Synthesis and Structural Characterization of a Dimeric Cobalt(I) Homoleptic Alkyl and an Iron(II) Alkyl Halide Complex

Abstract

The homoleptic cobalt(I) alkyl [Co{C(SiMe 2 Ph) 3 }] 2 (1) was prepared by reacting CoCl 2 with [Li{C(SiMe 2 Ph) 3 }(THF)] in a 1:2 ratio. Attempts to synthesize the corresponding iron(I) species led to the iron(II) salt [Li(THF) 4 ][Fe 2 (μ-Cl) 3 {C-(SiMe 2 Ph) 3 } 2 ] (2). Both 1 and 2 were characterized by X-ray crystallography, UV−vis spectroscopy, and magnetic measurements. The structure of 1 consists of dimeric units in which each cobalt(I) ion is σ-bonded to the central carbon of the alkyl group −C(SiMe 2 Ph) 3 and π-bonded to one of the phenyl rings of the −C(SiMe 2 Ph) 3 ligand attached to the other cobalt(I) ion in the dimer. The structure of 2 features three chlorides bridging two iron(II) ions. Each iron(II) ion is also σ-bonded to the central carbon of a terminal −C(SiMe 2 Ph) 3 anionic ligand. The magnetic properties of 1 reveal the presence of two independent cobalt(I) ions with S = 1 and a significant zero-field splitting of D = 38.0(2) cm −1 . The magnetic properties of 2 reveal extensive antiferromagnetic exchange coupling with J = −149(4) cm −1 and a large second-order Zeeman contribution to its molar magnetic susceptibility. Formation of the alkyl 1 and the halide complex 2 under similar conditions is probably due in part to the fact that Co(II) is more readily reduced than Fe(II).

A linear cobalt(II) complex with maximal orbital angular momentum from a non-Aufbau ground state

“…Synthesis and structure of a linear cobalt dialkyl complex Our attempts to synthesize Co(C(SiMe 3 ) 3 ) 2 from metathesis reactions of [C(SiMe 3 ) 3 ]salts and CoX 2 (X = Cl, Br, or I) gave only intractable amorphous black solids. Similar reactivity with [C(SiMe 3 ) 3 ]was reported previously, but after switching to [C(SiMe 2 Ph) 3 ] -(where Ph is phenyl), we found it possible to isolate the dimer [Co(C(SiMe 2 Ph) 3 )] 2 , a product formed by the in situ reduction of cobalt(II) (10). Thus, at least one challenge in isolating a dialkyl cobalt(II) complex is the strongly reducing nature of the carbanion.…”

Dispersion Forces, Disproportionation, and Stable High‐Valent Late Transition Metal Alkyls

“…Co(nor) 4 remains the only homoleptic, σ‐bonded cobalt alkyl to have been characterized. Other stable homoleptic, open‐shell, late transition metal alkyls are limited to a handful of neutral manganese(II) and iron(II) alkyls MnR 2 (R= ‐CH 2 Bu t , ‐CH(SiMe 3 ) 2 or ‐C(SiMe 3 ) 3 ) and Fe{C(SiMe 3 ) 3 } 2 as well as the M I complexes [M{C(SiMe 3 ) 3 } 2 ] − (M=Mn and Fe) and σ/π bonded [Co{C(SiMe 2 Ph) 3 }] 2 …”

“…Other stable homoleptic,o penshell, late transition metal alkyls are limited to ah andful of neutral manganese(II) and iron(II) alkyls MnR 2 (R = -CH 2 Bu t , [3] -CH(SiMe 3 ) 2 [4] or -C(SiMe 3 ) 3 [5] )a nd Fe{C-(SiMe 3 ) 3 } 2 [6] as well as the M I complexes [M{C(SiMe 3 ) 3 } 2 ] À (M = Mn and Fe) [7] and s/p bonded [Co{C(SiMe 2 Ph) 3 }] 2 . [8] Subsequently,C o(nor) 4 and Fe(nor) 4 were resynthesized and spectroscopically and structurally characterized by the groups of Theopold [9] and Hayton, [10] and Mo(nor) 4 was also reported. [11] Hayton, Figueroa and co-workers described the related homoleptic M IV species,M (N=C t Bu 2 ) 4 (M = Co, [12] Fe [10] ).…”

Trisyl-based multidentate ligands: synthesis and their transition-metal complexes

“…In summary, we have synthesized a series of trisyl-based multidentate ligands and isolated their lithium salts by using the newly designed synthon 1. Dimeric manganese(II) (4 and 5), iron(II) (6), cobalt(II) (7), and monomeric chromium(II) (8) were obtained by the reaction of lithium salts (3c and 3d) with MCl 2 (M = Cr, Mn, Fe, Co). Moreover, the preliminary reactivities of compound 4 were explored.…”

“…Besides their ability to stabilize low coordination complexes, 4,6,7 their ability to avoid side reactions caused by the strong reducing nature of carbanions is even more attractive to us. 8 Following our interest in ligands with cooperative coordination modes, we tried to synthesize a novel type ligand containing one or two trisyl moieties as carbanions, which would be linked together with a common coordination site, such as N or S atoms (Fig. 1(I)).…”