Titanium(III) Tetrahydroborates. Preparation and Crystal Structure of Ti(BH4)3(PMe3)2 Containing an Unusual Ti…H…B Agostic Interaction

James A. Jensen; Scott R. Wilson; Gregory S. Girolami

doi:10.1021/ja00223a015

Titanium(III) Tetrahydroborates. Preparation and Crystal Structure of Ti(BH₄)₃(PMe₃)₂ Containing an Unusual Ti…H…B Agostic Interaction

James A. Jensen, Scott R. Wilson, Gregory S. Girolami

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

Abstract

The reaction of trialkylphosphines with Ti(BH₄)₃(Et₂O), prepared in situ from TiCl₄ and LiBH₄ in diethyl ether, gives dark blue adducts of stoichiometry Ti(BH₄)₃(PR₃)₂, where PR₃ is PMe₃, PEt₃, PMe₂Ph, or P(OMe)₃. Magnetic susceptibility and ESR measurements indicate that these are monomeric titanium(III) species. An X-ray crystal structure of Ti(BH₄)₃(PMe₃)₂(orthorhombic; Pnma; a = 10.757 (1), b = 11.145 (2), c = 14.270 (3) Å; V= 1710.8 (8) Å³; Z = 4; R_F = 6.4%; R_wF = 4.8%) reveals an approximate trigonal-bipyramidal geometry, with the phosphines occupying the axial positions: Ti-P = 2.571 (3), 2.539 (3) A; P-Ti-P = 170.27 (9)°. One of the three equatorial BH₄^- groups is bidentate, Ti-H_b = 1.90 (6) Å, Ti—B = 2.40 (1) Å, B-H_b = 1.03 (7) Å, B-H = 1.00 (8) Å, whereas the other two BH₄^- groups possess unusual geometries involving interaction of the titanium center with one B-H bond in a “side-on” manner, Ti-H_b = 1.73 (7) Å, Ti-B = 2.27 (1) Å, B-H_b = 0.95 (6) Å, B-H_t= 0.96 (6) Å. This unusual interaction may be a type of Jahn-Teller distortion and closely resembles one proposed transition state for the activation of the isoelectronic molecule methane.

Original language	English (US)
Pages (from-to)	4977-4982
Number of pages	6
Journal	Journal of the American Chemical Society
Volume	110
Issue number	15
DOIs	https://doi.org/10.1021/ja00223a015
State	Published - Jul 1988

ASJC Scopus subject areas

Catalysis
General Chemistry
Biochemistry
Colloid and Surface Chemistry

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@article{4c149005720c4445a7f9d07bfdde7c85,

title = "Titanium(III) Tetrahydroborates. Preparation and Crystal Structure of Ti(BH4)3(PMe3)2 Containing an Unusual Ti…H…B Agostic Interaction",

abstract = "The reaction of trialkylphosphines with Ti(BH4)3(Et2O), prepared in situ from TiCl4 and LiBH4 in diethyl ether, gives dark blue adducts of stoichiometry Ti(BH4)3(PR3)2, where PR3 is PMe3, PEt3, PMe2Ph, or P(OMe)3. Magnetic susceptibility and ESR measurements indicate that these are monomeric titanium(III) species. An X-ray crystal structure of Ti(BH4)3(PMe3)2(orthorhombic; Pnma; a = 10.757 (1), b = 11.145 (2), c = 14.270 (3) {\AA}; V= 1710.8 (8) {\AA}3; Z = 4; RF = 6.4%; RwF = 4.8%) reveals an approximate trigonal-bipyramidal geometry, with the phosphines occupying the axial positions: Ti-P = 2.571 (3), 2.539 (3) A; P-Ti-P = 170.27 (9)°. One of the three equatorial BH4- groups is bidentate, Ti-Hb = 1.90 (6) {\AA}, Ti—B = 2.40 (1) {\AA}, B-Hb = 1.03 (7) {\AA}, B-H = 1.00 (8) {\AA}, whereas the other two BH4- groups possess unusual geometries involving interaction of the titanium center with one B-H bond in a “side-on” manner, Ti-Hb = 1.73 (7) {\AA}, Ti-B = 2.27 (1) {\AA}, B-Hb = 0.95 (6) {\AA}, B-Ht= 0.96 (6) {\AA}. This unusual interaction may be a type of Jahn-Teller distortion and closely resembles one proposed transition state for the activation of the isoelectronic molecule methane.",

author = "Jensen, {James A.} and Wilson, {Scott R.} and Girolami, {Gregory S.}",

year = "1988",

month = jul,

doi = "10.1021/ja00223a015",

language = "English (US)",

volume = "110",

pages = "4977--4982",

journal = "Journal of the American Chemical Society",

issn = "0002-7863",

publisher = "American Chemical Society",

number = "15",

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T1 - Titanium(III) Tetrahydroborates. Preparation and Crystal Structure of Ti(BH4)3(PMe3)2 Containing an Unusual Ti…H…B Agostic Interaction

AU - Jensen, James A.

AU - Wilson, Scott R.

AU - Girolami, Gregory S.

PY - 1988/7

Y1 - 1988/7

N2 - The reaction of trialkylphosphines with Ti(BH4)3(Et2O), prepared in situ from TiCl4 and LiBH4 in diethyl ether, gives dark blue adducts of stoichiometry Ti(BH4)3(PR3)2, where PR3 is PMe3, PEt3, PMe2Ph, or P(OMe)3. Magnetic susceptibility and ESR measurements indicate that these are monomeric titanium(III) species. An X-ray crystal structure of Ti(BH4)3(PMe3)2(orthorhombic; Pnma; a = 10.757 (1), b = 11.145 (2), c = 14.270 (3) Å; V= 1710.8 (8) Å3; Z = 4; RF = 6.4%; RwF = 4.8%) reveals an approximate trigonal-bipyramidal geometry, with the phosphines occupying the axial positions: Ti-P = 2.571 (3), 2.539 (3) A; P-Ti-P = 170.27 (9)°. One of the three equatorial BH4- groups is bidentate, Ti-Hb = 1.90 (6) Å, Ti—B = 2.40 (1) Å, B-Hb = 1.03 (7) Å, B-H = 1.00 (8) Å, whereas the other two BH4- groups possess unusual geometries involving interaction of the titanium center with one B-H bond in a “side-on” manner, Ti-Hb = 1.73 (7) Å, Ti-B = 2.27 (1) Å, B-Hb = 0.95 (6) Å, B-Ht= 0.96 (6) Å. This unusual interaction may be a type of Jahn-Teller distortion and closely resembles one proposed transition state for the activation of the isoelectronic molecule methane.

AB - The reaction of trialkylphosphines with Ti(BH4)3(Et2O), prepared in situ from TiCl4 and LiBH4 in diethyl ether, gives dark blue adducts of stoichiometry Ti(BH4)3(PR3)2, where PR3 is PMe3, PEt3, PMe2Ph, or P(OMe)3. Magnetic susceptibility and ESR measurements indicate that these are monomeric titanium(III) species. An X-ray crystal structure of Ti(BH4)3(PMe3)2(orthorhombic; Pnma; a = 10.757 (1), b = 11.145 (2), c = 14.270 (3) Å; V= 1710.8 (8) Å3; Z = 4; RF = 6.4%; RwF = 4.8%) reveals an approximate trigonal-bipyramidal geometry, with the phosphines occupying the axial positions: Ti-P = 2.571 (3), 2.539 (3) A; P-Ti-P = 170.27 (9)°. One of the three equatorial BH4- groups is bidentate, Ti-Hb = 1.90 (6) Å, Ti—B = 2.40 (1) Å, B-Hb = 1.03 (7) Å, B-H = 1.00 (8) Å, whereas the other two BH4- groups possess unusual geometries involving interaction of the titanium center with one B-H bond in a “side-on” manner, Ti-Hb = 1.73 (7) Å, Ti-B = 2.27 (1) Å, B-Hb = 0.95 (6) Å, B-Ht= 0.96 (6) Å. This unusual interaction may be a type of Jahn-Teller distortion and closely resembles one proposed transition state for the activation of the isoelectronic molecule methane.

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