Structures of [M_2(dimen)_4](Y)_2 (M = Rh, Ir; dimen = 1,8-Diisocyanomenthane; Y = PF_6, Tetrakis[3,5-bis(trifluoromethyl)phenyl]borate, B(C_6H_5)_4) Crystals Featuring an Exceptionally Wide Range of Metal−Metal Distances and Dihedral Twist Angles

Abstract

The binuclear complexes [M_2(dimen)_4](Y)_2 (M = Rh, Ir; dimen = 1,8-diisocyanomenthane; Y = PF_6, tetrakis[3,5-bis(trifluoromethyl)phenyl]borate), and B(C_6H_5)_4) have face-to-face structures with M−M distances between 3.60 and 4.48 Å, and square-planar unit twist angles between 0 and 17.2°. Ligand flexing and out-of-plane bending of the metal centers accommodate M−M distances longer than 3.9 Å; addition of a torsional deformation produces a twisted conformation for shorter M−M distances (<3.9 Å). Spectroscopic data indicate that there are two or more deformational isomers of Ir_2(dimen)_4^(2+) in solution