COMMUNICATIONS TO THE EDITOR
4116
ON THE STRUCTURE OF TETRABORANE
Sir: We have reinvestigated gaseous tetraborane by electron diffraction. The butane-like model with tetrahedral bond angles as reported by Bauerl is incompatible with our data; values of L B-B-B = 90" and LB-B-H = 133.5' do bring i t into agreement, but the latter angle is out of the question, especially for the "methylenic" hydrogen atoms. No exhaustive investigation of the butane-like structure was attempted, however, because a structure (Fig. 1) plausibly related to the known boron hydride structures' was discovered and shown
Vol. 75
established by Nordman and Lipscomb by the crystal structure investigation reported in the following Communication. The atomic arrangement is closely similar t o that of the apical groups in decaborane and is comparable to the arrangements in diborane and stable pentaborane. Approximate values for the numerous parameters of the Czv model are BI B2 = 18.5 A , B1 BZ = 1 7 6 b B? B i = 2 8 8 a (Dihedral LB1B3Ba-BIB3B,= 123'32') U i Ha = B2-11; = B2Hs = 1 19 A B1-H6 = 133 ii , BI-Hs = 1 13 H, in plane of BIB2B3 LE4-BI-€& = 118"20' arid LB1,~-B2-H7,s= 117"6'
A,
These values were obtained primarily from the radial distribution curve (Fig. 2 ) ; they were refined by a (necessarily incomplete) correlation treatment. The He parameters aFe highly uncertain, but the B-H distance 1.19 A. and the B-B bond distances warrant comparison with the crystal values. \?'e are indebted to Professor A. B. Burg and Mr. E. S. Kuljian for the samples of tetraborane and to the Office of Naval Research (Contract N6onr 24-1.123)for support during this investigation. l R I B U l I ~ \ \ U 18% A \ D C R E L L I V LABORATORIES M O R T O V E JO\IES OF CHEMISTRY, CALIFORVIA KEUVETHHEDBERC I\STITUTE OF TECHNOLOGY \-ERYER SCHOMAKER I'4541SE\A 1,C A L I F O R N I A cO\
Fig. 1.-The
(:ALE5
B4Hlostructure.
to be in excellent agreement with the diffraction pattern early in our and has since been
VISUAL
'TU 2,
1,
RADIAL
3,
4.
THEORETICAL
INTENSTY
DISTRIBUTION
A
6,
INTENSITY Cev
I
BUTANE-LIKE
eo,
40.
60,
80.
100,
q
Fig. 2.---Visual, radial distribution a n d theoretical intenThe theoretical intensity curves are for thc butane-like model with L R-B-B = 90" and L R-B-H = 133.5" and for the CzY model dewribed in the text. sity curves.
RECEIVED JUUE 30, 1953
THE MOLECULAR STRUCTURE OF B4Hlri
Sir: As a result of a complete analysis of 616 observed reflections from a single crystal of BdH10, we have determined the molecular structure. There are four molecules in a monoclinic unit cell having parameters a = 8.68, b = 10.14, c = 5.78A. and 0 = 105.9". The space group P21/n is unambiguous, and the twelve independent positional parameters of the boron atoms were determined from three-dimensional Fourier analysis. The hydrogen atoms were readily observable, and were also located more preciseIy from a threedimensional Fourier series from which the boron atoms had been subtracted. The molecular structure of B4H10 is shown in Fig. 1. No molecular symmetry elements are required by the space group of the crystal, but the molecular dimensions indicate that the symmetry of the isolated molecule is CZv. For brevity, we n n
Y
Y
_ I _ _ ~
(1) S. H. Bauer. THISJOUXNAL, 60, 805 (1838). (2) For references and discussion see K . Hedberg, hl. E. Jones, and V. Schomaker, Pmc. A ' d Acad. Sci. t'.S., 38, 679 (1952). (3) K. Hedberg, V. Schomaker and M. E. Jones, Paper E.D. 17, Second International Cungess of Crystallography, Stockholm, June 27-fuly 5 , 1951 The structure. althongh not mentioned i n the Ahstract, was presented at the meeting. (4) Quarterly Progress Report, October 23, 1951, Contract NBonr 24423.
d 6 .
Fig. 1.-The
molecular structure of B ~ H I O .
