Synthesis, characterization and reactions of some short chain alkoxycarbonyl molybdenum compounds [M][Mo(CO)5(COOR)] (M = PPN, Et4N and R = Me, Et, iPr) and [Ph4As]2[Mo(CO)4{(COOCH(CH3)2)2}]: X-ray structure of [Et4N]2[Mo4O13]

The short chain alkoxycarbonyl complexes of molybdenum, [PPN][Mo(CO)(5)(COOR)], [R = CH3, CH2CH3 and CH(CH3)(2)], have been synthesized by the addition of [Mo(CO)(6)] to a refluxing solution of [PPN][OR] in different alcohol solvents under a CO atmosphere. In the absence of CO, metal alkoxide complexes [Mo(CO)(5)(OR)] (R = CH2CH3 and CH(CH3)(2)) were formed. These new alkoxycarbonyl complexes were characterized by IR, H-1 and C-13 NMR spectroscopy, melting point and elemental analysis. When the CH3CN solution of the compounds [PPN][Mo(CO)(5)(COOCH(CH3)(2))] and [PPN][Mo(CO)(5)(OCH(CH3)(2))] were exposed to UV light the compounds decomposed to form the cluster compound [PPN](2)[Mo6O19]. The tetraethylammonium derivative, [Et4N][Mo(CO)(5)(COOCH3)], prepared from [Et4N][OCH3] and Mo(CO)(6) in methanolic solution also decomposed in CH3CN to form the new dark brown crystalline molybdenum oxo-cluster [Et4N](2)[Mo4O13]. The compound crystallizes in the monoclinic form with a space group of P 21/n. Addition of [Ph4As][OCH(CH3)(2)] to Mo(CO)(6) in a ratio of 4: 1 results in the formation of the bis(alkoxycarbonyl) complex, [Ph4As](2)[Mo(CO)(4){(COOCH(CH3)(2))(2)}]. The reaction of the methoxycarbonyl complex, [PPN][Mo(CO)(5)(COOCH3)] with synthesis gas in methanol at 125 degrees C gave methyl formate, formic acid and Mo(CO)(6). The same reaction as above in THF yielded methyl formate, methanol and formic acid. (C) 2011 Elsevier B. V. All rights reserved.