Characterization and Electronic Structures of Five Members of the Electron Transfer Series [Re(benzene-1,2-dithiolato)3]z (z = 1+, 0, 1−, 2−, 3−): A Spectroscopic and Density Functional Theoretical Study

Abstract

The reaction of ReCl(5) with 3 equiv of a benzene-1,2-dithiolate derivative in CH(3)CN produced, after the addition of [C(8)H(16)N]Br ([C(8)H(16)N](+) is 5-azonia-spiro[4,4]nonane), brownish-green crystals of [C(8)H(16)N][Re(tms)(3)] (1c) and [C(8)H(16)N][Re(Cl(2)-bdt)(3)] (2c), where (tms)(2-) represents 3,6-bis(trimethylsilyl)benzene-1,2-dithiolate and (Cl(2)-bdt)(2-) is 3,6-dichlorobenzene-1,2-dithiolate. Chemical reduction of [Re(bdt)(3)] (3b) with n-butyllithium in the presence of PPh(4)Br yielded [PPh(4)][Re(bdt)(3)] (3c), where (bdt)(2-) is benzene-1,2-dithiolate. The three monoanionic complexes possess a diamagnetic ground state (Re(V), d(2), S = 0). The crystal structures of 1c x 2 CH(3)CN and 2c x C(3)H(6)O have been determined by X-ray crystallography. The electrochemistry establishes that the complexes are members of electron transfer series involving a monocation [Re(V)(L(*))(2)(L)](+) (S = 0(?)), a neutral [Re(V)(L(*))(L)(2)](0) (S = 1/2), a monoanion [Re(V)(L)(3)](1-) (S = 0), a dianion [Re(IV)(L)(3)](2-) (S = 1/2), and a trianion [Re(III)(L)(3)](3-) (S = 1(?)). The unique X-band EPR spectrum of the neutral species clearly describes a diamagnetic Re(V) d(2) central ion with the unpaired electron located in a purely ligand-centered molecular orbital, whereas it is metal-centered in the dianionic form: a Re(IV) d(3) ion with three dithiolate(2-) ligands. S K-edge and Re L-edge X-ray absorption spectroscopy confirms these assignments and furthermore shows that the monoanion has a Re(V) central ion with three dianionic ligands. The geometrical and electronic structures of all members of the electron transfer series have been calculated by density functional theoretical methods, and the S K-pre-edge spectra have been simulated and assigned using a time-dependent DFT protocol.