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Group 4 Metal and Lanthanide Complexes in the Oxidation State +3 with Tris(trimethylsilyl)silyl Ligands.

ABSTRACT: A number of paramagnetic silylated d¹ group 4 metallates were prepared by reaction of potassium tris(trimethylsilyl)silanide with group 4 metallates of the type K[Cp₂MCl₂] (M = Ti, Zr, Hf). The outcomes of the reactions differ for all three metals. While for the hafnium case the expected complex [Cp₂Hf{Si(SiMe₃)₃}₂]^- was obtained, the analogous titanium reaction led to a product with two Si(H)(SiMe₃)₂ ligands. The reaction with zirconium caused the formation of a dinuclear fulvalene bridged complex. The desired [Cp₂Zr{Si(SiMe₃)₃}₂]^- could be obtained by reduction of Cp₂Zr{Si(SiMe₃)₃}₂ with potassium. In related reactions of potassium tris(trimethylsilyl)silanide with some lanthanidocenes Cp₃Ln (Ln = Ce, Sm, Gd, Ho, Tm) complexes of the type [Cp₃Ln Si(SiMe₃)₃]^- with either [18-crown-6·K]⁺ or the complex ion [18-crown-6·K·Cp·K·18-crown-6] as counterions were obtained. Due to d¹ or fⁿ electron configuration, unambiguous characterization of all obtained complexes could only be achieved by single crystal XRD diffraction analysis.

SUBMITTER: Zitz R

PROVIDER: S-EPMC6534343 | biostudies-literature | 2019 May

REPOSITORIES: biostudies-literature

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Group 4 Metal and Lanthanide Complexes in the Oxidation State +3 with Tris(trimethylsilyl)silyl Ligands.

Zitz Rainer R Hlina Johann J Arp Henning H Kinschel Dominik D Marschner Christoph C Baumgartner Judith J

Inorganic chemistry 20190508 10

A number of paramagnetic silylated d1 group 4 metallates were prepared by reaction of potassium tris(trimethylsilyl)silanide with group 4 metallates of the type K[Cp2MCl2] (M = Ti, Zr, Hf). The outcomes of the reactions differ for all three metals. While for the hafnium case the expected complex [Cp2Hf{Si(SiMe3)3}2]- was obtained, the analogous titanium reaction led to a product with two Si(H)(SiMe3</sub ...[more]

PMID: 31066552

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Project description:Complexes featuring lanthanide (Ln)-Si bonds represent a highly neglected research area. Herein, we report a series of open-shell Ln(II+) and Ln(III+) complexes bearing ?-bonded silyl and base-stabilized N-heterocyclic silylene (NHSi) ligands. The reactions of the Ln(III+) complexes Cp3Ln (Ln = Tm, Ho, Tb, Gd; Cp = cyclopentadienide) with the 18-crown-6 (18-cr-6)-stabilized 1,4-oligosilanyl dianion [(18-cr-6)KSi(SiMe3)2SiMe2SiMe2Si(SiMe3)2K(18-cr-6)] (1) selectively afford the corresponding metallacyclopentasilane salts [Cp2Ln({Si(SiMe3)2SiMe2}2)](-)[K2(18-cr-6)2Cp](+) [Ln = Tm (2a), Ho (2b), Tb (2c), Gd (2d)]. Complexes 2a-2d represent the first examples of structurally characterized Tm, Ho, Tb, and Gd complexes featuring Ln-Si bonds. Strikingly, the analogous reaction of 1 with the lighter element analogue Cp3Ce affords the acyclic product [Cp3CeSi(SiMe3)2SiMe2SiMe2Si(SiMe3)2-Cp3Ce](2-)2[K(18-cr-6)](+) (3) as the first example of a complex featuring a Ce-Si bond. In an alternative synthetic approach, the aryloxy-functionalized benzamidinato NHSi ligand Si(OC6H4-2-tBu){(NtBu)2CPh} (4a) and the alkoxy analogue Si(OtBu){(NtBu)2CPh} (4b) were reacted with Cp*2Sm(OEt2), affording, by OEt2 elimination, the corresponding silylene complexes, both featuring Sm(II+) centers: Cp*2Sm ? :Si(O-C6H4-2-tBu){(NtBu)2CPh} (6) and Cp*2Sm ? :Si(OtBu){(NtBu)2CPh} (5). Complexes 5 and 6 are the first four-coordinate silylene complexes of any f-block element to date. All complexes were fully characterized by spectroscopic means and by single-crystal X-ray diffraction analysis. In the series 2a-2d, a linear correlation was observed between the Ln-Si bond lengths and the covalent radii of the corresponding Ln metals. Moreover, in complexes 5 and 6, notably long Sm-Si bonds are observed, in accordance with a donor-acceptor interaction between Si and Sm [5, 3.4396(15) Å; 6, 3.3142(18) Å]. Density functional theory calculations were carried out for complexes 2a-2d, 5, and 6 to elucidate the bonding situation between the Ln(II+) or Ln(III+) centers and Si. In particular, a decrease in the Mayer bond order (MBO) of the Ln-Si bond is observed in the series 2a-2d in moving from the lighter to the heavier lanthanides (Tm = 0.53, Ho = 0.62, Tb = 0.65, and Gd = 0.75), which might indicate decreasing covalency in the Ln-Si bond. In accordance with the long bond lengths observed experimentally in complexes 5 and 6, comparatively low MBOs were determined for both silylene complexes (5, 0.24; 6, 0.25) .

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Dataset Information

Group 4 Metal and Lanthanide Complexes in the Oxidation State +3 with Tris(trimethylsilyl)silyl Ligands.

Publications

Group 4 Metal and Lanthanide Complexes in the Oxidation State +3 with Tris(trimethylsilyl)silyl Ligands.

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