tp(tBu,Me) =tris(3-Me-5-tBu-pyrazolyl)borate) with primary aliphatic amines H2 NR (R=tBu, Ad=adamantyl) led to lutetium methyl primary amide complexes [(Tp(tBu,Me) )LuMe(NHR)], the solid-state structures of which were determined by XRD analyses. The mixed methyl/tetramethylaluminate compounds [(Tp(tBu,Me) )LnMe({μ2 -Me}AlMe3 )] (Ln=Y, Ho) reacted selectively and in high yield with H2 NR, according to methane elimination, to afford heterobimetallic complexes: [(Tp(tBu,Me) )Ln({μ2 -Me}AlMe2 )(μ2 -NR)] (Ln=Y, Ho). X-ray structure analyses revealed that the monomeric alkylaluminum-supported imide complexes were isostructural, featuring bridging methyl and imido ligands. Deeper insight into the fluxional behavior in solution was gained by (1) H and (13) C NMR spectroscopic studies at variable temperatures and (1) H-(89) Y HSQC NMR spectroscopy. Treatment of [(Tp(tBu,Me) )LnMe(AlMe4 )] with H2 NtBu gave dimethyl compounds [(Tp(tBu,Me) )LnMe2 ] as minor side products for the mid-sized metals yttrium and holmium and in high yield for the smaller lutetium. Preparative-scale amounts of complexes [(Tp(tBu,Me) )LnMe2 ] (Ln=Y, Ho, Lu) were made accessible through aluminate cleavage of [(Tp(tBu,Me) )LnMe(AlMe4 )] with N,N,N',N'-tetramethylethylenediamine (tmeda). The solid-state structures of [(Tp(tBu,Me) )HoMe(AlMe4 )] and [(Tp(tBu,Me) )HoMe2 ] were analyzed by XRD., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Yttrocene-carboxylate complex [Cp*2Y(OOCAr(Me))] (Cp*=C5Me5, Ar(Me) =C6H2Me3-2,4,6) was synthesized as a spectroscopically versatile model system for investigating the reactivity of alkylaluminum hydrides towards rare-earth-metal carboxylates. Equimolar reactions with bis-neosilylaluminum hydride and dimethylaluminum hydride gave adduct complexes of the general formula [Cp*2Y(μ-OOCAr(Me))(μ-H)AlR2] (R=CH2SiMe3, Me). The use of an excess of the respective aluminum hydride led to the formation of product mixtures, from which the yttrium-aluminum-hydride complex [{Cp*2Y(μ-H)AlMe2(μ-H)AlMe2(μ-CH3)}2] could be isolated, which features a 12-membered-ring structure. The adduct complexes [Cp*2Y(μ-OOCAr(Me))(μ-H)AlR2] display identical (1)J(Y,H) coupling constants of 24.5 Hz for the bridging hydrido ligands and similar (89)Y NMR shifts of δ=-88.1 ppm (R=CH2SiMe3) and δ=-86.3 ppm (R=Me) in the (89)Y DEPT45 NMR experiments., (Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)