O-Sulfinate

Sulfur dioxide is capable of reacting with metal alkyl, aryl or u-allyl complexes in an insertion-type reaction to yield S-sulfinate (4), O-sulfinate (5) or 0,< -sulfinate complexes (6).13 It can also insert into the metal-metal bond in the cobalt complex (7) to give the S02-bridged complex (8).38... 

From the evidence cited above it has been assumed that the formation of the O-sulfinates is a common feature of the insertion reactions of coordinatively saturated transition metal alkyls and aryls. The kinetic studies discussed in Section III refer to the scission of the M—R bond which yields the appropriate metal sulfinate. 

Sulfinate ligands bind to transition metals as S-sulfLnate, O-sulfinate, or 0,0 -sulfi-nate isomers, the first two types having been demonstrated by x-ray crystallography A fourth structural type, M-S(0)-0R, has also been reported ... 

The various sulfinate isomers are usually distinguishable by the S-O stretching frequencies Although O- and 0,0 -sulfinate isomers are generally isolated from SO2 insertion reactions with non-transition and early transition metals such as Ti and Zr for the mid and late transition elements S-sulfinates predominate. However, exceptions exist, e.g. the O-sulfinate compound [Ni(02SCH3)(p3)](BPh4) . Work by Wojcicki and others has proven that many (if not all) SO2 insertions with Mo, Mn, and Re complexes proceed via O-sulfinate intermediates, which can subsequently rearrange to more stable... 

O-sulfinates formed by insertion reactions carried out in hquid SO2 also derives from Lewis acid complexation (by SO2) of unbound sulfinate oxygen ... 

The reaction of butadiene iron tricarbonyl, Fe(CO)3(C4H6), in liquid SO2 with BF3 leads to an interesting product containing an O-bonded RSO2 moiety A crystal structure analysis (Fig. 34) of the product showed the presence of allylic and O-sulfinate interactions with Fe, resulting from electrophilic attack of SO2 on the coordinated butadiene group. In addition, a BF3 group was found to be bound reversibly to the... 

The tetrahydro-l,3-oxazin-2-one (372) is prepared through the cyclization of the threo form of hydroxycarbamate (371) in contact with mesyl chloride, conversely the erythro isomer is O-sulfinated without undergoing cyclization. The removal of an A-Boc group under basic conditions is unusual, and it is proposed that the selective cyclization of the threo isomer occurs because, in its lowest energy conformation, the proximity of the ethoxycarbonyl group and the mesyloxy unit potentiates the ionization of the latter. Once formed, the mesyloxy anion assists deprotonation of the Boc group and hence the cyclization to the oxazine (Scheme 100) <87H(26)64i, 88H(27)667>. 

The migration (insertion) reaction may also occur in the case of many other unsaturated molecules such as SO2, CO2, N2, NO, nitriles, isonitriles, and ketones. The insertion of sulfur dioxide may proceed very rapidly. The NMR and IR measurements show that the reaction proceeds through O-sulfinates which subsequently undergo rearrangement to give stable S-sulfinates ... 

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