METATHESIS OF ACETYLENES BY (FLUOROALKOXY)TUNGSTENACYCLOBUTADIENE COMPLEXES AND THE CRYSTAL-STRUCTURE OF W(C3ET3)[OCH(CF3)2]3 - A HIGHER-ORDER MECHANISM FOR ACETYLENE METATHESIS
METATHESIS OF ACETYLENES BY (FLUOROALKOXY)TUNGSTENACYCLOBUTADIENE COMPLEXES AND THE CRYSTAL-STRUCTURE OF W(C3ET3)[OCH(CF3)2]3 - A HIGHER-ORDER MECHANISM FOR ACETYLENE METATHESIS
复制标题
DOI：
10.1021/om00088a019
复制
发表时间：
1984-01-01
期刊：
影响因子：
2.8
通讯作者：
ZILLER, JW
中科院分区：
文献类型：
--
作者：
FREUDENBERGER, JH;SCHROCK, RR;ZILLER, JW
另一方面，W(C3Et3)(OR)3在相对非配位的溶剂(戊烷、苯或甲苯；AH*=14.4(6)kcal moT1；5*=-22.8(2)EU)中以缔合机制缓慢地歧化乙炔。在乙醚或二甲醚存在下，由于溶剂辅助乙炔从WC3环上解离得到W(CET)(OR)3(乙醚)、(x=1或2)或W(CET)(OR)3(DME)中间体，歧化反应的速率要高得多。W(C3Et3)[OCH(CF3)2]3属三斜空间群PI[2]，晶胞参数为a=9.949(3)，b=16.419(4)，c=18.485(4)，a=93.53(2)，ç=93.53(6)，y=98.60(2)，Z=4。3(|0|)。两个独立的分子定义了结晶学的不对称单位。每一个都是一个三角双金字塔，在赤道平面上包含一个平面的WC3环系。这两个分子的主要不同之处在于/3-乙基的取向。在一个分子中，W-Ca键长为1.902(16)和1.864(14)A，W-Cs=2.093(14)A，Ca-C0=1.429(18)和1.437(21)A。轴向和赤道醇盐配体的W-OC角分别为129.4(9)、133.6(8)和138.6(10)，W-0距离分别为1.982(11)、1.962(12)和1.932(10)A，这与六氟异丙氧化物配体的给电子能力较差相一致。
WiCsEtsKOROs metathesizes acetylenes extremely rapidly by a dissociative mechanism, ie, via formation of putative W (CEt)(OR') 3. W (C3Et3)(OR) 3, on the other hand, slowly metathesizes acetylenes by an associative mechanism in relatively noncoordinating solvents (pentane, benzene, or toluene; AH*= 14.4 (6) kcal moT1; 5*=-22.8 (2) eu). In diethyl ether or in the presence of dme the rateof metathesis is much higher due (it is postulated) to the solvent assisted dissociation of an acetylene from the WC3 ring to give W (CEt)(OR) 3 (ether),(x= 1 or 2) or W (CEt)(OR) 3 (dme) intermediates. W (C3Et3)[OCH (CF3) 2] 3 crystallizes in the triclinic space group PI [No. 2] with a= 9.949 (3) Á, b= 16.419 (4) Á, c= 18.485 (4) Á, a= 112.81 (2), ß= 93.53 (6), y= 98.60 (2), and Z= 4. Diffraction data were refined to RF= 8.00% and RwP= 7.78% for 511 parameters refined against all 6439 unique data and RF= 5.04% and RwF= 5.55% for those 4540 data with [F0|> 3 (| 0|). Two independent molecules define the crystallographic asymmetric unit. Each is a trigonal bipyramid containing a planar WC3 ring system in the equatorial plane. The two molecules differ primarily inthe orientation of the/3-ethyl group. In one molecule the W-Ca bond lengths are 1.902 (16) and 1.864 (14) A with W-Cs= 2.093 (14) A and Ca-C0= 1.429 (18) and 1.437 (21) A. Axial and equatorial alkoxide ligands show similarW-OC angles of 129.4 (9), 133.6 (8), and 138.6 (10) and W-0 distances of 1.982 (11), 1.962 (12), and 1.932 (10) A, consistent with a poor-electron-donating ability by the hexafluoroisopropoxide ligand.