The tendency of tripodal amidozirconium and hafnium complexes to form hexacoordinate structures: alkali metal halide cages versus solvent adducts

Renner, Patrick; Galka, Christian H.; Memmler, Harald; Kauper, Uta; Gade, Lutz H.

doi:10.1016/s0022-328x(99)00486-6

Cited by 13 publications

(4 citation statements)

References 24 publications

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“…Amido ligands have emerged as extremely versatile tools for ligand design in the field of coordination chemistry. − Complexes with ligands containing coordinating nitrogen atoms can sometimes provide improved catalytic activity with respect to their oxygenated counterparts . From group 3 to group 12, a whole range of transition metal complexes involving a variety of nitrogen ligands have been fully documented and extended to lanthanides. − Many such complexes have demonstrated potential activities toward olefin polymerization, − ring-opening polymerization (ROP), synthesis of ammonia, metathesis, − and C–H activation. − For example, the catalytic cleavage of C–H/C–C bonds in higher alkanes (paraffins) is still a considerable challenge. Their transformation into lower alkanes is a highly temperature- and energy-intensive process.…”

Section: Introductionmentioning

confidence: 99%

Bipodal Surface Organometallic Complexes with Surface N-Donor Ligands and Application to the Catalytic Cleavage of C–H and C–C Bonds in n-Butane

et al. 2013

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We present a new generation of "true vicinal" functions well-distributed on the inner surface of SBA15: [(≡Si-NH2)(≡Si-OH)] (1) and [(≡Si-NH2)2] (2). From these amine-modified SBA15s, two new well-defined surface organometallic species [(≡Si-NH-)(≡Si-O-)]Zr(CH2tBu)2 (3) and [(≡Si-NH-)2]Zr(CH2tBu)2 (4) have been obtained by reaction with Zr(CH2tBu)4. The surfaces were characterized with 2D multiple-quantum (1)H-(1)H NMR and infrared spectroscopies. Energy-filtered transmission electron microscopy (EFTEM), mass balance, and elemental analysis unambiguously proved that Zr(CH2tBu)4 reacts with these vicinal amine-modified surfaces to give mainly bipodal bis(neopentyl)zirconium complexes (3) and (4), uniformly distributed in the channels of SBA15. (3) and (4) react with hydrogen to give the homologous hydrides (5) and (6). Hydrogenolysis of n-butane catalyzed by these hydrides was carried out at low temperature (100 °C) and low pressure (1 atm). While (6) exhibits a bis(silylamido)zirconium bishydride, [(≡Si-NH-)2]Zr(H)2 (6a) (60%), and a bis(silylamido)silyloxozirconium monohydride, [(≡Si-NH-)2(≡Si-O-)]ZrH (6b) (40%), (5) displays a new surface organometallic complex characterized by an (1)H NMR signal at 14.46 ppm. The latter is assigned to a (silylimido)(silyloxo)zirconium monohydride, [(≡Si-N═)(≡Si-O-)]ZrH (5b) (30%), coexistent with a (silylamido)(silyloxo)zirconium bishydride, [(≡Si-NH-)(≡Si-O-)]Zr(H)2 (5a) (45%), and a silylamidobis(silyloxo)zirconium monohydride, [(≡Si-NH-)(≡Si-O-)2]ZrH (5c) (25%). Surprisingly, nitrogen surface ligands possess catalytic properties already encountered with silicon oxide surfaces, but interestingly, catalyst (5) with chelating [N,O] shows better activity than (6) with chelating [N,N].

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Section: Introductionmentioning

confidence: 99%

Bipodal Surface Organometallic Complexes with Surface N-Donor Ligands and Application to the Catalytic Cleavage of C–H and C–C Bonds in n-Butane

et al. 2013

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“…1 H NMR (benzene-d6, 500 MHz): δ 3.950 (br m, 3 H, CH), 3.103 (br m, 4 H, OCH2), 1.692 (m, 3 H, CH2), 1.490 (m, 3 H, CH2), 0.646 (br sep, 3 H, 3 JHF ) 4.5 Hz, ZrCH3), 0.332 (br m, 6 H, OCH2CH3). 13 C{ 1 H} NMR (benzene-d6, 125.7 MHz): δ 141.60-135.32 (br m, C6F5), 66.10 (OCH2), 54.27 (CH), 48.56 (ZrCH3), 35.99 (CH2), 12.61 (OCH2CH3). 19 F NMR (benzene-d6, 376.5 MHz): δ -153.3 (br d, 6 F, 3 JFF ) 21 Hz, o-F), -164.5 (t, 6 F, 3 JFF ) 22 Hz, m-F), -170.5 (br m, 3 F, p-F).…”

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confidence: 99%

Zirconium Amide, Halide, and Alkyl Complexes Supported by Tripodal Amido Ligands Derived fromcis,cis-1,3,5-Triaminocyclohexane

Turculet

Tilley

2002

Organometallics

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Zirconium complexes containing the chelating triamido ligands [cis,cis-1,3,5-(C 6 F 5 N) 3 C 6 H 9 ] 3and {cis,cis-1,3,5-[3,5-(CF 3 ) 2 C 6 H 3 N] 3 C 6 H 9 } 3are reported. The dimethylamido complexes [cis,cis-1,3,5-(C 6 F 5 N) 3 C 6 H 9 ]ZrNMe 2 (NHMe 2 ) (3) and {cis,cis-1,3,5-[3,5-(CF 3 ) 2 C 6 H 3 N] 3 C 6 H 9 }-ZrNMe 2 (NHMe 2 ) (4) were prepared from Zr(NMe 2 ) 4 and cis,cis-1,3,5-(C 6 F 5 NH) 3 C 6 H 9 (1) or cis, 3, ) 2 C 6 H 3 NH] 3 C 6 H 9 (2), respectively. As determined by X-ray crystallography, an ortho fluorine atom in the triamido ligand of complex 3 is coordinated to the zirconium center. The zirconium chloride complexes [cis,cis-1,3,5-(C 6 F 5 N) 3 C 6 H 9 ]ZrCl (5) and {cis,cis-1,3,5-[3,5-(CF 3 ) 2 C 6 H 3 N] 3 C 6 H 9 }ZrCl(THF) 2 (6) were prepared from Np 3 ZrCl and 1 or 2, respectively. Compound 5 reacts with MeMgBr, LiCH(SiMe 3 ) 2 , LiCH 2 SiMe 3 , and PhCH 2 -MgCl to give the corresponding alkyl derivatives [cis,cis-1,3,5-( 8), [cis,cis-1,3,5-(C 6 F 5 N) 3 C 6 H 9 ]ZrCH 2 SiMe 3 (9), and [cis,cis-1,3,5-(C 6 F 5 N) 3 C 6 H 9 ]ZrCH 2 Ph ( 10). An X-ray crystallographic study of 8 reveals the presence of an R-agostic interaction, as well as the coordination of two ortho fluorines to the metal center. These interactions persist in solution, as indicated by NMR studies. Compound 6 reacts with MeMgCl and LiCH(SiMe 3 ) 2 to give the corresponding alkyl derivatives {cis,- 12). The methyl derivative 7 reacts with 3 equiv of xylyl isocyanide to yield [cis,cis-1,3,5-(C 6 F 5 N) 3 C 6 H 9 ]Zr{N(2,6-Me 2 C 6 H 3 )dCMeC[dCdN(2,6-Me 2 C 6 H 3 )]N(2,6-Me 2 C 6 H 3 )} (15), which was structurally characterized. Complex 15 features three molecules of xylyl isocyanide that have been coupled to give a diazazirconacycle with an exocyclic ketenimine group. The alkyl derivatives 7-12 react with hydrogen at elevated temperatures to yield ZrF species derived from the activation of the fluorinated substituents on the triamido ligands, presumably via reactive hydride intermediates.

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“…The structure of 6 is similar to 4 except that, in addition to coordination by iodide and the tris(N-arylamido-dimethylsilyl)methane, the uranium centre is coordinated by not one but two molecules of THF in a distorted octahedral geometry; an almost topologically identical structure was reported for [Zr(Cl){HC(SiMe 2 NAr¢) 3 }(THF) 2 ]. 54 Although salt elimination represents an effective route to preparing uranium-metal bonds, an alternative and attractive strategy is to react uranium-amides with metal hydrides to give uranium-metal bond formation with concomitant elimination of amine. 55 Additionally, such protonolysis chemistry can easily be carried out in non-polar solvents, which could be critical to the successful isolation of uranium-metal bonds, whereas salt elimination to form uranium-metal bonds tends to work best in polar media such as THF, which is a solvent vulnerable to ring opening decomposition and/or oxo-group abstraction.…”

Section: Resultsmentioning

confidence: 99%

Uranium(iv) amide and halide derivatives of two tripodal tris(N-arylamido-dimethylsilyl)methanes

et al. 2010

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Reaction of three equivalents of ArNH(2) (Ar = 3,5-Me(2)C(6)H(3)) with HC(SiMe(2)Br)(3) in the presence of the auxiliary base NEt(3) afforded the tripodal tris(N-arylamine-dimethylsilyl)methane HC{SiMe(2)N(H)Ar}(3) (1) in 83% yield. Three-fold deprotonation of 1 with n-butyllithium afforded the corresponding tri-lithium tris(N-arylamido-dimethylsilyl)methane etherate [HC{SiMe(2)N(Li)Ar}(3)(OEt(2))] (2) in 92% yield. Salt elimination reactions between 2 or the known complex [HC{SiMe(2)N(Li)Ar'}(3)(OEt(2))(2)] (3) (Ar' = 4-MeC(6)H(4)) with one equivalent of uranium(IV) tetrachloride afforded the corresponding tris(N-arylamido-dimethylsilyl)methane uranium(IV) chloride complexes as monomeric [U(Cl){HC(SiMe(2)NAr)(3)}(THF)] (4) and dinuclear [{HC(SiMe(2)NAr')(3)}U(Cl)(mu-Cl)U(THF)(2){(Ar'NSiMe(2))(3)CH}] (5) species in 70 and 90% crystalline yields, respectively. Treatment of 4 and 5 with one equivalent of trimethylsilyl iodide resulted in halide exchange and formation of [U(I){HC(SiMe(2)NAr)(3)}(THF)(2)] (6) and [U(I){HC(SiMe(2)NAr')(3)}(THF)] (7) in 85 and 90% yields, respectively. The heteroleptic amide [U(NCy(2)){HC(SiMe(2)NAr)(3)}(THF)] (8) was prepared from the reaction between 4 and one equivalent of lithium dicyclohexylamide and was isolated in 78% yield. Analogous attempts to prepare [U(NCy(2)){HC(SiMe(2)NAr')(3)}(THF)] (9) from 5 consistently resulted in intractable mixtures of products. Complexes 1-8 have been characterised by X-ray crystallography, NMR spectroscopy, FTIR spectroscopy, room temperature Evans method solution magnetic moments, and CHN micro-analyses.

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The tendency of tripodal amidozirconium and hafnium complexes to form hexacoordinate structures: alkali metal halide cages versus solvent adducts

Cited by 13 publications

References 24 publications

Bipodal Surface Organometallic Complexes with Surface N-Donor Ligands and Application to the Catalytic Cleavage of C–H and C–C Bonds in n-Butane

Bipodal Surface Organometallic Complexes with Surface N-Donor Ligands and Application to the Catalytic Cleavage of C–H and C–C Bonds in n-Butane

Zirconium Amide, Halide, and Alkyl Complexes Supported by Tripodal Amido Ligands Derived fromcis,cis-1,3,5-Triaminocyclohexane

Uranium(iv) amide and halide derivatives of two tripodal tris(N-arylamido-dimethylsilyl)methanes

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