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首页> 外文期刊>Organometallics >Isospecific styrene polymerization by chiral titanium complexes that contain a tetradentate [OSSO]-type bis(phenolato) ligand
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Isospecific styrene polymerization by chiral titanium complexes that contain a tetradentate [OSSO]-type bis(phenolato) ligand

机译：通过包含四齿[OSSO]型双（酚基）配体的手性钛配合物进行的异规苯乙烯聚合

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摘要

A series of titanium dichloro and di(isopropoxy) complexes with a 1,4-dithiabutanediyl-linked bis(4,6-disubstituted phenolato) ligand [Ti(OC6H2-6-R-1-4-R-2)(2){S(CH2)(2)S}X-2] (X = Cl, 2a-i, (OPr)-Pr-i, 3a-i; R-1 = H, Me, Pr-i, Bu-t, 2-phenyl-2-propyl; R-2 = H, Me, Bu-t, OMe, 2-phenyl-2-propyl) were synthesized by reacting the corresponding linked bis(phenol) (HOC6H2-6-R-1-4-R-2)(2){S(CH2)(2)S} (1a-i) with the titanium precursor TiX4. The NMR spectra of the dichloro complexes Ti(OC6H2-6-R-1-4-R-2)(2){S(CH2)(2)S}Cl-2] (2a-d) with small ortho substituents R-1 = H, Me, Pr-i are in agreement with a C-2-symmetrical helical structure, but the complexes become fluxional at higher temperatures. The corresponding di(isopropoxy) complexes [Ti(OC6H2-6-R-1-4-R-2)(2){S(CH2)(2)S}((OPr)-Pr-i)(2)] (3a-d) are fluxional in solution at room temperature due to rapid interconversion between the Delta and Delta isomers. In contrast, both dichloro and di(isopropoxy) complexes 2e-i and 3e-i with bulky ortho substituents R-1 = Bu-t and 2-phenyl-2-propyl exhibit a rigid C2-symmetrical helical structure in solution up to 100 C. The helical structure with trans-O,O, cis-S,S, cis-Cl,Cl ("alpha-cis") is confirmed by the single-crystal structure analysis of two dichloro complexes [Ti(OC6H2-6-R-1-4-R-2)(2){S(CH2)(2)S}Cl-2] (2e, R-1 = Bu-t, R-2 = Me; 2i, R-1, R-2 = 2-phenyl-2-propyl). Related dichloro and di(isopropoxy) complexes that contain a 1,5-dithiapentanediyl-linked bis(4,6-disubstituted phenolato) ligand [Ti(OC6H2-6R(1)-4-R-2)(2){S(CH2)(3)S}X-2] (R-1 = Bu-t; R-2 = Me, Bu-t, OMe; X = Cl, 5a-c; (OPr)-Pr-i, 6a-c) were synthesized in an analogous fashion and shown by NMR spectroscopy to be conformationally flexible at room temperature. This fluxionality can be explained by a twisting of one five-membered chelate ring, converting the trans-O,O ("alpha-cis") to the cis-O,O ("beta-cis") isomer. A crystal structure determination of ligand [Ti((OC6H2Bu2)-Bu-t-4,6)(2){S(CH2)(3)S}((OPr)-Pr-i)(2)] (6b) revealed the trans-O,O, cis-S,S, cis-Cl,Cl ("alpha-cis") isomer. Upon activation with methylaluminoxane, the stereorigid derivatives 2e-i efficiently polymerize styrene to give isotactic polystyrene, whereas the conformationally flexible complexes 2a-d produce atactic polystyrene with negligible activity. Under the same conditions, complexes with the 1,5-dithiapentanediyl-linked ligand 5a,b and 6b,c polymerized styrene syndiospecifically with low activity.
机译：一系列具有1,4-二硫代丁烷二基连接的双（4,6-二取代的酚基）配体[Ti（OC6H2-6-R-1-4-R-2）（2）的钛二氯和二（异丙氧基）配合物{S（CH2）（2）S} X-2]（X = Cl，2a-i，（OPr）-Pr-i，3a-i; R-1 = H，Me，Pr-i，Bu-t ，2-苯基-2-丙基; R-2 = H，Me，Bu-t，OMe，2-苯基-2-丙基）是通过使相应的连接双酚（HOC6H2-6-R-1）反应合成的带有钛前体TiX4的-4-R-2）（2）{S（CH2）（2）S}（1a-i）。具有小的邻位取代基R的二氯配合物Ti（OC6H2-6-R-1-4-R-2）（2）{S（CH2）（2）S} Cl-2]（2a-d）的NMR光谱-1 = H，Me，Pr-i与C-2对称的螺旋结构一致，但在更高的温度下，络合物变为熔体。相应的二（异丙氧基）络合物[Ti（OC6H2-6-R-1-4-R-2）（2）{S（CH2）（2）S}（（OPr）-Pr-i）（2）] （3a-d）是由于δ和δ异构体之间的快速相互转化而在室温下在溶液中的通量。相反，具有大的邻位取代基R-1 = Bu-t和2-苯基-2-丙基的二氯和二（异丙氧基）配合物2e-i和3e-i在溶液中的刚性C2对称螺旋结构高达100通过两个二氯配合物[Ti（OC6H2-6-）的单晶结构分析确认具有反式-O，O，顺式-S，S，顺式-Cl，Cl（“α-顺式”）的螺旋结构R-1-4-R-2）（2）{S（CH2）（2）S} Cl-2]（2e，R-1 = Bu-t，R-2 = Me; 2i，R-1， R-2 ＝ 2-苯基-2-丙基）。相关的二氯和二（异丙氧基）络合物，包含1,5-二硫杂戊烷二基连接的双（4,6-二取代苯酚基）配体[Ti（OC6H2-6R（1）-4-R-2）（2）{S（ CH2）（3）S} X-2]（R-1 = Bu-t; R-2 = Me，Bu-t，OMe; X = Cl，5a-c;（OPr）-Pr-i，6a- c）以类似方式合成，并通过NMR光谱法显示其在室温下具有构象柔性。这种通量性可以通过扭转一个五元螯合环，将反式-O，O（“α-顺式”）转化为顺式-O，O（“β-顺式”）异构体来解释。配体[Ti（（OC6H2Bu2）-Bu-t-4,6）（2）{S（CH2）（3）S}（（OPr）-Pr-i）（2）]的晶体结构测定（6b）揭示了反式-O，O，顺式-S，S，顺式-Cl，Cl（“α-顺式”）异构体。在用甲基铝氧烷活化后，立体刚性衍生物2e-i有效地使苯乙烯聚合以产生等规聚苯乙烯，而构象柔性配合物2a-d产生活性可忽略不计的无规聚苯乙烯。在相同条件下，与1,5-二硫戊戊二基连接的配体5a，b和6b，c的配合物间苯二酚特异性地聚合，活性低。

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