The MT literature does cover some prior work on extracting or augmenting partial lexicons using non-parallel corpora (Rapp, 1995;Fung and McKeown, 1997;Koehn and Knight, 2000;Haghighi et al., 2008).
none of these methods attempt to train end-to-end MT models, instead they focus on mining bilingual lexicons from monolingual corpora and often they require parallel seed lexicons as a starting point.