292 CHIMIA 2014, 68, Nr. 5 Foundations oF Coordination – alFred Werner

doi:10.2533/chimia.2014.292 Chimia 68 (2014) 292–296 © Schweizerische Chemische Gesellschaft Alfred Werner’s Role in the mid-20th Century Flourishing of American

Jay A. Labinger*

Abstract: The development of organic and physical chemistry as specialist fields, during the middle and end of the 19th century respectively, left inorganic behind as a decidedly less highly regarded subfield of chemistry. Despite Alfred Werner’s groundbreaking studies of coordination chemistry in the early 20th century, that inferior status remained in place – particularly in the US – until the 1950s, when the beginnings of a resurgence that eventually restored its parity with the other subfields can be clearly observed. This paper explores the extent to which Werner’s heritage – both direct, in the form of academic descendants, and indirect – contributed to those advances. Keywords: History of inorganic chemistry · Werner, Alfred

Historical Background ence, and some predicted for it little fur- latter by at least five-fold from the begin- ther growth.”[1] ning. Physical showed up in the 1880s and Modern chemistry is usually consid- almost immediately surpassed inorganic, ered to begin with Lavoisier, in the late “Organic chemistry was riding high…. which remained in its state of relative ne- 18th century, but its separation into distinct Inorganicchemistry,whichunderBerzelius glect well into the 20th century – indeed, sub-specialties was not generally recog- had been the dominant branch, was begin- by this measure (but not by others, as we nized until well into the 19th century. The ning to look like a poor relation.”[2] shall see shortly), even up to the present. earliest references to the terms ‘organic I have documented elsewhere[4] a dra- chemistry’ and ‘inorganic chemistry’ in “If we glance back over the labors of matic rise in the stature of inorganic chem- the Oxford English Dictionary both date the last fifty or sixty years, we recognize istry, particularly in the USA, beginning from around the same time – the late 1820s that organic chemistry has gone on pre- around the middle of the 20th century. and 1837 respectively – but their statures ponderating more and more over inor- Perhaps the first to explicitly recognize quickly diverged. Most of the important ganic.” [3] that development – in medias res, as it were developments over the next half-century – was Ronald Nyholm, in 1956: came from the organic realm, as we can see Towards the end of the 19th century, from a few (entirely typical) quotes from physical chemistry emerged as a competi- “Those of us who were familiar with the historians of chemistry: tor for organic’s prestige, with inorganic state of inorganic chemistry in universities relegated to a poor third-place showing. A twenty to thirty years ago will recall that at “Between 1870 and 1890 the rapid quantitative assessment of the respective that time it was widely regarded as a dull development of organic chemistry gave it levels of interest in the three subfields can and uninteresting part of the undergradu- such a relative prominence that the other be inferred from the frequency of appear- ate course….The factors primarily respon- branches of the science rather suffered in ance of the corresponding terms in books sible for the modern forward-looking spirit consequence. Inorganic chemistry par- in English, shown in Fig. 1. Consistent in inorganic chemistry are two external ticularly seemed to be drifting towards the with the OED entries, organic and inorgan- developments, which give it, first, a new discouraging position of a completed sci- ic first appeared in the 1820s and 1830s re- sense of purpose, and, second, new tools spectively, with the former outstripping the with which to achieve this purpose..”[5]

0.0000900%

0.0000800%

0.0000700%

0.0000600%

0.0000500%

organic chemistry 0.0000400%

0.0000300%

physical chemistry 0.0000200%

0.0000100% inorganicchemistry

*Correspondence: Dr. J. A. Labinger 0.0000000% California Institute of Technology 1800 1820 1840 1860 1880 1900 1920 1940 1960 1980 2000 Beckman Institute Fig. 1. Frequency of appearance of the phrases ‘organic chemistry’ (blue trace), ‘physical chemis- Pasadena, CA 90025, USA Tel.: +1 626 395 6520 try’ (red trace) and ‘inorganic chemistry’ (green trace) in books in English, 1800–2000. Generated E-mail: [email protected] using Google Books Ngram Viewer, http://books.google.com/ngrams. Foundations oF Coordination Chemistry – alFred Werner CHIMIA 2014, 68, Nr. 5 293

While I don’t agree with his assessment a b of the main causes – in my view the central 100 100 developments were internal, not external, to the field – unquestionably his perception that a sea-change was underway was accu- 80 80 rate and prescient. Fig. 2 summarizes some ic quantitative support for that claim (see ref. 60 [4] for a more complete presentation of 60 inorgan these data, as well as an explanation of the methodology used to collect them): activ- 40 40 ity in inorganic chemistry, as measured Percent by publications and presentations, shows a sharp upturn relative to that in organic 20 20 and physical chemistry beginning in the 1950s. The corresponding heightened rec- 0 0 ognition of the subfield, in terms of awards 1930s 1940s 1950s 1960s 1970s 1980s 1990s 2000s 1930s 1940s 1950s 1960s 1970s 1980s 1990s 2000s and honors, follows some 20 years later. Decade Decade By the end of the 20th century inorganic Fig. 2. Representation (as a percentage) of inorganic chemistry relative to the total of organic + has reached full parity with its previously physical + inorganic. a: Publications in Journal of the American Chemical Society (red circles); more prestigious relations according to all presentations at American Chemical Society national meetings (blue squares). b: Members of these metrics, even surpassing them in elected to the National Academy of Sciences (green triangles); winners of the ACS Award in Pure some aspects. Chemistry (black diamonds). Why did it take so long for inorganic chemistry to become respectable? My contention[4] is that, up until the mid-20th Werner’s (lack of) Successors influence on the development of coordina- century, it was viewed – not inaccurately – tion chemistry, it is probably not correct as a mostly descriptive, phenomenological Alfred Werner’s career has been stud- to talk about a Werner School of inorganic discipline, lacking the systematizing and ied extensively, most notably by George chemistry in Zürich or elsewhere….it is explanatory power that characterized first Kauffman,[8] and only the briefest of recaps quite surprising how few of Werner’s nu- organic and then physical chemistry. As is appropriate here. He began as an organic merous doctoral students went on to aca- one historian sums up: , completing his PhD dissertation demic careers. In part, the reason for this in 1890 in Zürich, at what was then known lies in the dominance of overseas students “Organic chemistry developed a pro- as the Polytechnikum (now the ETH) with in his research group. A majority of them gram of study, a language of discourse, and Arthur Hantzsch, on the stereochemistry of returned to their homelands after com- a system of explanation that was foreign organic nitrogen compounds. While work- pleting their studies in Zürich, but did not to the practitioners of an earlier general ing on his Habilitationsschrift (in the same establish local schools of coordination chemistry.” [6] area, at the same institution), he turned chemistry.” [10] his attention to the nature of coordination Indeed, for much of this period of his- compounds such as the metal-ammines – The ‘dominance of overseas students,’ tory inorganic chemistry was scarcely if of which understanding was completely including as we shall see a handful from at all distinguished, in most practitioners’ lacking at the time – probably (according the US, might account for the absence of minds, from a more nondescript ‘general to Kauffman) initially stimulated by need- a Werner school in , but none chemistry.’ One exception does stand out, ing to prepare a lecture on the topic in 1892. was established elsewhere either, includ- however: Alfred Werner’s groundbreaking Before the end of that year he came up with ing the UK: studies in coordination chemistry during his theoretical framework – published the the late 19th and early 20th century. That next year[9] – that successfully explained “The subject was essentially ignored work was brilliantly systematic and ex- essentially all known and forthcoming ob- by the great body of who asso- planatory, and certainly could, one might servations, and has endured, little changed, ciated it with the metal ammines whose have thought, have served to nucleate the to this day. Largely on the strength of that chemistry they regarded as dull and use- growth of inorganic chemistry – but it did triumph, he was called to the University of less. That view took a long time to die. It not, at least not for several decades: Zürich, where he remained until his death was still very much alive when I was a in 1919. student in Cambridge during the period “It was simply not true that coordina- During his 25+ years on the faculty, 1935–1940.” [11] tion complexes played a key role in inor- Werner supervised around 200 PhD stu- ganic chemistry either then [just before the dents and a number of (what we would Why? Kauffman offers two interpreta- First World War] or for 40 years ahead. now call) postdocs and visiting associates; tions – not identical, but both carrying a What Werner did do in his own fairly short some of these worked on organic topics, to flavor of (unintentional) intimidation: lifetime was to convince people that in this be sure, but the majority of his effort, espe- area…his theory was a satisfactory expla- cially from 1900 on, was focused on coor- “Werner’s work was so complete and nation.”[7] (emphasis in the original) dination chemistry.[8] Many commentators all-encompassing that for many years co- have been struck by the fact that, despite ordination chemistry was neglected be- The body of this paper will examine such an abundance of Werner-trained PhD cause most chemists thought that all the that delay – why a Wernerian school of in- chemists, virtually none chose to carry on important research had been done.” [12] organic chemistry did not develop prompt- with his research program, either before or ly – and try to trace Werner’s influence after his death: “Perhaps the impact of Werner’s pow- on the eventual renaissance of inorganic erful, authoritarian personality and the chemistry in the USA. “Although Werner had an enormous impression of his control and mastery of 294 CHIMIA 2014, 68, Nr. 5 Foundations oF Coordination Chemistry – alFred Werner

his field deterred most of those who had Fig. 3. First page of worked with him from any thought of fol- ref. [14], showing the lowing in his footsteps.”[8] way Werner typically credited his student Whatever the reason(s), with the ex- coworkers. ception of Paul Pfeiffer, none of Werner’s European students or associates went on to any significant accomplishments in in- organic chemistry. What about in the US?

Werner’s American Colleagues

Kauffman lists five Americans who did their doctoral work with Werner – Emil Grebe (1898), Walter Peters (1901), Jenny Kruh (1911), Victor L. King (1912), and Helen Somersby French (1913).[13] I have not been able to learn much about the first three, in part because of the rather haphaz- ard practices of authorial designation at the time, making it difficult to track people by publication record. Werner generally credited students only as responsible for the experimental part, citing himself as sole author, as in the example reproduced in Fig. 3,[14] the only reference to Grebe I have found. No paper appears to mention Kruh, but she did have a book published (by the University of California, in 1911) with the title ‘Über die inneren Metallkomplexsalze,’ presumably the con- tents of her PhD thesis. Kauffman’s com- French (1884–1975), but does refer to her Thomas P. McCutcheon, who published plete Werner bibliography[8] includes one thesis, which had the intriguing title ‘The a paper on asymmetric complexes paper ‘with’ W. Peters; unlike Grebe and Absorption Spectra of Certain Chromium with Werner in 1912,[21] joined the chem- Kruh, he apparently worked on a purely or- Salts.’[19] She subsequently returned to her istry department of the University of ganic project.[15] I have found no evidence alma mater, Wellesley College, where she Pennsylvania as an inorganic chemist, and of post-PhD careers in chemistry for any had been a faculty assistant before doing published a dozen or so inorganic papers, of these three students. There was a Walter her PhD, and remained as a professor of many on the chemistry of the heteropoly Peters (1876–?) who achieved some fame inorganic chemistry until 1950, publishing acids. Of those students who appear as co- as a chemist, even to the extent of having around a dozen papers – most of them in authors on those papers, only one – L. C. a reaction named for him – formation of coordination chemistry – during her career. W. Baker – appears to have continued in organomercurials from HgCl and sulfinic However, there is no indication that she the field, continuing to work on HPAs at 2 acids – but he can’t be the one Kauffman trained any students who continued in the Georgetown University. cites: this Peters received his PhD in field – indeed, one of her students recalls In all, then, there is little evidence of Strasbourg in 1903, and apparently never French discouraging her from going on to any major influence on the field through worked with Werner at all.[16] post-graduate work because “you’ll just Werner’s line of academic descendants. The two remaining students did work in get married”![20] Most left no trace in chemistry at all; chemistryintheUS,butneitherhadanysig- Werner’s two postdoctoral/visiting as- two were significant figures in American nificant impact on the development of the sociates (if there were only two) are easier chemistry, but not in inorganic; and two, field of inorganic chemistry.Victor L. King to trace; unlike his students, Werner was while continuing to contribute to the field, (1886–1958) was responsible for what is willing to grant them co-authorial credit did not establish a really major program of arguably the most significant of Werner’s (although perhaps not always reliably: see their own. publications (although he was given only Fig. 4![21]). Charles Holmes Herty (1867– the ‘with’ credit described above[17]), the 1938), a faculty member at the University first reported successful resolution of an of Georgia, spent the year 1899–1900 on Werner’s Influence on the American optically active . He sabbatical in Europe working with several Inorganic Renaissance spent the rest of a long and successful ca- distinguished chemists, including Walter reer in industrial chemistry, primarily with Nernst, in addition to Werner. Herty pub- Nyholm claimed that advances in phys- Calco (which subsequently became part of lished a paper with Werner on inorganic ical and theoretical methodology were pri- American Cyanamid), specializing in dye- compounds,[22] but although he had a very marily responsible for the (world-wide) stuffs and related technologies; there is no successful career in both academia and renaissance of inorganic chemistry.[5] My indication that he ever worked in coordina- industry – including a term as president view is that the main drivers were con- tion chemistry again.[18] of the American Chemical Society – after ceptual, not pragmatic, and were internal, Kauffman lists no Werner paper with returning to the US, he, like King, aban- not external, to the field; specifically, that the participation of Helen Somersby doned that field completely.[23] In contrast, burgeoning interest in mechanistic investi- Foundations oF Coordination Chemistry – alFred Werner CHIMIA 2014, 68, Nr. 5 295

Fig. 4. First page of Werner involve himself with X-ray crystal- ref. [21]: postdoc- lography, which was just beginning to take toral associate T. P. on the central role it has since occupied in McCutcheon did re- inorganic chemistry: ceive authorial credit, but in distorted form. “In view of Werner’s penchant for thinking in three-dimensional geometric terms…it is surprising that he did not apply his coordination theory directly to the do- main of crystallography. Yet he did not…. it remained for Paul Pfeiffer…and others to point out that crystal structures were in beautiful agreement with his coordination theory, as revealed by the then new experi- mental technique of X-ray diffraction.”[24]

If physical methodology is not the link, what is? I identify it as the crucial introduc- tion of mechanistic thinking to American inorganic chemistry, which can argu- ably be traced back to an individual who was directly and strongly influenced by Werner’s work. John Bailar, like Werner, started his career as an organic chem- ist, obtaining his PhD at the University of Michigan with Moses Gomberg. He was hired in 1928 by the University of Illinois at Urbana/Champaign, primar- ily to teach general chemistry, and be- came interested in some questions stu- dents raised about inorganic topics, such as isomerism; also he perceived that the great strength of the organic group at Illinois meant he would have little chance of staying on as an organic chemist.[25] In searching for a research program, he took his inspiration directly from Werner’s work, as Fred Basolo – one of Bailar’s most notable PhD students – later recounted:

“John believed that he should do re- search on an inorganic problem. After some time in the library, he found that pa- pers by Alfred Werner were of interest to him. These Werner metal complexes, with gations along with the upsurge in organo- tially responsible for the renaissance in geometric and stereo , could be transition metal chemistry effectively re- inorganic chemistry since World War II studied in a manner similar to that of or- made inorganic chemistry as a much more is the increasing application of physical ganic compounds. In fact, John did such a explanatory discipline, thus attracting an chemistry to the investigation of inorganic good job with his research on these systems aura of intellectual respectability that had compounds. If Werner were alive today, he that he is viewed by chemists as the ‘Father been previously lacking.[4] Whichever we would undoubtedly possess strong opin- of Coordination Chemistry in the US.’”[26] believe was the more important factor, can ions on this subject….[He] announced his we trace any of these new developments to intention to found ‘a new inorganic jour- That attribution of paternity was sup- Werner’s heritage? nal….inasmuch as the Zeitschrift für anor- ported by an external observer, the British Theoretical approaches to chemical ganische Chemie has gradually developed inorganic chemist Joseph Chatt: understanding (in the quantum mechanical so strongly in the physicochemical direc- sense that Nyholm is referring to) did not tion that it no longer meets the needs and “On my first visits to the United States, exist in Werner’s time, but physical/instru- expectations of the pure inorganic chem- I noted that there were only two types of co- mental methods of characterization (aside ist.’”[8] ordination chemists there, those who had from polarimetry, which already had a long been John Bailar’s students and those who history, and of course played a major role Nonetheless he did use some. Notably, had not, and the former appeared greatly in Werner’s research) were then coming he appears to have been one of the first to outnumber the latter.” [11] into use. However, Kauffman suggests that to explore the application of visible ab- Werner was not all that enthusiastic about sorption spectroscopy to coordination The importance of mechanistic ques- these developments: compounds, which appears in at least one tions in reactions of octahedral complexes doctoral thesis (that of French: see above), had been anticipated by Werner as early as “[A]nother of the trends which is par- though not in any publication.[8] Nor did 1912,[27,28] and Bailar’s first venture into 296 CHIMIA 2014, 68, Nr. 5 Foundations oF Coordination Chemistry – alFred Werner

the field followed Werner’s mechanistic in American academia: in 1983, fully a [13] I. Bernal, G. B. Kauffman, J. Chem. Educ. legacy: quarter of the inorganic faculty received 1989, 66, 293. [14] A. Werner, Z. Anorg. Chem. 1899, 21, 377. their PhD and/or postdoctoral training [15] A. Werner, Ber. 1906, 39, 185. “In 1893 Paul Walden [1863–1957] from that single ancestral line that traces [16] L. Beyer, E. Hoyer, Z. Anorg. Allg. Chem. 2011, discovered the very interesting inversion back to Bailar (Fig. 5) – and through him, 637, 1880. reaction which bears his name. It was an spiritually, to Werner. In that sense at least, [17] A. Werner, Ber. 1911, 44, 1887. extremely important discovery, for it called even though Werner’s own students and [18] G. B. Kauffman, ‘Classics in Coordination Chemistry, Part 1: The Selected Papers of attention to the chemists of that day that postdocs were relatively minor players, Alfred Werner’, Dover Publications, New York, reactions have mechanisms. It occurred the importance of Werner’s legacy to the 1968, pp. 157–8. to me that if we repeated Werner’s experi- inorganic boom that began in the mid-20th [19] G. B. Kauffman, Coord. Chem. Rev. 1975, 15, ment….we might also get an inversion.... century was enormous. 1. [20] N. H. Kolodny, J. A. Darlington, H. C. Mann, if we could get an inversion with an oc- E. R. Webster, ‘125 Years in the Chemistry tahedral model rather than a tetrahedral Received: February 17, 2014 Department at Wellesley College’, downloaded one, we might be able to rule out some of from the website http://www.wellesley.edu/ the theories which had been advanced for chemistry/departmenthistory. the inversion in reactions of the tetrahedral [1] F. J. Moore, ‘A ’ (revised [21] A. Werner, Mc. Cutcheon (sic), Ber. 1912, 45, 3281. organic molecules.”[29] by W. T. Hall), McGraw Hill, New York, 1918/1931, p. 237. [22] A. Werner, C. Herty, Z. Physik. Chem. 1901, 38, [2] T. H. Levere, ‘Transforming Matter: A History 331. In that experiment Bailar and his stu- of Chemistry from Alchemy to the Buckyball’, [23] From Wikipedia, http://en.wikipedia.org/wiki/ dent Robert Auten found that the reactions Johns Hopkins Press, Baltimore, 2001, p. 148. Charles_Herty. [24] G. B. Kauffman, ‘Classics in Coordination of l-cis-[Coen Cl ]+ (en = ethylenedi- [3] E. von Meyer, ‘A History of Chemistry from 2 2 Earliest Times to the Present Day’ (3rd English Chemistry, Part 3: Twentieth Century Papers’, amine) with potassium carbonate and sil- edition, translated by G. McGowan), Macmillan Dover Publications, New York, 1978, pp. 75–7. ver carbonate gave the d- and l-isomers of & Co., London, 1906, p. 417. [25] J. C. Bailar, interview by Theodore L. Brown [Coen (CO )]+ respectively, meaning that [4] J. A. Labinger, ‘Up from Generality: How at University of Illinois, Urbana, Urbana, 2 3 one of them had proceeded with inversion Inorganic Chemistry Finally Became a Illinois, 28 May & 17 June 1987, Philadelphia: Chemical Heritage Foundation, Oral History at the Co center, although their data did Respectable Field’, Springer, Heidelberg, 2013. [5] R. S. Nyholm, J. Chem. Educ. 1957, 34, 166. Transcript # 0073, 1987. not conclusively determine which one that [6] M. J. Nye, ‘Before Big Science: The Pursuit of [26] F. Basolo, ‘From Coello to inorganic chemistry: was; nor did they offer any conclusions or Modern Chemistry and Physics, 1800–1940’, a lifetime of reactions’, Kluwer, New York, even speculations about mechanism.[30] Twayne Publishers, New York, 1996, p. xv. 2002, p. 15. [7] C. A. Russell, ‘The Structure of Chemistry’, [27] A. Werner, Annalen 1912, 386, 1. Subsequently Bailar and others, most [28] A. Werner, Ber. 1912, 45, 3061. notably Basolo, found that both the reac- Unit 3. Open University Press, Milton Keynes, 1976. [29] G. B. Kauffman, G. S. Girolami, D. H. Busch, tivity and the mechanistic interpretation [8] G. B. Kauffman, ‘Alfred Werner, Founder of Coord. Chem. Rev. 1993, 128, 1. were rather more complex than originally Coordination Chemistry’, Springer, Berlin, [30] J. C. Bailar, R. W. Auten, J. Am. Chem. Soc. suspected.[31] But this work by Bailar and 1966. 1934, 56, 774. [31] F. Basolo, in ‘Werner Centennial’ (ACS his successors – many of whom were his [9] A. Werner, Z. Anorg. Chem. 1893, 3, 267. [10] E. C. Constable, C. E. Housecroft, Chem. Soc. Advances in Chemistry Series No. 62) 1967, direct academic descendants – sparked the Rev. 2013, 42, 1429. pp. 408–29. mechanistic turn that played a crucial role [11] J. Chatt, in ‘Coordination Chemistry: A Century in raising the image of inorganic chemistry of Progress’, Ed. G. B. Kauffmann, American to a par with that of organic and physical Chemical Society, Washington, 1994, p. xiv. chemistry. One representation of that im- [12] G. B. Kauffmann, in ‘Coordination Chemistry: A Century of Progress’, Ed. G. B. Kauffmann, pact can be seen from the extent to which American Chemical Society, Washington, 1994, those descendants dominated the field p. ix.

John Bailar Illinois

Fred Basolo Daryle Busch Bob Parry 10 other Northwestern Kansas Michigan/Utah 1st gen

Harry Gray 19 other 20 8 18 Columbia/Caltech 2nd gen 2nd gen 2nd gen 2nd gen

26 10 1 6 3rd gen 3rd gen 3rd gen 3rd gen

13 2 4th gen 4th gen

1 5th gen

Fig. 5. Family tree of inorganic faculty in US PhD-granting departments in 1983 whose academic descent traces back to Bailar’s group.