Tri(1-adamantyl)phosphine: Exceptional Catalytic Effects Enabled by the Synergy of Chemical Stability, Donicity, and Polarizability

Abstract

Tri(1-adamantyl)phosphine, a simple yet long-absent homoleptic phosphine, has finally been prepared. The simplicity of this compound beguiles its exceptional properties. The electron-releasing character eclipses all other alkylphosphines. The phosphine geometry and overall size are also more compact than anticipated, which may occur as a result of dispersion forces. We believe the donicity, marked resistance towards cyclometallation or P−C bond scission, and also substantial polarizability engendered by the three diamondoid fragments together account for the phenomenal performance of Pd-PAd 3 catalysts during Suzuki-Miyaura coupling reactions. A correlation analysis is also described that provides support for polarizability as a potentially general influence on the properties of tertiary phosphines. 1 Introduction 2 Synthesis of Tri(1-adamantyl)phosphine 3 Reactions of Tri(1-adamantyl)phosphine Palladium Complexes 4 Electronic and Steric Properties of Tri(1-adamantyl)phosphine 5 Conclusion Key words phosphine, ligand, catalysis, cross-coupling, palladium, diamondoid Liye Chen (right) is originally from Dalian, China. In 2008, he obtained a BS in chemistry from Tsinghua University in Beijing, China and then completed post-undergraduate research at the Shanghai Institute of Organic Chemistry. Currently, Liye is a Ph.D. candidate at Princeton in Brad Carrow's laboratory and is pursuing catalyst and reaction discovery and development. Brad Carrow (left) obtained his B.S. in chemistry from the Missouri University of Science and Technology in 2003. He received his in Ph.D. in 2011 from the University of Illinois at Urbana-Champaign following work in the laboratories of John F. Hartwig. After completing his graduate studies, he was a postdoctoral fellow and then an assistant professor in the laboratories of Kyoko Nozaki at the University of Tokyo. Since Fall 2013, he has been an assistant professor of chemistry at Princeton University. His research interests revolve around transition-metal catalysis in the context of sustainable organic synthesis, polymer synthesis, and strong bond activation.

A Glove-Box- and Schlenk-Line-Free Protocol for Solid-State C–N Cross-Coupling Reactions Using Mechanochemistry

“…We then turned our attention to air-stable tri(1-adamantyl)phosphine (Ad3P), which was first synthesized by Carrow and co-workers. [46][47][48][49][50] This ligand is sterically similar to t-Bu3P but has been discovered to be more electron-donating. [46][47][48][49][50] We thus reasoned that Ad3P might exhibit better catalytic properties than t-Bu3P for the solid-state mechanochemical C−N cross-coupling reactions.…”

“…[46][47][48][49][50] This ligand is sterically similar to t-Bu3P but has been discovered to be more electron-donating. [46][47][48][49][50] We thus reasoned that Ad3P might exhibit better catalytic properties than t-Bu3P for the solid-state mechanochemical C−N cross-coupling reactions. Pleasingly, the reaction using Ad3P proceeded efficiently under mechanochemical conditions to furnish 3a in good yield (72%; Table 1, entry 2).…”

Triflic Acid-Promoted Adamantylation and tert-Butylation of Pyrene: Fluorescent Properties of Pyrene-Decorated Adamantanes and a Channeled Crystal Structure of 1,3,5-Tris(pyren-2-yl)adamantane

“…The adamantyl group seemed especially interesting because physicochemical properties of adamantyl-substituted compounds may be different from those of their tert -butyl-substituted counterparts. 7 Moreover, in contrast to the tert -butyl group, the rigid adamantane scaffold offers a possibility of attachment, via the Friedel–Crafts chemistry, of the two, three, or four aryl group to the tertiary carbons. It has been demonstrated that di-, tri-, and tetraaryl adamantanes have a great tendency to form various types of supramolecular systems in the solid state (e.g., encapsulating crystals 8 and were used in syntheses of porous aromatic frameworks).…”

Capturing the Most Active State of a Palladium(0) Cross-Coupling Catalyst

“…We thus synthesized an analogue of 12, 14), to test whether formation of side products is suppressed by this ligand exchange to potentially aid attempted isolation of a low coordinate Pd(0) species. We observed that reaction of complex 14 with C6F5B(OH)2 indeed afforded a single observable species by 31 P NMR (δP = 91.6 ppm, 75%, Fig 5A) under otherwise identical conditions that generated a mixture of products from P t Bu3-coordinated complex 12 (Fig 4B). Notably, this synthesis by TM with a palladium hydroxide occurs cleanly to form a product (15) even with reduced boronic acid loading compared to those in the earlier cationic TM reactions at low temperature.…”

“…In this study, we report definitive solution spectroscopic and crystallographic characterization of catalytically relevant Pd(0) complexes coordinated by a single monodentate ancillary ligand PAd3 (Ad = 1-adamantyl) (Fig 1C). The use of PAd3, recently reported by our group, was key to accelerating B-to-Pd TM at a sufficiently low temperature to stabilize coordinatively unsaturated Pd(0) [30][31][32][33][34] .…”