Germylenes with thiacycloheptynes

Thus, the sign of the observed polarization of the Me protons of the product 22 (absorption) is unambiguous evidence of the formation of an intermediate triplet 1,3-biradical 23T, and this fact, in turn, means that 16 enters the reaction with 21 in the excited triplet state. The end product 22 is formed after the triplet-singlet conversion of the triplet biradical 23t followed by cyclization of the singlet biradical 23s (Scheme 11), while the triplet biradical 23T also reverts to the initial reagents. Only this reverse reaction could explain the negative polarization (emission) of the Me protons of the initial thiacycloheptyne 21. It should be noted that the process described in Scheme 11 is the first example of a reaction of the excited triple state of germylene 1676. 

Because of the known capability of digermenes to insert into multiple bonds3,4, it is reasonable to start the present discussion with the reactions which occur in the photolysis of 26 in the presence of unsaturated trapping agents. Similarly to germylene 16, digermene 28 could insert into the triple bond of thiacycloheptyne 21 with the formation of digermacyclobutene 30. 

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