Dihydrogen and Acetylene Activation by a Gold(I)/Platinum(0) Transition Metal Only Frustrated Lewis Pair

Abstract

ABSTRACT:The first example of a Frustrated Lewis Pair (FLP) solely constructed around transition metal centers is described in this work. We have focused on the established capacity of Au(I) and Pt(0) complexes to act as Lewis acidic and basic fragments, respectively, while employing sufficiently bulky P t Bu 3 and terphenyl phosphine ligands. This avoids formation of metallic Lewis adducts and confers the Au(I)/Pt(0) pair a remarkable capacity to activate dihydrogen and acetylene molecules in a fashion that closely resembles that of traditional main group FLP systems. As a consequence, unusual heterobimetallic Au(I)/Pt(II) complexes containing hydride (-H), acetylide (-C≡CH) and vinylene (-HC=CH-) bridges have been isolated.The recent development of Frustrated Lewis Pairs (FLPs) has catapulted the chemistry of main group elements beyond its well-established limits, achieving reactivity patterns that were once restricted to transition metals (TMs).1 A prominent example with profound implications in metal-free catalytic hydrogenations, 2 is the activation of dihydrogen by phosphine/borane pairs. Despite their importance, the catalytic usefulness of FLPs is nevertheless limited to mainly hydrogenation and a few other reactions, 3 possibly as a consequence of the reluctance of main group elements to participate in electron-transfer and other fundamental organometallic reactions, which are key elementary steps in transition metal catalysis.Incorporation of TMs into FLPs is therefore a promising objective 4 and, as such, it has attracted recently considerable attention, as exemplified by the pioneering work of the groups of Wass 5 and Erker 6 on Zr/phosphine pairs and related systems. Although some TMs, in particular Pt(0) complexes, 7 have been employed as Lewis base (LB) partners in FLP-like designs, no examples of transition metal-only FLPs (TMOFLPs), where both the acidic and the basic functions are constructed on TMs, seen to be known, 8 despite the existence of a large number of heterobimetallic systems capable of activating small molecules in a fashion reminiscent of FLPs. 9,10Cationic Au(I) and neutral Pt(0) complexes have a well-known capacity to behave as LA and LB fragments, respectively. Hence, they were envisioned as suitable building blocks to frame an intermolecular TMOFLP. To attain frustration, triflimide Au(I) complex [Au(NTf 2 )(PMe 2 Ar Dipp2 )] (1), 11 containing the bulky terphenyl phosphine PMe 2 Ar Dipp2 (Ar Dipp2 = C 6 H 3 -2,6-(C 6 H 3 -2,6-i Pr 2 ) 2 ), 12 and the Pt(0) species [Pt(P t Bu 3 ) 2 ] (2), were utilized as FLP constituents. The present contribution reports the results of our preliminary investigation into the activation of H 2 and C 2 H 2 by the resulting cationic Au(I)/Pt(0) TMOFLP.Although the main 1 H and 31 P{ 1 H} NMR features of complexes 1 and 2 remained unaltered when their C 6 D 6 solutions were combined, upon mixing, the initially colorless solutions of 1 and 2 distinctly became bright yellow. Furthermore, in CD 2 Cl 2 as the solvent, the 31 P{ 1 H} NMR resonances of ...

Nickel as a Lewis Base in a T‐Shaped Nickel(0) Germylene Complex Incorporating a Flexible Bis(NHC) Ligand

“…1 This includes the concepts of back bonding, as well as Z-type ligands 2 and metal-only Lewis pairs 3 for the most basic metals, with the latter leading to metalonly frustrated Lewis pairs. 4 In agreement with the increase in basicity for the heavier transition elements, 1,5 little has been reported so far on the chemistry of nickel Lewis bases, 3,6 in stark contrast to platinum. 3 Among the most basic compounds of nickel are the dicoordinate Ni(0) complexes, which are linear and highly reactive.…”

Realization of Lewis Basic Sodium Anion in the NaBH3− Cluster

“…Then, metal Lewis basicity has seen a prosper of research activity, and numerous novel Lewis pairs have been prepared featuring the interaction between Lewis basic transition metals and Lewis acidic ligands . Compared to classic metal–ligand bond, this weak yet electronically reverse metal→LA interaction holds the promise for a novel type of metal–ligand cooperativity in catalytic reactions, and open doors to many applications involving H 2 storage and activation, olefin hydrogenation, CO 2 fixation, etc …”

Realization of Lewis Basic Sodium Anion in the NaBH3− Cluster

“…Then, metal Lewis basicity has seen a prosper of research activity, and numerous novel Lewis pairs have been prepared featuring the interaction between Lewis basic transition metals and Lewis acidic ligands . Compared to classic metal–ligand bond, this weak yet electronically reverse metal→LA interaction holds the promise for a novel type of metal–ligand cooperativity in catalytic reactions, and open doors to many applications involving H 2 storage and activation, olefin hydrogenation, CO 2 fixation, etc …”