We consider the transfer of a two-species Bose-Einstein condensate into an optical lattice with a density such that that a Mott-insulator state with one atom per species per lattice site is obtained in the deep lattice regime. Depending on collision parameters the result could be either a 'mixed' or a 'separated' Mott-insulator phase. Such a 'mixed' two-species insulator could then be photo-associated into an array of dipolar molecules suitable for quantum computation or the formation of a

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... ar molecular condensate. For the case of a ^87Rb-^41K two-species BEC, however, the large inter-species scattering length makes obtaining the desired 'mixed' Mott insulator phase difficult. To overcome this difficulty we investigate the effect of varying the lattice frequency on the mean-field interaction and find a favorable parameter regime under which a lattice of dipolar molecules could be generated.