2‐Adamantyl Complexes of Platinum

Abstract

Dedicated to the memory of Paul von Ragué Schleyer, who made modern adamantyl chemistry possible.Abstract: The first adamantyl platinum complexes were isolated and characterized, namely [(COD)Pt(2-Ad)Cl], [(dppe)Pt(2-Ad)Cl], [(COD)Pt(2-Ad)Me] and, [(dppe)Pt(2-Ad)Me] {COD = 1,5cyclooctadiene, dppe = 1,2-bis(diphenylphosphino)ethane, Ad = adamantyl}. These complexes show considerable stability, including resistance to heating to 125°C in solution for several days. It is therefore concluded that previously existing road Adamantane, the simplest diamondoid molecule, has great potential for use in advanced materials, [1] drug development, [2] and ligands for organometallic catalysis. [3] Due to adamantane's innate chemical stability, the synthetic tool kit for the functionalization of the adamantyl group is still quite limited, in contrast to the situation for other alkyls. The exceptional donating ability of the adamantyl group at both the 1-adamantyl (bridgehead) and 2-adamantyl (bridge) positions makes transformations that involve carbocations rather straightforward. Conversely, many transformations involving carbanions, which are routine for other alkyls, are very difficult for adamantyls. [4] Arguably, efficient future procedures for functionalization of adamantane will be transition metal mediated, in particular for the bridge position, which in comparison to the bridgehead position, is much less accessible through radical pathways. [5] Despite substantial initial interest in adamantane within the organometallic community, largely due to adamantane's resistance to -elimination, progress in adamantyl metal chemistry over the last several decades has been very slow. [6] The reason for this is twofold; first, the synthesis of adamantyl anions, specifically lithium and Grignard compounds, is fraught with highly erratic yields and side reactions, [7] and reliable zinc chemistry has only recently been developed. [7b,7c] Second, homoleptic metal adamantyl complexes [8] have proven to be extremely insoluble, [a]

Synthesis of Molybdenum Imido 2-Adamantylidene Complexes through α Hydrogen Abstraction

“…This process led us to consider preparing 2-adamantylidene (Adene) complexes from 2-adamantyl (2-Ad) complexes as a consequence of the well-known resistance to formation of a CC bond within an adamantyl cage . Well-characterized 2-adamantyl and 2-adamantylidene transition-metal complexes have been reported only relatively recently. What are proposed to be Cr­(2-Ad) 4 and Fe­(2-Ad) 4 have been reported, but their insolubility prevented their full characterization and confirmation.…”

“…A solution of 2-AdMgBr in diethyl ether was prepared from commercially available 2-AdZnBr and magnesium. After optimization of the literature procedures, 80–90% yields of 2-adamantylmagnesium bromide (2-AdMgBr) were obtained free of 2,2′-biadamantane and adamantane. Alkylation of Mo­(NAr) 2 (Cl) 2 (DME) (Ar = 2,6- i -Pr 2 C 6 H 3 ) with titrated solutions of 2-AdMgBr gave Mo­(NAr) 2 (2-Ad) 2 in 75% yield as a bright red-orange pentane-soluble solid, which upon addition of triflic acid in the presence of 1,2-dimethoxyethane gave Mo­(NAr)­(Adene)­(OTf) 2 (DME) ( 1 , Adene = 2-adamantylidene) in 71% yield as a yellow-orange solid (Scheme ).…”