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JIM JOSEPHUS GABRILLO MINGLAN
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Ruthenlum and Osmium Complexes Having the Bis (sily) Chelate Li*'*.'and
Xantsil [(9.9-Dimethylxanthene-4.5-diyl) bis (dimethylsilyl)] : Synthesis.
Structure. Reactivity, and Catalysis
( 7. ( l) ; )
- h
4.5-)4) ) k 7. ()
flL'= fXantsil [(9.9--))
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7JL, .{ 1"f c )/'_-" :, + ,
D l*;C ; J J; t ;
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0 ' ./ , f' j)
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Introduction
Chapter -
Ruthenium and Osmium Carbonyl Complexes Containing Xantsil
Chapter 3
Reactivity of Ru(xantsil)(CO)(11*'-C*,H CH3) with Arenes, a Diene,
;
Chapter l
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and Some 2-Electron Donors
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Chapter 4
Reactivity of Ru(xantsil)(CO)( "-C* H5CH3) with Organosilanes:
Synthesis, Structure, anci Reactivity of Bis(silylene) Ruthenium
{f
Complexes Containing Xantsil
;
Chapter 5
Summary
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Abstract
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In this work, I investigated the synthesis, structure, reactlvity and application to catalysis of several rutheniun
1 and
;
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osmium complexes supported by the bis(silyl) chelate igand xantsil [(9,9-dimethylxanthene-4,5-
;
diy'l)bis(dimethylsilyl)]. Usual metal-silicon bonds in transition metal complexes are known to be highl}' re< ctive.
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i
and thus are easily removed from the metal. The chelate li_"*and xantsil is expected to prevent this elimination. Silyl
;
;
llgands are chosen because they are known to be exceptionally strong (r -donors and have a high trans effect. which
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can affect the properties of the metal center. Furthermore, silyl ligands are expected to stabilize highly reactive,
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- 269 -
L
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;
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coordinatively unsaturated metai centers, which can be catalys'ts for various transition metal-catalyzed reactions.
;
This paper discusses how these properties of xantsil affect the structure and how they enhance the reactivity and
catalytic performance of the complexes.
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In Chapter 2, the synthesis of several ruthenium and osmium mononuclear and trinuclear carbonyl complexes
supported by xantsil and the effect of xantsil on the structure and reactivity of the complexes are described.
Oxidative addition of xantsil-H! (1) or 2,7-di-t-butylxantsil-H2 (2) with M=i(CO)i2 (M = Ru, 90 min; Os, 2 days) in
refluxing toluene produced the mononuclear carbonyl complexes M(xantsil)(CO)* (3: M = Ru, 4: M = Os) and
Ru(2,f -di-t-butylxantsil)(CO)* (3-'Bu) (.eq. 2.1). The crystal structures show that the molecules of 3 and 4 both have
a distorted octahedral _"*eometry due to electronic effects caused by the (1 -donating xantsiL Unusually iong M-Si
bonds were also observed and these are caused by steric repulsion amon_"* the silyl methyl _ *roups and the equatorial
CO Iigands as induced by the chelate xantsrl.
Trinuclear carbonyl complexes M3(xantsil)( ,u -H)2(CO)1*, (5: M = Ru, 6: M = Os) were obtained from the reactions
of I with M3(CO)1,,(MeCN) (M = Ru, Os) (eq. 2.2). The crystal structure of 5 clearly shows that xantsil serves as a
bridging ligand to one Ru-Ru bond and probably helps prevent the fragmentation of the Ru3 core.
Heating 3 in toluene for 3 h led to the formation of the arene complex Ru(xantsil)(CO)( -C,jH5CH=j) (7).
The replacement of three CO Iigands for a toluene molecule is thought be induced by the xantsil ligand which is
capable of stabilizin*** intermediates by dative bonding of the xanthene oxygen atom to ruthenium (Scheme 2.1).
In Chapter 3, the reactivity of 7 toward arenes, a butadiene, and two electron donors such as PMe: and CN 3u
was investigated. By these experiments, it was prove-d that 7 is a source of highly reactive, coordinatively
unsaturated species "Ru(xantsil)(CO)" (Scheme 3.1). In the presence ofexcess benzene andp-xylene, the toluene
ligand was exchanged for the arenes to give, in quantitative yields, Ru(xantsil)(CO)( G-arene) (8: arene = benzene,
9: arene = p-xylene) within 1-3 h at room temperature. With excess 2,3-dimethyl-1,3-butadiene,
Ru(xantsil)(CO)( *-2,3-dimethyl-1,3-butadiene) (10) was obtained after heating at 65 ] for 3 hours. In 10, xantsil
serves as a terde-ntate ligand. With excess PMe3 or CN 3u, complexes Ru(xantsil)(CO)(L): (1 1 : L = PMe3, 12: L =
CN'Bu) were obtained. In the absence of electron donors, 7 formed the dimer [Ru( *-xantsil)(CO)]2 (13) in ndecane at 140 ]..
In Chapie 4, complex 7 was shown to catalyze the oligomerization/deoligomerization reaction of HSiMe!SiMe
to give H(SiMe2),,Me (rt = 1-5 at r.t., n = 1-8 at 90 O in two days (eq. 4.1). So far there has been no report yet of a
Ru complex which catalyzes this reaction. A plausible mechanism involves silyl(silylene) complexes as key
intermediates (Scheme 4.1), . Bis(silylene) complexes Ru(xantsil)(CO)(H){ SiMe "'(OR)" 'SiMe! } (1 4: R = Me, 1 5:
R = 'Bu), , the stabillzed form of the silyl(.silylene) complexes, were obtained by the stoichiometric reaction of 7 with
HSiMe*SiMe20R (R = Me, 'Bu) (eq. 4.2). The crystal structure of 1 5 confirrned the presence of a dative bond from
xanthene oxy_ en to the metal. With excess ROH (R = Me. Et) in CH2C12, 15 was converted to
Ru(xantsil)(CO)(H){SiMe2"'(OR)"'SiMe } ( 4: R = Me, 16: R = Et) immediately and quantitatively at room
temperature (eq. 4.3). Compound 14 was converted to 1 6 within 30 minutes by the reaction of excess EtOH but did
not react with 'BuOH (Scheme 4.2). Most of the previously reported transition metal bis(sily]ene) complexes
ML,{ SiMe="'(OR)"'SiMe= } react with alcohols via addition of R'OH to the- Ru=Si bond to forrn hydrido(bis(silyl)
complexes ML.(H)(SiMe,OR')(SiMe,OR). In the case of the Ru(xantsil)(CO)(H){SiMe="'(OR)"'SiMe,}
complexes, formation of Ru(xantsil)(CO)(H){SiMe="'(OR')"'SiMe=} together with the elimination of ROH is
preferred over that of the formal Ru(VI) complex Ru(xantsil)(CO)(H)(H)(SiMe=0R')(SiMe=0R). In CH=Cl=, 14 and
5 slowly chan_ *ed to the dimer 13 together with unidentified silicon-containing byproducts within 3-5 days (eq.
- 270 -
; .
lrt'
4.4). In toluene-d or benzene-dti, the reaction of 4 with excess MeOH Ied to the formation of Ru(xantsil)(CO)( tiarene-d) (7-d : arene-d = toluene-d . 8-d, : arene-d = benzene-di;) at room temperature within 1-3 h, with
Me2Si(OMe)2 and H2 as byproducts (eq. 4.5). These reactions show that the bis(silyiene) complexes are hi_O_hly
electrophilic and are easily attacked by nucleophiles resulting into the elimination of the silylene moieties.
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論文審査の結果の要旨
重き } き 多
この論文は,新しいビス(シリル)キレート配位子であるxantsi1[(9,9一ジメチルキサンテンー4、5一ジイル)
ビス(ジメチルシリル)]を含む単核および三核ルテニウムおよびオスミウム錯体の合成,構造,反応性お
よび触媒作用について,著者が行った研究を記述したものである。本研究の主な成果を次に列記する。
(!)配位子'前駆体xantsil-H2とM,、(CO)i2(M=Ru,Os)とをトルエンに溶かし,還流することにより,xantsil
をキレート配位子として含む単核錯体M(xan童s11)(CO),を主生成物として得た。xantsi1のケイ素上のメチル
基とエクア1・リアル位のカルボニル配位子との立体反発のために,金属一ケイ素結合(Ru-Si:2.563(av〉A,
Os-Si:2、579(av)A)はいずれも既知のものの中で最長であった。またxants11-H,と外れ易いアセトニトリル
配位子を持つ触、(CO)1、、(CH、￡N)2(M=Ru,Os)との室温以下での反応により,xantsllが2つのR11原子に架橋
配位した三枝錯体RU3(xants11〉(H)2(CO)1[、が高収率で得られた。
(2)■11述の単核ルテニウム錯体Ru(xants11)(CO)1は,トルエン中でさらに還流することにより3つのCO配
位子が1つのトルエン配位子で置換された錯体Ru(xantsll)(CO)(116-toluene)に定量的に変換された。さらに
この錯体は他の様々なアレーンやジエン,PMe,1,CNIBu等と室温.で容易に反応し,トルエン配位予がこれ
らの配位子で置換された錯体をほぼ定量的に与えた。この結果は,Ru(xantsil)(CO)(ηli-toluene)は配位不飽
和活性種Ru(xantsi1)(CO)の優れた前駆体となることを示唆している。
(3)実際にRu(xantsll)(CO)(η6-toluene)はヒドロジシランHSiMe,SiMe二,の重合/解重合反応を室温で起こす
優れた触媒となることがわかった。またこの反応はシリル(シリレン)錯体を中間体として進行してい
ることが,上記単核錯体とHSIMe,SiMe20R(R=OBu、OMe)との反応でビス(シリレン)錯体
Ru(xantsil)(CO){SiMe2…0(R)…SiMejが定量的に生成することから明らかになった。興味深いことに,こ
の錯体中ではxantsi1配位子は酸素でも金属に配位し,三座配位子として働いていることが分った。これら
事
の研究は,シリル基を支持配位子とする遷移金属錯体の合成と触媒作用の化学を新しく開拓したものと
して,極めて高く評価できる。
本論文は著者が自立して研究活動を行うに必要な高度の研究能力と学識を有していることを示してい
る。したがって,JimJosephusGabrilloMinglana提出の論文は,博」■f(理学)の学位論文として合格と認
める。
一276一
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