Department of Chemistry, University of California Berkeley, Berkeley, California 94720, United States.
Inorg Chem. 2021 Aug 16;60(16):11830-11837. doi: 10.1021/acs.inorgchem.1c01400. Epub 2021 Jul 28.
Terminal, π-basic moieties occupy a prominent position in the stabilization of unusual or reactive inorganic species. The electron-releasing, π-basic properties of phosphinimides (PN) have been employed to stabilize electron-deficient early transition metals and lanthanides. In principle, a ligand field comprised of terminal PN groups should enable access to high-valent states of late first row transition metals. Herein, we report a new class of multidentate phosphinimide ligands to logically explore this hypothesis. Access to such ligands is made possible by a new procedure for the electrophilic amination of rigid, sterically encumbering, multidentate phosphines. Such frameworks facilitate terminal PN coordination to cobalt as demonstrated by the synthesis of a trinuclear Co complex and a homoleptic, three-coordinate Co complex. Interestingly, the Co complex exhibits an exceedingly rare = 2 ground state. Combined XRD, magnetic susceptibility, and DFT studies highlight that terminally bound PNs engage in strong dπ-pπ interactions that present a weak ligand field appropriate to stabilize high-spin states of late transition metals.
在稳定非常规或反应性无机物种方面，末端的π-碱性部分占据着重要的地位。膦亚胺（PN）的供电子π-碱性性质已被用于稳定缺电子的早期过渡金属和镧系元素。原则上，由末端 PN 基团组成的配体场应该能够获得高价态的第一过渡金属。在此，我们报告了一类新型的多齿膦亚胺配体，以逻辑上探索这一假设。通过一种新的方法实现了对刚性、空间位阻大的多齿膦的亲电胺化，从而获得了这样的配体。此类框架促进了末端 PN 与钴的配位，这一点已通过三核 Co 配合物和同配位的三配位 Co 配合物的合成得到证明。有趣的是，Co 配合物表现出非常罕见的 = 2 基态。结合 XRD、磁化率和 DFT 研究，突出了末端结合的 PN 之间存在强 dπ-pπ相互作用，它们提供了一个较弱的配体场，适合稳定后期过渡金属的高自旋态。
