Reactions of Pentafulvene Complexes of Titanium with Carbonyl Compounds − Diastereoselective Synthesis of σ,π-Chelate Complexes with Cp~O Ligands

Abstract

The compound Cp*Ti[η6‐C5H4C(H)(tBu)]Cl (1) reacts with ketones, aldehydes, and esters to give σ,π‐chelate complexes with Cp~O ligands through insertion of the carbonyl group into the Ti−C(H)(tBu) bond. Starting from diastereomerically pure 1, the reaction with symmetric ketones R2CO led to the formation of two diastereomeric products. The diastereomeric ratio could be controlled by steric and electronic properties of the substituent R. Thus, this procedure provides an easy approach to complexes with Cp~O ligands where new chiral centres are formed directly in the coordination sphere of the metal atom through a side‐differentiated attack of the carbonyl compound at the titanium atom. All products were thoroughly characterized. Crystal structure determinations were carried out on 2a, 3a, 5, 6b, and 9a. (© Wiley‐VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Synthesis and Reactivity of Bis(η5:η1-pentafulvene)zirconium Complexes

“…69 This elongation can be attributed to the strong ring strain of the metallacycles, whereas the steric effects of the substituents at C6 and C21 have a minimal impact. 67 As expected, the NMR spectra of the enantiomeric compounds 7 and 8 show one set of signals; in addition, the values are within the anticipated range. In contrast, the spectra of 9 indicate a 1:2 mixture of products.…”

“…Of significance is the length of the newly formed C6–C21 bond (1.575(2) Å ( 7 ), 1.599(2) Å ( 8 ), 1.629(2)/1.635(2) Å ( 9 )), which is considerably longer than a typical C–C single bond; that for especially 9 is comparable to other reported extremely long alkane C–C single bonds . This elongation can be attributed to the strong ring strain of the metallacycles, whereas the steric effects of the substituents at C6 and C21 have a minimal impact …”

Synthesis and Reactivity of Bis(η5:η1-pentafulvene)zirconium Complexes

“…69 This elongation can be attributed to the strong ring strain of the metallacycles, whereas the steric effects of the substituents at C6 and C21 have a minimal impact. 67 As expected, the NMR spectra of the enantiomeric compounds 7 and 8 show one set of signals; in addition, the values are within the anticipated range. In contrast, the spectra of 9 indicate a 1:2 mixture of products.…”

“…Of significance is the length of the newly formed C6–C21 bond (1.575(2) Å ( 7 ), 1.599(2) Å ( 8 ), 1.629(2)/1.635(2) Å ( 9 )), which is considerably longer than a typical C–C single bond; that for especially 9 is comparable to other reported extremely long alkane C–C single bonds . This elongation can be attributed to the strong ring strain of the metallacycles, whereas the steric effects of the substituents at C6 and C21 have a minimal impact …”

From Organic Azides through Titanium Triazenido Complexes to Titanium Imides

“…The newly formed bond between the nitrogen atom and the C exo atom N1–C31 (1.508 Å) is slightly elongated compared to normal N–C sp³ bonds (1.47 Å). Similarly elongated bond lengths were observed for a broad range of insertion products of, for example, nitriles, aldehydes, and ketones into the Ti–C exo bond of 1 …”

Reaction of Pentafulvene Titanium and Zirconium Complexes with Phosphorus Ylides: Stoichiometric Reactions and Catalytic Intramolecular Proton Shuttles

“…Both metal centers show a tetrahedral distorted geometry, owing to the Ct1–​Ti–Ct2 (132.6° and 136.8°) and Cl–​Ti–O angles (96.73(2)° and 95.4(3)°). The Ti–O distances are similar to 1.8469(5) Å and 1.8884(10) Å and are within range of a single bond ,, as well as the new C10–C11 bonds with 1.5679(11) Å and 1.5416(18) Å, respectively. , …”

Synthesis and Reactivity of Bis(η5:η1-pentafulvene)zirconium Complexes

“…69 This elongation can be attributed to the strong ring strain of the metallacycles, whereas the steric effects of the substituents at C6 and C21 have a minimal impact. 67 As expected, the NMR spectra of the enantiomeric compounds 7 and 8 show one set of signals; in addition, the values are within the anticipated range. In contrast, the spectra of 9 indicate a 1:2 mixture of products.…”

“…Of significance is the length of the newly formed C6–C21 bond (1.575(2) Å ( 7 ), 1.599(2) Å ( 8 ), 1.629(2)/1.635(2) Å ( 9 )), which is considerably longer than a typical C–C single bond; that for especially 9 is comparable to other reported extremely long alkane C–C single bonds . This elongation can be attributed to the strong ring strain of the metallacycles, whereas the steric effects of the substituents at C6 and C21 have a minimal impact …”

From Organic Azides through Titanium Triazenido Complexes to Titanium Imides

“…The newly formed bond between the nitrogen atom and the C exo atom N1–C31 (1.508 Å) is slightly elongated compared to normal N–C sp³ bonds (1.47 Å). Similarly elongated bond lengths were observed for a broad range of insertion products of, for example, nitriles, aldehydes, and ketones into the Ti–C exo bond of 1 …”

Reaction of Pentafulvene Titanium and Zirconium Complexes with Phosphorus Ylides: Stoichiometric Reactions and Catalytic Intramolecular Proton Shuttles

“…Both metal centers show a tetrahedral distorted geometry, owing to the Ct1–​Ti–Ct2 (132.6° and 136.8°) and Cl–​Ti–O angles (96.73(2)° and 95.4(3)°). The Ti–O distances are similar to 1.8469(5) Å and 1.8884(10) Å and are within range of a single bond ,, as well as the new C10–C11 bonds with 1.5679(11) Å and 1.5416(18) Å, respectively. , …”

Synthesis and Reactivity of Bis(η5:η1-pentafulvene)zirconium Complexes

“…69 This elongation can be attributed to the strong ring strain of the metallacycles, whereas the steric effects of the substituents at C6 and C21 have a minimal impact. 67 As expected, the NMR spectra of the enantiomeric compounds 7 and 8 show one set of signals; in addition, the values are within the anticipated range. In contrast, the spectra of 9 indicate a 1:2 mixture of products.…”

“…Of significance is the length of the newly formed C6–C21 bond (1.575(2) Å ( 7 ), 1.599(2) Å ( 8 ), 1.629(2)/1.635(2) Å ( 9 )), which is considerably longer than a typical C–C single bond; that for especially 9 is comparable to other reported extremely long alkane C–C single bonds . This elongation can be attributed to the strong ring strain of the metallacycles, whereas the steric effects of the substituents at C6 and C21 have a minimal impact …”

From Organic Azides through Titanium Triazenido Complexes to Titanium Imides

“…The newly formed bond between the nitrogen atom and the C exo atom N1–C31 (1.508 Å) is slightly elongated compared to normal N–C sp³ bonds (1.47 Å). Similarly elongated bond lengths were observed for a broad range of insertion products of, for example, nitriles, aldehydes, and ketones into the Ti–C exo bond of 1 …”

Reaction of Pentafulvene Titanium and Zirconium Complexes with Phosphorus Ylides: Stoichiometric Reactions and Catalytic Intramolecular Proton Shuttles

“…Both metal centers show a tetrahedral distorted geometry, owing to the Ct1–​Ti–Ct2 (132.6° and 136.8°) and Cl–​Ti–O angles (96.73(2)° and 95.4(3)°). The Ti–O distances are similar to 1.8469(5) Å and 1.8884(10) Å and are within range of a single bond ,, as well as the new C10–C11 bonds with 1.5679(11) Å and 1.5416(18) Å, respectively. , …”