Substitution reactivity of [Mo3(μ3-O)(μ3-CCH3)(μ-O2CCHCl2)6(CH3OH)3] O2CCHCl2 (Mo3) and the crystallization of a deca-molybdenum cluster [Mo10O10(μ3-O)8(μ-O)8(py)8](py)2 from Mo3 in pyridine

By heating the trinuclear acetate-bridged molybdenum cluster, [Mo 3 ( mu 3-O)( mu 3-CCH 3 )( mu -O 2 CCH 3 ) 6 (H 2 O) 3 ] + in neat dichloroacetic acid for 4 h (T = 115 degrees C), a new trinuclear molybdenum cluster with chemical formula [Mo 3 ( mu 3-O)( mu 3-CCH 3 )( mu -O 2 CCHCl 2 ) 6 (CH 3 OH) 3 ] + (abbreviated as Mo 3 ) was synthesized. After precipitation from solution with DI water and redissolution in methanol, red crystals formed after one week at 10 degrees C. To quantify the rate of substitution of the terminal methanol ligands, crystals of the trinuclear cluster were dissolved in 0.1 M pyridine- d 5 and monitored over time using 1 H NMR (T = 297 - 310 K). The rate constant for substitution was found to be k 298K obs = 1.87 x 10-4 s- 1 and activation parameters equal to Delta H double dagger obs = 116 (+/- 7) kJ/mol and Delta S double dagger obs = 74 (+/- 23) J mol-1 K-1 . In an attempt to substitute the terminal methanol ligands using concentrated pyridine, a decamolybdenum cluster with a cube-like polyoxomolybdate core was discovered ([Mo 10 O 10 ( mu 3-O) 8 ( mu-O) 8 (py) 8 ] (py) 2 ) (abbreviated as Mo 10 ). Herein, we describe the synthesis, crystallographic data, and substitution reactivity of [Mo 3 ( mu 3-O)( mu 3-CCH 3 )( mu -O 2 CCH 2 Cl 2 ) 6 (CH 3 OH) 3 ]O 2 CCHCl 2 and report on the unexpected formation of [Mo 10 O 10 ( mu 3-O) 8 ( mu-O) 8 (py) 8 ](py) 2 from neat pyridine.