Benzylidyne Bridges from Diphenylacetylene and a Methylidyne Bridge from Methylmagnesium Chloride

Abstract

Preparation of the dimeric starting compound [(C5H2 tBu3-1,2,4)Fe(μ-Br)]2 (1) gave a small amount of its green sodium bromide adduct [(C5H2 tBu3-1,2,4)Fe(μ-Br)2Na(DME)2] (2). Reduction of 1 under argon in the presence of diphenylacetylene yielded dark red [(C5H2 tBu3-1,2,4)Fe(μ-CPh)]2 (3) containing two bridging benzylidyne ligands resulting from diphenylacetylene scission. The dicobalt methylidyne complex [{(C5HiPr4)Co}2(μ-CH)(μ-H)] (5) was obtained in high yield from the reaction of [(C5HiPr4)Co(μ-Cl)]2 (4) with two equivalents of methylmagnesium chloride. According to DFT calculations the dinuclear alkylidyne complexes 3 and 5 contain d6 metal centers, namely, iron(II) (3) and cobalt(III) (5). Whereas the benzylidyne ligands of the iron complex 3 display an empty orbital of p z character at the bridging carbon atom, the p z orbital of the methylidyne carbon in the dicobalt complex 5 is filled with a lone pair of electrons.

Reactivity studies on [Cp′Fe(μ-I)]2: nitrido-, sulfido- and diselenide iron complexes derived from pseudohalide activation

“…15 ). Consistent with [Cp′Fe(μ-CPh)] 2 , 47 a closer inspection of the NBO orbitals confirmed the absence of any (direct) Fe–Fe bonding interactions in complex 5 .…”

“… 9 In contrast, for the iron alkylidyne derivative [Cp′Fe(μ-CPh)] 2 , which also features a short Fe–Fe distance of 2.3558(4) Å, DFT computations and NBO analyses indicate no direct Fe–Fe bonding interaction; and the benzylidyne ligands should instead be considered as deprotonated phenylcarbene fragments coordinated to two [Cp′Fe] + fragments; thus, forming a low-spin iron( ii ) complex ( Chart 2 ). 47 …”

“…We will present a more detailed analysis of the bonding in 5 , especially in comparison to [Cp′Fe(μ-P)] 2 ( ref. 9 ) and [Cp′Fe(μ-CPh)] 2 , 47 in our computational details section. However, the Cp′ cent –Fe distance of 1.74 Å in 5 compares well with the values found in [Cp′Fe(μ-P)] 2 (1.73 Å) 9 and [Cp′Fe(μ-CPh)] 2 (1.74 Å); 47 and it is also consistent with an S = 0 ground state.…”

“…9 ) and [Cp′Fe(μ-CPh)] 2 , 47 in our computational details section. However, the Cp′ cent –Fe distance of 1.74 Å in 5 compares well with the values found in [Cp′Fe(μ-P)] 2 (1.73 Å) 9 and [Cp′Fe(μ-CPh)] 2 (1.74 Å); 47 and it is also consistent with an S = 0 ground state. To further address the electronic structure, the 57 Fe Mössbauer spectrum and solid-state magnetic susceptibility data for 5 were recorded ( vide infra ).…”

Iron(II) High‐Spin and Low‐Spin Complexes from Pentaisopropylcyclopentadienyliron(II) Bis(trimethylsilyl)amide

“…Another entry into a variety of iron(II) half‐sandwich complexes with or without π‐acceptor ligands uses bulky alkylcyclopentadienyl ligands to avoid ferrocene formation. The halides [ 4 CpFe(µ‐Br)] 2 ( 4 Cp = C 5 H i Pr 4 ), [ 5 CpFe(µ‐Br)] 2 ( 5 Cp = C 5 i Pr 5 ), or [Cp′′′Fe(µ‐X)] 2 (Cp′′′ = 1,2,4‐ t Bu 3 C 5 H 2 ; X = I, Br) are stable enough to be stored under inert gas for synthetic use.…”