Amide derivatives of tantalum and a niobium-promoted ring opening of 3,5-lutidine

Jeffrey B. Bonanno; Adam S. Veige; Peter T. Wolczanski; Emil B. Lobkovsky

doi:10.1016/S0020-1693(02)01308-7

Amide derivatives of tantalum and a niobium-promoted ring opening of 3,5-lutidine

Jeffrey B. Bonanno, Adam S. Veige, Peter T. Wolczanski, Emil B. Lobkovsky

Research output: Contribution to journal › Article › peer-review

47 Scopus citations

Abstract

Various tantalum amide compounds were prepared in an attempt to observe C-N bond activation. Addition of lithium amides to THF solutions of (silox)₂TaCl₃ (3) in the presence of trace amounts of the corresponding amine afforded (silox)₂TaCl₂NR₂ (NR₂=NMe₂, 4-NMe₂; N(CH₂)₃CH₂, 4-pyrr; N(CH₂)₄CH₂, 4-pip). Treatment of 4-pyrr with EtMgCl and 4-pip with MeMgBr provided (silox)₂TaEt₂(N(CH₂)₃CH ₂) (5-pyrr-Et₂) and (silox)₂TaMe₂(N(CH₂)₄CH ₂) (5-pip-Me₂). Thermolysis of 5-pip-Me₂ generated CH₄ and η²-imine complex (silox)₂Ta(CH₃)(η²-NC₅H ₉) (6). In contrast, 5-pyrr-Et₂ thermally degraded to the ethylene adduct, (silox)₂(C₄H₈N)Ta(η²-C ₂H₄) (7-pyrr) and C₂H₆. Na/Hg reductions of 4-pyrr and 4-pip in the presence of 1 equiv. C₂H₄ generated 7-pyrr and (^tBu₃SiO)₂(C₅H₁₀N) Ta(η²-C₂H₄) (7-pip); under an excess of C₂H₄, tantallacyclopentane (silox)₂(C₄H₈N)TaCH₂(CH ₂)₂CH₂ (8-pyrr) was prepared. With pyridine present, Na/Hg reduction of 4-pyrr and 4-pip provided η²-pyridine complexes (silox)₂(C₄H₈N)Ta(η²-(N,C)- NC₅H₅) (9-pyrr) and (silox)₂(C₅H₁₀N)Ta(η²-(N,C)- NC₅H₅) (9-pip). Treatment of 9-pyrr and 9-pip with 1 equiv. CH₃NH₂ in C₆D₆ revealed the formation of tantalum imido derivatives (silox)₂(C₄H₈N)Ta=NMe (10-pyrr) and (silox)₂(C₅H₁₀N)Ta=NMe (10-pip), respectively, via the α-pyridyl-methylimido complex, (silox)₂Ta(NMe)(NC₅H₄) (11). Na/Hg reduction of (silox)₃NbCl₂ (13) in the presence of excess 3,5-lutidine afforded (silox)₃Nb(η²-3,5-Me₂-NC₅H ₃) (2-3,5-Lut), which was heated for 4 days at 120°C to give (silox)₂NbN-cis-CH=CMe-cis-CH=CMe-trans-CH=CHCMe₂Si ^tBu₂O (14), whose structure was confirmed by X-ray crystallography. The direct participation of a silox group in the ring opening is a rare occurrence for this typically ancillary ligand, and provides another pathway for C-N bond activation relevant to hydrodenitrogenation (HDN).

Original language	English (US)
Pages (from-to)	173-184
Number of pages	12
Journal	Inorganica Chimica Acta
Volume	345
DOIs	https://doi.org/10.1016/S0020-1693(02)01308-7
State	Published - Mar 10 2003
Externally published	Yes

Keywords

3,5-Lutidine
Amide derivatives
Metallacycle
Niobium
Pyridine
Ring-opening
Siloxide
Tantalum

ASJC Scopus subject areas

Physical and Theoretical Chemistry
Inorganic Chemistry
Materials Chemistry

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10.1016/S0020-1693(02)01308-7

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@article{a4abc1c0b8c14bfaafe76815cbf51c3d,

title = "Amide derivatives of tantalum and a niobium-promoted ring opening of 3,5-lutidine",

abstract = "Various tantalum amide compounds were prepared in an attempt to observe C-N bond activation. Addition of lithium amides to THF solutions of (silox)2TaCl3 (3) in the presence of trace amounts of the corresponding amine afforded (silox)2TaCl2NR2 (NR2=NMe2, 4-NMe2; N(CH2)3CH2, 4-pyrr; N(CH2)4CH2, 4-pip). Treatment of 4-pyrr with EtMgCl and 4-pip with MeMgBr provided (silox)2TaEt2(N(CH2)3CH 2) (5-pyrr-Et2) and (silox)2TaMe2(N(CH2)4CH 2) (5-pip-Me2). Thermolysis of 5-pip-Me2 generated CH4 and η2-imine complex (silox)2Ta(CH3)(η2-NC5H 9) (6). In contrast, 5-pyrr-Et2 thermally degraded to the ethylene adduct, (silox)2(C4H8N)Ta(η2-C 2H4) (7-pyrr) and C2H6. Na/Hg reductions of 4-pyrr and 4-pip in the presence of 1 equiv. C2H4 generated 7-pyrr and (tBu3SiO)2(C5H10N) Ta(η2-C2H4) (7-pip); under an excess of C2H4, tantallacyclopentane (silox)2(C4H8N)TaCH2(CH 2)2CH2 (8-pyrr) was prepared. With pyridine present, Na/Hg reduction of 4-pyrr and 4-pip provided η2-pyridine complexes (silox)2(C4H8N)Ta(η2-(N,C)- NC5H5) (9-pyrr) and (silox)2(C5H10N)Ta(η2-(N,C)- NC5H5) (9-pip). Treatment of 9-pyrr and 9-pip with 1 equiv. CH3NH2 in C6D6 revealed the formation of tantalum imido derivatives (silox)2(C4H8N)Ta=NMe (10-pyrr) and (silox)2(C5H10N)Ta=NMe (10-pip), respectively, via the α-pyridyl-methylimido complex, (silox)2Ta(NMe)(NC5H4) (11). Na/Hg reduction of (silox)3NbCl2 (13) in the presence of excess 3,5-lutidine afforded (silox)3Nb(η2-3,5-Me2-NC5H 3) (2-3,5-Lut), which was heated for 4 days at 120°C to give (silox)2NbN-cis-CH=CMe-cis-CH=CMe-trans-CH=CHCMe2Si tBu2O (14), whose structure was confirmed by X-ray crystallography. The direct participation of a silox group in the ring opening is a rare occurrence for this typically ancillary ligand, and provides another pathway for C-N bond activation relevant to hydrodenitrogenation (HDN).",

keywords = "3,5-Lutidine, Amide derivatives, Metallacycle, Niobium, Pyridine, Ring-opening, Siloxide, Tantalum",

author = "Bonanno, {Jeffrey B.} and Veige, {Adam S.} and Wolczanski, {Peter T.} and Lobkovsky, {Emil B.}",

note = "Funding Information: The National Science Foundation (CHE-9816134) and Cornell University are gratefully acknowledged.",

year = "2003",

month = mar,

day = "10",

doi = "10.1016/S0020-1693(02)01308-7",

language = "English (US)",

volume = "345",

pages = "173--184",

journal = "Inorganica Chimica Acta",

issn = "0020-1693",

publisher = "Elsevier BV",

}

TY - JOUR

T1 - Amide derivatives of tantalum and a niobium-promoted ring opening of 3,5-lutidine

AU - Bonanno, Jeffrey B.

AU - Veige, Adam S.

AU - Wolczanski, Peter T.

AU - Lobkovsky, Emil B.

N1 - Funding Information: The National Science Foundation (CHE-9816134) and Cornell University are gratefully acknowledged.

PY - 2003/3/10

Y1 - 2003/3/10

N2 - Various tantalum amide compounds were prepared in an attempt to observe C-N bond activation. Addition of lithium amides to THF solutions of (silox)2TaCl3 (3) in the presence of trace amounts of the corresponding amine afforded (silox)2TaCl2NR2 (NR2=NMe2, 4-NMe2; N(CH2)3CH2, 4-pyrr; N(CH2)4CH2, 4-pip). Treatment of 4-pyrr with EtMgCl and 4-pip with MeMgBr provided (silox)2TaEt2(N(CH2)3CH 2) (5-pyrr-Et2) and (silox)2TaMe2(N(CH2)4CH 2) (5-pip-Me2). Thermolysis of 5-pip-Me2 generated CH4 and η2-imine complex (silox)2Ta(CH3)(η2-NC5H 9) (6). In contrast, 5-pyrr-Et2 thermally degraded to the ethylene adduct, (silox)2(C4H8N)Ta(η2-C 2H4) (7-pyrr) and C2H6. Na/Hg reductions of 4-pyrr and 4-pip in the presence of 1 equiv. C2H4 generated 7-pyrr and (tBu3SiO)2(C5H10N) Ta(η2-C2H4) (7-pip); under an excess of C2H4, tantallacyclopentane (silox)2(C4H8N)TaCH2(CH 2)2CH2 (8-pyrr) was prepared. With pyridine present, Na/Hg reduction of 4-pyrr and 4-pip provided η2-pyridine complexes (silox)2(C4H8N)Ta(η2-(N,C)- NC5H5) (9-pyrr) and (silox)2(C5H10N)Ta(η2-(N,C)- NC5H5) (9-pip). Treatment of 9-pyrr and 9-pip with 1 equiv. CH3NH2 in C6D6 revealed the formation of tantalum imido derivatives (silox)2(C4H8N)Ta=NMe (10-pyrr) and (silox)2(C5H10N)Ta=NMe (10-pip), respectively, via the α-pyridyl-methylimido complex, (silox)2Ta(NMe)(NC5H4) (11). Na/Hg reduction of (silox)3NbCl2 (13) in the presence of excess 3,5-lutidine afforded (silox)3Nb(η2-3,5-Me2-NC5H 3) (2-3,5-Lut), which was heated for 4 days at 120°C to give (silox)2NbN-cis-CH=CMe-cis-CH=CMe-trans-CH=CHCMe2Si tBu2O (14), whose structure was confirmed by X-ray crystallography. The direct participation of a silox group in the ring opening is a rare occurrence for this typically ancillary ligand, and provides another pathway for C-N bond activation relevant to hydrodenitrogenation (HDN).

AB - Various tantalum amide compounds were prepared in an attempt to observe C-N bond activation. Addition of lithium amides to THF solutions of (silox)2TaCl3 (3) in the presence of trace amounts of the corresponding amine afforded (silox)2TaCl2NR2 (NR2=NMe2, 4-NMe2; N(CH2)3CH2, 4-pyrr; N(CH2)4CH2, 4-pip). Treatment of 4-pyrr with EtMgCl and 4-pip with MeMgBr provided (silox)2TaEt2(N(CH2)3CH 2) (5-pyrr-Et2) and (silox)2TaMe2(N(CH2)4CH 2) (5-pip-Me2). Thermolysis of 5-pip-Me2 generated CH4 and η2-imine complex (silox)2Ta(CH3)(η2-NC5H 9) (6). In contrast, 5-pyrr-Et2 thermally degraded to the ethylene adduct, (silox)2(C4H8N)Ta(η2-C 2H4) (7-pyrr) and C2H6. Na/Hg reductions of 4-pyrr and 4-pip in the presence of 1 equiv. C2H4 generated 7-pyrr and (tBu3SiO)2(C5H10N) Ta(η2-C2H4) (7-pip); under an excess of C2H4, tantallacyclopentane (silox)2(C4H8N)TaCH2(CH 2)2CH2 (8-pyrr) was prepared. With pyridine present, Na/Hg reduction of 4-pyrr and 4-pip provided η2-pyridine complexes (silox)2(C4H8N)Ta(η2-(N,C)- NC5H5) (9-pyrr) and (silox)2(C5H10N)Ta(η2-(N,C)- NC5H5) (9-pip). Treatment of 9-pyrr and 9-pip with 1 equiv. CH3NH2 in C6D6 revealed the formation of tantalum imido derivatives (silox)2(C4H8N)Ta=NMe (10-pyrr) and (silox)2(C5H10N)Ta=NMe (10-pip), respectively, via the α-pyridyl-methylimido complex, (silox)2Ta(NMe)(NC5H4) (11). Na/Hg reduction of (silox)3NbCl2 (13) in the presence of excess 3,5-lutidine afforded (silox)3Nb(η2-3,5-Me2-NC5H 3) (2-3,5-Lut), which was heated for 4 days at 120°C to give (silox)2NbN-cis-CH=CMe-cis-CH=CMe-trans-CH=CHCMe2Si tBu2O (14), whose structure was confirmed by X-ray crystallography. The direct participation of a silox group in the ring opening is a rare occurrence for this typically ancillary ligand, and provides another pathway for C-N bond activation relevant to hydrodenitrogenation (HDN).

KW - 3,5-Lutidine

KW - Amide derivatives

KW - Metallacycle

KW - Niobium

KW - Pyridine

KW - Ring-opening

KW - Siloxide

KW - Tantalum

UR - http://www.scopus.com/inward/record.url?scp=0037430621&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0037430621&partnerID=8YFLogxK

U2 - 10.1016/S0020-1693(02)01308-7

DO - 10.1016/S0020-1693(02)01308-7

M3 - Article

AN - SCOPUS:0037430621

SN - 0020-1693

VL - 345

SP - 173

EP - 184

JO - Inorganica Chimica Acta

JF - Inorganica Chimica Acta

ER -

Amide derivatives of tantalum and a niobium-promoted ring opening of 3,5-lutidine

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Keywords

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