LEO H. SOMMER AND LESLIEJ . T Y L ~
1030
Acknowledgment.-The authors wish to acknowledge the assistance of Dana Ridgley in the preparation of the vanadium compounds. This work was supported by Contract Xo. ONR-367(00) -.
~
~_.___.___~___.___~____
VOl. '76
between the University of Coiinccticut :md t h e office Of Research. ~
~
~
~
~
~
~
~
~
,
"
.
STORR, CONS. -~ _ _ _ ~ ~~.~ ~ .
~-
( ~ O N T R I U C T I O NFROM T H E SCHOOL OF CHEMISTRY AND PHYSICS,
~
TIXE PESNSTLVANIA
STATE COI,LEGE]
Steric Effects of the f-Butyl Group in Organosilicon Compounds' BY LEOH. SOMMER ASD LESLIEJ. Tur,~n RECEIVED JULY 29, 1963 Steric elTccts of tlir i butyl group liave made possible thc synthesis of ii new class of orgunosilicoii c.u:npouiitls, d i d k y l r f i ominosilanes. Silanctliols coiitaining a l-butyl group are extremely resistant toward coiidensation iii coinparison with ortlii i x y dialliylsilanetliol~,
Previously,2 we reported the synthesis of t-butyltrichlorosilane, t-butyltrimethylsilane and di-tbutyldichlorosilane, as comprising the first exaniples of I-alkylorganosilicon compounds. These substances were prepared through the use of t-butyllitliium, i t having been shown that t-al'ql Grignard reagents fail to give t-alkylorganosilicon compounds with a variety of starting materials under a wide range of conditions. In extension of our previous synthesis of di-tbu tyldichlorosilane, we have now prepared three additional dialkyldichlorosilanes containing a tbutyl group, by the general reaction t-BuLi
+ RSiCl, --+ t-BuRSiCin
where R is methyl, phenyl and n-hexadecyl. In sharp contrast to the reaction of t-butyllithium with t-butyltrichlorosilane which gave a 50% yield of di-t-butyldichlorosilane after four days a t 3 the present reactions proceeded smoothlv a t reflux required only three or four hours temperature (:iio), for completion and gave yields of about io%. Xtteinpts t o effect the synthesis of tri-t-butylchlorosilane froin t-butyllithiuni and di-t-butyldichlorosilane even a t an elevated temperature of l(i0' mct with failurc.2,4 11.e turn now to a consideration of the product.; obtained by ;mimonolysis arid hydrolysis OF the alwve four t-butyldichl:,rosilaries, substances whose prajicrties show in striking fashion the prof;)uii:l. iiifluence exerted by the t-butyl group in inhibitin-: interiiiolccular condensation of difunctional silanes. I t has long been known that the silicon-chlorine h n d reacts readily with ammonia. Thc reaction o f trial1;ylclilorosilaiies with liquid ammonia glvcs excellent yields of the corresponding trialkylarninosilane, except in the reaction of trimethylchlorosilanti which gives the dimer, Me$iXHSiMeX, hexa( 1 ) Paper 38 in a series 7 '0
, >r yL
OC.
*
1,4534 1,5198 1 ,3604 M.p. 83".
Calcii.
Found
21 .:3 21 .:3 16.1 16.1 14.5 14.ti 8.2 84 B.p. 190" a t 737 mm.
Calcd.
Found
21.2 16.1 11 4 8.2
21.1 16.0 14.4
7.7
1101. wt. Calcd. Foundn
132 174 191 343
137 179 190 364
X-ield,
%
ii5 50 80 85
nary silanediols. Thus, t-butylrnethylsilanediol may gave t-butyltnethyldichlorosilane. Table I gives pertiiient be distilled a t lSi0 aiid recovered largely uii- (lata on the iiew chlorosilanes. Synthesis of t-Butyldiaminosilanes .-The procedure used changed. for t-butylrriethyldia~iiii~osilatie will bc described as repreIt is of some interest to note that the silariedivls seiitative of the iiiethod ettiployed for all of these conialso are obtained readily by hydrolysis of the cor- powitls. X 500-cc. three-iiecked flask, equipped with a reresponding diaminosilanes. In the reaction with flux coiidriiwr, stirrer and dropping fuiinel, was iinmer\ed in a I)ry Ice-acetotie-bath. In this was placed 126 cc. of relatively small-size reagents such as water the liquid aninioiiia. Then, there was added, during 30 minsteric effects of i-butyl groups on silicon are, as utes, a solution of 34 g., 0.2 mole, of t-butylinethyldichloroexpected, of much lesser importance than in the silane in 225 cc. of pentane. T h e mixture was stirred vigself-condensation reactions of substances contain- orously during the addition and for three hours as the excess a~nriioniawas allowed t o distil from the mixture. ing these groups. The aintnonium chloride formed was filtered from the reHydrolysis of t-but~ldiinetliylclil~~r~~silane, pre- action mixture, washed thoroughly with pentane and dried. pared by reaction of f-butyllithium with dimethyl- A quantitative yield, 21.0 g . , was obtained. T h e pentane ciichlorosilane, gave in excellent yield t-butyldi- ~ v a bstripped from the mixture. The residue was a solid at temperature. An attempt to distil the product a t rcinethylsilanol, a clear water-white liquid with a room duced pressure was made. However, difficulty was enpowerful camphoric odor. X solution of this sila- countered, because a t low pressure t h e boiling point was beno1 in concentrated sulfuric acid when poured on low the melting point and extensive sublimation occurred. ice failed to give the siloxane, as did also refluxing Fractionation of the sublimed solid a t atmospheric pressure a 6
