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(C(20)H(18)N(2)O(2))O(2)]·2C(3)H(7)NO ((Ph)LMoO(2), 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(C(36)H(56)N(2)O(2))O(2)]·2CH(3)OH ((Cy)LMoO(2), 2b), is based on a cyclo-hexyl backbone. These complexes crystallized as solvated species, 1b·2DMF and 2b·2MeOH. The salan ligands (Ph)LH(2) (1a) and (Cy)LH(2) (2a) coordinate to the molybdenum center in these complexes 1b and 2b in a κ(2) N,κ(2) O fashion, forming a distorted octa-hedral geometry. The Mo-N and Mo-O distances are 2.3475†(16) and 1.9567†(16)†à , respectively, in 1b while the corresponding measurements are Mo-N = 2.3412†(12)†à , and Mo-O = 1.9428†(10)†à for 2b. A key geometrical feature is that the N-Mo-N angle of 72.40†(4)° in (Cy)LMoO(2) is slightly less than that of the (Ph)LMoO(2) 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 (Ph)LMoO(2).