Institut de Ciència de Materials de Barcelona (CSIC), Campus U.A.B. 08193 Bellaterra, Spain.
Chemistry. 2011 Apr 11;17(16):4429-43. doi: 10.1002/chem.201003330. Epub 2011 Mar 8.
Oxidation of closo-carboranyl diphosphines 1,2-(PR(2))(2)-1,2-closo-C(2)B(10)H(10) (R=Ph, iPr) and closo-carboranyl monophosphines 1-PR(2)-2-R'-1,2-closo-C(2)B(10)H(10) (R=Ph, iPr, Cy; R'=Me, Ph) with hydrogen peroxide, sulfur and elemental black selenium evidences the unique capacity of the closo-carborane cluster to produce uncommon or unprecedented P/P(E) (E=S, Se) and P=O/P=S chelating ligands. When H(2)O(2) reacts with 1,2-(PR(2))(2)-1,2-closo-C(2)B(10)H(10) (R=Ph, iPr), they are oxidized to 1,2-(OPR(2))(2)-1,2-closo-C(2)B(10)H(10) (R=Ph, iPr). However, when S and Se are used, different reactivity is found for 1,2-(PPh(2))(2)-1,2-closo-C(2)B(10)H(10) and 1,2-(PiPr(2))(2)-1,2-closo-C(2)B(10)H(10). The reaction with sulfur produces mono- and dioxidation products for R=Ph, whereas Se produces the mono-oxidation product only. For R=iPr, only monooxidation takes place with S, and the second C(c)-PiPr(2) bond breaks to yield 1-SPiPr(2)-1,2-closo-C(2)B(10)H(11). When Se is used, only 1-SePiPr(2)-1,2-closo-C(2)B(10)H(11) is formed. The potential of the mono-chalcogenide carboranyl diphosphines 1-EPPh(2)-2-PPh(2)-1,2-closo-C(2)B(10)H(10) (E=S, 9; Se, 15) to behave as unsymmetric chelating bidentate ligands was studied for different metal complexes, different solvents and in the solid state. Dechalcogenation takes place in each case. Computational studies provided information on the P=E (E=S, Se) bonds. Steric effects block the bonding ability of the P=E group due to interactions between the chalcogen and the neighbouring hydrogen atoms (three from the phenyl rings and one from the carborane cluster). The electronic effects originate from the strongly electron-withdrawing character of the closo carborane cluster, which polarizes the P=E (E=S, Se) bond towards the phosphorus atom. As a consequence, the E atom is the electron-poor site and the P atom the electron-rich site in the P=E bond.
氧化闭笼-carboranyl 二膦 1,2-(PR(2))(2)-1,2-closo-C(2)B(10)H(10) (R=Ph, iPr) 和 closo-carboranyl 单膦 1-PR(2)-2-R'-1,2-closo-C(2)B(10)H(10) (R=Ph, iPr, Cy; R'=Me, Ph) 与过氧化氢、硫和元素硒的反应证明了闭笼硼烷簇独特的产生不常见或前所未有的 P/P(E) (E=S, Se) 和 P=O/P=S 螯合配体的能力。当 H(2)O(2)与 1,2-(PR(2))(2)-1,2-closo-C(2)B(10)H(10) (R=Ph, iPr) 反应时，它们被氧化为 1,2-(OPR(2))(2)-1,2-closo-C(2)B(10)H(10) (R=Ph, iPr)。然而，当使用 S 和 Se 时，对于 1,2-(PPh(2))(2)-1,2-closo-C(2)B(10)H(10) 和 1,2-(PiPr(2))(2)-1,2-closo-C(2)B(10)H(10)，发现不同的反应性。硫的反应产生 R=Ph 的单氧化和二氧化产物，而 Se 仅产生单氧化产物。对于 R=iPr，S 只发生单氧化，第二个 C(c)-PiPr(2)键断裂，生成 1-SPiPr(2)-1,2-closo-C(2)B(10)H(11)。当使用 Se 时，仅形成 1-SePiPr(2)-1,2-closo-C(2)B(10)H(11)。单-硫属元素 carboranyl 二膦 1-EPPh(2)-2-PPh(2)-1,2-closo-C(2)B(10)H(10) (E=S, 9; Se, 15) 作为不对称螯合双齿配体的潜力研究了不同的金属配合物、不同的溶剂和固态。在每种情况下都发生脱硫。计算研究提供了有关 P=E (E=S, Se) 键的信息。由于硫属元素与相邻氢原子(来自苯基环的三个和来自硼烷簇的一个)之间的相互作用，空间位阻阻止了 P=E 基团的键合能力。电子效应源于 closo 硼烷簇的强吸电子特性，它使 P=E (E=S, Se) 键向磷原子极化。因此，在 P=E 键中，E 原子是缺电子位点，而 P 原子是富电子位点。
