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 00:00:00 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, Vol. 36, Issue 8; Other Information: PBD: 9 Apr 1997
• Country of Publication: United States
• Language: English

Related Subjects

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