New main group ferrocenyldithiocarbamates and conversion to ferrocene oxazolidine-2-thione and -2-one

Three new main group ferrocenyldithiocarbamate complexes viz. {Pb[(FcCH2)(CH2CH-2OH)NCS2)]2}·(FcCH2-3-oxazolidine-2-thione)·(H2O) (1), {Sb[(FcCH2)(CH2CH-2OH)NCS2)]3} (2) and {Bi[(FcCH2)(CH2CH-2OH)NCS2)]3} (3), (Fc = ferrocenyl) have been synthesized and characterized by elemental analyses, IR, 1H and 13C NMR spectroscopy and X-ray crystallography. X-ray analyses for 1 indicates a distorted trigonal bipyramidal geometry around Pb(II) and a cyclised product 3-ferrocenylmethyl-oxazolidine-2-thione (4) cocrystallizes with 1. The geometry around Sb(III) in 2 is pseudo-octahedral while 3 forms a dimer displaying a distorted square antiprism geometry around the Bi(III) center. Several attempts to synthesize the pure cyclised product 3-ferrocenylmethyl-oxazolidine-2-thione (4) using Pb, Pb(II) salts failed but 4 was fortuitously obtained in an attempt to synthesize the Cu(I) cluster by comproportionation of {Cu[(FcCH2)(CH2CH-2OH)NCS2)]2} using copper powder. Interestingly, varying the reaction time yielded another completely desulfurized cyclised product 3-ferrocenylmethyl-oxazolidine-2-one (5). Both 4 and 5 have been characterized using spectroscopic techniques and X-ray crystallography and the possible mechanism for the conversion of {Cu[(FcCH2)(CH2CH-2OH)NCS2)]2} to 3-ferrocenylmethyl-oxazolidine-2-thione (4) have been explained with the help of periodic UV-Vis. and ESI-MS experiments. This investigation will pave a new pathway for the synthesis of similar cyclised products using similar safer and sustainable reaction condition.