Di- and trinuclear complexes with the mono- and dianion of 2,6-bis(phenylamino)pyridine: High-field displacement of chemical shifts due to the magnetic anisotropy of quadruple bonds
Fa. Cotton et al., Di- and trinuclear complexes with the mono- and dianion of 2,6-bis(phenylamino)pyridine: High-field displacement of chemical shifts due to the magnetic anisotropy of quadruple bonds, INORG CHEM, 40(12), 2001, pp. 2778-2784
The monoanion of 2,6-bis(phenylamino)pyridine (HBPAP(-)) has been found to
support quadruply bonded Cr-2(4+) and Mo-2(4+) units in Cr-2(HBPAP)(4) (1)
and Mo-2(HBPAP)(4) (2). The corresponding dianion BPAP(2-) was able to stab
ilize the trinuclear complexes, (TBA)(2)Cr-3(BPAP)(4) (3) and (TBA)(2)Ni-3(
BPAP)(4) (4), where TBA is the tetrabutylammonium cation. The dinuclear com
plexes have the typical paddlewheel configuration with Cr-Cr distances of a
bout 1.87 Angstrom and a Mo-Mo distance of 2.0813(5) Angstrom and exhibit a
high-field displacement of the corresponding N-H signals caused by the mag
netic anisotropy of the quadruple bonds. For the trinuclear complexes, 3 ha
s a linear chain of three chromium atoms arranged in an unsymmetrical fashi
on with two chromium atoms paired to give a quadruply bonded unit (Cr-Cr di
stance: 1.904(3) Angstrom) and an isolated, square planar Cr-II unit at 2.5
89(3) Angstrom from the dimetal unit. On the other hand, the three nickel a
toms in 4 are evenly spaced, having Ni...Ni distances of 2.3682(8) Angstrom
. The trinuclear compounds show a twisted conformation with an overall tors
ion angle of about 30 degrees.