Oxidation of cyclic amines by molybdenum(II) and tungsten(II) halocarbonyls, [M(CO)4X2]2 (M = Mo, W; X = Cl, Br)

Abstract

The molybdenum(II) and tungsten(II) halocarbonyls, [M(CO)4X2]2 (M = Mo, W; X = Cl, Br) react with a large excess of the nitrogen bases, 1-methylpyrrolidine, 1-methylpiperidine, 1-ethylpiperidine and 2-ethylpiperidine to give aminecarbonyl complexes of the type M(CO)3L3 (L= alkylamine). Excess piperidine reacts with the tungsten halocarbonyls, [W(CO)4X2]2 (X = Cl, Br), to give the trans isomer of the complex, W(CO)3(C5H11N)3. The halogens were recovered as the amminium salts, amine, HX. The oxidized amine dimerized to form a yellow product which was recovered as an oily liquid but in very small amounts. However, in the reaction between Mo(CO)4Br2 and 1-ethylpiperidine, a yellow crystalline solid, with a melting point of 224 oC was recovered in sufficient amounts for elemental analysis, melting point and spectral data. Its mass spectrum showed a molecular ion peak at m+/z = 222, a clear evidence that the oxidized amine dimerizes. The cyclic dibasic amine piperazine, C4H10N2 is not, however, oxidized by these halocarbonyls but rather it reacts by substituting some CO groups to form products of the type, M(CO)3(C4H10N2)2X2 (M = Mo, W; X = Cl, Br). Products were characterized by elemental analysis, IR, UV, 1H NMR and mass spectrometry.