2 Homometallic Alkoxides

isolobality of CR 0 and W⊲OR⊳3 is apparent:
where R D Me, Et, Pr n .
Homometallic Alkoxides 153
W2⊲OBu t ⊳6 C RC CR hexane
! 2⊲Bu t O⊳3W CR ⊲2.366⊳
W2⊲OBu t ⊳6 C 2EtC CR ! 2⊲Bu t O⊳3W CR C EtC CEt ⊲2.367⊳
where R D Ph, SiMe3, —CHDCH2
W2⊲OR⊳6 C 2py C R 0 C CR 0 ! W2⊲OR⊳6⊲ -C2R 0 2 ⊳⊲py⊳x ⊲2.368⊳
(R D Bu t ;R 0 D H; x D 1. R D Pr i ;R 0 D H; x D 2. R D CH2Bu t ;R 0 D Me; x D 2)
W2⊲OR⊳6 C 3R 0 C CR 0 ! W2⊲OR⊳6⊲ -C4R 0 4⊳⊲C2R 0 2⊳ ⊲2.369⊳
where R D Pr i ,CH2Bu t ;R 0 D H, Me. 1046,1047
The last reaction (Eq. 2.370) is favoured for less sterically demanding combinations
of ligands.
Although W2⊲OBu t ⊳6 does not react with PhC CPh 1043 at room temperature, its
reaction in molar ratios between 1:1 and 3:1 at about 70 Ž C in toluene produces
W2⊲OBu t ⊳4⊲ -CPh⊳2 and W2⊲OBu t ⊳4⊲PhC CPh⊳2 in moderate yields. 1044
Furthermore, the reaction of W2⊲OBu t ⊳6 with EtC CEt at 75–80 Ž C for
about three days affords moderate yields of a remarkable hexanuclear product,
[W3⊲OBu t ⊳5⊲ -O⊳⊲ -CEt⊳O]2, which has been characterized by X-ray crystallography.
1045
Reaction of Mo2⊲OBu t ⊳6 with phenylacetylene in pentane produces the alkylidyne
complex Mo⊲ CC6H5⊳⊲OBu t ⊳3 in 60% yield 1049 (Eq. 2.370):
Mo2⊲OBu t ⊳6 C C6H5C CH ! ⊲Bu t O⊳3Mo CC6H5 ⊲2.370⊳
In the presence of quinuclidine (quin), both Mo⊲ CC6H5⊳⊲OBu t ⊳3⊲quin⊳ and
Mo⊲ CH⊳⊲OBu t ⊳3⊲quin⊳ have been identified.
W2⊲OBu t ⊳6 C RC N ! ⊲Bu t O⊳3W N C ⊲Bu t O⊳3W CR ⊲2.371⊳
where R D Me, Ph.
In contrast, W2⊲OCMe2⊲CF3⊳⊳6 reacts reversibly with acetonitrile 1048 to form addition
complex W2⊲OCMe2⊲CF3⊳⊳6⊲NCCH3⊳.
4.17.1.5 Reactions with ketones or aldehydes
W2⊲OCH2Bu t ⊳6⊲py⊳2 reacts with ketones or aldehydes in hydrocarbon solvents at room
temperature to afford alkenes by a reductive coupling and deoxygenation of the C–O
bonds 1050 according to Eq. (2.372):
W2⊲OCH2Bu t ⊳6⊲py⊳2 C 2R2CDO 22°C
!
hexane
W2O2⊲OCH2Bu t ⊳6 C R2CDCR2 C 2py
⊲2.372⊳