Titanocene Borane σ-Complexes

Muhoro, Clare N.; He, Xiaoming; Hartwig, John F.

doi:10.1021/ja9900757

Cited by 143 publications

(95 citation statements)

References 67 publications

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“…[14] They also found that the reaction of [Ti(Cp) 2 (PMe 3 ) 2 ] with PhSiH 3 gives a close analogue of 1, namely, the silane s complex [Ti(Cp) 2 (PMe 3 )(h 2 -H 3 SiPh)]. [15] A complex reported by Hartwig et al [16] as [Ti(Cp) 2 (h 2 -HBcat')(h 2 -H 3 SiPh)] (cat' = catechol) was later suggested to be a silylborato complex [Ti(Cp) 2 (h 2 -H 2 Bcat')(SiH 2 Ph)] on the basis of theoretical studies. [17] No fully authenticated, classical mononuclear silyl hydride complex of Ti IV has been reported to date.…”

Section: Introductionmentioning

confidence: 89%

Nonclassical Titanocene Silyl Hydrides

Ignatov

Rees

Tyrrell

et al. 2004

Chemistry A European J

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The titanocene silyl hydride complexes [Ti(Cp)2(PMe3)(H)(SiR3)] [SiR3=SiMePhCl (6), SiPh2Cl (7), SiMeCl2 (8), SiCl3 (9)] were prepared by HSiR3 addition to [Ti(Cp)2(PMe3)2] and were studied by NMR and IR spectroscopy, X-ray diffraction (for 6, 8, and 9), and DFT calculations. Spectroscopic and structural data established that these complexes exhibit nonclassical Ti-H-Si-Cl interligand hypervalent interactions. In particular, the observation of silicon-hydride coupling constants J(Si,H) in 6-9 in the range 22-40 Hz, the signs of which we found to be negative for 8 and 9, is conclusive evidence of the presence of a direct Si-H bond. The analogous reaction of [Ti(Cp)2(PMe3)2] with HSi(OEt)3 does not afford the expected classical silyl hydride complex [Ti(Cp)2(PMe3)(H)[Si(OEt)3]], and instead NMR-silent titanium (apparently TiIII) complex(es) and the silane redistribution product Si(OEt)4 are formed. The structural data and DFT calculations for the compounds [Ti(Cp)2(PMe3)(H)(SiR3)] show that the strength of interligand hypervalent interactions in the chlorosilyl complexes decreases as the number of chloro groups on silicon increases. However, in the absence of an Si-bound electron-withdrawing group trans to the Si-H moiety, a silane sigma complex is formed, characterized by a long Ti-Si bond of 2.658 A and short Si-H contact of 1.840 A in the model complex [Ti(Cp)2(PMe3)(H)(SiMe3)]. Both the silane sigma complexes and silyl hydride complexes with interligand hypervalent interactions exhibit bond paths between the silicon and hydride atoms in Atoms in Molecules (AIM) studies. To date a classical titanocene phosphane silyl hydride complex without any Si-H interaction has not been observed, and therefore titanocene silyl hydrides are, depending on the nature of the R groups on Si, either silane sigma complexes or compounds with an interligand hypervalent interaction.

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Section: Introductionmentioning

confidence: 89%

Nonclassical Titanocene Silyl Hydrides

Ignatov

Rees

Tyrrell

et al. 2004

Chemistry A European J

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“…Hartwig 2 ] in 1996 on the basis of NMR spectroscopy, X-ray diffraction, and MP2 calculations. [52,53] There are indeed no examples of structures incorporating a M(h 2 -C-H) 2 fragment, but it is interesting to mention some related agostic structures. The cationic iridium complex [Ir(H) 2 (PtBu 2 Ph) 2 ]…”

Section: Structures With Two S Ligandsmentioning

confidence: 99%

The σ‐CAM Mechanism: σ Complexes as the Basis of σ‐Bond Metathesis at Late‐Transition‐Metal Centers

2007

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Complexes in which a sigma-H--E bond (E=H, B, Si, C) acts as a two-electron donor to the metal center are called sigma complexes. Clues that it is possible to interconvert sigma ligands without a change in oxidation state derive from C--H activation reactions effecting isotope exchange and from dynamic rearrangements of sigma complexes (see Frontispiece). Through these pathways, metathesis of M--E bonds can occur at late transition metals. We call this process sigma-complex-assisted metathesis, or sigma-CAM, which is distinct from the familiar sigma-bond metathesis (typical for d(0) metals and requiring no intermediate) and from oxidative-reductive elimination mechanisms (inherently requiring intermediates with changed oxidation states and sometimes involving sigma complexes). There are examples of sigma-CAM mechanisms in catalysis, especially for alkane borylation and isotope exchange of alkanes. It may also occur in silylation and alkene hydrogenation.

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“…[23] More recently, reactions involving Me 3 P ¥ BH 3 and Me 3 P ¥ BH 2 BH 2 ¥ PMe 3 have resulted in BÀH bond activation and led to structurally characterized examples of mononuclear and dinuclear metal boryl complexes. [24] In addition, sborane [25] complexes and h 1 -borane [26] complexes have also been reported.…”

Section: Introductionmentioning

confidence: 99%

Chemistry of Phosphine–Borane Adducts at Platinum Centers: Synthesis and Reactivity of Pt^II Complexes with Phosphinoborane Ligands

Jaska

Dorn

Lough

et al. 2002

Chemistry A European J

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Reaction of [Pt(PEt(3))(3)] with the primary and secondary phosphine-borane adducts PhRPH x BH(3) (R=H, Ph) resulted in oxidative addition of a P-H bond at the Pt(0) center to afford the complexes trans-[PtH(PPhR x BH(3))(PEt(3))(2)] (1: R=H; 2: R=Ph). The products 1 and 2 were characterized by (1)H, (11)B, (13)C, (31)P, and (195)Pt NMR spectroscopy, and the molecular structures were verified by X-ray crystallography. In both cases, a trans arrangement of the hydride ligand with respect to the phosphidoborane ligand was observed. When 2 was treated with PhPH(2) x BH(3), a novel phosphidoborane ligand-exchange reaction occurred which yielded 1 and Ph(2)PH x BH(3). Treatment of 2 with one equivalent of depe (depe=1,2-bis(diethylphosphino)ethane) resulted in the formation of the complex cis-[PtH(PPh(2) x BH(3))(depe)] (3), in which the hydride ligand and the phosphidoborane ligand are in a cis arrangement. Treatment of 3 with PhPH(2) x BH(3) was found to result in an exchange of the phosphidoborane ligands to give the complex cis-[PtH(PPhH x BH(3))(depe)] (4) and Ph(2)PH x BH(3). Complex 4 was found to undergo further reaction in the presence of PhPH(2) x BH(3) to give meso-cis-[Pt(PPhH x BH(3))(2)(depe)] (5) and rac-cis-[Pt(PPhH x BH(3))(2)(depe)] (6).

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Titanocene Borane σ-Complexes

Cited by 143 publications

References 67 publications

Nonclassical Titanocene Silyl Hydrides

Nonclassical Titanocene Silyl Hydrides

The σ‐CAM Mechanism: σ Complexes as the Basis of σ‐Bond Metathesis at Late‐Transition‐Metal Centers

Chemistry of Phosphine–Borane Adducts at Platinum Centers: Synthesis and Reactivity of Pt^II Complexes with Phosphinoborane Ligands

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Titanocene Borane σ-Complexes

Cited by 143 publications

References 67 publications

Nonclassical Titanocene Silyl Hydrides

Nonclassical Titanocene Silyl Hydrides

The σ‐CAM Mechanism: σ Complexes as the Basis of σ‐Bond Metathesis at Late‐Transition‐Metal Centers

Chemistry of Phosphine–Borane Adducts at Platinum Centers: Synthesis and Reactivity of PtII Complexes with Phosphinoborane Ligands

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Product

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Chemistry of Phosphine–Borane Adducts at Platinum Centers: Synthesis and Reactivity of Pt^II Complexes with Phosphinoborane Ligands