Organomolybdenum chemistry

Structure of Mo(CH3)5, a simple organomolybdenum compound.[1]

Organomolybdenum chemistry is the chemistry of chemical compounds with Mo-C bonds. The heavier group 6 elements molybdenum and tungsten form organometallic compounds similar to those in organochromium chemistry but higher oxidation states tend to be more common.[2]

Mo(0) and more reduced states

Molybdenum hexacarbonyl is the precursor to many substituted derivatives. It reacts with organolithium reagents to give anionic acyls which can be O-alkylated to give Fischer carbenes.

Structure of (mesitylene)molybdenum tricarbonyl.

Mo(CO)6 reacts with arenes to give piano-stool complexes such as (mesitylene)molybdenum tricarbonyl. Cycloheptatrienemolybdenum tricarbonyl, which is related to (arene)Mo(CO)3, reacts with trityl salts to give the cycloheptatrienyl complex:[3]

(C7H8)Mo(CO)3 + (C6H5)3C+ → [(C7H7)Mo(CO)3]+ + (C6H5)3CH
Structure of Cycloheptatrienemolybdenum tricarbonyl.

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 by metal vapor synthesis and reductive routes from molybdenum(V) chloride.[6]

Mo(II)

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 from cyclopentadienylmolybdenum tricarbonyl dimer (X = halide, hydride, alkyl).[8]

Treating molybdenum(II) acetate with methyllithium gives Li4[Mo2(CH3)8].

Mo(IV)

With the formula of the type Cp2MoX2 molybdocene dichloride (X = Cl) and molybdocene dihydride (X = H) are both known as are ansa metallocene analogues.

Molybdocene dihydride.

Mo(V) and Mo(VI)

Mo(CH3)5, Mo(CH3)6, and salts of [Mo(CH3)7]- are known.[5]

Oxo and imide (RN=) ligands are found in several high oxidation state organomolybdenum compounds. The complexes (C5R5)MoO2X are illustrative.[9] Schrock's Mo-based olefin metathesis catalysts feature molybdenum(VI) centers supported by alkoxide, alkylidene, and imido ligands.[10]

Organotungsten compounds

Tungsten analogues of almost all organoMo compounds are known. Some notable examples include hexamethyltungsten and analogues of Schrock olefin metathesis catalysts.

Applications

Mo-based catalysts are useful for olefin metathesis.[10]

Trisamidomolybdenum(VI) alkylidyne complexes catalyze alkyne metathesis.[11]

In the Kauffmann olefination, molybdenum(III) chloride and methyllithium form an organometallic complex capable of carbonyl olefination.[12]

See also

  • Other bonds of carbon with elements in the periodic table:
Compounds of carbon with other elements in the periodic table
CH He
CLi CBe CB CC CN CO CF Ne
CNa CMg CAl CSi CP CS CCl CAr
CK CCa CSc CTi CV CCr CMn CFe CCo CNi CCu CZn CGa CGe CAs CSe CBr CKr
CRb CSr CY CZr CNb CMo CTc CRu CRh CPd CAg CCd CIn CSn CSb CTe CI CXe
CCs CBa CHf CTa CW CRe COs CIr CPt CAu CHg CTl CPb CBi CPo CAt Rn
Fr CRa Rf Db CSg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og
↓
CLa CCe CPr CNd CPm CSm CEu CGd CTb CDy CHo CEr CTm CYb CLu
Ac CTh CPa CU CNp CPu CAm CCm CBk CCf CEs Fm Md No Lr
Chemical bonds to carbon
Core organic chemistry Many uses in chemistry
Academic research, but no widespread use Bond unknown

References

  1. ↑ Beatrice Roessler, Sven Kleinhenza, Konrad Seppelt (2000). "Pentamethylmolybdenum". Chemical Communications: 1039–1040. doi:10.1039/b000987n.
  2. ↑ Poli, R. (2008). "High oxidation state organomolybdenum and organotungsten chemistry in protic environments". Coord. Chem. Rev. 252: 1592–1612. doi:10.1016/j.ccr.2007.11.029.
  3. ↑ M. L. H. Green, D. K. P. Ng "Cycloheptatriene and -enyl Complexes of the Early Transition Metals" Chemical Reviews 1995, volume 95, pp. 439-73. doi:10.1021/cr00034a006
  4. ↑ 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.
  5. 1 2 Flower, K. R. (2007). "Molybdenum compounds without CO or isonitrile ligands". In Mingos, D. Michael P.; Crabtree, Robert H. Comprehensive Organometallic Chemistry III. 5. pp. 513–595. doi:10.1016/B0-08-045047-4/00072-8.
  6. ↑ 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: 5931–5942. doi:10.1021/ic400145f.
  7. ↑ 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
  8. ↑ Synthesis of Organometallic Compounds: A Practical Guide Sanshiro Komiya Ed. S. Komiya, M. Hurano 1997
  9. ↑ Kuehn, F. E.; Santos, A. M.; Herrmann, W. A. (2005). "Organorhenium(VII) and Organomolybdenum(VI) Oxides: Syntheses and Application in Olefin Epoxidation". Dalton Trans.: 2483–2491. doi:10.1039/b504523a.
  10. 1 2 R.R. Schrock (1986). "High-oxidation-state molybdenum and tungsten alkylidene complexes". Acc. Chem. Res. 19 (11): 342. doi:10.1021/ar00131a003.
  11. ↑ Wei Zhang, Yunyi Lu, Jeffrey S. Moore (2007). "Preparation of a Trisamidomolybdenum(VI) Propylidyne Complex". Org. Synth. 84: 163. doi:10.15227/orgsyn.084.0163. Wei Zhang, Hyeon Mo Cho, Jeffrey S. Moore (2007). "Preparation of a Carbazole-Based Macrocycle via Precipitation-driven Alkyne Metathesis". Org. Synth. 84: 177. doi:10.15227/orgsyn.084.0177.
  12. ↑ 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.
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