Generation of a Ni₃ Phosphinidene Cluster from the Ni(0) Synthon, Ni(η³-CPh₃)₂

Abstract

Reaction of NiCl2 in THF with 2 equiv of Li­(CPh3) at −25 °C results in formation of Ni­(η3-CPh3)2 (1) in moderate yield. Complex 1 was fully characterized, which included analysis by X-ray crystallography. In the solid state, 1 features an η3 binding mode of its trityl ligands, resulting in a structure that is reminiscent of the archetypal Ni­(II) organometallic, bis­(η3-allyl)­nickel. In addition, complex 1 has proved to be an excellent Ni(0) synthon. For example, reaction of 1 with excess CO resulted in formation of Ni­(CO)4 along with Gomberg’s dimer. Similarly, reaction of 1 with 4 equiv of PPh3 resulted in formation of Ni­(PPh3)4 (2). Presumably, its ability to function as a Ni(0) source is derived from the relatively high stability of the trityl radical, which results in weak Ni–C bonds that are susceptible to homolytic cleavage. Finally, reaction of 1 with 2 equiv of PPh3, in an attempt to form a larger Ni cluster, resulted in formation of [Ni3(μ3-PPh)­(μ-PPh2)2(PPh3)3] (3) in moderate yield. Its phosphide and phosphinidene ligands are derived from the formal reduction of the PPh3 ligand.

Synthesis of Bis(trityl)iron(II) and Formation of the Iron(0)-Stabilized o,o-Isomer of Gomberg’s Dimer

“…The latter complex represents the first observation of the o , o -isomer of Gomberg’s dimer, which differs from the usual α, p -isomer found in solution and the solid-state, and provides a further understanding of this historically important system. Additionally, given our preliminary results, we suggest that 1 could function as a precursor to low-valent Fe APNCs, a class of materials that has resisted isolation thus far. ,, …”

“…Reaction of Fe­(OAc) 2 with 2 equiv of in situ generated [Li]­[CPh 3 ] ,, in THF at −25 °C results in the formation of [Fe­(η 5 -CPh 3 ) 2 ] ( 1 ), which can be isolated as a deep red crystalline solid in 22% yield after workup from CH 2 Cl 2 /hexanes (Scheme ). We ascribe the low yield of 1 to the unwanted reduction of Fe­(OAc) 2 by [Li]­[CPh 3 ], which results in the formation of low-valent Fe-containing products.…”

“… In addition, the 13 C­{ 1 H} NMR spectrum of this mixture displays a resonance at 211 ppm, which matches the 13 C NMR chemical shift reported for [Fe­(CO) 5 ] (Figure S5). Similarly, the reaction of [Ni II (η 3 -CPh 3 ) 2 ] with CO forms [Ni­(CO) 4 ], although in this case the reaction is essentially instantaneous …”

“…10,11 Recently, we completed the characterization of bis(trityl)nickel(II), [Ni II (η 3 -CPh 3 ) 2 ], which we subsequently employed as an Ni(0) synthon for the synthesis of atomically precise nanoclusters (APNCs). 12 During the course of this work, we realized that the analogous Fe complex, [Fe II (CPh 3 ) 2 ], was unknown. Given the paucity of Fe(0) synthons, 13−17 we pursued its synthesis to evaluate its utility as a APNC precursor.…”

Understanding the Early Stages of Nickel Sulfide Nanocluster Growth: Isolation of Ni3, Ni4, Ni5, and Ni8 Intermediates

“…[ 21–23 ] For example, we recently used [Ni II (η 3 ‐CPh 3 ) 2 ] as a source of Ni(0) to generate the low‐valent phosphinidene cluster, [Ni 3 (PPh)(PPh 2 ) 2 (PPh 3 ) 3 ]. [ 24 ] Similarly, Roy and co‐workers recently employed the commercially available Ni(0) synthon, [Ni(1,5‐cod) 2 ], to generate a series of low‐valent Ni phosphinidene clusters. [ 25 ] Steigerwald and co‐workers have also employed [Ni(1,5‐cod) 2 ] as a source of Ni(0) to access low‐valent, chalcogenide‐capped Ni nanoclusters.…”