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Oxygen activation and catalytic aerobic oxidation by Mo(iv)/(vi) complexes with functionalized iminophenolate ligandsElectronic supplementary information (ESI) available. CCDC 1476035-1476040 and 1486756. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c6dt01692h
Synthesis of molybdenum( vi ) dioxido complexes 1-3 , coordinated by one or two functionalized iminophenolate ligands HL1 or HL2 , bearing a donor atom side chain or a phenyl substituent, respectively, allowed for systematic investigation of the oxygen atom transfer (OAT) reactivity of such complexe...
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| Summary: | Synthesis of molybdenum(
vi
) dioxido complexes
1-3
, coordinated by one or two functionalized iminophenolate ligands
HL1
or
HL2
, bearing a donor atom side chain or a phenyl substituent, respectively, allowed for systematic investigation of the oxygen atom transfer (OAT) reactivity of such complexes towards phosphanes. Depending on stoichiometry and employed phosphane (PMe
3
or PPh
3
), different molybdenum(
iv
) and molybdenum(
v
) complexes
4-7
were obtained. Whereas molybdenum(
iv
) complexes
4
and
5
, bearing a terminal PMe
3
ligand, readily reacted with molecular O
2
to form oxido peroxido complexes
8
and
9
, phosphane free μ-oxido bridged dinuclear molybdenum(
v
) complexes
6
and
7
proved to be stable towards oxidation with molecular O
2
under ambient conditions. Single-crystal X-ray diffraction analyses revealed different isomeric structures in the solid state for dioxido complexes
1
and
2
in comparison with oxido phosphane complex
5
, dinuclear oxido μ-oxido complex
6
and oxido peroxido complexes
8
and
9
, pointing towards an isomeric rearrangement during OAT. Compounds
1
and
2
were furthermore tested for their ability to catalyze the aerobic oxidation of PMe
3
and PPh
3
. A significant difference in catalytic activity has been observed in the oxidation of PMe
3
, where complex
1
bearing donor atom functionalized ligands led to higher conversion and selectivity than complex
2
coordinated by phenyl iminophenolate ligands. In the oxidation of PPh
3
, complex
2
leads to higher conversion compared to
1
. In a control experiment, phenyl-based dinuclear μ-oxido complex
7
, derived from complex
2
, was found to be catalytically active, which suggests a lower energy barrier for disproportionation into [MoO(L)
2
] and [MoO
2
(L)
2
] in comparison with methoxypropylene based compound
6
, a prerequisite for subsequent reactivity toward molecular O
2
.
Dioxidomolybdenum(
vi
) complexes coordinated by functionalized bidentate iminophenolate ligands undergo oxygen atom transfer to PMe
3
to yield molybdenum(
iv
) oxido phosphino species that readily react with molecular O
2
to form molybdenum(
vi
) oxido peroxido complexes. |
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| ISSN: | 1477-9226 1477-9234 |
| DOI: | 10.1039/c6dt01692h |