The diamagnetic nature of the complex suggested that a MoMo bond might have been formed. ROESY cross peaks showed that two chemically different ligand spheres are present as part of one and the same molecule. The recorded N NMR shift (N = 147 ppm) differs significantly from that of the free aniline (tBu)(Ar)NH (N = 289 ppm), thus indicating that the ligand is metal-bound. High barriers for rotation about the NAr bond render the ortho-H atoms on the aryl ring diastereotopic on the NMR timescale; one of them resides in the anisotropy cone of a neighboring aryl ring and is therefore highly shielded (H = 4.19 ppm). The structure of 11 in the solid state confirms the conclusions drawn from the NMR data; to the best of our knowledge, 11 is the first example of a heterodimeric species of the type [X3MoMoY3] (Figure ). Truly perplexing is that fact that 11 incorporates an intact "Cummins fragment" as one of the subunits, even though complex 1 is famous for not engaging in metal-metal triple bonding otherwise. The Newman-type projection shows that the ligands are not perfectly staggered about the MoMo axis, despite their bulk; 45 the smallest torsion (O1-Mo1-Mo2-N1) is only 39.6° (rather than 60°). The arguably most striking feature, however, is the unusually long MoMo distance of 2.2955(7) Å) (see below).