Unusual magnetic properties of a two-coordinate heteroleptic linear cobalt(ii) complex

Abstract

The synthesis and characterization of two-coordinate cobalt(ii) complexes CoAr'(2) (1) and Ar'CoN(SiMe(3))(2) (2) (Ar' = C(6)H(3)-2,6-(C(6)H(3)-2,6-(i)Pr(2))(2)) are reported. The magnetic data for 2 show that it has an unexpectedly high mu(eff) of 5.65 mu(B) whereas the bent complex 1 has a significantly lower moment.

Conformational Isomerism in Monomeric, Low‐Coordinate Group 12 Complexes Stabilized by a Naphthyl‐Substituted m‐Terphenyl Ligand

“…Indeed, this naphthyl configuration brings the hydrogen atom on C(15) into proximity with the Zn 2+ ion: Zn ⋅⋅⋅ C(15) 2.872(2) Å; c.f. [Co(2,6‐Dipp 2 C 6 H 3 ) 2 ], which has Co ⋅⋅⋅ C 2.878 Å9 (crystallographic van der Waals radii are 2.0 and 2.1 Å for Co and Zn, respectively) 45. Although this Zn ⋅⋅⋅ C distance is smaller than the sum of the van der Waals radii for these elements (3.8 Å), any interaction between the Zn and flanking naphthyl moieties is likely to be weak.…”

“…This ligand configuration also facilitates the formation of an intramolecular CH ⋅⋅⋅ π‐electron interaction between an aryl proton in the 7‐position of the C(7) ring and the centroid of the C(33) aryl ring of a naphthyl substituent (H(14) ⋅⋅⋅ centroid 2.8798(10) Å; C(14)H(14) ⋅⋅⋅ centroid 132.89(19)°, Figure 2) and a longer interaction between an aryl proton in the 2‐position of the C(33) ring and the centroid of the C(17) aryl ring of the naphthyl substituent [H(34) ⋅⋅⋅ centroid 3.0835(10) Å; C(34)H(34) ⋅⋅⋅ centroid=157.89(16)°) 46. 47 It is conceivable that such CH ⋅⋅⋅ π interactions could also contribute to the bending in the C‐Zn‐C moiety; Power and co‐workers have suggested that such interactions may contribute to the bent geometry at the cobalt(II) centre in [Co(2,6‐Dipp 2 C 6 H 3 ) 2 ],9 and the influence of these interactions on the conformation of solid‐state structures has been documented 47. Concomitant with this CH ⋅⋅⋅ π interaction, there is a slight deviation from planarity for the C(7) naphthyl ring (torsion angle 4.84(8)°) and the C(33) naphthyl ring (torsion angle 3.78(9)°) in 1 .…”

“…[4][5][6] The steric demands of these ligands have facilitated the isolation of compounds featuring new quintuple-bonding interactions, for example, [2,6-Dipp 2 C 6 H 3 Cr] 2 (Dipp = 2,6-iPr 2 C 6 H 3 ) and derivatives, [7,8] complexes exhibiting unusual magnetic properties, [9] rare examples of low-coordinate, transition-metal complexes in + 1 oxidation state [10][11][12][13][14] and two-coordinate transition-metal M II complexes. [9,[15][16][17] For Group 12, recent advances have come from the use of sterically demanding m-terphenyl ligands in the stabilization of the first homologous series of Group 12 M I À M I complexes; [2,6-Dipp 2 C 6 H 3 M] 2 complexes were synthesized by reduction of the iodide complexes [MI(2,6-Dipp 2 C 6 H 3 )] n (M = Zn, n = 2; M = Cd, n = 2; M = Hg, n = 1) [18][19][20] and reports of new ZnÀZr bonds. [21] With regards to the m-terphenyls, the 1-naphthyl-substituted ligand 2,6-Naph 2 C 6 H 3 À has been comparatively underutilized in the stabilization of low-coordinate, highly reactive compounds, and yet it possesses intriguing features that in-fluence the structures of its bis(terphenyl) complexes.…”

“…Although it is only very recently that m ‐terphenyls have been exploited in this research area, they are now proving to be versatile ligands for the stabilization of d‐block complexes featuring unusual coordination modes 4–6. The steric demands of these ligands have facilitated the isolation of compounds featuring new quintuple‐bonding interactions, for example, [2,6‐Dipp 2 C 6 H 3 Cr] 2 (Dipp=2,6‐ i Pr 2 C 6 H 3 ) and derivatives,7, 8 complexes exhibiting unusual magnetic properties,9 rare examples of low‐coordinate, transition‐metal complexes in +1 oxidation state10–14 and two‐coordinate transition‐metal M II complexes 9. 15–17 For Group 12, recent advances have come from the use of sterically demanding m ‐terphenyl ligands in the stabilization of the first homologous series of Group 12 M I M I complexes; [2,6‐Dipp 2 C 6 H 3 M] 2 complexes were synthesized by reduction of the iodide complexes [MI(2,6‐Dipp 2 C 6 H 3 )] n (M=Zn, n =2; M=Cd, n =2; M=Hg, n =1)18–20 and reports of new ZnZr bonds 21…”

“…Crystal structure of 2·OEt 2 with displacement ellipsoids set at the 40 % probability level. Hydrogen atoms, with the exception of H(9) and H(35), and the lattice diethyl ether solvent molecule, are omitted for clarity.…”