Crystal structures of trans-acetyl­dicarbon­yl(η(5)-cyclo­penta­dien­yl)(1,3,5-tri­aza-7-phosphaadamantane)molybdenum(II) and trans-acetyl­di­carbon­yl(η(5)-cyclo­penta­dien­yl)(3,7-diacetyl-1,3,7-tri­aza-5-phosphabi­cyclo­[3.3.1]nona­ne)molyb­den­um(II)

The title compounds, [Mo(C(5)H(5))(COCH(3))(C(6)H(12)N(3)P)(CO)(2)], (1), and [Mo(C(5)H(5))(COCH(3))(C(9)H(16)N(3)O(2)P)(C(6)H(5))(2)))(CO)(2)], (2), have been prepared by phosphine-induced migratory insertion from [Mo(C(5)H(5))(CO)(3)(CH(3))]. The mol­ecular structures of these complexes are quite similar, exhibiting a four-legged piano-stool geometry with trans-disposed carbonyl ligands. The extended structures of complexes (1) and (2) differ substanti­ally. For complex (1), the molybdenum acetyl unit plays a dominant role in the organization of the extended structure, joining the mol­ecules into centrosymmetrical dimers through C—H⋯O inter­actions with a cyclo­penta­dienyl ligand of a neighboring mol­ecule, and these dimers are linked into layers parallel to (100) by C—H⋯O inter­actions between the molybdenum acetyl and the cyclo­penta­dienyl ligand of another neighbor. The extended structure of (2) is dominated by C—H⋯O inter­actions involving the carbonyl groups of the acetamide groups of the DAPTA ligand, which join the mol­ecules into centrosymmetrical dimers and link them into chains along [010]. Additional C—H⋯O inter­actions between the molybdenum acetyl oxygen atom and an acetamide methyl group join the chains into layers parallel to (101).