s. c. Srinivasanl and D. R. Wiles Carleton university Ottawa 1, Ontario, Canada
The Nitrogen Glove A technique for handling air-sensitive compounds
O f t e n during the course of laboratory work it is found desirable to have controlled atmospheres. The common tools for such control of atmospheres are the glove bag,? the Schlenk tube,s and controlled atmosphere boxes, in addition, of course, to closed glass or metal systems. The glove bag is a big plastic hag (the smallest of these available is 17 X 17 in.) fitted with plastic arms that serve as gloves and an opening'through which objects can be placed inside the bag and which can later he sealed. However, even the smallest available glove bag is sometimes unwieldy. Further, even though removal of oxygen and water from inside the bag can be achieved, in principle, by repeated i d a t i o n and deflation of the bag, experience in this laboratory has shown that even after several such operations (as many as eight) the atmosphere inside the bag was not conducive to the handling of compounds such as manganocene and manganesepentacarbonyl hydride. Schlenk tubes lack versatility. Indeed, the tube is simple in design (consisting of a test tube with a stopcock fixed as a side arm). These tubes are best used for simple transfer of materials under a flow of inert gas. There is also a risk of loss of material either by mechanical means or owing to the volatile nature of the compound being transferred. The controlled atmosphere boxes are at present the accepted means of providing well-controlled atmospheres. These boxes are, however, expensive and to some extent unwieldy. A simple technique has been developed in this laboratory4* which permits rapid and convenient attainment of controlled atmospheres a t low cost, by using disposable polyethylene gloves. The fingers of the glove serve conveniently as compartments for reagents or small equipment, or for attaching larger equipment. An inlet and an outlet tube for the gas stream are fitted either by making appropriate-sized holes in the bag, sealing the edges with adhesive tape after inserting the tube, or by inserting such tubes at the wrist end and eventually, in either case, closing this end. The outlet tube can be connected to a second glove by means 1 Present address: University of Wiswnsin, Madison, Wisc. 53706. Supplied by I'R, Instruments for Research and Industry, 108 Franklin Ave., Cheltenham, Pa. 19012. a KING, R. B., Organometallic Synthesis," Vol. I. Academic Press, New York and London, 1965, p. 4. 'SRINIVASAN, S. C., P1I.D. Thesis, Carleton University, Jsnu-
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DEJONG, I. G., SEINIVASAN, S. C., AND WILES,D. R., Can.J . Chenz., 47, 1327 (1969). 348
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Journal o f Chemical Educcrfion
of rubber tubing so that with a gentle gas stream back diffusion of air into the glove can be prevented. Alternatively, a more vigorous stream of nitrogen serves to keep the air out. Clearly, only small equipment, sometimes specially designed with space limitations in mind, and limited amounts of reagent can be installed within a glove, especially if several separate items are needed. Our use has involved work with air-sensitive and radioactive materials; examples are 1 ) opening of radiosctive samples in s. nitrogen atmosphere 2) mixing of highly air-sensitive carriers such as msnganocene with the radioactive material 3) synthesis of air-sensitive wmpounds such as NaMn(C0)s and N G H s 4) handling of air sensitive materials preparatory to the use of a vacuum line, vapor phase chromatograph, or the like
Many other examples should suggest themselves. Glove Set-Up and Procedure
The following general procedure is used 1) A s m d cut is made a t one of the fingers of the bag so as to make a hole just big enough for a glass inlet tube to be inserted. The tube is then 6xed securely using sdhesive tape (masking tape was found suitable for this purpose). 2) The inlet tube is connected to a source of nitrogen or other gas. 3) A careful inventory of d l the necessary appamtus is made. If the operation is too wmplex, or, if too many pieces of apparatus are required, the operation is broken into convenient steps involving sepsrttte or connected gloves. The equipment and reagents are plrtced in the glove (or gloves). 4) An outlet tube and, if required, other connecting tubes me fixed to the top of the wrist end, again using tape, and this open end is now sealed wmpletely. The outlet tube may have a constridion to limit the outflow rate, but, as noted in (7) below, a constriction is not always desirable. 5) A stream of nitrogen (or other gas) is admitted into the glove a t such B rate that the glove stmts to bulge slowly; the excess passes out via the outlet tube. 6) After it has expanded fully, the glove is squeezed to drive out most gas. Operations (5) and (6) are now repeated a few times to flush out residual air. 7) The fingers and the equipment in the fingers are not well flushed by repeating (5) and (6). For this purpose a long glass tube, narrow enough to slide in through the cutlet tube into the fingers, is used. This tube is drawn into a small diameter a t its outlet end, so that it can reach into the finger tips. Nitrogen is passed through this tube while still maintaining nitrogen flow through the regular inlet. With the help of this tube equipment and reagents are individually flushed with nitrogen. Thk operstion is perhaps the most important one. Solvents can be purged in the same way. There is no need to remove this tube subsequently if it does not wme in the way of subsequent manipulations. 8) The bag is now ready for operation. Experiments involving such techniques as transfer of material, mixing of solvents,
or dissolution of solids can d be carried out by external manipulation of the apparatus inside the glove. I n spite of the rapid flow of nitrogen, there is usually no direct draft over the mterial being handled.
TO VACUUM
The glove may be discarded after every experiment. This eliminates problems arising from chemical or radioactive contamination. For larger scale operations a slight modification is made. One or more of the fingers can be cut open and the neck of a large flask inserted through the hole and sealed with tape. Clamping of the individual flasks in this case is essential, of course. Experiments
Manganocene and HMn(C0)a have been handled repestedly using this technique without diEculty.'+Three experiments will be described here for the sake of illustration. Handling of Manganocene. Pure manganocene was prepared from a crude sample obtained from K & K Laboratories, Inc. The crude sample was dissolved in tetrahydrofuran (THF) in the nitrogen glove and filtered through a. sintered-glass funnel B (see the figure). The filtration was effectedby applying nitrogen pressure on top of the funnel. The tube, A, now containing the filtrate (puremanganocene in THF) was fittedinto a ground glass joint C which is provided with a stopcock leading to a vacuum system. The glass assembly containing the filtrate was then attached to a vacuum line, evacuated, and the T H F was subsequently vacuum distilled into another vessel provided in the vacuum system, care being taken to avoid bumping of the liquid. Manganocene, which is not very volatile, was left behind. After all the T H F had been distilled, nitrogen was let in and the assembly (A and C) was removed with the stopcock closed and installed in mother nitrogen glove which contained aspatula and a ground &ass cap. After filling the second bag with nitrogen the tube was detached from the top assembly C. The manganocene sticking to the walls of the tube was loosened using a spatula. and the tube was capped for storage. Whenever desired, small portioas could be taken from thia tube by using similar procedures but employing a small funnel to introduce these portions into weighed tubes which again, could be tightly cspped. By weighing the capped tube after transfer the weight of e&h sample is obtained. Synthesis qf CHaMn(C0)a. Basically, the standard method" was used, with some madificetions. NaMn(C0). was svnthesized by &ng an excess of sodium amalpm with a THF salution of Mn2(CO)uin a glass tube. The reaction was complete in a few minutes. This tube was sealed to the nitrogen glove through a finger tip and, after sealing and purging of the glove, the tube was cracked open. The T H F solution of NaMn(C0)b was transferred (using the purging tube as a transfer pipet) to a. round bottomed flask attached to another finger of the glove. The flask was held a t - 2 2 T with CCl, slush and a cold solution of 0.9 ml CHJ in 2 ml T H F wss added (from another finger). The reaction flask was capped and allowed to stand in the dark a t -22'C for 2 hr. Past this stage the nitrogen atmosphere is no longer necessary and the usual methodJ was followed.
[lure MnCqin THF Diagram illustrating th. use of a "nitrogen glove" in ihe flltr~tionof a THF solution of manganocene (MnCp&
Gas Chromatngraphy of CHaMn(CO)a and HMn(C0)s. We have developed a gas chromatographic method for the separation of CH8Mn(CO)6and HMn(CO)s in connection with our studies on the recoil chemistly of 'Mn in CHIC~&M~(CO)~.'Neutron irradiated CHaCs&Mn(CO)r in a sealed quarts tube was opened in a nitrogen glove and transferred to a tube containing a pentane solution of HMn(CO)s and CHsMn(C0)s carriers. A hypodermic needle was inserted through the wall of the glove and used to witbdraw an aliquot of the solution. This solution was transferred to the inlet of a gas chromatograph either by withdrawing it from the glove or better by passing the needle directly out through the wall of the glove to the inlet port. The s m d needle hales are easily covered with cellulose tape, and cause no interference with the operation of the glove. A note of warning must be included here. This method could prove dangerous for the handling of highly volatile and toxic compounds such as, for example, Ni(CO)& if performed on an open bench. I t is suggested that such aperetions be carried out in an efficient fumehood with the outlet of the nitrogen glove connected to appropriate trap or traps for the toxic mttterial. Adequate planning must also recede such experiments with respect to disposal of the glove and the contents in theend.
The authors wish to acknowledge useful discussions with Dr. J. A. Young, Department of Chemistry, Carleton University, in the preparative stage of this manuscript.
Volume 48, Number 5, Moy 1971
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