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

摘要

A study regarding the interaction of several ortho ring-substituted N,N'-diarylformamidinate 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 have shown that while all of these ligands form the well-known paddlewheel type 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 highly 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, respectively]. 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 the ortho substituents and the Cr-2(4+) moiety. [References: 13]