2012 Intro Organologam
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Transcript of 2012 Intro Organologam
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Mekanisme Reaksi Kimia Anorganik Reaksi Organologam
Referensi:
James E.Huheey, Ellen A.Keither, Richard L. Keiter. 1993. Inorganic Chemistry: Principles of Structure and Reactivity Fourth Edition. Harper
Collins College, New York (Bab 13, 15)
Miessler, Tarr, Inorganic Chemistry, 2nd Edition, 1999.
Shriver, Atkins, Inorganic Chemistry, 3rd Edition, 1999.
RH Crabtree, The Organometallic Chemistry of the Transition Metals, Wiley 2001
Online : http://www.chem.ox.ac.uk/icl/dermot.html
Lecture Notes online: www.ocw.mit.edu
Lecture Note yang telah dibagikan (Mencakup 2/3 materi, bahasa Indonesia)
Help : ruang dosen, e-mail, phone
Pertemuan I- tugas terstruktur
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Kimia Organologam
Definisi Kimia Organologam
Aturan 18 elektron: Electron Counting (pertemuan I)
Ligan Organometal (pertemuan II)
Reaksi Kompleks Organologam (pertemuan III-V)
Adisi Oksidatif
Eliminasi Reduktif
Proses Substitusi
Reaksi Insersi
Eliminasi Alfa-Hidrida dan Abstraksi
Eliminasi Beta-Hidrida
Aplikasi dalam reaksi katalitik (pertemuan 5-7) (Dengan Luasnya Kajian Kimia Organologam-hanya ada 7 pertemuan,
Bahasan per minggu dan slide power point dapat sedikit berubah
dari rencana pembelajaran)
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Mekanisme Reaksi Kimia Anorganik Reaksi Organologam
Organometallic compounds are compounds wherein the metal is bonded through carbon to an organic molecule, radical or ion.
senyawaan yang mengandung ikatan LOGAM KARBON
Dari yang telah anda pelajari:Cr(CO)6 Hingga: senyawa sandwich dengan sistem ligan organik tak jenuh pi terdelokalisasi
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BASED ON ORGANOMETALLICS JOURNAL:
"organometallic" compound will be defined as one in which there is a bonding interaction (ionic or covalent, localized or delocalized) between one or more carbon atoms of an organic group or molecule and a main group, transition, lanthanide, or actinide metal atom (or atoms).
organic derivatives of the metalloids (boron, silicon, germanium, arsenic, and tellurium) will be included in this definition.
metal-containing compounds which do not contain metal-carbon bonds will be considered as well. Such compounds may include, inter alia, representatives from the following classes: molecular metal hydrides; metal alkoxides, thiolates, amides, and phosphides; metal complexes containing organo-group 15 and 16 ligands; metal nitrosyls...."
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Historical Perspective
1827 Zeises Salt Na[PtCl3C2H4]-seny org.logam pertama
1847 Frankland, Zn(Et)2, first metal alkyl
1900 Grignard, organomagnesium halides
1907 Pope and Peachey, PtMe3I, first transition metal s-alkyl
1917. Schenk, lithium alkyls
1931 Heiber, Fe(CO)4H2 first transition metal hydride
1951. Pauson and Miller, ferrocene
1955 Fisher, bis arene metal complex
1973. Fisher, Cr(CO)4(CR), first carbyne complex
1983. Bergman, Graham, C-H bond activation
1983 Green, Brookhart, agostic metal-hydrogen interaction
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The Nobel Prize in Chemistry 2010
Richard F. Heck, Ei-ichi Negishi, Akira Suzuki
Richard
F. Heck
American
citizen.
Born
1931
Ei-ichi
Negishi
Japanese
citizen.
Born
1935
Akira
Suzuki
Japanese
citizen.
Born
1930
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Why the Heck Bother with the Heck Reaction: Applications in Industry and Total Synthesis
Non-Steroidal
Anti-inflammatory drugs
Sunscreen Agents
Flavourings
Cosmetic Additives
Key Steps in Total Synthesis O
O O
ACB
L.F. Tietze and T. Grote,
J. Org. Chem., 1994, 59, 192
J.J. Masters, D.K. Jung,
W.G. Bornmann and
S.J. Danishefsky,
Tetrahedron Lett., 1993, 34, 7253
O
NH
NSO2Ph
Taxol
Skeleton
CC-1065
Skeleton
MeO
O
O
2-Ethylhexyl trans-4-methoxycinnamate
MeO
O
O
Isoamyltrans-4-methoxycinnamate
COOH
CH3
MeO(s)-Naproxen
Br
MeO
MeO
Heck reaction
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The Nobel Prize in Chemistry 2010
The Suzuki reaction
Suzuki reaction to
develop organic
polymers that emit
light when a current
runs through them.
The goal is to
improve super-thin
OLED (organic light-
emitting diode)
displays.
Suzuki reaction to
develop new light-
capturing
molecules. These
can be spray-
painted onto a
surface and could
become a part of
future flat solar cell
The Suzuki reaction
has been used to
develop variants of the
antibiotic vancomycin.
These variants are
effective against
strains of bacteria that
are otherwise resistant
(MRSA)
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Ligan Organik tidak jenuh
Dapat berikatan dengan logam melalui lebih dari 1 cara Contoh Allyl
* Sbg alkil berikatan dgn logam melalui satu atom karbon
* melalui sistem elektron , ketiga atom karbonnya
berikatan dengan logam (hapticity, h)
M
M
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Hapto (h) Number
Jumlah atom terkonjugasi pada ligan yang terikat ke logam
h5-C5H5 pentahaptosiklopentadienil
Sebagai ligan C5H5 disebut siklopentadienil (Cp)
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eta-x was originally developed to indicate how many contiguous donor atoms of a -system were coordinated to a metal center. Hapticity is another word
used to describe the bonding mode of a ligand to a metal center. An h5-
cyclopentadienyl ligand, for example, has all five carbons of the ring bonding to the
transition metal center.
hx values for all-carbon based ligands where the x value is odd usually
indicate anionic carbon ligands (e.g., h5-Cp, h1-CH3, h1-allyl or h3-allyl, h1-
CH=CH2). The # of electrons donated (ionic method of electron counting) by the
ligand is usually equal to x + 1. Even hx values usually indicate neutral carbon -
system ligands (e.g., h6-C6H6, h2-CH2=CH2, h4-butadiene, h4-cyclooctadiene).
The # of electrons donated by the ligand in the even (neutral) case is usually just
equal to x.
hx
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.
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mu-x is the nomenclature used to indicate the presence of a bridging ligand between two or more metal centers. The x refers to the number of metal
centers being bridged by the ligand. Usually most authors omit x = 2 and just use
m to indicate that the ligand is bridging the simplest case of two metals.
mx
There are two different general classes of bridging ligands:
1) Single atom bridges
2) Two donor atoms separated by a bridging group (typically organic)
Ta2 (m-t-Bu-CC-t-Bu) (m-Cl)2Cl2(THF)2 Mo2(m-CH2P(Me)2CH2)4
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Ordering Inorganic/organometallic chemists generally do NOT use IUPAC naming rules.
There are some qualitative rules that most authors seem to use in American
Chemical Society (ACS) publications:
in formulas with Cp (cyclopentadienyl) ligands, the Cp usually comes first, followed by the metal center: Cp2TiCl2
other anionic multi-electron donating ligands are also often listed in front of the metal, e.g., trispyrazolylborate anion (Tp)
in formulas with hydride ligands, the hydride is sometimes listed first. Rules # 1 & 2, however, take precedence over this rule: HRh(CO)(PPh3)2 and
Cp2TiH2
bridging ligands are usually placed next to the metals in question, then followed by the other ligands (note that rules 1 & 2 take precedence):
Co2(m-CO)2(CO)6 , Rh2(m-Cl)2(CO)4 , Cp2Fe2(m-CO)2(CO)2
anionic ligands are often listed before neutral ligands: RhCl(PPh3)3, CpRuCl(=CHCO2Et)(PPh3) (neutral carbene ligand), PtIMe2(CCR)(bipy).
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Ordering Inorganic/organometallic chemists generally do NOT use IUPAC naming rules.
There are some qualitative rules that most authors seem to use in American
Chemical Society (ACS) publications:
in formulas with Cp (cyclopentadienyl) ligands, the Cp usually comes first, followed by the metal center: Cp2TiCl2
other anionic multi-electron donating ligands are also often listed in front of the metal, e.g., trispyrazolylborate anion (Tp)
in formulas with hydride ligands, the hydride is sometimes listed first. Rules # 1 & 2, however, take precedence over this rule: HRh(CO)(PPh3)2 and
Cp2TiH2
bridging ligands are usually placed next to the metals in question, then followed by the other ligands (note that rules 1 & 2 take precedence):
Co2(m-CO)2(CO)6 , Rh2(m-Cl)2(CO)4 , Cp2Fe2(m-CO)2(CO)2
anionic ligands are often listed before neutral ligands: RhCl(PPh3)3, CpRuCl(=CHCO2Et)(PPh3) (neutral carbene ligand), PtIMe2(CCR)(bipy).
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Problem: Sketch structures for the following:
a) CpRuCl(=CHCO2Et)(PPh3)
b) Co2(m-CO)2(CO)6 (Co-Co bond, several possible structures)
c) trans-HRh(CO)(PPh3)2 [Rh(+1) = d8]
d) Ir2(m-Cl)2(CO)4 [Ir(+1) = d8]
e) Cp2TiCl2
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Aturan 18 elektron
Mirip dengan aturan Oktet, analogi s2p6d10
Sering dilanggar
Berguna untuk penghitungan dan perkiraan reaktivitas
Terdapat dua cara: ionik dan kovalen
Yang harus diketahui : muatan formal, d electron count
Metode ionik: menghilangkan ligan daril ogam dan jika perlu menambah elektron ke tiap ligan adar terbentuk kulit valensi tertutup (closed valence shell).
Contoh jika kompleks memenuhi oktet, mengambil NH3 berarti mengambil NH3-
gugus metil sebagai 2 elektron donor., berhubung logam bermuatan positif maka
nantinya d-electron countnya harus dikurangi satu. Lihat contoh
Metode kovalen: menghilangkan seluruh ligan dalam bentuk netral. Misal amonia dihilangkan sebagai molekul netral dengan sepasang elektron bebas. Mana amonia
adalah 2 elektron donor netral. Jika ligannya NH3 maka yang diambil berbentuk NH3
radikal, sebagai satu donor elektron, kemana yang satunya pergi? Dihitung pada
logam, kedudukan logam dihitung sebagai d-electron terisi penuh, misal Fe selalu 8.
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ATURAN 18 ELEKTRON, WHY?
Contoh Cr(CO)6. interaksi d orbital Cr Ligan CO merupakan ligan s-
donor (HOMO) dan -akseptor (LUMO)
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Penambahan 1 elektron akan memberikan populasi pada orbital eg-antibonding-destabilisasi
Pengurangan 1 el akan mengurangi t2g (bonding karena pengaruh CO sebagai - akseptor )-destabilisasi, maka 18e paling stabil
Sifat s-donor CO meninggikan energi eg
Sifat - akseptor CO menurunkan t2g
Selain s-donor - akseptor bisa jadi tidak mematuhi aturan 18 elektron
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Perkecualian untuk Zn(en)32+ (spesies dgn 22 elektron)
* orbital t2g dan eg terisi.
* en merupakan s-donor yg tdk sekuat ligan CO maka elektron
pada orbital eg tidak cukup antibonding, dan bisa ditempati dengan
stabil dengan penambahan 4 elektron
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TiF62- (Spesies dengan 12 elektron)
Ligan F- merupakan ligan dengan -donor sebaik s-donor.
-donor pada F- mendestabilisasi orbital t2g sehingga agak antibonding
Spesie TiF62- mempunyai 12 elektron pada orbital s bonding dan tidak ada
elektron pada orbital antibonding t2g dan eg
Konfigurasi 18 elektron kompleks stabil dengan ligan -akseptor yang kuat .
Termasuk utk geometri trigonal bipyramida (Fe(CO)5) dan geometri
tetragonal (Ni(CO)4).
Untuk geometri square planar, konfigurasi yg stabil adalah 16 elektron.
Khususnya utk kompleks logam d8
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Kompleks dengan aturan 16 e
Biasanya unsur blok d diseb. kanan khususnya group 9 dan 10
Tabel senyawaan organologam dgn aturan 16 dan 18
Biasanya < 18 e Biasanya 18 e 16 atau 18 e
Sc
Y
La
Ti
Zr
Hf
V
Nb
Ta
Cr
Mo
W
Mn
Tc
Re
Fe
Ru
Os
Co
Rh
Ir
Ni
Pd
Pt
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PERHITUNGAN ELEKTRON DLM KOMPLEKS
Cr(CO)6
Fe(CO)4PPh3
Cr
6 CO
Total
Fe
4CO
PPh3
Total
6 e
12 e
18 e
8 e
8 e
2 e
18 e
36
-
.
Ni(PF3)4
[Mn(CO)5]-
[Co(CO)4]-
Mn2(CO)10
Ni
4 PF3
Total
Mn
5 CO
Muatan
Total
Co
4 CO
Muatan
2 Mn
10 CO
Mn Mn
Total
10 e
8 e
18 e
7 e
10 e
1 e
18 e
9 e
8 e
1 e
14 e
20 e
2 e
36 e
Co2(CO)8
[PtCl4]2-
HMn(CO)5
2 Co
8 CO
Co Co
Total
Pt
4 Cl
Muatan
Total
Mn
5 CO
H
Total
18 e
16 e
2 e
36 e
10 e
4 e
2 e
16 e
7 e
10 e
1 e
18 e
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-
.
38
-
.
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Tentukan electron counts dengan kedua metode untuk
a. [Fe(CO)42-
b. [(5-C5H5)2Co]+
c. (3-C5H5)(5-C5H-5-)Fe(CO)
d. Co2(CO)8 (satu ikatan bridging Co-Co)
e. IrCl(CO)(PPh3)2
dengan membandingkan beda hasil kedua metode perhitungan
electron tentukan logam transisi deret pertama untuk kompleks 18
elektron (kecuali e. 16 elektron)berikut
a. [M(CO)3PPh3]-
b. HM(CO)5
c. (4-C8H8)M(CO)3
d. [(5-C5H5)2(Co)3]2
e. [M(CN)4]2-
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Aturan 18 Elektron
Q : Ngapain repot-repot ngitung elektron?
A : Dasar untuk mempelajari struktur dan reaktivitas reaksi organologam.
Tidak beda jauh dari struktur Lewis.
Maka,perhitungan seharusnya otomatis, perhitungan seharusnya bukan dengan menghapal ligan tapi memahami karakteristik sharing elektron dalam kompleks
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Perkiraan Reaktivitas
(C2H4)2PdCl2 (C2H4)(CO)PdCl2
(C2H4)PdCl2
(C2H4)2(CO)PdCl2
?
CO- C2H4
- C2H4CO
dissociative
associative
Most likely associative:
16-e PdII
18-e PdII
16-e PdII
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Cr(CO)6 Cr(CO)5(MeCN)
Cr(CO)5
Cr(CO)6(MeCN)
?
MeCN- CO
- COMeCN
dissociative
associative
Perkiraan Reaktivitas
Almost certainly dissociative:
18-e Cr(0)
16-e Cr(0)
18-e Cr(0)
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Electron counting Q : Terus kalo saya ngitung elektron hasilnya 16
atau 14 artinya apa?
A : Struktur dengan elektron count dibawah ideal disebut kekurangan elektron (electron-deficient )atau tidak jenuh (coordinatively unsaturated).
Mempunyai valence orbitals(orbital kosong) .
Membuatnya bersifat elektrofilik, bisa diserang nukleofilik.
Bisa sangat reaktif, menyerang hidrokarbon atau mengikat gas mulia
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Reactivity of electron-deficient compounds
Fe(CO)5h
- COFe(CO)4
THF Fe(CO)4(THF)
18-e Fe(0)
unreactive
16-e Fe(0)
very reactive 18-e Fe(0)
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Q : Trus kalo electron counting ketemunya lebih dari 18, terlalu banyak maksudnya apa?
A : Jumlah net kovalen bonds kecil valenceorbital tidak cukup tersedia untuk elektron ini
An ionic model is required to explain part of the bonding.
Ikatan bersifat lemah Relatif jarang untuk logam transisi, biasanyaterjadi
karena reduksi (= penambahan elektron).
Elektron bisa berada pada L-M bonding orbitals atau pada metal-centered lone pairs.
Metal-centered orbitals punya energi tinggi atom metal dengan suatu lone pair adalah s-donor
(nucleophile).
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Belajar mengenal muatan dan donor untuk ligan umum
Cationic 2e- donor: NO+ (nitrosil)
Neutral 2e- donors: PR3 (phosphines), CO (carbonyl), R2C=CR2 (alkenes), RCCR (alkynes, can also donate 4 e-), NCR (nitriles)
Anionic 2e- donors: Cl- (chloride), Br- (bromide), I- (iodide), CH3
- (methyl), CR3- (alkyl), Ph- (phenyl), H-
(hydride) bisa donor 4 e- tapi untuk perhitungan awal hitung sebagai2e- donors (kecuali jadi bridging ligands): OR- (alkoxide), SR- (thiolate), NR2
- (inorganic amide), PR2-
(phosphide)
Anionic 4e- donors: C3H5- (allyl), O2
- (oxide), S2- (sulfide), NR2
- (imido), CR2
2- (alkylidene) and from the previous list: OR- (alkoxide), SR- (thiolate), NR2
- (inorganic amide), PR2-
Anionic 6e- donors: Cp- (cyclopentadienyl), N3- (nitride)
Cara Mempercepat Electron Counting
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Ligands, Charges, and Donor #s
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Ligands, Charges, and Donor #s
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Lewis Base Ligands -- Halides
X
XX X
F , , , Cl Br I
Increasing polarizability
Primary Halides
Strongest nucleophilefor low oxidation statemetals centers
MM
M
MM
M
2e- terminal 4e- -bridgingm 6e- -bridgingm3
Common Misconception: The halides are anionic ligands, so they are NOT
electron-withdrawing ligands. In organic chemistry the halogens can be
considered neutral ligands and do drain electron density from whatever they are
attached to. But here they are anionic and are perfectly happy with that charge.
Their electronegativity makes the halides poor donor ligands. As one moves from F- to I-, the donor ability increases as the electro-negativity drops.
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