Michael Charles Kerby

Reactions of MO2(O2CMe)4with amines and diamines: A structural and thermal study of stepwise acetate displacement and hydrogen bonding

Abstract MO 2 (O 2 CMe) 4 ( 1 ) reacts with the neat bidentate diamines Me(H)NCH 2 CH 2 N(H)ME ( N , N′ -dmed), H 2 NCH 2 CH 2 CH 2 NH 2 (pda), H 2 NCH 2 CH 2 NMe 2 ( N , N -dmed), and H 2 NCH 2 CH 2 N(H)Me ( N -med) to form the compounds 1 ∞ [MO 2 (O 2 CMe) 4 ( N , N′ -dmed)] ( 4 ), ∞[MO 2 (O 2 CMe) 4 (pda)] ( 5 ), {[Mo 2 (O 2 CMe) 3 ( N , N -dmed) 2 ] + [(O 2 CMe)] − } 2 ( 6 ), and {[MO 2 (O 2 CMe) 3 ( N -med) 2 ] + [(O 2 CMe)] − } 2 · N -med ( 7 ), respectively. Compounds 4 - 7 possess MoMo quadruple bonds (MoMo = 2.11(2) A, ave) and weak axial MoN bonds (MoNa ax = 2.7(1) A, ave). Compound 4 exhibits a kinked, one-dimensional chain structure comprising MO 2 (O 2 CMe) 4 units linked by N , N′ -dmed ligands. The amine hydrogens are weakly hydrogen-bonded to adjacent O 2 CMe oxygens (N ⋯ O = 3.09(9) A). Compound 5 crystallizes in a linear one-dimensional chain structure with a four-fold disorder in the pda chain. Conversely, compounds 6 and 7 display structures resulting from acetate displacement from the MO 2 centre. Each Mo atom possesses a chelating diamine with the NH 2 group bound in the equatorial position previously occupied by the displaced acetate moiety. Two [MO 2 (O 2 CMe) 3 (diamine) 2 ] + units are linked together via hydrogen bonding between the equatorial NH 2 diamine hydrogens and the oxygens of the displaced acetate groups. The polar monoamines MeNH 2 and NH 3 do not affect acetate displacement presumably due to their inability to overcome entropic effects of the bidentate acetate ligands. Compounds 4 - 7 expel the diamine ligands in the solid state and reform crystalline 1 (XRD). The temperatures of amine expulsions occur at or below the boiling points of the pure diamine liquids. Crystal data for 4 at 20°C: triclinic P 1 , a = 8.784(3); b = 12.945(6), c = 8.663(3) A; α = 91.73(3)°, β = 97.23(3)°, γ = 101.45(4)°;