Exocyclic Bond Cleavage in Oxaphosphirane Complexes?
Exocyclic Bond Cleavage in Oxaphosphirane Complexes?
复制标题
DOI：
10.1002/chem.201201057
复制
发表时间：
2012-10-01
影响因子：
4.3
通讯作者：
Streubel, Rainer
中科院分区：
文献类型：
--
作者：
Espinosa, Arturo;Streubel, Rainer
第一个计算洞察力的内在强度的环外键磷氧杂磷杂环己烷？P-五羰基金属（0）配合物1？af（M=Cr，Mo）是使用一组P？R衍生物（R=Me、tBu、CPh 3）。而环外P的均裂？R键被发现总是不利的（中性复合物），异裂导致碳阳离子R+部分和oxaphosphiranide复合物2-构成的能量最低的过程，特别是如果R是庞大的，可以稳定的正电荷，即三苯基甲基（三苯甲基），有效地。P所需的能量。M键断裂约为30千卡？mol ~（-1），随着R取代基的增加（从Me到三苯甲基）和从Cr到Mo的变化而减小。配合物1的反应性？af对氧化和还原单电子转移（SET）反应进行了分析，使用键强度相关的描述符（VBSD）方法的简易变化，从而使综合有用的策略解决解络合和P-官能化的设计。还原SET反应与钠萘使选择性P？M键断裂（即，解络合）的情况下，P-Me和P-tBu取代，而还原P？R键裂解的P-三苯甲基配合物1的情况下，有利于？c，f，并导致形成（阴离子）氧杂磷酰胺配合物2-，其可被视为进一步P-官能化的潜在关键中间体。
A first computational insight into the intrinsic strength of exocyclic bonds to phosphorus in oxaphosphirane ?P-pentacarbonylmetal(0) complexes 1?af (M=Cr, Mo) is provided using a set of P?R derivatives (R=Me, tBu, CPh3). Whereas homolytic cleavage of the exocyclic P?R bond was found to be always unfavored (for neutral complexes), heterolytic cleavage leading to a carbocation R+ moiety and the oxaphosphiranide complex 2- constitutes the lowest-energy process, especially if R is bulky and can stabilize the positive charge, that is, triphenylmethyl (trityl), efficiently. The energies required for P?M bond cleavage are about 30 kcal?mol-1, and decrease with the increasing bulk of the R substituent (from Me to trityl) and ongoing from Cr to Mo. The reactivities of complexes 1?af towards oxidative and reductive single electron transfer (SET) reactions were analyzed using the facile variation of bond-strength-related descriptors (VBSD) methodology, thus enabling the design of synthetically useful strategies addressing decomplexation and P-functionalization. Reductive SET reactions with sodium naphthalenides enable selective P?M bond cleavage (i.e., decomplexation) for the case of P-Me and P-tBu substitution, whereas reductive P?R bond cleavage is favored in the case of the P-trityl complexes 1?c,f, and results in the formation of the (anionic) oxaphosphiranide complex 2-, which may be regarded as a potential key intermediate for further P-functionalization.