Tris(trimethylsilyl)silyl substituted alkali- and transition metal guaiazulenides [Elektronische Ressource] / by Yun Xiong

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1 Tris(trimethylsilyl)silyl Substituted Alkali- and Transition Metal Guaiazulenides Dissertation Submitted in Partial Fulfilment of the Requirements for the Degree of Doctor of Natural Science -Dr.rer.nat.- In the Institute of Inorganic and Analytical Chemistry Department of Chemistry and Pharmacy at Johannes Gutenberg - University of Mainz by Yun Xiong from P. R. China Mainz 2004 I1 INTRODUCTION ........................................................................................................................................ 1 1.1 ALKALI METAL HYPERSILANIDES............................................................................................................... 1 1.2 COORDINATION CHEMISTRY OF AZULENE SYSTEM ...................................................................................... 4 2 RESEARCH PROCESS.............. 14 2.1 THEORETICAL ANALYSIS........................................................................................................................... 14 2.2 MONO-HYP SUBSTITUTED ALKALIMETAL GUAIAZULENIDES...................................................................... 17 2.2.1 Addition ......................................................................................................................................... 17 2.2.1.1 Addition of Lithium Hypersilanide to Guaiazulene...........................................................................

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1

Tris(trimethylsilyl)silyl Substituted Alkali-
and Transition Metal Guaiazulenides



Dissertation

Submitted in Partial Fulfilment of the Requirements for the Degree of
Doctor of Natural Science
-Dr.rer.nat.-

In the Institute of Inorganic and Analytical Chemistry

Department of Chemistry and Pharmacy

at

Johannes Gutenberg - University of Mainz


by

Yun Xiong

from P. R. China





Mainz 2004



I
1 INTRODUCTION ........................................................................................................................................ 1
1.1 ALKALI METAL HYPERSILANIDES............................................................................................................... 1
1.2 COORDINATION CHEMISTRY OF AZULENE SYSTEM ...................................................................................... 4
2 RESEARCH PROCESS.............. 14
2.1 THEORETICAL ANALYSIS........................................................................................................................... 14
2.2 MONO-HYP SUBSTITUTED ALKALIMETAL GUAIAZULENIDES...................................................................... 17
2.2.1 Addition ......................................................................................................................................... 17
2.2.1.1 Addition of Lithium Hypersilanide to Guaiazulene....................................................................................17
2.2.1.2 Addition of Potassium Hypersilanide to Guaiazulene................................................................................17
2.2.1.3 Addition of Cesium Hypersilanide to Guaiazulene19
2.2.2 NMR Spectroscopy......... 21
12.2.2.1 H NMR Spectroscopy...............................................................................................................................21
132.2.2.2 C NMR Spectroscopy26
292.2.2.3 Si NMR Spectroscopy..............................................................................................................................27
72.2.2.4 Li NMR Spectroscopy28
2.2.3 Molecular Structures of Compounds 1 and 2a .............................................................................. 29
2.2.3.1 Molecular Structure of [Li(6-Hyp-Hgual)] (1) .........................................................................................29 2
2.2.3.2 Molecular Structure of (thf) ⋅ K(6-Hyp-Hgual) (2a)..................................................................................33 4
2.3 MONO-HYP SUBSTITUTED METALLOCENE DERIVATIVES .......................................................................... 35
2.3.1 Reactions ...................................................................................................................................... 35
2.3.1.1 Metathesis of M(6-Hyp-Hgual) (M=Li, K) with MnBr , FeCl .................................................................35 2 2
2.3.1.2 Metathesis of K(8-Hyp-Hgual) with FeCl ................................................................................................37 2
2.3.1.3 Reaction of K(6-Hyp-Hgual) with NiCl or other Metal Halides..............................................................37 2
2.3.2 NMR Spectroscopy ....................................................................................................................... 39
2.3.2.1 NMR Spectra of Fe(6-Hyp-Hgual) (6) and Fe(8-Hyp-Hgual) (7) ...........................................................39 2 2
12.3.2.1.1 H NMR Spectroscopy.........................................................................................................................40
132.3.2.1.2 C NMctroscopy...........42
292.3.2.1.3 Si NMR Spectroscopy............................................................................................................43
2.3.2.2 NMR Spectroscopy of (3-Hyp-6-Hgua) (9)...............................................................................................43 2
12.3.2.2.1 H NMR Spectroscopy............43
132.3.2.2.2 C NMctroscopy...........46
292.3.2.2.3 Si NMR Spectroscopy...........47
2.3.3 Molecular Structures of Compounds 5, 6, 7, 8, and 9 .................................................................. 47
2.3.3.1 Molecular Structures of (RR)- and (SS)-M(6-Hyp-Hgual) (M=Mn 5, Fe 6, and Ni 8) ..........................47 2
2.3.3.2 Molecular Structure of Fe(8-Hyp-Hgual) (7)............................................................................................55 2
2.3.3.3 Conformation Analysis of (R,S)-Fe(6-Hyp-Hgual) (6) and (R,S)-Fe(8-Hyp-Hgual) (7)59 2 2
2.3.3.4 Molecular Structure of (3-Hyp-6-Hgual) (9)60 2
2.4 MONO-HYP SUBSTITUTED METALLOCENE DICHLORIDE DERIVATIVES...................................................... 62
2.4.1 Reactions ....................................................................................................................................... 62
2.4.1.1 Reaction of TiCl with K(6-Hyp-Hgual)(2) ................................................................................................62 3
2.4.1.2 Reactions of MCl (M=Zr(IV), Hf(IV)) with K(6-Hyp-Hgual) (2)..............................................................63 4
2.4.1.3 Reaction of ZrCp*Cl with K(6-Hyp-Hgual).............................................................................................64 3
2.4.2 NMR Spectroscopy ........................................................................................................................ 64
12.4.2.1 H NMR Spectroscopy...............................................................................................................................64
132.4.2.2 C NMR Spectroscopy67
292.4.2.3 Si NMR Spectroscopy..............................................................................................................................67
2.4.3 Molecular Structures of 10, 11 and 12 ..........................................................................................68
2.5 BIS-HYP SUBSTITUTED LITHIUM GUAIAZULENIDE .................................................................................... 73
2.5.1 Bis-Hyp Substituted Guaiazulene ................................................................................................. 73
2.5.1.1 Reaction......................73
2.5.1.2 NMR Spectroscopy......74
12.5.1.2.1 H NMR Spectroscopy ........................................................................................................................74
132.5.1.2.2 C NMR Spectroscopy77
292.5.1.2.3 Si NMR Spectroscopy.......................................................................................................................77
2.5.1.3 Molecular structure of 2,6-bis(Hyp)-H gua (14) .......................................................................................78 2
2.5.2 Bis-Hyp Substituted Lithium Guaiazulenide.................................................................................. 79
2.5.2.1 Reaction .....................................................................................................................................................79
2.5.2.2 NMR Spectroscopy......81
12.5.2.2.1 H NMR Spectroscopy...........81
132.5.2.2.2 C NMR Spectroscopy81
292.5.2.2.3 Si NMR Spectroscopy...........82
72.4.2.2.4 Li NMR Spectroscopy............83
2.5.2.3 Molecular Structure of [Li(2,6-bis(Hyp)-Hgual)] (15).............................................................................83 2
II
3 EXPERIMENT SECTION ........................................................................................................................ 87
3.1 GENERAL COMMENTS ............................................................................................................................. 87
3.2 CHARACTERIZATION................................................................................................................................87
3.2.1 Element Analysis............................................................................................................................ 87
3.2.2 Melting Point................................................................................................................................. 87
3.2.3 NMR-Spectroscopy......... 87
3.2.4 X-ray diffraction analysis .............................................................................................................. 88
3.3 SYNTHESIS AND CHARACTERIZATION........................................................................................................ 88
3.3.1 Syntheses of Reactants................................................................................................................... 88
3.3.1.1 Synthesis of Si(SiMe )88 3 4
3.3.1.2 Synthesis of KSi(SiMe ) ............................................................................................................................89 3 3
3.3.1.3 Synthesis of LiSi(SiMe )90 3 3
3.3.1.4 Synthesis of CsSi(SiMe ) ...........................................................................................................................91 3 3
3.3.2 Syntheses and Characterization of New Compounds .................................................................... 91
3.3.2.1 [Li(6-Hyp-Hgual)] (1) ..............................................................................................................................91 2
3.3.2.2 K(6-Hyp-Hgual) (2) and K(8-Hyp-Hgual) (3) ...........................................................................................93
3.3.2.3 Cs(6-Hyp-Hgual) (4)..................................................................................................................................95
3.3.2.4 Mn(6-Hyp-Hgual) (5)96 2
3.3.2.5 Fe(6-Hyp-Hgual) (6).97 2
3.3.2.6 Fe(8-Hyp-Hgual) (7)..99 2
3.3.2.7 Ni(6-Hyp-Hgual) (8)100 2
3.3.2.8 (3-Hyp-6-Hgua) (9).100 2
3.3.2.9 Ti(6-Hyp-Hgual) Cl (10).........................................................................................................................102 2 2
3.3.2.10 Zr(6-Hyp-Hgual) Cl (11)....................................................................................................................103 2 2
3.3.2.11 Hf(6-Hyp-Hgual) Cl (12)104 2 2
*3.3.2.12 ZrCp (6-Hyp-Hgual)Cl ⋅KCl (13).......................................................................................................105 2
3.3.2.13 2,6-bis(Hyp)-H gua (14)......................................................................................................................106 2
3.3.2.14 [Li(2,6-bis(Hyp)-Hgual)] (15)............................................................................................................107 2
4 SUMMARY............................................................................................................................................... 110
5 APPENDIX......................... 125
5.1 CRYSTALLOGRAPHIC DATA FOR LI(6-HYP-HGUAL) ................................................................................. 125
5.2 CRYSTALLOGRAPHIC DATA FOR (THF) ⋅[K(6-HYP-HGUAL)].................................................................... 127 4
5.3 CRYSTALLOGRAPHIC DATA FOR 2,6-BIS(HYP)-H GUA ............................................................................. 130 2
5.4 CRYSTALLOGRAPHIC DATA FOR LI(2,6-BIS(HYP)-HGUAL)....................................................................... 132
5.5 CRYSTALLOGRAPHIC DATA FOR MN(6-HYP-HGUAL) .............................................................................. 136 2
5.6 CRYSTALLOGRAPHIC DATA FOR FE(6-HYP-HGUAL) ............................................................................... 140 2
5.7 CRYSTALLOGRAPHIC DATA FOR FE(8-HYP-HGUAL) 143 2
5.8 CRYSTALLOGRAPHIC DATA FOR NI(6-HYPHGUAL) 149 2
5.9 CRYSTALLOGRAPHIC DATA FOR (3-HYP-6-H GUA) ................................................................................ 152 2 2
5.10 CRYSTALLOGRAPHIC DATA FOR TI(6-HYP-HGUAL) CL ......................................................................... 154 2 2
5.11 CRYSTALLOGRAPHIC DATA FOR ZR(6-HYP-HGUAL) CL ........................................................................ 158 2 2
5.12 CRYSTALLOGRAPHIC DATA FOR HF(6-HYP-HGUAL) CL 162 2 2
6 LIST OF ABBREVIATIONS................................................................................................................... 166
7 NUMBERING LIST OF THE NEW COMPLEXES ............................................................................. 167
8 LITERATURE........................................................................................................................................... 168












1


1 Introduction

1.1 Alkali Metal Hypersilanides

Bulky silyl groups, such as tris(tertiary-butyl)silyl, triphenylsilyl, and tris(trimethylsilyl)silyl,
due to their good electron releasing properties and large steric demand, can be employed as
protection groups in the synthesis of organic compounds to build regio- and stereo-selective
1, 2, 3collection of C-C bonds under mild reaction conditions . They can also stabilize some
reactive intermediated state and/or metal centre in unusual oxidation state, which established
4, 5, 6their important positions in the organometallic synthesis of low valent main group- and
7transition metal complexes.


SiMeCMe 33
SiSiSi SiMeCMe 33
SiMeCMe 33
Tris(tertiary-butyl)silyl Triphenylsilyl Tris(trimethylsilyl)silyl

Fig. 1 Several bulky silyl groups


Tris(trimethylsilyl)silyl group, -Si(SiMe ) , which is named also as hypersilyl, and in the 3 3
8following will be abbreviated as “Hyp” , has some advantages as an overloaded reactive
substituent. The possibility of cleavage of the Si-Si bonds leads abundant further reactions,
9 10e.g. for the synthesis of polysilane , silyene (Me Si) Si=CR(OSiMe ) etc.. Recently the 3 2 3
development of the combination of metallocene units with the architectural diversity of
11dendrimers makes the hypersilyl chemistry have more fascinating prospect . The
introduction of hypersilyl group to metallocene units should offer possibility to furnish new
12 materials with interesting physical and chemical properties .

Traditionally, lithiumsilanides are easy to synthesize, simply to purify and trouble free to
manipulate when compare with their heavier alkali metal homologues. Therefore,
lithiumsilanides are the most widely used reagents in the organometallic chemistry for
synthesis of transition metal silyl compounds, for the generation of silenes, and for a number
1, 13, 14of other purposes . The synthesis and crystal structure of lithium silanides have been
extensively studied. Early in 1960´s Gilman and Smith have designed and synthesized some
15, 16, 17bulky silyl compounds . From tetrakis(trimethylsilyl)silane they obtained firstly in situ
18lithium hypersilanide .


2

Eq. 1
THF
Si(SiMe ) + MeLi LiSi(SiMe ) + SiMe3 4 3 3 4



19 20, 21Later it was isolated as DME and THF solvated complexes.


MeO OMe
Li
(Me Si) Si OMe3 3
Si(SiMe )3 3MeO
Li
MeO OMe



SiMe3O
O Li Si SiMe3
O SiMe3


Fig. 2 Solvated LiSi(SiMe )3 3


The first synthesis of base-free lithium hypersilanide was investigated by Klinkhammer with
22transmetallation between mercury-dihypersilanide and elemental lithium in n-pentane .



SiMe3LiMe Si
3
SiMeSi 3SiMe Si3
SiMe3LiMe Si3

Fig. 3 Dimeric structure of base-free LiSi(SiMe )3 3


The possibility to produce this reagent in high outputs through conversion of
23chlorohypersilane ClHyp with lithium powder in toluene was recognized by Weidlein .




3
Eq. 2

toluene
ClSi(SiMe ) + 2 Li LiSi(SiMe ) + LiCl3 3 3 3


Lithium hypersilanide, although so widely accepted, for about three decades has rarely been
the subject of variation. In 1990´s K. W. Klinkhammer has systematically investigated the
syntheses and structures of base-free alkali metal hypersilanides MSi(SiMe ) (M=Li, Na, K, 3 3
24Rb, Cs) . Through transmetallation of the dihypersilyl derivatives of the zinc group with
alkali metals he obtained firstly the heavy homologues of lithium hypersilanide. All of them
possess dimeric structure as shown for LiHyp in Fig. 3.

Eq. 3

EHyp + 2M 2MHyp + E (E=Zn, Cd, Hg)2
(M=Li, Na, K, Rb, Cs)


In 1998 Marschner reported a new pathway of synthesis of potassium hypersilanide from
25tetrakis(trimethylsilyl)silane . Analogue to Gilman´s method for synthesis of lithium
thypersilanide, Marschner used KO Bu instead of MeLi in the metallation reaction.

Eq. 4
THF
t tSi(SiMe ) + KO Bu KSi(SiMe ) + Me SiO Bu3 4 3 3 3


Potassium hypersilanide can be crystallized from the reaction mixture as THF solvate, but on
prolonged heating in dynamic vacuum it can be even obtained in solvent-free form. Therefore,
the Maschner-route gives a less hazardous access to solvent-free potassium hypersilanide than
the mentioned trans-metallation route with the hypersilyl derivatives of the zinc group, where
poisonous starting materials and side-products occur.

The Marschner-route is also suitable for syntheses of RbHyp and CsHyp, where the reagent
t t tKOBu in Eq. 4 is replaced with RbOBu and CsOBu, respectively. Perhaps owing to the
hazards and costs of Rb and Cs, rubidium- and cesiumhypersilanides have not been
extensively used in synthesis. Similar to LiHyp, NaHyp can not be obtained with Marschner-
route. Owing to its relatively difficult synthesis the research and application of sodium-
hypersilanide is also still deficient.

The heavier alkali metal hypersilanide showed in our research group some advantages. The
26application of potassium hypersilanide for the synthesis of CuHyp is a typical instance .

Nowadays, the reactivity of hypersilyl compounds of the group 1 elements, especially lithium
27, 28, 29, 30, 31, hypersilanide, with compounds of the p, d and f block metals or metalloid halides
32, 33, 34, 35, 36 37, 38, 39 40, 41, 42, 43 , with organometallic compounds , and with organic halides keep
increasing research interest. However, the research of their reactivity with unsaturated system
has been reported rarely. Only some much smaller silylmetallic reagents such as lithium-
44 45trimethylsilanide LiSiMe or lithiumdimethylphenylsilylanide LiSiMe Ph etc. are by far 3 2
4
the most investigated in the reactions with organic unsaturated systems. The research on the
related α,β-unsaturated ketones showed that the smallest lithium silanide reagent LiSiH in 3
46,47, 48general attack via 1,2-addition , whereas lithium trimethylsilanide LiSiMe as well as 3
49, 50, 51, 52, 53, 54silylcuprates and silylzincates attack via 1,4-addition .


1.2 Coordination Chemistry of Azulene System

Azulene and its derivatives, such as guaiazulene (7-isopropyl-1,4-dimethyl-azulen), and
chamazulene (7-ethyl-1,4-dimethyl-azulene) etc., are stable cyclic-π-conjugated hydrocarbons.
With the conjugated π-electrons they undergo easy electrophilic and nucleophilic reactions.



R R´
8
1 79
2 6
10
3 54
R
R, R´=H, azulen; R=Me, R´=iPr, guaiazulene, R=Me, R´=Et, chamazulene

Fig. 4 Azulene system


55, 56, 57, 58, 59 Theoretical calculation of the electron density in azulene revealed that the carbon
atoms C1/C3 possess the highest electron density, followed by C9/C10, C5/C7 and C2.


0.914 1.014
1.079 8 79
1 1.018 6 0.9341.003 2
10
53 4

Fig. 5 Theoretically calculated electron density in azulene


Electrophiles therefore attack preferably at C1/C3, and most electrophilic substitutions take
60, 61, 62place in these two positions . If C1/C3 are blocked by other substituents, the position
C5/C7 will become the alternative places to be attacked. In some cases, owing to the steric
demand of the introducing substituents, C2 is preferably attacked instead of C1/C3. In
nucleophilic reactions, C4/C8 and C6 possessing smaller electron density will be attacked
preferably.

Some of the known reactions, moreover, lead to derivatives of the stable ionic aromatic
systems cyclopentadienide and tropylium, respectively. Already in azulene itself the seven-
5
membered ring has a tendency to give one of its π-electrons to the five-membered ring, so that
each of the two rings has just 6 π-electrons and fulfil the Hueckel rule. Thus, in azulene a
significant dipole moment exists between the five-membered ring and the seven-membered
ring, and the five-membered ring is at the negative end of the dipole. The observed dipole
63 64moment in azulene is 0.95D , which is close to the calculated value of 1.23D .





Fig. 6 Polarity properties in azulene


Like electron-rich aromatic compounds, azulene systems undergo electrophilic halogenation,
nitration, sulfonation and acylation.

Both of the pseudo-Cp section in the five-membered ring and the pseudo-tropylium section in
the seven-membered ring in azulene form easy π-complexes with metal ions. Azulene- or
guaiazulene-metal π-complexes have been obtained via ligand substitution, red-ox reaction of
azulene or guaiazulene with metal halides or activated metals, as well as nucleophilic addition.


65Via ligand substitution Behrens obtained (azulene)-(benzene)Mo (Eq. 5) and (azulene)-
(benzene)Mo-M(CO) (M=Cr, Mo and W) (Eq. 6). 3

Eq. 5

MoMo
o95 C, 5 d, toluene
(azulen)-(benzene)-Mo

Eq. 6

[(CH CN) M(CO) ]3 3 3
Mo MMo COreflux, 5h, THF
OC CO
M=Cr, Mo, W


6
In the complexes the metal atoms (M=Cr, Mo and W) are coordinated by azulene via either
6 4η - or η -mode, respectively, leading to a valence electron count on each metal atom of just
18. Azulene as ligand did not change its π-electron distribution between two rings.

However, it is found that in most complexes the π-electrons in the ligands azulene or
guaiazulene are polarized due to the coordination. Thus, the five-membered ring always tends
5to coordinate to metals as pseudo-Cp ligand in η -mode. For the seven-membered ring
different bonding modes are observed, depending on the conditions (Fig. 7).

The partly substitution of carbonyl by azulene or guaiazulene enriched the coordination
chemistry of azulene system. Through thermal reaction of azulene or guaiazulene with metal-
carbonyl compounds a series of mixed multinuclear azulene- or guaiazulene-metal-carbonyls
66, 67, 68, 69 of iron, ruthenium, molybdenum, and manganese were reported since 1958. The
70 71 71crystal structures of [C H Fe (CO) ] (I) , [C H Fe (CO) ] (II) , [C H Ru (CO) ] (III) , 10 8 2 5 15 18 2 5 15 18 2 5
72, 73 74 75, 76[C H Mo (CO) ] (IV) , [C H Mo (CO) ] (V) , [C H Mn (CO) ] (VI) , and 10 8 2 6 15 18 2 6 10 8 2 6
77[C H Mn (CO) (VII) were determined by X-ray diffraction analyses. 15 18 2 6



R
M(CO) R, R´=H, M=Fe, I2
R R=Me, R´=iPr,
M=Fe, II;M(CO)3 M=Ru, III

R
+ M (CO)x y
R
R reflux Mo(CO)3 R, R´=H, IV
R
R´ R=Me, R´=iPr, V
Mo(CO)3

Mn(CO)3
RR´
R, R´=H, VI
R=Me, R´=iPr, VII
(OC) Mn3 R
M (CO) =Fe(CO) , Ru (CO) , Mo(CO) , Mn (CO)x y 5 3 12 6 2 10


Fig. 7 Reactions of azulene or guaiazulene with metal-carbonyl


In all these compounds the five-membered ring coordinates to metals as a pentahapto ligand,
whereas the seven-membered ring coordinated to metal atoms either as trihapto or pentahapto
ligand. In each case, 18 valence electron complexes are obtained.

The coordination chemistry of azulene or guaiazulene with metal-carbonyl can be understood
as following: