Molybdenum hexacarbonyl is the precursor to many substituted derivatives. It reacts with organolithium reagents to give anionic acyls which can be O-alkylated to giveFischer carbenes.
Reduction of Mo(CO)6 gives [Mo(CO)5]2− which is formally Mo(-II).[4]
CO-free Mo(0) compounds tend to be more reducing and kinetically labile than the carbonyl complexes.[5] Examples include bis(benzene)molybdenum (Mo(C6H6)2) and tris(butadiene)molybdenum. Such compounds can be prepared bymetal vapor synthesis and reductive routes frommolybdenum(V) chloride.[6]
Halogenation of Mo(CO)6 gives Mo(II) carbonyl halides, which are also versatile precursors.[7] One large collection of compounds have the formula (C5R5)Mo(CO)3X, derived fromcyclopentadienylmolybdenum tricarbonyl dimer (X = halide, hydride, alkyl).[8]
Mo(CH3)5, Mo(CH3)6, and salts of [Mo(CH3)7]− are known.[5]
Oxo andimide (RN=) ligands are found in several high oxidation state organomolybdenum compounds. The complexes (C5R5)MoO2X are illustrative.[9] Schrock's Mo-basedolefin metathesis catalysts feature molybdenum(VI) centers supported byalkoxide,alkylidene, and imido ligands.[10]
Molybdenum neopentylidyne complexes endowed with sterically demanding phenolates or branched fluorinated alkoxides catalyze alkyne metathesis.[11] However, preparation of these catalysts is problematic by the standard Schrock procedure. The trisalkoxide species 17 is active at room temperature.[12]
Treating these Mo(III) complexes with dichloromethane gives methylidyne complex and a monochloride.[13] The alkylidene complex tolerates basic amines andsulfides, which deactivate the more Lewis acidic complex such as Schrock complex. Higher gem-dichlorides RCHCl2 give longer-lived catalyst.[14] To reconvert the chloride byproduct, they addedmagnesium in reaction. Thep-nitrophenolate is a very active catalyst.[15] On the other hand, alcoholysis of 21 with atridentate ligand leading to still longer lifetime and better substrate scope.[16]
^Green M. L. H., Ng D. K. P. (1995). "Cycloheptatriene and -enyl Complexes of the Early Transition Metals".Chemical Reviews.95 (2):439–73.doi:10.1021/cr00034a006.
^Ellis, J. E. (2003). "Metal Carbonyl Anions: from [Fe(CO)4]2− to [Hf(CO)6]2− and Beyond".Organometallics.22 (17):3322–3338.doi:10.1021/om030105l.
^Stephan, G. C.; Naether, C.; Peters, G.; Tuczek, F. (2013). "Molybdenum 17- and 18-Electron Bis- and Tris(Butadiene) Complexes: Electronic Structures, Spectroscopic Properties, and Oxidative Ligand Substitution Reactions".Inorg. Chem.52 (10):5931–5942.doi:10.1021/ic400145f.PMID23627292.
^Joseph L. Templeton "Four-Electron Alkyne Ligands in Molybdenum(II) and Tungsten(II) Complexes" Advances in Organometallic Chemistry 1989, Volume 29, Pages 1–100.doi:10.1016/S0065-3055(08)60352-4
^Synthesis of Organometallic Compounds: A Practical Guide Sanshiro Komiya Ed. S. Komiya, M. Hurano 1997
^Kuehn, F. E.; Santos, A. M.; Herrmann, W. A. (2005). "Organorhenium(VII) and Organomolybdenum(VI) Oxides: Syntheses and Application in Olefin Epoxidation".Dalton Trans. (15):2483–2491.doi:10.1039/b504523a.PMID16025165.
^Kauffmann, T. (1997). "Organomolybdenum and organotungsten reagents. 7. Novel reactions of organomolybdenum and organotungsten compounds: additive-reductive carbonyl dimerization, spontaneous transformation of methyl ligands into μ-methylene ligands, and selective carbonylmethylenation".Angew. Chem. Int. Ed. Engl.36:1259–1275.doi:10.1002/anie.199712581.
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