Reactions and photochemistry of transition metals with hydrogen and methane via matrix isolation FT-IR spectroscopy. [FT-IR (Fourier transform infrared)]

Miscellaneous · Tue Jan 01 00:00:00 EST 1991

OSTI ID:7165666

Xiao, Z

The reactions of transition and main group metals, including Ca, Sc, Ti, V, Cr, Mo, Zn, Ga and Ge, with molecular hydrogen have been investigated using FT-IR matrix isolation spectroscopy. The reactions of gallium with methane in Ar, Kr and pure methane matrices have been studied. All the above metals (except Ge) encounter an energy barrier and require photoexcitation to insert into the H-H bond to form MH[sub 2]. Bond angles for the dihydrides (MH[sub 2]) of the above metals have been estimated through measured relative intensities of symmetric and asymmetric stretching modes. CaH[sub 2], and ZnH[sub 2] are linear (or near linear) molecules, while ScH[sub 2], TiH[sub 2], VH[sub 2], CrH[sub 2], MoH[sub 2], GaH[sub 2] and GeH[sub 2] are bent. The stretching force constants for MH[sub 2] have been calculated with a diatomic approximation and increase across the row (from Ca to Zn). A correlation between the stretching force constants and the size of the metals and the involvement of 3d electrons in bonding appears to exist. Monohydrides of V, Mo, Ga, and trihydrides of Sc, Cr, Mo have been isolated as results of photoreactions of the respective metals with H[sub 2]. Formation of polyhydrides was observed in the reactions of atomic Ti, and Mo with H[sub 2]. Reactions of metal dimers and trimers with hydrogen have been observed. Species with terminal hydrogens resulting from the insertion of the dimers of Ca, Sc, Ti, Cr, Ga and Ge into the H-h bond have been identified as the reaction products of photolysis. Spontaneous reactions of Ga[sub 2] with H[sub 2] yield Ga[sub 2]H[sub 2] with two bridging hydrogens. A ligand-free molecular coordinate dihydrogen complex with the calcium dimer, Ca[sub 2](H[sub 2])[sub 2], was observed in Kr matrices. Photolysis with UV light produces methylgallium hydride, CH[sub 3]GaH, in the reactions of gallium with methane in Ar, Kr and pure methane matrices.

• Research Organization: Rice Univ., Houston, TX (United States)
• OSTI ID: 7165666
• Resource Relation: Other Information: Thesis (Ph.D.)
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
74 ATOMIC AND MOLECULAR PHYSICS
HYDROGEN
PHOTOCHEMICAL REACTIONS
METHANE
TRANSITION ELEMENTS
INFRARED SPECTRA
MATRIX ISOLATION
INTERMOLECULAR FORCES
ALKANES
CHEMICAL REACTIONS
ELEMENTS
HYDROCARBONS
METALS
NONMETALS
ORGANIC COMPOUNDS
SPECTRA
400500* - Photochemistry
664200 - Spectra of Atoms & Molecules & their Interactions with Photons- (1992-)