β-Elimination and insertion of CNR in transient pentamethylcyclopentadienyl-imido-tantalum dialkyl complexes. X-ray structure of [TaCp*{N(2,6-Me2C6H3)}(CH2CH2)(PMe3)]
Abstract:The transient dialkyl complexes [TaCp*R 2 (NAr)] (Cp* = C 5 Me 5 ; R=Et, n-Pr; Ar =2,6-Me 2 C 6 H 3 ), obtained by alkylation of [TaCp*Cl 2 (NAr)] with two equiv. of RMgCl in diethylether at low temperature, react with one equiv. of PMe 3 to give [TaCp*(NAr)(CH 2 CHR)(PMe 3 )] (R =H1, Me2) after i-elimination and reductive elimination of alkane. When the same alkylation is carried out and then one equiv. of CN(2,6-Me 2 C 6 H 3 ) is added after heating to room temperature, the alkyl iminoacyl insertion products… Show more
“…The longest Ta−C Cp* bonds involve again the two carbon atoms trans to the imido ligand. The Ta−N(4) bond length, 1.772(5) Å, lies within the range expected for a triple bond and is comparable with the values of the Ta−imido nitrogen values found in 14 , 1.790(15) Å, in [TaCp*( N -C 6 H 3 i Pr 2 )-2,6)Cl 2 ], 1.780(5) Å, in [TaCp*Cl 2 (NAr)],7a 1.774(5) Å, in [TaCp*Me(NAr){N(Ar)C(Me)CMe 2 }],7c 1.784(4) Å, in [TaCp*Me(NAr)(η 2 -NArCCMe 2 CMe= NAr)],7c 1.812(8) Å, and in [TaCp*(NAr)(CH 2 CH 2 )(PMe 3 )], 1.833(4) Å (Ar = 2,6-Me 2 C 6 H 3 ) . The Ta−N(4)−C(34) angle is almost linear, 173.3(5)°.…”
The imido-amido complex [TaCp*(N t Bu)Cl(NH t Bu)], 1, was isolated from the reaction of [TaCp*Cl 4 ] with 3 equiv of LiNH t Bu. The dimethyl [TaCp*(N t Bu)Me 2 ], 2, and chloro-methyl [TaCp*(N t Bu)ClMe], 3, complexes were obtained by methylation of [TaCp*(N t Bu)Cl 2 ] with 2 equiv of LiMe and 1 equiv of ZnMe 2 , respectively. Metathetical reactions of complex 3 with alkali metal salts MX (M ) Na, X ) OMe; M ) Li, X ) O t Bu, NH t Bu) afforded the new imido-methyl compounds [TaCp*(N t Bu)MeX] (X ) OMe 4, O t Bu 5, NH t Bu 6). Insertion of CNR (R ) 2,6-Me 2 C 6 H 3 ) into the Ta-NH t Bu and Ta-Me bonds of the imido-pentamethylcyclopentadienyl complexes 1-6 gave the η 2 -iminocarbamoyl compound [TaCp*(N t Bu)Cl-{η 2 -C(NH t Bu)dNR}], 7, and the η 2 -iminoacyl compounds [TaCp*(N t Bu)X{η 2 -C(Me)dNR}] (X ) Me 8, Cl 9, OMe 10, O t Bu 11, NH t Bu 12), which under appropriate thermal conditions react with a second equivalent of CNR (R ) 2,6-Me 2 C 6 H 3 ) to give the double insertion imineη 2 -iminoacyl products [TaCp*(N t Bu)X{η 2 -C[C(Me)dNR]dNR}] (X ) Me 13, Cl 14, OMe 15, O t Bu 16, NH t Bu 17). When compound 17 was heated at 140 °C for 3 days, an intramolecular proton migration occurred to give the η 2 -diamidoalkene complex [TaCp*(N t Bu){η-N t Bu-C(NHR)dC(Me)-η-NR}], 18. All of the new compounds were characterized by IR, 1 H NMR, and 13 C NMR spectroscopy, and the molecular structures of 14 and 18 were studied by X-ray diffraction methods.
“…The longest Ta−C Cp* bonds involve again the two carbon atoms trans to the imido ligand. The Ta−N(4) bond length, 1.772(5) Å, lies within the range expected for a triple bond and is comparable with the values of the Ta−imido nitrogen values found in 14 , 1.790(15) Å, in [TaCp*( N -C 6 H 3 i Pr 2 )-2,6)Cl 2 ], 1.780(5) Å, in [TaCp*Cl 2 (NAr)],7a 1.774(5) Å, in [TaCp*Me(NAr){N(Ar)C(Me)CMe 2 }],7c 1.784(4) Å, in [TaCp*Me(NAr)(η 2 -NArCCMe 2 CMe= NAr)],7c 1.812(8) Å, and in [TaCp*(NAr)(CH 2 CH 2 )(PMe 3 )], 1.833(4) Å (Ar = 2,6-Me 2 C 6 H 3 ) . The Ta−N(4)−C(34) angle is almost linear, 173.3(5)°.…”
The imido-amido complex [TaCp*(N t Bu)Cl(NH t Bu)], 1, was isolated from the reaction of [TaCp*Cl 4 ] with 3 equiv of LiNH t Bu. The dimethyl [TaCp*(N t Bu)Me 2 ], 2, and chloro-methyl [TaCp*(N t Bu)ClMe], 3, complexes were obtained by methylation of [TaCp*(N t Bu)Cl 2 ] with 2 equiv of LiMe and 1 equiv of ZnMe 2 , respectively. Metathetical reactions of complex 3 with alkali metal salts MX (M ) Na, X ) OMe; M ) Li, X ) O t Bu, NH t Bu) afforded the new imido-methyl compounds [TaCp*(N t Bu)MeX] (X ) OMe 4, O t Bu 5, NH t Bu 6). Insertion of CNR (R ) 2,6-Me 2 C 6 H 3 ) into the Ta-NH t Bu and Ta-Me bonds of the imido-pentamethylcyclopentadienyl complexes 1-6 gave the η 2 -iminocarbamoyl compound [TaCp*(N t Bu)Cl-{η 2 -C(NH t Bu)dNR}], 7, and the η 2 -iminoacyl compounds [TaCp*(N t Bu)X{η 2 -C(Me)dNR}] (X ) Me 8, Cl 9, OMe 10, O t Bu 11, NH t Bu 12), which under appropriate thermal conditions react with a second equivalent of CNR (R ) 2,6-Me 2 C 6 H 3 ) to give the double insertion imineη 2 -iminoacyl products [TaCp*(N t Bu)X{η 2 -C[C(Me)dNR]dNR}] (X ) Me 13, Cl 14, OMe 15, O t Bu 16, NH t Bu 17). When compound 17 was heated at 140 °C for 3 days, an intramolecular proton migration occurred to give the η 2 -diamidoalkene complex [TaCp*(N t Bu){η-N t Bu-C(NHR)dC(Me)-η-NR}], 18. All of the new compounds were characterized by IR, 1 H NMR, and 13 C NMR spectroscopy, and the molecular structures of 14 and 18 were studied by X-ray diffraction methods.
“…X-ray-quality crystals of 1 were obtained from a saturated diethyl ether solution, and the solid-state structure determined (Figure ) confirms the coordination geometry deduced from spectroscopic data. At 1.78 Å, the Ta−N(imido) bond length falls well within the range observed previously for terminal Ar−NTa species (1.765−1.833 Å). ,− Notably, the Ta−N(amino) bond trans to the imido group (2.51 Å) is elongated in comparison to the cis amino bond (2.40 Å). The Ta−Cl bonds (2.37 and 2.44 Å) and the Ta−N(amido) bond (2.01 Å) are similar to the metrical parameters seen in related species. ,− 1 ORTEP diagram (50% probability) of ( i Pr 2 -tacn)TaCl 2 NR ( 1 ).…”
A new i Pr 2 -tacn --supported alkyl tantalum species, (Me 3 SiCH 2 ) 2 (RNd)Ta(µ-CH 2 SiMe 3 )(µ-η 1 :η 3 -i Pr 2tacn)Li (R ) 2,6-i Pr 2 C 6 H 3 ; 2), was synthesized and found to undergo R-H abstraction under gentle heating to form the alkylidene (Me 3 SiCH 2 )(RNd)Ta(µ-CHSiMe 3 )(µ-η 1 :η 3i Pr 2 -tacn)Li ( 3). The syntheses and crystal structures of 2 and 3 and their precursor (( i Pr 2 -tacn)TaCl 2 (dNR) (1)) are described, as well as kinetic data for the first-order thermolysis reaction producing 3.
“…The distance from the tantalum atom to the Cp* ring centroid is 2.233(4) Å, a value that is normal for monocyclopentadienyltantalum complexes . The tantalum−oxygen bond lengths [mean value 1.943(8) Å; see Table ] are within the normal range expected for Ta−μ 3 -O bonds …”
The reaction of Cp*TiMe3 with 3 equiv of [Ir(μ-OH)(COD)]2 affords the new heterometallic
organometallic oxide Cp*Ti(μ3-O)3[Ir(COD)]3 (3). Reaction of Cp*TaMe4 with 4 equiv of [M(μ-OH)(COD)]2 (M = Rh, Ir) yields complexes Cp*Ta(μ3-O)4[M(COD)]4 [M = Rh (5), Ir (6)]. The
structure of compound 5 has been determined by X-ray diffraction. Complexes 5 and 6 react
with the alcohol 3-CN-4,6-Me2-2-OH−C5HN to yield the corresponding rhodium (7) or iridium
(8) alkoxide complexes. The structure of complex 8 has been determined by X-ray diffraction.
Reaction of [Rh(μ-OH)(COD)]2 with thiolacetic acid gives rise to a thioacetate complex [Rh(μ-SCOCH3)(COD)]2 (9).
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