The invention herein described was made in the course of or under a contract thereunder with the United States Air Force Systems Command.
This invention relates to the preparation of Binor-S. More particularly, the invention relates to the preparation of Binor-S. from norbornadiene. Still more particularly, the invention relates to the catalytic dimerization of norbornadiene to Binor-S using a three-component catalyst system.
Binor-S, upon further processing, can be converted into a component of a high energy fuel which can be used in either jet or rocket propulsion. Jet propulsion includes a jet engine which can be used for a missile plane and others and includes the three basic types, i.e., ramjet, turbo-jet and pulse jet. The term rocket generally refers to a device containing its own oxygen or oxidizing agent.
Binor-S is known by the systematic chemical name of endo-cis-endo-heptacyclo(5.3.1.1.sup.2,6.1.sup.4,12.1.sup.9,11.0.sup.3,5.0 .sup.8,10)-tetradecane. Its melting point is about 65.degree. C. It has a net volumetric heat of combustion of about 178,570 BTU/gallon.
Preparation of Binor-S is disclosed in an article in the Journal of the American Chemical Society, [88:21] Nov. 5, 1966, pages 4890-4894. The article is titled ".pi.-Complex Multicenter Reactions Promoted by Binuclear Catalysts Systems. "Binor-S", a New Heptacyclotetradecane via Stereospecific Dimerization of Bicycloheptadiene", by G. N. Schrauzer, et al. Disclosed is the dimerization of bicycloheptadiene (also known as norbornadiene) to Binor-S using metal salts of cobalt carbonyl hydrides (e.g., Zn(Co(C0).sub.4).sub.2). A Lewis acid, such as AlBr.sub.3, can be used as a cocatalyst with the transition metal carbonyl catalyst. Another related article appears in Tetrahedron Letters, No. 8, 1970, pages 543-545 titled "New Catalysts of Stereospecific Norbornadiene Dimerization to "Binor-S", by G. N. Schrauzer et al. This second article discloses the use of RhCl[P(C.sub.6 H.sub.5).sub.3 ].sub.3 as a catalyst with BF.sub.3 0(C.sub.2 H.sub.5).sub.2 as a cocatalyst for the dimerization of nobornadiene to Binor-S. The former two form a heterogenous catalyst system.
A metal-cobalt carbonyl complex useful as a catalyst in the polymerization of norbornadiene is disclosed in U.S. Pat. No. 3,679,722. Also, U.S. Pat. No. 3,676,474 discloses a multinuclear .pi.-complex having at least two metal cobalt bonds which can be used as a catalyst in the dimerization of norbornadiene.
Catalytic dimerization of norbornadiene to Binor-S using a two component catalytic system of tris(triphenylphosphine) rhodium chloride and diethylaluminum chloride or ethylaluminum dichloride or aluminum ethylsesquichloride is disclosed in a related application, Ser. No. 631,978, filed Nov. 14, 1975, now U.S. Pat. No. 4,031,150.
Norbornadiene is also known as bicyclo(2.2.1)heptadiene-2,5. A method of preparation is disclosed in U.S. Pat. No. 2,875,256 issued February 24, 1959. Norbornadiene will be referred to as NBD hereinafter. NBD can be represented by either one of the following structural formulas: ##STR1##
During the dimerization of NBD more than one dimer is possible. G. N. Schrauzer, in his review "On Transition Metal-Catalyzed Reaction of Norbornadiene and the Concept of a Complex Multicenter Processes" in Advances on Catalysis 18, 373 (1968) Acad. Press, describes the fourteen theoretically possible dimers of NBD. And any and each of the dimers described therein have different physical and chemical properties.
Thus, a specific synthesis problem in the dimerization of NBD, as can be visualized from the fourteen theoretically possible isomers, is to obtain both excellent selectivity and conversion to the desired isomer at as low an economic cost as possible.