Crystal structures of two dioxomolybdenum complexes stabilized by salan ligands featuring phenyl and cyclo-hexyl backbones

Two cis-dioxomolybdenum complexes based on salan ligands with different backbones are reported. The first complex, dioxido{2,2'-[l,2-phenyl-enebis(imino-methyl-ene)]bis-(phenolato)}molybdenum(VI) di-methyl-formamide disolvate, [Mo(C₂₀H₁₈N₂O₂)O₂]·2C₃H₇NO (^PhLMoO₂, 1b), features a phenyl backbone, while the second complex, (6,6'-{[(cyclo-hexane-1,2-di-yl)bis(aza-nedi-yl)]bis-(methyl-ene)}bis-(2,4-di-tert-butyl-phenolato))dioxidomolybdenum(VI) methanol disolvate, [Mo(C₃₆H₅₆N₂O₂)O₂]·2CH₃OH (^CyLMoO₂, 2b), is based on a cyclo-hexyl backbone. These complexes crystallized as solvated species, 1b·2DMF and 2b·2MeOH. The salan ligands ^PhLH₂ (1a) and ^CyLH₂ (2a) coordinate to the molybdenum center in these complexes 1b and 2b in a κ² N,κ² O fashion, forming a distorted octa-hedral geometry. The Mo-N and Mo-O distances are 2.3475 (16) and 1.9567 (16) Å, respectively, in 1b while the corresponding measurements are Mo-N = 2.3412 (12) Å, and Mo-O = 1.9428 (10) Å for 2b. A key geometrical feature is that the N-Mo-N angle of 72.40 (4)° in ^CyLMoO₂ is slightly less than that of the ^PhLMoO₂ angle of 75.18 (6)°, which is attributed to the flexibility of the cyclo-hexane ring between the nitro-gen as compared to the rigid phenyl ring in the ^PhLMoO₂.