Three-Coordinate Rhodium Complexes in Low Oxidation States.

The isolation of simultaneously low-coordinate and low-valent compounds is a timeless challenge for preparative chemists. This work showcases the preparation and full characterization of tri-coordinate rhodium(-I) and rhodium(0) complexes as well as a rare rhodium(I) complex. Reduction of [{Rh(μ-Cl)(IPr)(dvtms)}2 ] (1, IPr=1,3-bis(2,6-diisopropylphenyl)imidazolyl-2-ylidene; dvtms=divinyltetramethyldisiloxane) with KC8 gave the trigonal complexes K[Rh(IPr)(dvtms)] and [Rh(IPr)(dvtms)], whereas the cation [Rh(IPr)(dvtms)]+ results from their oxidation or by abstraction of chloride from 1 with silver salts. The paramagnetic Rh0 complex is a unique fully metal-centered radical with the unpaired electron in the dz2 orbital. The Rh(-I) complex reacts with PPh3 with replacement of the NHC ligand, and behaves as a nucleophile, which upon reaction with [AuCl(PPh3 )] generates the trigonal pyramidal complex [(IPr)(dvtms)Rh-Au(PPh3 )] with a metal-metal bond between two d10 metal centers.