Timosheva Natalya V., Chandrasekaran A., Prakasha T. K., Day Roberta O., Holmes Robert R.
Department of Chemistry, Box 34510, University of Massachusetts, Amherst, Massachusetts 01003-4510.
Inorg Chem. 1996 Oct 23;35(22):6552-6560. doi: 10.1021/ic960538z.
Analogous to the formation of CH(2)(t-Bu)(2)C(6)H(2)OP(Ph)(O(2)C(6)Cl(4)) (1), the new bicyclic tetraoxyphosphoranes CH(2)(t-Bu)(2)C(6)H(2)OP(Et)(O(2)C(6)Cl(4)) (3) and CH(2)ClC(6)H(3)OP(Ph)(O(2)C(6)Cl(4)) (4) were synthesized by the oxidative addition of the appropriate cyclic phosphines with o-tetrachlorobenzoquinone. For the formation of CH(2)(t-Bu)(2)C(6)H(2)OP(Ph)(O(2)C(2)Ph(2)) (2), a similar reaction was followed with the use of benzil (PhCOCOPh) in place of o-tetrachlorobenzoquinone. X-ray analysis of 1-3 revealed trigonal bipyramidal geometries and provided evidence for the first series of complexes in the absence of ring strain in which the least electronegative group, ethyl or phenyl, is located in an axial position, in violation of the electronegativity rule. Thus, the two oxygen-containing ring systems occupied two different sets of positions in the trigonal bipyramid (TBP) with the eight-membered rings at diequatorial sites. X-ray analysis of 4 revealed a trigonal bipyramidal geometry with electron-withdrawing chlorine substituents on each ring assumed the more conventional geometry with the rings occupying axial-equatorial positions and the phenyl group located in the remaining equatorial site. The fact that molecular mechanics calculations favorably reproduced the observed geometries suggests that a steric contribution associated with the ring tert-butyl groups for 1-3 is partly responsible in favoring diequatorial ring occupancy for the eight-membered ring. NMR data supported rigid pentacoordinated structures in solution at 23 degrees C. Phosphorane 1 crystallizes in the orthorhombic space group Fdd2 with a = 44.787(5) Å, b = 34.648(8) Å, c = 10.3709(9) Å, and Z = 16. Phosphorane 2 crystallizes in the orthorhombic space group Pna2(1) with a = 20.658(8) Å, b = 10.342(2) Å, c = 19.879(6) Å, and Z = 4. Phosphorane 3 crystallizes in the orthorhombic space group Pcmn with a = 9.807(2) Å, b = 16.632(4) Å, c = 23.355(3) Å, and Z = 4. Phosphorane 4 crystallizes in the monoclinic space group C2/c with a = 35.699(5) Å, b = 12.187(2) Å, c = 14.284(3) Å, beta = 107.08(1) degrees, and Z = 8. The final conventional unweighted residuals are 0.0395 (1), 0.0518 (2), 0.0540 (3), and 0.0868 (4).
与CH(2)(叔丁基)(2)C(6)H(2)OP(Ph)(O(2)C(6)Cl(4)) (1)的形成类似，新型双环四氧磷杂环戊烷CH(2)(叔丁基)(2)C(6)H(2)OP(Et)(O(2)C(6)Cl(4)) (3)和CH(2)ClC(6)H(3)OP(Ph)(O(2)C(6)Cl(4)) (4)通过合适的环状膦与邻四氯苯醌的氧化加成反应合成。对于CH(2)(叔丁基)(2)C(6)H(2)OP(Ph)(O(2)C(2)Ph(2)) (2)的形成，使用联苯甲酰(PhCOCOPh)代替邻四氯苯醌进行了类似反应。对1 - 3的X射线分析揭示了三角双锥几何构型，并为第一系列配合物提供了证据，即在不存在环张力的情况下，电负性最小的基团，乙基或苯基，位于轴向位置，这违反了电负性规则。因此，两个含氧环系统在三角双锥(TBP)中占据两组不同的位置，八元环位于赤道位置。对4的X射线分析揭示了一种三角双锥几何构型，每个环上带有吸电子氯取代基，呈现出更传统的几何构型，环占据轴向 - 赤道位置，苯基位于剩余的赤道位置。分子力学计算能够很好地再现观察到的几何构型这一事实表明，与1 - 3中环叔丁基相关的空间效应部分地导致了八元环倾向于占据赤道位置。核磁共振数据支持了在23℃下溶液中的刚性五配位结构。磷杂环戊烷1在正交空间群Fdd2中结晶，a = 44.787(5) Å，b = 34.648(8) Å，c = 10.3709(9) Å，Z = 16。磷杂环戊烷2在正交空间群Pna2(1)中结晶，a = 20.658(8) Å，b = 10.342(2) Å，c = 19.879(6) Å，Z = 4。磷杂环戊烷3在正交空间群Pcmn中结晶，a = 9.807(2) Å，b = 16.632(4) Å，c = 23.355(3) Å，Z = 4。磷杂环戊烷4在单斜空间群C2/c中结晶，a = 35.699(5) Å，b = 12.187(2) Å，c = 14.284(3) Å，β = 107.08(1)°，Z = 8。最终的常规未加权残余分别为0.0395 (1)、0.0518 (2)、0.0540 (3)和0.0868 (4)。
