Ligating properties of thionitrosoamines: III. Carbonyl complexes of rhodium(I) and rhodium(III) containing N-thionitrosodimethylamine

Abstract

Me 2NNS reacts with [Rh(CO) 2Cl] 2 to produce the complex cis-Rh(SNNMe 2)(CO) 2Cl ( 1). The latter undergoes reversible CO substitution by Me 2NNS to give the complex trans-Rh(SNNMe 2) 2(CO)Cl ( 2a). Complexes 1 and 2a, in solution lose CO and Me 2NSS, respectively, to give the complex trans-(μ-Cl) 2[Rh(SNNMe 2)(CO)] 2 ( 3). Complex 1 can also be prepared by bubbling CO through a CH 2Cl 2 solution of Rh(SNNMe 2)(diene)Cl (diene = 1,5-cyclooctadiene ( 4a), norbornadiene ( 4b)) obtained by a bridge-splitting reaction of Me 2NNS with [Rh(diene)Cl] 2. 1 and 2a react with EPh 3 (E = P, As, Sb) to give the complexes trans-Rh(EPh 3) 2(CO)Cl. The complexes trans-Rh(E′Ph 3) 2(CO)X (X = Cl, E′ = As, Sb; X = Br, NCS, E′ = As) undergo reversible E′Ph 3 displacement upon treatment with Me 2NNS to give the complexes trans-Rh(SNNMe 2) 2(CO)X (X = Cl ( 2a), Br ( 2b), NCS ( 2c)). Oxidative additions of Br 2, I 2, or HgCl 2 to 2a produce stable adducts, while the reaction of 2a with CH 3I gives an inseparable mixture of the adduct Rh(SNNMe 2) 2(CO)(CH 3)ClI and the acetyl derivative Rh(SNNMe 2) 2(CH 3CO)ClI. A mixture of the acetyl derivative (μ-Cl) 2[Rh(SNNMe 2)(CH 3CO)I] 2 and the adduct (μ-Cl) 2[Rh(SNNMe 2)(CO)(CH 3)I] 2 is obtained by treating 1 with CH 3I. The IR spectra of all the compounds are consistent with S-coordination of Me 2NNS. Because of the restricted rotation around the NN bond, the 1H NMR spectra of the new compounds exhibit two quadruplets in the range 3.5–4.3δ when 4 J(HH) = 0.7–0.5 Hz. When 4 J(HH) < 0.5 Hz, the perturbing effect of the quadrupolar relaxation of the 14N nucleus obscures the spin-spin coupling and two broad signals are observed in the range 3.6–4δ.