TY - JOUR
T1 - Use of an aryldiamine pincer ligand in the study of tantalum alkylidene-centered reactivity
T2 - Tantalum-mediated alkene synthesis via reductive rearrangements and wittig-type reactions
AU - Abbenhuis, Hendrikus C L
AU - Faiken, Nantko
AU - Grove, David M.
AU - Jastrzebski, Johann T B H
AU - Kooijman, Huub
AU - Van Der Sluis, Paul
AU - Smeets, Wilberth J J
AU - Spek, Anthony L.
AU - Van Koten, Gerard
PY - 1992
Y1 - 1992
N2 - The potentially terdentate, monoanionic aryldiamine ligand {C6H3(CH2NMe2)2-2,6} - provides an excellent tool for the study of tantalum alkylidene-centered reactivity. Transmetallation of [TaCl3(CH-t-Bu)(THF)2] with 1/2[Li{C6H3
- (CH2NMe2)2-2,6}]2 affords the alkylidene complex [TaCl2{C6H3(CH2NMe2) 2-2,6}(CH-t-Bu)] (1) in 90% yield. Complex 1 belongs to the space group Cc with a = 12.983 (2) Å, b = 12.384 (1) Å, c - 11.969 (1) Å, β= 95.43 (1)°, and Z = 4. The hexacoordinate tantalum center in 1 has an irregular ligand array in which the aryldiamine ligand adopts a new pseudofacial N,C,N-coordination mode. A Wittig-type reaction of the alkylidene complex 1 with acetone or benzaldehyde affords [TaCl2{C6H3(CH2NMe2) 2-2,6)(μ-O)]2 (2) in virtually quantitative yield. A similar reaction of 1 with PhCH = NR affords [TaCl2(C6H3(CH2NMe2) 2-2,6)(NR)] (R = Me, SiMe3). Complex 2 belongs to the space group Pc with a = 10.800 (4) Å, b = 11.804 (3) Å, c = 12.539 (4) Å, β= 108.67 (3)°, and Z = 2. Complex 2 is a dimer with bridging oxo functions and has a distorted pentagonal bipyramidal ligand array around each tantalum center. Complex 1 with ethene and propene gives a rearrangement reaction that affords alkene adducts [TaCl2{C6H3(CH2NMe2) 2,6}(H2C=CHR)] (R = CH2-t-Bu and Me, respectively). [TaCl2{C6H3(CH2NMe2) 2-2,6}(H2C=CHCH2-t-Bu)] belongs to the space group P1̄ with a = 8.320 (1) Å, b = 9.041 (2) Å, c = 14.054 (3) Å, α = 94.53 (2)°, β= 90.75 (2)°, γ = 92.86 (2)°, and Z = 2. The overall structure is distorted pentagonal bipyramidal. The chirality in the coordinated alkene determines the conformation of both five-membered Ta-C-C-C-N chelate rings. NMR experiments show the alkene complexes to be rigid in solution; the bonding of the alkene to the metal center is best described as resulting in a metallacyclopropane unit.
AB - The potentially terdentate, monoanionic aryldiamine ligand {C6H3(CH2NMe2)2-2,6} - provides an excellent tool for the study of tantalum alkylidene-centered reactivity. Transmetallation of [TaCl3(CH-t-Bu)(THF)2] with 1/2[Li{C6H3
- (CH2NMe2)2-2,6}]2 affords the alkylidene complex [TaCl2{C6H3(CH2NMe2) 2-2,6}(CH-t-Bu)] (1) in 90% yield. Complex 1 belongs to the space group Cc with a = 12.983 (2) Å, b = 12.384 (1) Å, c - 11.969 (1) Å, β= 95.43 (1)°, and Z = 4. The hexacoordinate tantalum center in 1 has an irregular ligand array in which the aryldiamine ligand adopts a new pseudofacial N,C,N-coordination mode. A Wittig-type reaction of the alkylidene complex 1 with acetone or benzaldehyde affords [TaCl2{C6H3(CH2NMe2) 2-2,6)(μ-O)]2 (2) in virtually quantitative yield. A similar reaction of 1 with PhCH = NR affords [TaCl2(C6H3(CH2NMe2) 2-2,6)(NR)] (R = Me, SiMe3). Complex 2 belongs to the space group Pc with a = 10.800 (4) Å, b = 11.804 (3) Å, c = 12.539 (4) Å, β= 108.67 (3)°, and Z = 2. Complex 2 is a dimer with bridging oxo functions and has a distorted pentagonal bipyramidal ligand array around each tantalum center. Complex 1 with ethene and propene gives a rearrangement reaction that affords alkene adducts [TaCl2{C6H3(CH2NMe2) 2,6}(H2C=CHR)] (R = CH2-t-Bu and Me, respectively). [TaCl2{C6H3(CH2NMe2) 2-2,6}(H2C=CHCH2-t-Bu)] belongs to the space group P1̄ with a = 8.320 (1) Å, b = 9.041 (2) Å, c = 14.054 (3) Å, α = 94.53 (2)°, β= 90.75 (2)°, γ = 92.86 (2)°, and Z = 2. The overall structure is distorted pentagonal bipyramidal. The chirality in the coordinated alkene determines the conformation of both five-membered Ta-C-C-C-N chelate rings. NMR experiments show the alkene complexes to be rigid in solution; the bonding of the alkene to the metal center is best described as resulting in a metallacyclopropane unit.
UR - http://www.scopus.com/inward/record.url?scp=0001495917&partnerID=8YFLogxK
M3 - Article
AN - SCOPUS:0001495917
SN - 0002-7863
VL - 114
SP - 9773
EP - 9781
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 25
ER -