The Charge Transfer Approach to Heavier Main‐Group Element Radicals in Transition‐Metal Complexes

Abstract

The Co and Fe complexes 1Co and 1Fe with a coordinated phosphorus radical were easily obtained through a charge-transfer approach from the M precursors LM (tol) (M=Co, Fe; L=CH(MeC=NDipp) , Dipp=2,6-iPr C H ) to the diazafluorenylidene-substituted phosphaalkene 1. Structural, magnetic, and computational studies on 1Co and 1Fe indicate a weak antiferromagnetic interaction between the high-spin M ion and the phosphorus radical, resulting in a triplet and quartet ground state, respectively. Complexes 1Co and 1Fe are the first examples of phosphorus-radical-coordinated transition-metal complexes synthesized by charge transfer, providing a new approach to access radicals of heavier main-group elements.

A high-spin diradical dianion and its bridged chemically switchable single-molecule magnet

“…The Fe–N bond lengths (1.963(2) and 1.968(2) Å) are comparable to those in the diazafluorenylidene-substituted phosphaalkene radical anion coordinated iron complex (1.980(2) and 1.968(2) Å). 21 The bond lengths in the 2,7- t Bu 2 -PTO moiety of 2 are comparable to those in 1 ( Table 1 ), which suggest that 2,7- t Bu 2 -PTO is also most likely in the diradical dianion state. Therefore, two-electron transfer to 2,7- t Bu 2 -PTO occurs in the reaction, and the iron atoms are in the oxidation state of two.…”

“…It has been spectroscopically and structurally characterized. Intrigued by the facile access of 1 and our previous phosphorus radical anion-coordinated Fe II complex exhibiting single-molecule magnetic properties, 21 we were interested in applying the 2,7- t Bu 2 -PTO diradical dianion to construct SMMs. Then, the reaction of 2,7- t Bu 2 -PTO and two molar equivalents of LFe I (toluene) 22 was performed in toluene at room temperature, from which reddish brown crystals of 2 were isolated ( Fig.…”

“…It has been spectroscopically and structurally characterized. Intrigued by the facile access of 1 and our previous phosphorus radical anion-coordinated Fe II complex exhibiting single-molecule magnetic properties, 21 we were interested in applying the Fig. 2 Two-electron reductions of 1 and 2 affording 1K 2 and 2K 2 , respectively.…”

“…S4 †), which confirms the presence of high-spin tetrahedral Fe II ions in 2. 21,27 Crystals of 1K 2 and 2K 2 suitable for X-ray diffraction analysis were grown from THF solutions at -20 °C (Fig. 4).…”

The Charge Transfer Approach to Heavier Main‐Group Element Radicals in Transition‐Metal Complexes

“…Complexes 1Co and 1Fe crystallize in the orthorhombic space group Pccn,and they are isotypic (Figure 1). [14] TheTM atom features adistorted tetrahedral geometry,and the MÀN bonds (2.068(2) and 2.094(2) in 1Co;2 .146(3) and 2.114-(2) in 1Fe)c onnecting to the phosphaalkene moiety are longer than the M À Nbonds (1.932(2) and 1.941(2) in 1Co; 1.980(2) and 1.968(2) in 1Fe)linking to the b-diketiminato ligand. TheP ÀCb onds in 1Co (1.760(3) )a nd 1Fe (1.757-(3) )a re substantially elongated in comparison to that in 1 (1.690(2) ), but are comparable to that in the phosphaal-kene radical anion (1.757(4) ), [4b] indicating the radical forms of the phosphaalkene moieties in 1Co and 1Fe.Inother words,upon coordination to 1,one-electron transfer from the M I center to the phosphaalkene group occurs concomitantly, and the zwitterionic phosphaalkene radical anion-M II cation adducts 1Co and 1Fe are formed.…”