The Structures of the Interhalogen Compounds. I. Chlorine Trifluoride at −120°C

Abstract

A technique has been developed for handling the extremely reactive interhalogen compounds which makes it possible to investigate their structures by x-ray diffraction at low temperatures. As the first step in a program of study of the interhalogen group the crystal structure of chlorine trifluoride has been determined at −120°C. The chlorine trifluoride molecule is planar with the point group symmetry mm. The Cl atom is bonded to one F atom at 1.621A and to two F atoms at 1.716A. The F–Cl–F bond angle is 86°59′. In the succeeding pages of this journal, a parallel investigation of the vapor phase by microwave spectroscopy is presented by Dr. D. F. Smith. The molecular configuration is identical in the two cases.

The crystal structure of α-dimethyltellurium dichloride

“…It should be noted, however, that the organic groups in these cases have all been aromatic and bulkier than the methyl groups of the present example. Precedent for the type of apparent internal strain observed in (CH3)2TeC1 ~ is found in C1F 3 (Burbank & Bensey, 1953 ;Smith, 1953). In this planar molecule, the axial F-C1-F bond angle of 174 ° is bisected to give two F-C1-F bond angles of 87 °.…”

The crystal structure of iron pentacarbonyl

“…The hO1 intensity data were therefore obtained from a set of precession photographs of the [010] zone. The low-temperature technique used for these photographs was essentially that described by Burbank & Bensey (1952) in which the crystal is maintained in a stream of cold nitrogen gas which is itself surrounded by an envelope of warm, scrupulously dry air. This technique was used also for a set of Weissenberg photographs of the [001] zone; the double-slit layerline screen described by Hanson (1958) was used to allow access to the crystal and goniometer head.…”

A redetermination of the orthorhombic IF7 structure

“…However, certain facts essential to the treatment that follows are not generally available (Burbank & Bensey, 1957a) and will be presented here. Liquid IF7 was sealed in a fluorothene (trifluoromonochloropolyethylene) capillary with a nominal inside diameter of 0-5 mm.…”

“…The experimental technique used to obtain the IF7 diffraction data has been documented in detail (Burbank & Bensey, 1953a, 1957a. However, certain facts essential to the treatment that follows are not generally available (Burbank & Bensey, 1957a) and will be presented here.…”

“…Donohue (1959) made the categorical statement that the interpretation of the crystal structure was incorrect and that the molecular symmetry in orthorhombic IF7 was D~h. Recently Lohr & Lipscomb (1962) have reported a recalculation based on the Burbank & Bensey (1957a) data using the BusingLevy (1959a) least squares program. It is claimed that the recalculation provides a quantitative statistical basis for Donohue's statement.…”