Assignment Tokoh Organometallic Gilman

 

ACADEMICS ACHIEVEMENTS / ACCOMPLISHMENT MADE BY PROF. HENRY GILMAN

In 1919, Dr. Gilman recalls, the chemistry program at Iowa State was “very modest - 15 or 18 undergraduate majors and perhaps a dozen graduate students. But there was a nice esprit de corps. They were young and enthusiastic. They all worked quite hard. And Dr. Henry Gilman had a nice, easy, personal relationship with the students.” The hard The  hard work, the esprit de corps and the results were recognized and in 1923 he was named professor of organic chemistry at Iowa State. Within six months of his arrival at Iowa State, Professor Gilman submitted his first of many man y papers dealing with the Grignard reagent, influenced perhaps by the interests of his Harvard mentor, Professor E.P. Kohler. Beginning at a time when Iowa State had little financial support for research, Professor Gilman has made contributions so enormous - over 1000 articles, books, and chapters in books bear his name - that a brief summary cannot treat them justly. The principal themes have been heterocyclic chemistry and organometallic chemistry. Professor Gilman’s interest in heterocyclic chemistry was stimulated by a desire to find new uses for furfural, a by-product of the corn industry. This led ultimately to new sources of raw materials for nylon, to new pesticides, to new antimalarials and to new herbicides. Another phase of this research concerning heterocyclic compounds involved the synthesis and study of derivatives of phenothiazine, many of which are useful pharmaceuticals today. In addition to these extensive investigations in the heterocyclic field, he has published a number of articles concerning long-chain aliphatic and organofluorine compounds. However, Professor Gilman’s first and continuing love has been has  been organometallic chemistry. Starting from a few scattered observations in the literature and inspired by the Grignard reagent studies, he developed that branch of science now known k nown as organometallic chemistry. His research  papers describe the organic chemistry of aluminum, arsenic, barium, beryllium, bismuth, cadmium, calcium, copper, gallium, germanium, gold, iridium, lead, lithium, magnesium, mercury, phosphorus, platinum, potassium, selenium, silicon, silver, sodium, thallium, tin, uranium and zinc. His initial interest in organomagnesiurn chemistry led to extensive studies of organolithium compounds. This pioneering research made possible the wide use of these versatile v ersatile

 

reagents in organic synthesis synthesis and provided the background for the preparation of polymer polymerss such as polyethylene and cis-polyisoprene. Through the years, many other honors and awards have come to Professor Gilman. He was elected to the National Academy of Science in 1945. In 1951, he received two American Chemical Society awards: the Iowa Award and the Midwest Award. He has been selected as Fellow of the Chemical Society (London), a signal honor limited to forty persons. At Iowa State, the chemistry  building has been named Henry Gilman Hall and the annual Gilman Lectures were initiated in 1914. For many years, Professor Gilman has been an international leader in the organic chemistry of silicon and his fundamental discoveries in this field contributed to the development of silicone  polymers and many related industrial products. His many and outstanding contributions to the organosilicon field were acknowledged when, in 1962, he was named the first recipient of the American Chemical Society’s Frederic Stanley Kipping Award in Organosilicon Chemistry. In 1976, he was one of three foreign scientists to be elected to honorary membership in the British Royal Society. The following year, 1977, he was presented the American Chemical Society’s Priestly Medal “for distinguished services to chemistry”; this gold medal is considered the highest honor in U.S. chemistry. During his lifetime, Gilman completed 1020 papers, 584 of which were published after he  became blind in 1947. In 1936, the Journal of Organic Chemistry was created by Gilman with the help of M.S. Kharasch. In 1938, he published a two-volume textbook titled Organic Chemistry: An Advanced Treatise, the first major organic chemistry textbook, with each chapter being contributed by leading leaders in the U.S. Subsequent additions were published in 1943 and another two editions in 1953. Gilman reagents are named after him.

 

Gilman’s research interests have focused on “unnatural products”, that is, organometallic compounds that must be prepared and manipulated manipulate d in the absence of air and moisture. Some of his most important individual discoveries discoveries have also involved “unnatural chemical behavior”, by a given element. For example, the halogen-lithium exchange process (eq. l), which was discovered, independently, by Gilman and by Wittig in 1938 shows that the nonmetallic halogens can behave like metals in being exchanged for them. He rightly judged that the average organic chemist overestimated the experimental difficulties in working with organometallics and underassessed their value. A sampling of his efforts to correct this false impression is worth listing: (1) the  preparation of hydrocarbons from the coupling of alkyl sulfonates and Grignard reagents, (2) the conjugate addition of Grignard reagents to a,β-unsaturated a,β-unsaturated anils, (3) the formation of ketones from RLi and R’COOLi, (4) the preparation of preparation  of organocuprates, R,CuLi, (5) the preparation of ketones from R 2Cd and R’COX, the use of tetrahydrofuran to accelerate accelerate hydrogen-lithium hydrogen-lithium exchanges and the preparation of organolithium reagents from the cleavage cleavag e of ethers and sulfides in THF. ArX + n-BuLi + ArLi + n-BuX

(1)

Conversely, in his pioneering research on triorganosilylmetallic compounds (R 3  Si -  M+, eq. 2), Gilman demonstrated that the metalloid, silicon, could exhibit nonmetallic traits very similar to those of carbon (R 3 C  –  M +, eq. 3):

This change in the apparent polarity of an atom in certain bonding situations has been designated in recent years. Gilman’s work provides some of  the  the earliest, most telling examples. Although the hydrogen-lithium exchange was not discovered by Gilman (eq. 4), he expanded its scope almost  beyond recognition to encompass RH substrates of RH + n-BuLi + RLi + n-BuH

(4)

little discernible acidity. This work drew upon another of his abiding research themes, namely the substitution chemistry of oxygen- and nitrogen-containing heterocycles. With these substrates Gilman developed novel substitution processes based on hydrogen-lithium exchange, which led to nuclear substitution different from conventional substitution processes (eq. 5).

 

 

This unique synthetic approach was also applied by Gilman to derivatives of furan, dibenzothiophene, phenothiazine, carbazole, pyridines, quinolines and acridines and has led to a host of compounds of value as pesticides, herbicides, antimalarials, anti-infective and antidepressants. Very recently, the role of such lithiations in heterocyclic synthesis has taken on great importance. During the latter half of his career, Gilman devoted a steadily increasing effort to the chemistry of organosilicon compounds having two or more silicon atoms in a chain or ring. In devising the various synthetic routes to such unusual compounds, in assessing the chemical reactivity of the Si-Si bond and in developing d eveloping reliable methods for structure determination, Gilman achieved the pioneering crest of his productive life. The Tetrakis(trimethylsilyl)silane is one of many organosilicon compounds first reported by Gilman et al. a l.

 

 

Figure 1 Tetrakis (trimethylsilyl)silane, (TMS)

In recognition of this, he was named the first recipient of the Frederic Stanley Kipping Award in Organosilicon Chemistry in 1962. All in all, threading through all these broader research themes was Gilman’s continual interest in useful applications of organometallic reagents for organic synthesis, here are the list of awards receive by b y this scientist:

  Elected to National Academy of Sciences, 1945

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  Iowa Award and Midwest Award of American Chemical Society, 1951

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  Honorary Fellow of the British Chemical Society, 1961

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  First American Chemical Society Frederic Stanley Kipping Award in Organosilicon

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Chemistry, 1962

  Distinguished Fellowship Awards, Iowa Academy of Sciences, 1975

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  Priestley Medal of the American Chemical Society, 1977

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  Iowa Governor's Science Medal, 1982

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INTERESTING THINGS ABOUT PROF. HENRY GILMAN

 No one person has had a greater influence nor contributed more to the field of organometallic chemistry than Henry Gilman. His impact on chemistry has received wide recognition. Without his broad pioneering research, his remarkable drive and his warm personality, those working in organometallic chemistry would find this a far less interesting branch of chemistry che mistry than it is today. Professor Gilman’s former students speak of him with respect and affection. He has often, and with some justification, been referred to as a stem taskmaster who demanded hard work and  perfection from his students; but he asked no more than he was willing willing to give. A research director at one of our large chemical companies once remarked that he found that former Gilman students not only knew their chemistry but also had been taught precision in chemical reporting. Professor Gilman is a person of highest integrity with a strong sense of ethics; these attributes were also part of the “Gilman training.” While demanding and unyielding on a professional level, Professor Gilman was always kind, thoughtful and helpful to his students on a personal level. He would loan money and arrange medical care or legal assistance when needed. He was always available for personal advice when his students were having difficulties. In addition, he has been ever helpful to his students and former students in finding suitable employment, making a change in employment and arranging for postdoctoral studies, especially studies abroad. One former student has written to Professor Gilman: “You probably are bored are bored with eulogies about your contributions to chemistry. But how many people realize what a lovely lob you had in tennis? Or what a fantastic left hand you played in handball? Or what a delightful conversationalist you can be?” can  be?” Indeed, Dr. Gilman is superb at conversation - articulate and knowledgeable in many areas, a good story teller but also a good listener. In group conversations there may be one person who is quiet and not participating; in such situations Professor Gilman has often been observed to stop, turn, and ask just the right question to make sure all are included. Throughout his career, Professor Gilman has been known for his splendid lectures, beautifully delivered with an absence of lecture notes.

 

In 1947, due to a combination of glaucoma and detachment of a retina Henry Gilman  became blind in one eye and lost most of his vision vision in the other. He was forced to rely on his wife wife and students to act as his eyes, to read and write for him. His wife was almost always at his side to guide him in unfamiliar places and inform him of the people around him. Remarkably, he continued much of his work and never let his loss of sight hinder his skills. It could be argued that the majority of Gilman’s work was done after 1947. In 1973, the current chemistry building at Iowa State University was renamed Henry Gilman Hall.

REFERENCES

Eaborn, C. (1990). "Henry Gilman. 9 May 1893-7 November 1986". Biographical Memoirs of Fellows of the Royal Society. 36: 152. doi:10.1098/rsbm.1990.0028. Eisch, John J. (2002). "Henry Gilman: American Pioneer in the Rise of Organometallic Orga nometallic Chemistry in

Modern

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Technology".

Organometallics.

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5439 – 5463. 5463.

doi:10.1021/om0109408. Eisch, J. J. (1988). Henry Gilman (1893 – 1986). 1986). Journal of Organometallic Chemistry, 338(3), 281 – 287. 287. doi:10.1016/0022-328x (88)80001-9 Gilman, H.; Smith, C. L. (1967). "Tetrakis(trimethylsilyl)silane". Journal of Organometallic Chemistry. 8: 245-253. doi:10.1016/S0022-328X (00)91037-4