Mechanistic studies of the thermolysis of tetraneopentyltitanium(IV). 2. Solid state and ultra-high-vacuum studies of the chemical vapor deposition of tic films

Jinwoo Cheon, Lawrence H. Dubois, Gregory S. Girolami

Research output: Contribution to journalArticle

32 Citations (Scopus)

Abstract

The chemical pathway responsible for the conversion of the organotitanium compound tetraneopentyltitanium to titanium carbide has been studied under chemical vapor conditions and on single crystals in ultra-high vacuum. For every equivalent of TiNp4 consumed in the deposition process, 3.28 equiv of neopentane and 0.16 equiv of isobutane are produced; other organic species are also formed but in relatively small amounts. About 93% of the carbon and hydrogen originally present in the precursor can be accounted for in these products. Thermolysis of the specifically deuterated analogue Ti(CD2CMe3)4 yields a 2.25:1 ratio of neopentane-d3 and neopentane-d2; this result combined with a kinetic isotope effect of 4.9 at 385 K shows unequivocally that the first step in the deposition pathway under CVD conditions is α-hydrogen abstraction. The α-hydrogen abstraction step produces 1 equiv of neopentane and a titanium alkylidene, which undergoes further α- (and eventually γ-) hydrogen activation processes to generate the second and third equivalents of neopentane. In the last stages of the thermolysis sequence, neopentyl (or neopentyl-derived) organic groups evidently fragment and generate the carbon atoms that eventually form the titanium carbide phase. Spectroscopic studies with IR and HREELS techniques have also been carried out in order to provide additional evidence about the nature of the species present when single crystal surfaces dosed with TiNp4 are heated. A hand at 1121 cm-1 is tentatively ascribed to the υ(M=C) hand of surface-bound neopentylidene groups.

Original languageEnglish
Pages (from-to)6814-6820
Number of pages7
JournalJournal of the American Chemical Society
Volume119
Issue number29
DOIs
Publication statusPublished - 1997 Jul 23

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Tics
Thermolysis
Ultrahigh vacuum
Vacuum
Chemical vapor deposition
Hydrogen
Titanium carbide
Single crystal surfaces
Butanes
Carbon
Hand
Isotopes
Titanium
Chemical activation
Vapors
Single crystals
Atoms
Kinetics
neopentane

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

Cite this

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title = "Mechanistic studies of the thermolysis of tetraneopentyltitanium(IV). 2. Solid state and ultra-high-vacuum studies of the chemical vapor deposition of tic films",
abstract = "The chemical pathway responsible for the conversion of the organotitanium compound tetraneopentyltitanium to titanium carbide has been studied under chemical vapor conditions and on single crystals in ultra-high vacuum. For every equivalent of TiNp4 consumed in the deposition process, 3.28 equiv of neopentane and 0.16 equiv of isobutane are produced; other organic species are also formed but in relatively small amounts. About 93{\%} of the carbon and hydrogen originally present in the precursor can be accounted for in these products. Thermolysis of the specifically deuterated analogue Ti(CD2CMe3)4 yields a 2.25:1 ratio of neopentane-d3 and neopentane-d2; this result combined with a kinetic isotope effect of 4.9 at 385 K shows unequivocally that the first step in the deposition pathway under CVD conditions is α-hydrogen abstraction. The α-hydrogen abstraction step produces 1 equiv of neopentane and a titanium alkylidene, which undergoes further α- (and eventually γ-) hydrogen activation processes to generate the second and third equivalents of neopentane. In the last stages of the thermolysis sequence, neopentyl (or neopentyl-derived) organic groups evidently fragment and generate the carbon atoms that eventually form the titanium carbide phase. Spectroscopic studies with IR and HREELS techniques have also been carried out in order to provide additional evidence about the nature of the species present when single crystal surfaces dosed with TiNp4 are heated. A hand at 1121 cm-1 is tentatively ascribed to the υ(M=C) hand of surface-bound neopentylidene groups.",
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Mechanistic studies of the thermolysis of tetraneopentyltitanium(IV). 2. Solid state and ultra-high-vacuum studies of the chemical vapor deposition of tic films. / Cheon, Jinwoo; Dubois, Lawrence H.; Girolami, Gregory S.

In: Journal of the American Chemical Society, Vol. 119, No. 29, 23.07.1997, p. 6814-6820.

Research output: Contribution to journalArticle

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AU - Cheon, Jinwoo

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