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

Me2NNS reacts with [Rh(CO)2Cl]2 to produce the complex cis-Rh(SNNMe2)(CO)2Cl (1). The latter undergoes reversible CO substitution by Me2NNS to give the complex trans-Rh(SNNMe2)2(CO)Cl (2a). Complexes 1 and 2a, in solution lose CO and Me2NSS, respectively, to give the complex trans-(μ-Cl)2[Rh(SNNMe2)(CO)]2 (3). Complex 1 can also be prepared by bubbling CO through a CH2Cl2 solution of Rh(SNNMe2)(diene)Cl (diene = 1,5-cyclooctadiene (4a), norbornadiene (4b)) obtained by a bridge-splitting reaction of Me2NNS with [Rh(diene)Cl]2. 1 and 2a react with EPh3 (E = P, As, Sb) to give the complexes trans-Rh(EPh3)2(CO)Cl. The complexes trans-Rh(E′Ph3)2(CO)X (X = Cl, E′ = As, Sb; X = Br, NCS, E′ = As) undergo reversible E′Ph3 displacement upon treatment with Me2NNS to give the complexes trans-Rh(SNNMe2)2(CO)X (X = Cl (2a), Br (2b), NCS (2c)). Oxidative additions of Br2, I2, or HgCl2 to 2a produce stable adducts, while the reaction of 2a with CH3I gives an inseparable mixture of the adduct Rh(SNNMe2)2(CO)(CH3)ClI and the acetyl derivative Rh(SNNMe2)2(CH3CO)ClI. A mixture of the acetyl derivative (μ-Cl)2[Rh(SNNMe2)(CH3CO)I]2 and the adduct (μ-Cl)2[Rh(SNNMe2)(CO)(CH3)I]2 is obtained by treating 1 with CH3I. The IR spectra of all the compounds are consistent with S-coordination of Me2NNS. Because of the restricted rotation around the NN bond, the 1H NMR spectra of the new compounds exhibit two quadruplets in the range 3.5-4.3δ when 4J(HH) = 0.7-0.5 Hz. When 4J(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.