Abstract
The reaction of [Mo(η-C5Me5)Cl4] with the ortho-, meta-, or para-iodo-functionalized anilines 2-IC6H4NH2, 3-IC6H4NH2, 4-IC6H4NH2 yields imido or amine products of the type [Mo(η-C5Me5)Cl2(IC6H4N)] (2-I, 1, 3-I, 3, 4-I, 5) or [Mo(η-C5Me5)Cl4(IC6H4NH2)] (3-I, 2, 4-I, 4), respectively, depending on the reaction stoichiometry/conditions; we were unable to isolate an amine complex of the 2-I derivative. The reaction of [Mo(η-C5Me5)Cl4] with one equivalent of 2-I,4-FC6H3NH2 in the presence of Et3N afforded [Mo(η-C5Me5)Cl2(2-I,4-FC6H3N)]·MeCN (6·MeCN), which, upon exposure to air, afforded the Mo(VI) imido complex [Mo(η-C5Me5)Cl3(2-I,4-FC6H3N)] (7). For comparative studies, the structure of the aniline (C6H5NH2)-derived complex [Mo(η-C5Me5)Cl2(2-C6H3N)] (8) has also been prepared. The molecular structures of 1–8 have been determined and reveal packing in the form of zig-zag chains or ladders. The complexes catalyze, in the presence of benzyl alcohol under N2, the ring-opening polymerization (ROP) of ε-caprolactone affording relatively low molecular weight products. The MALDI-ToF spectra indicate that a number of polymer series bearing a variety of end groups are formed. Conducting the ROPs as melts or under air results in the isolation of higher molecular weight products, again bearing a variety of end groups. Kinetic studies reveal the aniline-derived imido complex 8 performs best, whilst a meta-iodo substituent and a Mo(V) centre are also found to be beneficial. The structures of the side products 2-IC6H4NH3Cl and 3-IC6H4NH3Cl are also reported.
Highlights
Molybdenum, and to a lesser extent tungsten, organoimido chemistry has been of interest for a number of decades given its relevance to a number of areas, olefin metathesis [1]
TheThe molecular structure shown with selected bond lengths and at angles given in the caption
Amine or organoimido species can be accessed depending on conditions for the 3- and 4-iodoanilines; for the
Summary
Molybdenum, and to a lesser extent tungsten, organoimido chemistry has been of interest for a number of decades given its relevance to a number of areas, olefin metathesis [1]. We have previously investigated the chemistry of [W(η-C5 Me5 )Cl4 ] as an entry point to new half-sandwich species and have reported the structures of a number of products, including the diamido complex {W(η-C5 Me5 )Cl2 [1,2-(HN) C6 H4 ]} [3], as well as imido, hydrazido, amino acid derived chelates [4], and functionalized 6,12-epiiminodibenzo[b,f][1.5]diazocine ligands [5]. We were attracted to the use of iodo-substituted organomido groups as a stabilizing motif given their tendency to be involved in intermolecular bonding in the solid state. Such interactions are useful for crystal engineering, halogen-catalyzed reactions, and even in drug design [23,24,25]
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