From owner-chemistry.,at,.ccl.net Mon May 4 16:23:00 2020 From: "JPD-workstation_home djukic#,#unistra.fr" To: CCL Subject: CCL: Explanation on specific metal reactivity Message-Id: <-54058-200504142649-16004-PrnEnkXTJfOUWY3Jd7m4iA ~~ server.ccl.net> X-Original-From: JPD-workstation_home Content-Language: fr Content-Type: multipart/alternative; boundary="------------1A33B126696C262A176C3D60" Date: Mon, 4 May 2020 20:26:37 +0200 MIME-Version: 1.0 Sent to CCL by: JPD-workstation_home [djukic#,#unistra.fr] This is a multi-part message in MIME format. --------------1A33B126696C262A176C3D60 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable Hi Sebastian, You are right. However, you will find out readily that some issues are=20 unanswered/unsolved still today. One example is for instance the reactivity of M-H bonds in transfers to=20 organic substrates.=C2=A0 What is being actually transfered and how=C2=A0= depends=20 a lot not only on the metal, its oxidation state, the ligand retinue but=20 perhaps also on "environmental factors". It is indeed easy to draw a simplified picture of the earth from the=20 moon, things get tougher when one gets on the surface. This potential review you are mentioning should be a critical one made=20 > from the "surface", and should confront experimental evidence (for the=20 more documented cases) to theory. Best. JP Le 04/05/2020 =C3=A0 15:18, Sebastian Kozuch seb.kozuch[a]gmail.com a =C3= =A9crit=C2=A0: > Sent to CCL by: Sebastian Kozuch [seb.kozuch[a]gmail.com] Hi Per-Ola, > This was actually useful. I guess that a thorough discussion like=20 > this, considering the difficulties in obtaining such information,=20 > should be written in a review or perspective article. So here is a=20 > challenge for the organometallic community ;) > > Best, > Sebastian > > On 4/5/20 9:55 AM, Norrby, Per-Ola Per-Ola.Norrby=3Dastrazeneca.com wro= te: >> >> Hi Sebastian, >> >> I guess most of your answers here will point out that the question is=20 >> wrong. There are plenty of metals that do each of the tasks you have=20 >> pointed out. I=E2=80=99d say the least specific one is hydrogenation, = the=20 >> worlds largest asymmetric catalytic process uses Rh, not Ir. But I=20 >> guess you want to find out why some metals seem ideally balanced and=20 >> thus have gained high popularity. I=E2=80=99ll just address cross coup= ling=20 >> here. It=E2=80=99s all a question of balance. As you yourself have pus= hed=20 >> earlier, each of these cases are catalytic cycles, and for an=20 >> efficient catalytic coupling cycle you need to have two states that=20 >> are easily accessible, with similar energies. Additionally, for=20 >> robustness, you only want these states, not any others, to be=20 >> accessible. Furthermore, organic reactions can diverge if you start=20 >> forming radicals (even though that reactivity can be tamed, with=20 >> effort). If you want to avoid radicals, go for something that has=20 >> only closed shell states. This would exclude first row transition=20 >> metals, each of which have easily accessible open shell states. But=20 >> to reiterate, sometimes we want to pay the effort to fine-tune the=20 >> reactivity of these metals and limit the side paths. You can do much=20 >> more efficient coupling with Fe, Ni, or even Cu than with Pd, but due=20 >> to the presence of additional oxidations states, each system must be=20 >> optimized, you don=E2=80=99t have =E2=80=9Coff-the-shelf=E2=80=9D solu= tions tat always work. >> >> Staying in the second or third row, the second row is generally=20 >> favored by price. Then, why Pd? Obviously it has two easily=20 >> accessible oxidation states, 0 and +2. Other states can be reached,=20 >> but only under forcing or bimetallic conditions. The energies of=20 >> these two states happen to be in a range suitable for the needed=20 >> reactions, mostly because aryl halides are very common. If we had=20 >> focused on diazonium salts instead, you=E2=80=99d find that other meta= ls=20 >> would become optimal, but for safety reasons, we will not. What=20 >> alternatives are there? Rh is used, but if you go to closed shell, it=20 >> has to utilize the +1,+3 cycle. The cost of reaching +3 seems to be=20 >> high for simple aryl halides, and the high charge of +3 would make it=20 >> sensitive, reducing robustness. How about Ru? Both 0 and +4 seems to=20 >> require too much energy, and the odd numbers would be open shell. A=20 >> bimetallic +2,+3 should be possible, but stabilizing a multimetallic=20 >> catalyst in only the bimetallic state seems hard and not overly=20 >> robust (there are solutions, for specific problems). I could continue=20 >> like this, but it would be very long, you=E2=80=99d have to explain fo= r every=20 >> metal exactly why it has the wrong balance, and for every metal, you=20 >> could probably use those arguments to come up with the exception,=20 >> where that metal too would be a coupling catalyst. Even more so for=20 >> hydrogenation; I don=E2=80=99t think there is a single metal that hasn= =E2=80=99t been=20 >> used to hydrogenate something. >> >> Metathesis is harder to elucidate, there you need the perfect balance=20 >> between single and double bonds to metal at a single oxidation state.=20 >> I don=E2=80=99t know enough of the details, but Ru, Mo, and Os seem to= do it=20 >> well, and there have been reports of first row also, I believe. It=E2=80= =99s=20 >> very much in the sensitivity to side reactions, air, water, etc=E2=80=A6 >> >> Cheers, >> >> Per-Ola >> >> *From:* owner-chemistry+per-ola.norrby=3D=3Dastrazeneca.com*_*ccl.net=20 >> *On=20 >> Behalf Of *Sebastian Kozuch seb.kozuch]^[gmail.com >> *Sent:* den 2 maj 2020 16:19 >> *To:* Norrby, Per-Ola >> *Subject:* CCL: Explanation on specific metal reactivity >> >> Sent to CCL by: Sebastian Kozuch [seb.kozuch^gmail.com] >> >> For all the computational organometallists out there: >> >> Why Ir and not other metals catalyses hydrogenation? >> >> Why Pd for cross-coupling? >> >> Why Ru for metathesis? >> >> I cannot find any specific explanation that connects a metal to its=20 >> reaction. Tons of mechanistic studies and reviews, without=20 >> explanations on why this metal and only this metal for this reactions. >> Is this info hidden or unknown? Any good paper or book? >> >> Thanks, >> Sebastian >> >> CHEMISTRY*_*ccl.net or use: E-mail to administrators:=20 >> CHEMISTRY-REQUEST*_*c= cl.net=20 >> or use Before posting, check=20 >> wait time at:=20 >> http://www.ccl.net=20 >> Job: http://www.ccl.net/jobs=20 >> Conferences:=20 >> http://server.ccl.net/chemistry/announcements/conferences/=20 >> Search=20 >> Messages: http://www.ccl.net/chemistry/searchccl/index.shtml RTFI:=20 >> http://www.ccl.net= /chemistry/aboutccl/instructions/=20 >> >> >> ----------------------------------------------------------------------= -- >> >> *Confidentiality Notice: *This message is private and may contain=20 >> confidential and proprietary information. If you have received this=20 >> message in error, please notify us and remove it from your system and=20 >> note that you must not copy, distribute or take any action in=20 >> reliance on it. Any unauthorized use or disclosure of the contents of=20 >> this message is not permitted and may be unlawful. >> > > --=20 > =E2=80=97=E2=80=97=E2=80=97=E2=80=97=E2=80=97=E2=80=97=E2=80=97=E2=80=97= =E2=80=97=E2=80=97=E2=80=97=E2=80=97=E2=80=97=E2=80=97=E2=80=97=E2=80=97=E2= =80=97=E2=80=97=E2=80=97=E2=80=97=E2=80=97=E2=80=97=E2=80=97=E2=80=97=E2=80= =97=E2=80=97=E2=80=97=E2=80=97=E2=80=97=E2=80=97=E2=80=97=E2=80=97=E2=80=97= =E2=80=97 > .........Sebastian Kozuch......... > ......Department of Chemistry..... > Ben-Gurion University of the Negev > .........kozuch*_*bgu.ac.il......... > ......www.bgu.ac.il/~kozuch/...... > =CB=AD=CB=AD=CB=AD=CB=AD=CB=AD=CB=AD=CB=AD=CB=AD=CB=AD=CB=AD=CB=AD=CB=AD= =CB=AD=CB=AD=CB=AD=CB=AD=CB=AD=CB=AD=CB=AD=CB=AD=CB=AD=CB=AD=CB=AD=CB=AD=CB= =AD=CB=AD=CB=AD=CB=AD=CB=AD=CB=AD=CB=AD=CB=AD=CB=AD=CB=AD > -=3D This is automatically added to each message by the mailing script=20 > =3D- To recover the email address of the author of the message, please=20 > change the strange characters on the top line to the .:. sign. 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Hi Sebastian,


You are right.

However, you will find out readily that some issues are unanswered/unsolved still today.

One example is for instance the reactivity of M-H bonds in transfers to organic substrates.=C2=A0 What is being actually transfered and how=C2=A0 depends a lot not only on the metal, its oxidation state, the ligand retinue but perhaps also on "environmental factors".

It is indeed easy to draw a simplified picture of the earth from the moon, things get tougher when one gets on the surface.

This potential review you are mentioning should be a critical one made from the "surface", and should confront experimental evidence (for the more documented cases) to theory.

Best.
JP


Le 04/05/2020 =C3=A0 15:18, Sebastian = Kozuch seb.kozuch[a]gmail.com a =C3=A9crit=C2=A0:
Sent to CCL by: Sebastian Kozuch [seb.kozuch[a]gmail.com] Hi Per-Ola,
This was actually useful. I guess that a thorough discussion like this, considering the difficulties in obtaining such information, should be written in a review or perspective article. So here is a challenge for the organometallic community ;)

Best,
Sebastian

On 4/5/20 9:55 AM, Norrby, Per-Ola Per-Ola.Norrby=3Dastrazeneca.com wrote:

Hi Sebastian,

=C2=A0

I guess most of your answers here will point out that the question is wrong. There are plenty of metals that do each of the tasks you have pointed out. I=E2=80= =99d say the least specific one is hydrogenation, the worlds largest asymmetric catalytic process uses Rh, not Ir. But I guess you want to find out why some metals seem ideally balanced and thus have gained high popularity. I=E2=80=99ll j= ust address cross coupling here. It=E2=80=99s all a question of b= alance. As you yourself have pushed earlier, each of these cases are catalytic cycles, and for an efficient catalytic coupling cycle you need to have two states that are easily accessible, with similar energies. Additionally, for robustness, you only want these states, not any others, to be accessible. Furthermore, organic reactions can diverge if you start forming radicals (even though that reactivity can be tamed, with effort). If you want to avoid radicals, go for something that has only closed shell states. This would exclude first row transition metals, each of which have easily accessible open shell states. But to reiterate, sometimes we want to pay the effort to fine-tune the reactivity of these metals and limit the side paths. You can do much more efficient coupling with Fe, Ni, or even Cu than with Pd, but due to the presence of additional oxidations states, each system must be optimized, you don=E2=80=99t have =E2=80=9Coff-the-shelf=E2=80=9D solutions tat always work.

=C2=A0

Staying in the second or third row, the second row is generally favored by price. Then, why Pd? Obviously it has two easily accessible oxidation states, 0 and +2. Other states can be reached, but only under forcing or bimetallic conditions. The energies of these two states happen to be in a range suitable for the needed reactions, mostly because aryl halides are very common. If we had focused on diazonium salts instead, you=E2=80=99d find that o= ther metals would become optimal, but for safety reasons, we will not. What alternatives are there? Rh is used, but if you go to closed shell, it has to utilize the +1,+3 cycle. The cost of reaching +3 seems to be high for simple aryl halides, and the high charge of +3 would make it sensitive, reducing robustness. How about Ru? Both 0 and +4 seems to require too much energy, and the odd numbers would be open shell. A bimetallic +2,+3 should be possible, but stabilizing a multimetallic catalyst in only the bimetallic state seems hard and not overly robust (there are solutions, for specific problems). I could continue like this, but it would be very long, you=E2=80=99d have to explain for every metal e= xactly why it has the wrong balance, and for every metal, you could probably use those arguments to come up with the exception, where that metal too would be a coupling catalyst. Even more so for hydrogenation; I don=E2=80=99t think there is a single= metal that hasn=E2=80=99t been used to hydrogenate something.<= /o:p>

=C2=A0

Metathesis is harder to elucidate, there you need the perfect balance between single and double bonds to metal at a single oxidation state. I don=E2=80=99t know en= ough of the details, but Ru, Mo, and Os seem to do it well, and there have been reports of first row also, I believe. It=E2=80= =99s very much in the sensitivity to side reactions, air, water, etc=E2=80=A6

=C2=A0

Cheers,

=C2=A0

Per-Ola

=C2=A0

From: owner-chemistry+per-ola.norrby=3D=3D= astrazeneca.com*_*ccl.net <owner-chemistry+per-ola.norrby= =3D=3Dastrazeneca.com*_*ccl.net> On Behalf Of Sebastian Kozuch seb.kozuch]^[gmail.com Sent: den 2 maj 2020 16:19
To: Norrby, Per-Ola <Per-Ola.Norrby*_*astrazeneca.c= om>
Subject: CCL: Explanation on specific metal reactivity

=C2=A0

Sent to CCL by: Sebastian Kozuch [seb.kozuch^gmail.com]

For all the computational organometallists out there:

Why Ir and not other metals catalyse= s hydrogenation?

Why Pd for cross-coupling?

Why Ru for metathesis?

I cannot find any specific explanation that connects a metal to its reaction. Tons of mechanistic studies and reviews, without explanations on why this metal and only this metal for this reactions.
Is this info hidden or unknown? Any good paper or book?
Thanks,
Sebastian

=C2=A0

CHEMISTRY*_*ccl.net or use: E-mail to administrators: CHEMISTRY-REQUEST*_*ccl.net o= r use Before pos= ting, check wait time at: http://www.ccl.net Job: http://www.ccl.net/jobs Conferences: http://server.ccl.net/chemistry/announcements/conferences/<= /a> Search Messages: http://www.ccl.net/chemistry/searchccl/index.shtml RTFI: http://www.ccl.net/chemistry/aboutccl/instructions/

Confidentiality Notice: This message is private and may contain confidential and proprietary information. If you have received this message in error, please notify us and remove it from your system and note that you must not copy, distribute or take any action in reliance on it. Any unauthorized use or disclosure of the contents of this message is not permitted and may be unlawful.


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.........Sebastian Kozuch.........
......Department of Chemistry.....
Ben-Gurion University of the Negev
.........kozuch*_*bgu.ac.il.........
......www.bgu.ac.il/~kozuch/......
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