ca01 only detailed ToC 1..24

2.6.9 Miscellaneous Complexes 133
ç 5 -Cyclopentadienyl(2,2-dimethylpropyl)nitrosyl(triphenylsilanolato)molybdenum(II)
(65); Typical Procedure: [115]
See Section 2.6.4.4.
2.6.8.5 Method 5:
From Complexes Containing Doubly Bonded Heteroelement Ligands
Like the synthesis of alkyl compounds by selective protonation of carbene groups (Section
2.6.8.4), ligands with metal-heteroatom single bonds may be obtained from oxo or
imido complexes via a single-proton-transfer reaction, as illustrated for 103 in Scheme
47. Alternatively, the metal-heteroatom bond may be protonated twice, with the external
acid (HX) providing the M-X bond of the final product, as in the synthesis of 104. The
replacement of an oxo or imido ligand with two singly bonded ligands may induce other
modifications in the molecule, notably Æ-hydrogen elimination from an alkyl group,
transforming it into a carbene ligand (see Section 2.6.1.1.3).
Scheme 47 Syntheses from Complexes Containing Doubly Bonded
Heteroelement Ligands [102,152]
W(Cp ∗ ) 2( O) + HBF 4 OEt 2
WMeCp ∗ (
NPh) 2
+
TfOH
Et2O 50%
Et2O 80%
[W(Cp ∗ ) 2(OH)] + BF 4 −
103
WMeCp ∗ (OTf) 2(
104
Hydroxobis(pentamethylcyclopentadienyl)tungsten(IV) Tetrafluoroborate (103): [102]
A soln of [W(Cp*) 2(=O)] (120 mg, 0.26 mmol) in Et 2O (10 mL) was treated with HBF 4 • OEt 2
(excess) at –78 8C. The mixture was warmed to rt and the product was deposited as a white
solid which was isolated by filtration; yield: 75 mg (50%); IR (Nujol) í~ max: (WO-H) 3340 (s,
br) cm –1 ; 1 H NMR (benzene-d 6, ä): 1.88 (s, C 5Me 5).
2.6.9 Product Subclass 9:
Miscellaneous Complexes
Synthesis of Product Subclass 9
2.6.9.1 Method 1:
Allylidene Complexes from Cyclopropenes
Ring-opening reactions of 3,3-disubstituted cyclopropenes yield allylidene complexes, a
synthetic route of particular utility for the generation of ruthenium-based alkene metathesis
catalysts. [47] This methodology has been extended to tungsten allylidene compounds
using tungsten(IV) oxo [177] or imido [178] precursors (Scheme 48). These reactions proceed
via initial formation of the ç 2 -cyclopropene adduct 105, followed by ring opening. Metathesis
of the chloride ligands with electron-withdrawing alkoxide groups furnishes alkene
metathesis catalysts 106 (see Section 2.6.1.5).
NPh)
for references see p 135