Chromium(II) complexes bearing 2-substituted N,N '-diarylformamidinate ligands

A study regarding the interaction of several ortho ring-substituted N,N'-di arylformamidinate ligands ((DPhF)-F-X, X=Me, OMe, Cl and Br) with the Cr-2( 4+) moiety has been undertaken. X-Ray diffraction and spectroscopic data ha ve shown that while all of these ligands form the well-known paddlewheel ty pe complex Cr-2((DPhF)-F-X)(4), 1 [X=Me, OMe, Cl and Br; Cr-Cr=1.925(1), 2. 140(2), 2.208(2) and 2.272(2) Angstrom, respectively], two of them form hig hly unusual A-frame type complexes with short Cr-Cr bonds, and the smallest M-X-M angle ever reported in an A-frame structure. These are Cr-2(mu-Cl)(( DPhF)-F-X)(3), 2 [X=Cl and Br; Cr-Cr=1.940(1) and 1.940(2) Angstrom, respec tively]. For some of the paddlewheel complexes, the elongation of the metal -metal bond distance out of the 'super-short' range (Cr-Cr > 2.00 Angstrom) has been attributed to the presence of axial interactions between two of t he ortho substituents and the Cr-2(4+) moiety.