Reinhard Schmutzler–A memoir

With the death of Reinhard Schmutzler on July 26, 2014, inorganic chemistry worldwide has suffered a significant loss of one of the notable characters of the latter half of the 20th century. For over 50 years he was a towering figure in phosphorus chemistry worldwide, not only because of his prodigious research output, but also because of his extraordinarily enthusiastic cultivation of personal contacts. The number of chemists who visited Reinhard and his wife Gudrun at their home in Wolfenbüttel (and earlier in Loughborough) must be in the hundreds. I was privileged to be a close friend and colleague of Reinhard's for over 40 years, and it is an honor to have the opportunity to record some of my memories of those years, both personal and professional.

Reinhard was born on July 28, 1934, in Schwabach, a small town in northern Bavaria, just south of the city of Nürnberg. Unlike most Bavarians, his family was Protestant, and this family background was important in shaping his character. His childhood was dominated by the war, and particularly by the tragic death of his older brother Armin, a young soldier in the German army, when Reinhard was only about 10 years old. Reinhard excelled at school, studied chemistry at Würzburg University, and went on to do his Ph.D. at the University of Stuttgart under the supervision of Professor F. Seel.

Although already interested in an academic career, Reinhard was unhappy with the then common German practice of Habilitation, whereby young academics, after their Ph.D., had to work as juniors to an established professor before being able to start an independent research career. Consequently, he took up a post at DuPont, the large American chemical company in Wilmington, Delaware, which had a vigorous and well-financed research department, equal, or even higher in status to most universities. Here he developed a research program into phosphorus-fluorine compounds, encouraged by the young director of research at DuPont, Earl Muetterties, who had already recognized the value of new analytical techniques like NMR and X-ray crystallography. Reinhard's work at DuPont was extremely successful, and he rapidly became well known for his work in the field.

While at DuPont, Reinhard was able to spend a year at Cambridge University, where he worked with and met a range of inorganic chemists working in the department. The department was one of the best, if not the best, in Britain, and was ably chaired by Professor H. Emeleus. The atmosphere in the department inspired him, on his return to America, to consider taking up the academic career he had spurned earlier. Without the Habilitation needed to get an appointment in Germany, he started applying for posts in Britain. His research record made him an outstanding candidate, and in 1966 he was offered a post of Senior Lecturer at Loughborough University of Technology.

So it was in the autumn of 1966 that I first met Reinhard, while I was completing my Ph.D. thesis. I had been studying at Leicester University for three years, under the supervision of Dr. R.D.W. Kemmitt and Professor M.C.R. Symons, and was looking for a post-doctoral position, preferably in the same geographical area. An enquiry at the University of Loughborough had indicated that Reinhard was due to take up his position as Senior Lecturer in Inorganic Chemistry on January 1, 1967, and there was a post of Research Fellow available in the department, for which I was invited to apply.

Our first meeting, during a visit by Reinhard and his wife to Loughborough, was immediately successful. Although my Ph.D. topic, physical inorganic chemistry, using ESR spectroscopy, was somewhat distant from Reinhard's research interests in phosphorus and fluorine chemistry, we found common ground at a personal level, since I spoke passable German (Reinhard's English was of course better) and we shared an interest in German railways, both having grown up in an era when steam locomotives were common in our respective countries. My appointment was duly confirmed (bureaucracy was much less in those days, I don't remember any formal interview process) and I was able to start work at Loughborough on November 1, 1966, two full months before Reinhard was due to take up his position.

Over the following five years I grew to know Reinhard extremely well, and was closely involved in his research work. In Loughborough he soon came to realize that Loughborough was not Cambridge. The university was not a totally new foundation, but had arisen from the upgrading of a College of Advanced Technology (CAT), which had been noted more for its sporting achievements than its academic merit. Under the Robins plan of the new government funds had been made available to raise several CATs to university status, and Reinhard's appointment was a consequence of this policy. However, many of the staff, including the head of chemistry, had been in post for several years, and were certainly not of the calibre of the researchers in Cambridge that had so inspired Reinhard two years previously. Also, the contrast in funding between DuPont and Loughborough could not have been starker. An abiding memory is the anger repeatedly caused to Reinhard when he would get free samples of chemicals sent to him by industrial contacts in the USA (DuPont obviously included) only to be presented with a bill for £40 to £50 from a shipping agent who had handled the importation of the goods through London airport. Many of his “free samples” would have cost him less to buy on the open market.

Despite such difficulties, Reinhard rapidly established a viable and successful research group in Loughborough. In addition to myself he quickly recruited two German post-doctoral workers, Manfred Fild, who had just completed his Ph.D. with Professor Glemser in Göttingen, and Rolf Singer, who was on secondment from Bayer AG, one of the largest chemical companies in Germany. Manfred's wife, Inge, who had also been a student of Glemser's, also joined the research group, though in an unpaid capacity. Within a year Reinhard also recruited three English Ph.D. students, Stephen Peake, Richard Dunmur, and Michael Hewson.

So what of the chemistry that this new research group was doing? During his time at DuPont, Reinhard had developed a fruitful synthetic method of reacting fluorophosphorus compounds with trimethylsilyl derivates of elements such as nitrogen, oxygen, sulphur, etc., which resulted in the cleavage of trimethylfluorosilane and the formation of a P-N, P-O, or P-S bond. This enabled the synthesis of a wide variety of phosphorus fluorides, particularly because the reactions proceeded stoichiometrically where there were multiple P-F bonds. Where the silyl derivatives were multifunctional P-N-P compounds were accessible, and a wide variety of cyclic compounds could also be synthesised.

Preparation of the silyl derivatives needed for this synthesis was generally achieved by reacting trimethylchlorosilane with amines or other N-H groups, but a practical problem often occurred here in that the ammonium salts produced by the reaction of the HCl released with excess amine (or added tertiary amines such as triethylamine or pyridine) were often present as an extremely fine solid, which tended to clog up the filtration medium (usually glass sinter filters), making separation of the amine hydrochloride a difficult process. Of course all this work had to be carried out under anhydrous conditions, most fluorophosphorus compound being hydrolytically sensitive. In cases where phosphorus(III) compounds were involved there also arose the question of oxygen sensitivity, but since we usually worked under a nitrogen atmosphere, this was not really an additional problem.

For the characterization of the products of these reactions NMR became the usual method of choice. The presence in our products of hydrogen, phosphorus, and fluorine nuclei (all with 100% abundance of spin ½ nuclei) made the spectra complicated, but usually first-order, so relatively easily analyzed. The exceptions were symmetrical diphosphorus compounds, such as diazadiphosphetidines ((RNPX₃)₂), which formed spin systems of the [AX_n]₂ type, which are always second-order, and require more sophisticated analysis. Here the group was helped by Robin Harris, whom Reinhard had got to know before coming to England, who was one of the pioneers of the analysis of such symmetrical spin systems. His group, then at the University of East Anglia in Norwich, had developed computer programs for these analyses, and these rapidly became part of our arsenal.

The other important role of NMR was in the study of the fluxional behavior of five-coordinate phosphorus compounds. It had already been established that these were usually of a trigonal bipyramidal structure, which implies the presence of two different ligand sites, axial and equatorial. However, many compounds, starting with PF₅, only show a single signal for the fluorine atoms (with the expected spin-spin coupling to the central ³¹P nucleus). This was explained by the occurrence of a rapid exchange process between the different fluorine environments, known as Berry pseudorotation, named after R.S. Berry, who first proposed the mechanism. The process is so rapid (more precisely, the free energy barrier of the process is so low) that even lowering the temperature to -100º fails to slow it down sufficiently for separate ¹⁹F signals to be observed. The same process is also observed in tetrafluorophosphoranes, RPF₄, where again a single ¹⁹F signal is observed. Trifluorophosphoranes, R₂PF₃, however, show separate signals for the two axial and one equatorial fluorine atoms. The preference for fluorine, rather than R groups, to occupy the axial sites means that the energy barrier to pseudorotation is now much higher.

However, Reinhard had already discovered that if dialkylaminotetrafluorophosphoranes, (R₂NPF₄) were cooled to −80º, two separate ¹⁹F signals were indeed observed. This was originally interpreted as indicating that the barrier to pseudorotation was higher than in alkyl- or aryltetrafluorophosphoranes, but in fact the probable explanation is that what is being slowed down is the rotation about the P-N bond. This hypothesis is supported by the fact that if unsymmetrical compounds (e.g. RR'NPF₄) are studied, three ¹⁹F signals are observed at low temperature, the two fluorine atoms in the same plane as the RR' groups on nitrogen now being in different environments. Pseudorotation, if still occurring, will not put these two fluorines into identical environments, nor into the same environment as the two other fluorines, which must be perpendicular to the aforementioned plane. The shifts of the two non-identical fluorines, as well as their P-F couplings, are noticeably lower than those of the two identical fluorines, indicating that the ground-state structure is the one where the RR'N- plane is in line with the two axial fluorines.

This restricted rotation about a P-N bond found a parallel in the case of N-methyl-2-pyrrolyltetrafluorophosphorane, where the restricted rotation is about a P-C bond. The fact that the carbon atom involved is in a π-system is relevant, but it is interesting that a similar effect is not seen in simple aryl derivatives, like phenyltetrafluorophosphorane.

While such research was progressing in Loughborough Reinhard's reputation was becoming more widely known, and it was therefore perhaps no surprise that in 1968 he received an “invitation” (the German word is “Ruf,” literally “call”) to a chair at the Technical University in Braunschweig in Germany. Mildly surprising was the fact that he still did not have his Habilitation, but that was perhaps a sign that German universities were (if slowly) modernizing.

Clearly this move would have serious consequences for the members of his group. Rolf Singer had already returned to his job with Bayer, and Manfred and Inge Fild had moved to Amherst, Massachusetts, where Manfred had a post-doctoral position with Professor R.R. Holmes. I was quite pleased to take up the invitation to Braunschweig (my wife, then starting a career as a librarian, less so), as were both Richard Dunmur and Michael Hewson, though neither of them spoke any German. Stephen Peake, who had only one year left of his Ph.D. opted to stay in Loughborough.

So it came about that I took up my post (Wissenschaftlicher Assistent) in Braunschweig, once again, two months before Reinhard arrived. Braunschweig already had a flourishing inorganic chemistry department, headed by Professor Ulrich Wannagat, a distinguished silicon chemist. He was some ten years older than Reinhard, and was more representative of the older style of German professor. The two men never really saw eye to eye, and disputes about sharing departmental facilities were commonplace. In theory they had equal status, though their chairs were labelled A and B, and Wannagat knew that A came before B.

The late 1960s were the time of important developments in NMR, particularly in the introduction of pulsed Fourier Transform techniques. This effectively allowed the acquisition of spectra in a matter of seconds, so that hundreds, or even thousands of spectra, stored in a digital computer, could be added together, increasing the signal to noise ratio by a factor of √n, where n is the number of scans. This made the measurement of ¹³C spectra accessible, and had obvious advantages for ³¹P spectra, which have lower sensitivity than ¹H or ¹⁹F spectra. It was in 1971 that Braunschweig was able to acquire its first Fourier transform spectrometer, so that we were now able to add ¹³C measurements to our spectroscopic studies. The instrument was however shared with the organic chemists, so time for inorganic studies was limited. ¹⁹F and ³¹P studies remained our principal methods of investigation.

As the research group established itself in Braunschweig, it gradually become more German in character, Most research students were now German, though Reinhard, with his world-wide contacts, was still able to recruit a number of foreign post-doctoral workers and guest researchers. One such, with whom I established a particularly close relationship, was George Doak, from the University of North Carolina in Chapel Hill. He had just retired after a distinguished career, one of his outstanding achievements being the synthesis of anti-syphilis drugs containing arsenic. Not perhaps having travelled as widely as chemists now do, he was unfamiliar with many aspects of German life, and often expressed his somewhat bemused wonderment at the differences between Germany and his home in the U.S.A. One memorable event was when he and I made a short visit to East Germany (strictly the German Democratic Republic), the border of which of course was only 30 miles from Braunschweig. At the time I had a little mini-van, of English construction, and in this we drove first to Berlin, where we were met by Professor Lothar Kolditz, a well-known fluorine chemist. We were not totally aware that, in addition to his post at the Humboldt University, he was also influential in the Ministry of Education, so a high-ranking party official. From Berlin we proceeded to Halle, where we arrived very late at night, my van having developed electrical problems in the wet and foggy weather. In Halle, then a centre for phosphorus chemistry in the GDR, we met Professors Issleib and Tschach, both of whom I had previously met at phosphorus chemistry conferences. Professor Issleib, I believe, had also been a visitor in Braunschweig.

This visit, quite exciting for both of us, had obviously been arranged by Reinhard, who was quite exceptional in his range of contacts to chemists throughout the world. Where he found the time and energy to maintain all the contacts he had I never really understood. Political differences, such as between East and West in the sixties and seventies, did not seem to concern or disturb him; he let his chemistry do the talking. A stream of visitors came to Braunschweig, and were all invited to Reinhard's home in Wolfenbüttel, some ten miles outside Braunschweig. These visitors had, of course, a very positive influence on his co-workers, and I can personally record how my subsequent career was affected by Reinhard's encouragement of world-wide interactions.

Much as I enjoyed my professional life in Braunschweig, it gradually became clear that I had questions to answer about my future career. Was I happy to settle in Germany, or should I be looking to return to Britain? A decision had to be made in 1971, when my post came up for renewal. It was becoming increasingly hard to justify my continuation as a Wissenschaftlicher Assistent, a temporary post intended for younger researchers, and I decided to take up a post-doctoral position with Robin Harris at the University of East Anglia. I had already realised that NMR spectroscopy was more suited to my abilities than preparative chemistry, and Robin Harris provided an excellent opportunity to further my experience in NMR. So it was that in November 1971 I said goodbye to Reinhard, and started out as an NMR spectroscopist in Norwich.

Less than two years later I moved to Bristol, a post that later became permanent, and I remained there until my retirement in 2007. Throughout that time I remained in contact with Reinhard and his family, visiting them frequently. We often attended the same conferences, particularly the series of ICPC (International Conference of Phosphorus Chemistry), where Reinhard was often a plenary lecturer. His travels were however curtailed in 1985 when, on a typically hectic and busy lecture tour in the U.S.A. he suffered a massive stroke, which saw him in intensive care for a month. Gudrun flew out to care for him, and eventually he returned to Germany. He made a slow, but steady recovery, and resumed his academic duties, though inevitably with an (only slightly) reduced intensity.

Despite his recovery, health problems were to play an increasing role in his life. Possibly as a result of the medication needed to treat his stroke, he developed kidney problems, which led to him needing regular dialysis. Although this initially severely restricted his ability to travel, matters improved when he acquired a portable dialysis machine, which enabled him to travel, though not as widely as previously. A further enhancement came when he received a kidney transplant, which led to a significant improvement in his ability to travel, though naturally not to the extent he had done before his stroke.

Despite the improvement offered by his kidney transplant, he developed yet another problem in the form of peripheral neuropathy, a condition where the nerves transmit feelings of (often severe) pain to the brain, even when there is no condition that should be causing the pain. Painkillers can do something to alleviate, but not remove, the condition; the consequence was that Reinhard was in considerable, or often severe, discomfort for the final few years of his life. Given his health problems, he was indeed fortunate to have the love and care of Gudrun to support him through an extremely difficult time.

My last direct contact with Reinhard was a phone call just two months before his death. That he telephoned me was in itself unusual; his preferred method of contact had always been the written word, latterly including e-mail, but by then even writing had become difficult. Gudrun had encouraged him to telephone some of his closest friends to re-establish contact, but unfortunately it was to be a single occasion.

Reinhard's legacy, in the form of his published scientific work, is of exceptional merit and value to the world of chemistry. He will also be remembered by a wide circle of friends and colleagues, who all, in their different ways, will keep his memory alive.