调控有机金属环的应变和聚合性：含C-Si、C-P和C-S桥的二茂铁[2]环的合成、结构及开环聚合行为

Tuning the strain and polymerizability of organometallic rings: the synthesis, structure, and ring-opening polymerization behavior of [2]ferrocenophanes with C-SI, C-P, and C-S bridges.

作者信息

Resendes R, Nelson J M, Fischer A, Jäkle F, Bartole A, Lough A J, Manners I

机构信息

Contribution from the Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 3H6, Canada.

出版信息

J Am Chem Soc. 2001 Mar 14;123(10):2116-26. doi: 10.1021/ja002750e.

DOI:10.1021/ja002750e

PMID:11456856

Abstract

A series of novel [2]ferrocenophanes with unsymmetrical C-E bridges has been prepared in which the covalent radius of the second-row element, E, and hence the ring strain present is varied. Species [Fe(eta-C(5)Me(4))(eta-C(5)H(4))CH(2)ER(x)] (7, ER(x) = SiMe(2); 8a, ER(x) = PPh; 8b, ER(x) = PMes; 9, ER(x) = S) were synthesized via reaction of the PMDETA (N,N,N',N' ',N' '-pentamethyldiethylenetriamine) adduct of [(eta-C(5)H(4)Li)Fe(eta-C(5)Me(4))CH(2)Li] with Cl(2)ER(x) (E = Si or P) or S(SO(2)Ph)(2). Studies of 7-9 by single-crystal X-ray diffraction confirmed the presence of ring-tilted structures: for 7, alpha (angle between the planes of the Cp rings) = 11.8(1) degrees; for 8a, alpha(average) = 14.9(3) degrees; for 8b, alpha(average) = 18.2(2) degrees; and for 9, alpha = 18.5(1) degrees. The least tilted compound, 7, was found to be resistant to thermal, anionic, and transition metal catalyzed ROP. In contrast, the significantly more tilted compounds 8a, 8b, and 9 were all found to polymerize thermally with small negative values of DeltaH(ROP) of ca. 10-20 kJ.mol(-1) determined by DSC. Whereas thermal ROP of 8a yielded the soluble high molecular weight polycarbophosphaferrocene (eta-C(5)Me(4))Fe(eta-C(5)H(4))CH(2)PPh (11), species 9 formed the insoluble polycarbothiaferrocene (eta-C(5)Me(4))Fe(eta-C(5)H(4))CH(2)S (14). Attempted anionic ROP of 8a and 9 with (n)BuLi was unsuccessful and treatment of 8a with CF(3)SO(3)Me resulted in the formation of the novel phosphonium salt [(eta-C(5)Me(4))Fe(eta-C(5)H(4))CH(2)PMePh][CF(3)SO(3)] (13), which was found to be resistant to thermal ROP as a result of its less strained structure (for 13, alpha = 11.4(7) degrees ). Treatment of 9 with CF(3)SO(3)Me or BF(3).Et(2)O resulted in the first example of cationic ROP for a transition metal-containing heterocycle to yield polycarbothiaferrocene 14. In the presence of excess 2,6-di-tert-butylpyridine as a selective proton trap, ROP of 9 was only observed with CF(3)SO(3)Me, and not BF(3).Et(2)O, which indicated that Me(+) and H(+) are the probable cationic initiators, respectively. Thermal copolymerization of 9 with trimethylene sulfide resulted in the isolation of the soluble, high molecular weight, random copolymer (eta-C(5)Me(4))Fe(eta-C(5)H(4))CH(2)S (CH(2))(3)S, 15.

摘要

已制备出一系列具有不对称C-E桥的新型[2]二茂铁并环化合物，其中第二周期元素E的共价半径不同，因而存在的环张力也不同。通过[(η-C₅H₄Li)Fe(η-C₅Me₄)CH₂Li]的PMDETA（N,N,N',N'',N''-五甲基二亚乙基三胺）加合物与Cl₂ERₓ（E = Si或P）或S(SO₂Ph)₂反应，合成了化合物[Fe(η-C₅Me₄)(η-C₅H₄)CH₂ERₓ]（7，ERₓ = SiMe₂；8a，ERₓ = PPh；8b，ERₓ = PMes；9，ERₓ = S）。通过单晶X射线衍射对7 - 9进行研究，证实存在环倾斜结构：对于7，α（两个茂环平面之间的夹角） = 11.8(1)°；对于8a，α（平均值） = 14.9(3)°；对于8b，α（平均值） = 18.2(2)°；对于9，α = 18.5(1)°。发现倾斜程度最小的化合物7对热、阴离子和过渡金属催化的开环聚合反应具有抗性。相比之下，倾斜程度明显更大的化合物8a、8b和9都能发生热聚合反应，通过差示扫描量热法测定其开环聚合反应的ΔH(ROP)为较小的负值，约为10 - 20 kJ·mol⁻¹。虽然8a的热开环聚合反应生成了可溶性的高分子量聚碳磷二茂铁[(η-C₅Me₄)Fe(η-C₅H₄)CH₂PPh]ₙ（11），但化合物9形成了不溶性的聚碳硫二茂铁[(η-C₅Me₄)Fe(η-C₅H₄)CH₂S]ₙ（14）。用(n)BuLi对8a和9进行阴离子开环聚合反应未成功，用CF₃SO₃Me处理8a得到了新型鏻盐[(η-C₅Me₄)Fe(η-C₅H₄)CH₂PMePh][CF₃SO₃]（13），由于其结构应变较小（对于13，α = 11.4(7)°），发现它对热开环聚合反应具有抗性。用CF₃SO₃Me或BF₃·Et₂O处理9得到了含过渡金属杂环阳离子开环聚合反应的首个实例，生成了聚碳硫二茂铁14。在过量的2,6 - 二叔丁基吡啶作为选择性质子捕获剂存在下，仅观察到9与CF₃SO₃Me发生开环聚合反应，而与BF₃·Et₂O不发生反应，这表明Me⁺和H⁺分别可能是阳离子引发剂。9与三亚甲基硫醚的热共聚合反应得到了可溶性的高分子量无规共聚物[(η-C₅Me₄)Fe(η-C₅H₄)CH₂S]ₙ[(CH₂)₃S]ₘ，15。