Silanol-Based Pincer Pt(II) Complexes: Synthesis, Structure, and Unusual Reactivity

Aiming at the generation of a silanone intramolecularly bound to platinum, we prepared pincer-type PSiP silanol Pt(II) complexes. While a stable silanone complex was not isolated, unusual reactivity modes, involving its possible intermediacy, were observed. Treatment of the new PSiH2P-type ligand (o-IPr2PC6H4)2SiH2 (7) with (Me2S)2Pt(Me)Cl yields the pincer-type hydrosilane complex [{(o- iPr2PC6H4)2SiH}PtCl] (8), which upon Ir(I)-catalyzed hydrolytic oxidation gives the structurally characterized silanol complex [{(o- iPr2PC6H4)2SiOH}PtCl] (3). Complex 3, comprising in its structure the nucleophilic silanol fragment and electrophilic Pt(II)−Cl moiety, exhibits dual reactivity. Its reaction with the non-nucleophilic KB(C6F5)4 in fluorobenzene leads to the ionic complex [{(o- iPr2PC6H4)2SiOH}Pt]+ [(C6F5)4B]− (9), which reacts with CO to yield the structurally characterized [{(o- iPr2PC6H4)2SiOH}PtCO]+ [(C6F5)4B]− (10). Treatment of 3 with non-nucleophilic bases leads to unprecedented rearrangement and coupling, resulting in the structurally characterized, unusual binuclear complex 11. The structure of 11 comprises two different fragments: the original O−Si−Pt(II)−Cl pattern, and the newly formed silanolate Pt(II)−H pattern, which are connected via a disiloxane bridge. Complex 9 undergoes a similar hydrolytic rearrangement in the presence of iPr2NEt to give the mononuclear silanolate Pt(II)−H complex 17. Both these rearrangement-coupling reactions probably involve the inner-sphere generation of an intermediate silanone 14, which undergoes nucleophilic attack by the starting silanol 3 to yield complex 11, or adds a water molecule to yield complex 17. X-ray diffraction studies of 3, 10, and 11 exhibit a very short Si−Pt bond length (2.27−2.28 Å) in the neutral complexes 3 and 11 that elongates to 2.365 Å in the carbonyl complex 10. A significantly compressed geometry of the silanolate platinum(II)-hydride fragment B of the binuclear complex 11 features a Pt(2)−O(2)−Si(2) angle of 100.4 (3)° and a remarkably short Pt(2)···Si(2) [2.884 (3) Å] distance.

针对分子内与铂结合的硅酮（silanone）的合成，我们制备了钳型（pincer-type）PSiP型硅烷醇二价铂（Pt(II)）配合物。尽管未能分离得到稳定的硅酮配合物，但观察到了涉及该物种可能作为中间体的非常规反应模式。将新型PSiH₂P型配体(o-IPr₂PC₆H₄)₂SiH₂（7）与(Me₂S)₂Pt(Me)Cl反应，得到钳型硅烷氢配合物[{(o-iPr₂PC₆H₄)₂SiH}PtCl]（8）；该配合物经一价铱（Ir(I)）催化的水解氧化反应，得到经结构表征的硅烷醇配合物[{(o-iPr₂PC₆H₄)₂SiOH}PtCl]（3）。配合物3的结构中包含亲核性硅烷醇片段与亲电性Pt(II)−Cl单元，表现出双重反应性。其与非亲核性四(五氟苯基)硼酸钾（KB(C₆F₅)₄）在氟苯中反应，生成离子型配合物[{(o-iPr₂PC₆H₄)₂SiOH}Pt]⁺[(C₆F₅)₄B]⁻（9）；该离子配合物可与一氧化碳（CO）反应，得到经结构表征的[{(o-iPr₂PC₆H₄)₂SiOH}PtCO]⁺[(C₆F₅)₄B]⁻（10）。用非亲核碱处理配合物3，会发生前所未有的重排与偶联反应，得到经结构表征的非常规双核配合物11。配合物11的结构包含两种不同片段：原始的O−Si−Pt(II)−Cl单元，以及新生成的硅烷醇盐Pt(II)−H单元，二者通过二硅氧烷桥连接。配合物9在iPr₂NEt存在下也会发生类似的水解重排，得到单核硅烷醇盐Pt(II)−H配合物17。上述两类重排偶联反应可能均通过中间体硅酮14的内层生成过程实现：中间体14可被起始原料硅烷醇3亲核进攻得到配合物11，或与水分子加成得到配合物17。对配合物3、10和11的X射线衍射（X-ray diffraction）研究显示，中性配合物3与11中存在极短的Si−Pt键长（2.27~2.28 Å），而在羰基配合物10中该键长伸长至2.365 Å。双核配合物11的硅烷醇盐铂(II)-氢片段B具有显著压缩的几何构型，其Pt(2)−O(2)−Si(2)键角为100.4(3)°，且Pt(2)···Si(2)间距极短，达2.884(3) Å。