Dinuclear (d{sup 3}-d{sup 3}) diolate complexes of molybdenum and tungsten. 2. Derivatives of 2,2{prime}-methylenebis(6-tert-butyl-4-methylphenoxide). Direct observation of the conversion of bridged to chelate isomers (M = Mo) and reversible carbon-hydrogen bond oxidative addition (M = W)

Journal Article · Wed Apr 09 04:00:00 EDT 1997 · Inorganic Chemistry

DOI:https://doi.org/10.1021/ic961429n· OSTI ID:543056

Chisholm, M H; Huang, Jui-Hsien; Huffman, J C; Parkin, I P ^[1]

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1. Indiana Univ., Bloomington, IN (United States)

Hydrocarbon solutions of Mo{sub 2}(NMe{sub 2}){sub 6} and 2,2{prime}-methylenebis(6-tert-butyl-4-methylphenol)({ge}2 equiv), HO(2,2{prime}-methylenebis(6-tert-butyl-4-methylphenol)) CH{sub 2}(2,2{prime}-methylenebis(6-tert-butyl-4-methylphenol)) OH, yield Mo{sub 2}(NMe{sub 2}){sub 2}(O(2,2{prime}-methylenebis(6-tert-butyl-4-methylphenol))CH{sub 2}(2,2{prime}-methylenebis(6-tert-butyl-4-methylphenol))O){sub 2}, I, which exists in bridged Ib and chelated Ic isomers. These are formed under kinetic control, and recrystallization allows the separation of Ib (orange cubes) from Ic (yellow cubes) both of which have been crystallographically characterized. In each there is an ethane-like O{sub 2}NMo{triple_bond}MoO{sub 2}N core with Mo-Mo = 2.2 {Angstrom} (average). In Ib the two O(2,2{prime}-methylenebis(6-tert-butyl-4-methylphenol))CH{sub 2}(2,2{prime}-methylenebis(6-tert-butyl-4-methylphenol))O ligands span the Mo{triple_bond}Mo bond yielding a molecule of C{sub 2} symmetry. In Ic the molecule has near-C{sub 2} symmetry in the solid state, but in solution there is either rapid rotation about the M{triple_bond}M bond or the anti-rotamer is preferred. In benzene-d{sub 6}, Ib and Ic do not interconvert at 110 {degrees}C over a period of days. However, the addition of pyridine or acetonitrile causes the isomerization of Ib to Ic, thereby establishing that Ic is the thermodynamic isomer. The rate of conversion of Ib to Ic has been shown to be dependent on the square of the concentration of added pyridine: k{sub obs} = k[py]{sup 2}. From the temperature dependence of k{sub obs}, we determine {Delta}H{sup {double_dagger}} = 19 ({+-}1) kcal/mol and {Delta}S{sup {double_dagger}} =-25 ({+-}3) eu for the pyridine-promoted isomerization of Ib to Ic. 25 refs., 10 figs., 9 tabs.

• OSTI ID: 543056
• Journal Information: Inorganic Chemistry, Journal Name: Inorganic Chemistry Journal Issue: 8 Vol. 36; ISSN 0020-1669; ISSN INOCAJ
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
40 CHEMISTRY
ACETONITRILE
BOND ANGLE
BOND LENGTHS
CARBON
CHELATES
CHEMICAL BONDS
CONCENTRATION RATIO
CRYSTALLOGRAPHY
HYDROCARBONS
HYDROGEN
ISOMERIZATION
ISOMERS
LIGANDS
MOLECULAR STRUCTURE
MOLYBDENUM COMPLEXES
NMR SPECTRA
PYRIDINE
QUALITATIVE CHEMICAL ANALYSIS
RECRYSTALLIZATION
ROTATIONAL STATES
SYMMETRY
SYNTHESIS
TUNGSTEN COMPLEXES