Synthesis and characterization of new metal--metal bonded species. II. Crystal and molecular structure of dimeric niobium(III) and tantalum(III) bromide adducts with tetrahydrothiophene. Direct stereochemical evidence of bonding electron density in confacial bioctahedra with metal--metal double bonds

Journal Article · Mon May 01 04:00:00 EDT 1978 · Inorg. Chem.; (United States)

DOI:https://doi.org/10.1021/ic50183a033· OSTI ID:6760410

Templeton, J L; Dorman, W C; Clardy, J C; McCarley, R E

The previously reported niobium dimer Nb/sub 2/Br/sub 6/(SC/sub 4/H/sub 8/)/sub 3/ and the recently prepared tantalum analogue Ta/sub 2/Br/sub 6/(SC/sub 4/H/sub 8/)/sub 3/ have been characterized by complete structure determinations. Both compounds exist in the solid state as molecular confacial bioctahedrons with the two metal atoms of each dimer displaced from the center of their idealized octahedra toward one another. The Nb--Nb distance of 2.728 (5) A and the Ta--Ta distance of 2.710 (2) A are in accord with a formal metal--metal double bond. A distinctive feature of the structures is the unusually close approach of the two bromines in bridging positions of the confacial bioctahedra; this separation of only 3.30 A is attributed to stereochemical activity of the two metal--metal ..pi..-bonding electrons. Nb/sub 2/Br/sub 6/(SC/sub 4/H/sub 8/)/sub 3/ crystallized in P anti l space group with Z = 2 and rho(calcd) = 2.49 g cm/sup -3/ for a unit cell of dimensions a = 15.088 (8) A, b = 12.121 (6) A, c = 8.981 (2) A, ..cap alpha.. = 112.93 (3)/sup 0/, ..beta.. = 77.32 (2)/sup 0/, and ..gamma.. = 125.23 (2)/sup 0/. Least-squares refinement of the structure resulted in a conventional agreement factor R/sub 1/ of 0.109 for 1870 reflections having F/sup 2/ greater than 3 sigma (F/sup 2/). Crystals of Ta/sub 2/Br/sub 6/(SCRH/sub 8/)/sub 3/ belonged to the P anti l space group with Z = 2 and rho(calcd) = 2.98 g cm/sup -3/. The cell dimensions were ..cap alpha.. = 12.08 (1) A, b = .74 (1) A, c = 8.98 (1) A, ..cap alpha.. = 83.98 (5)/sup 0/, ..beta.. = 112.45 (5)/sup 0/, and ..gamma.. = 105.40 (5)/sup 0/. An R factor of 0.069 resulted from least-squares refinement of 1930 data points with F greater than 3 sigma (F). 4 figures, 5 tables.

• Research Organization: Ames Lab., IA
• OSTI ID: 6760410
• Journal Information: Inorg. Chem.; (United States), Journal Name: Inorg. Chem.; (United States) Vol. 17:5; ISSN INOCA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ADDUCTS
ASYMMETRY
BOND ANGLE
BOND LENGTHS
BROMINE COMPOUNDS
CHEMICAL BONDS
COHERENT SCATTERING
COMPLEXES
CRYSTAL LATTICES
CRYSTAL STRUCTURE
DIFFRACTION
DIMERS
DOUBLE BONDS
ELECTRON DENSITY
ENERGY LEVELS
HALOGEN COMPOUNDS
LEAST SQUARE FIT
MAXIMUM-LIKELIHOOD FIT
MOLECULAR STRUCTURE
NIOBIUM COMPLEXES
NUMERICAL SOLUTION
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
SAMPLE PREPARATION
SCATTERING
STRUCTURAL CHEMICAL ANALYSIS
SYNTHESIS
TANTALUM COMPLEXES
TRANSITION ELEMENT COMPLEXES
TRICLINIC LATTICES
X-RAY DIFFRACTION