螯合的d(0)金属烯烃配合物[η(5):η(1)-C(5)R(4)SiMe(2)N(t)Bu]Ti(OCMe(2)CH(2)CH(2)CH=CH(2))(+)（R = H，Me）的溶液结构和动力学性质：“受限几何构型”催化剂中[η(5):η(1)-C(5)R(4)SiMe(2)N(t)Bu]Ti(R')(烯烃)(+)中间体的模型

Solution structures and dynamic properties of chelated d(0) metal olefin complexes [eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]Ti(OCMe(2)CH(2)CH(2)CH=CH(2))(+) (R = H, Me): Models for the [eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]Ti(R')(olefin)(+) intermediates in "constrained geometry" catalysts.

作者信息

Carpentier J F, Maryin V P, Luci J, Jordan R F

机构信息

Department of Chemistry, The University of Iowa, Iowa City, Iowa 52242, USA.

出版信息

J Am Chem Soc. 2001 Feb 7;123(5):898-909. doi: 10.1021/ja003209l.

DOI:10.1021/ja003209l

PMID:11456623

Abstract

To model the Ti-olefin interaction in the putative [eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]Ti(R')(olefin)(+) intermediates in "constrained geometry" Ti-catalyzed olefin polymerization, chelated alkoxide olefin complexes [eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]Ti(OCMe(2)CH(2)CH(2)CH=CH(2))(+) have been investigated. The reaction of [eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]TiMe(2) (1a,b; R = H, Me) with HOCMe(2)CH(2)CH(2)CH=CH(2) yields mixtures of [eta(5)-C(5)R(4)SiMe(2)NH(t)Bu]TiMe(2)(OCMe(2)CH(2)CH(2)CH=CH(2)) (2a,b) and [eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]TiMe(OCMe(2)CH(2)CH(2)CH=CH(2)) (3a,b). The reaction of 2a/3a and 2b/3b mixtures with B(C(6)F(5))(3) yields the chelated olefin complexes [[eta(5): eta(1)-C(5)R(4)SiMe(2)N(t)Bu]Ti(OCMe(2)CH(2)CH(2)CH=CH(2))][MeB(C(6)F(5))(3)] (4a,b; 71 and 89% NMR yield). The reaction of 2b/3b with [Ph(3)C][B(C(6)F(5))(4)] yields [[eta(5): eta(1)-C(5)Me(4)SiMe(2)N(t)Bu]Ti(OCMe(2)CH(2)CH(2)CH=CH(2))][B(C(6)F(5))(4)] (5b, 88% NMR yield). NMR studies establish that 4a,b and 5b exist as mixtures of diastereomers (isomer ratios: 4a/4a', 62/38; 4b/4b', 75/25; 5b/5b', 75/25), which differ in the enantioface of the olefin that is coordinated. NMR data for these d(0) metal olefin complexes show that the olefin coordinates to Ti in an unsymmetrical fashion primarily through C(term) such that the C=C pi bond is polarized with positive charge buildup on C(int). Dynamic NMR studies show that 4b/4b' undergoes olefin face exchange by a dissociative mechanism which is accompanied by fast inversion of configuration at Ti ("O-shift") in the olefin-dissociated intermediate. The activation parameters for the conversion of 4b to 4b' (i.e., 4b/4b' face exchange) are: DeltaH = 17.2(8) kcal/mol; DeltaS = 8(1) eu. 4a/4a' also undergoes olefin face exchange but with a lower barrier (DeltaH = 12.2(9) kcal/mol; DeltaS = -2(3) eu), for the conversion of 4a to 4a'.

摘要

为了模拟在“受限几何构型”钛催化烯烃聚合反应中假定的[η(5):η(1)-C(5)R(4)SiMe(2)N(t)Bu]Ti(R')(烯烃)(+)中间体中的钛-烯烃相互作用，对螯合醇盐烯烃配合物[η(5):η(1)-C(5)R(4)SiMe(2)N(t)Bu]Ti(OCMe(2)CH(2)CH(2)CH=CH(2))(+)进行了研究。[η(5):η(1)-C(5)R(4)SiMe(2)N(t)Bu]TiMe(2)（1a,b；R = H, Me）与HOCMe(2)CH(2)CH(2)CH=CH(2)反应生成[η(5)-C(5)R(4)SiMe(2)NH(t)Bu]TiMe(2)(OCMe(2)CH(2)CH(2)CH=CH(2))（2a,b）和[η(5):η(1)-C(5)R(4)SiMe(2)N(t)Bu]TiMe(OCMe(2)CH(2)CH(2)CH=CH(2))（3a,b）的混合物。2a/3a和2b/3b混合物与B(C(6)F(5))(3)反应生成螯合烯烃配合物[[η(5):η(1)-C(5)R(4)SiMe(2)N(t)Bu]Ti(OCMe(2)CH(2)CH(2)CH=CH(2))][MeB(C(6)F(5))(3)]（4a,b；NMR产率分别为71%和89%）。2b/3b与[Ph(3)C][B(C(6)F(5))(4)]反应生成[[η(5):η(1)-C(5)Me(4)SiMe(2)N(t)Bu]Ti(OCMe(2)CH(2)CH(2)CH=CH(2))][B(C(6)F(5))(4)]（5b，NMR产率为88%）。核磁共振研究表明，4a,b和5b以非对映异构体混合物的形式存在（异构体比例：4a/4a'，62/38；4b/4b'，75/25；5b/5b'，75/25），它们在配位烯烃的对映面上有所不同。这些d(0)金属烯烃配合物的核磁共振数据表明，烯烃主要通过C(末端)以不对称方式与钛配位，使得C=Cπ键极化，C(内部)上积累正电荷。动态核磁共振研究表明，4b/4b'通过解离机制进行烯烃面交换，该过程伴随着烯烃解离中间体中钛处构型的快速翻转（“O-迁移”）。4b转化为4b'（即4b/4b'面交换）的活化参数为：ΔH = 17.2(8) kcal/mol；ΔS = 8(1) eu。4a/4a'也进行烯烃面交换，但对于4a转化为4a'，其能垒较低（ΔH = 12.2(9) kcal/mol；ΔS = -2(3) eu）。