“…One phenyl ring on the BINO ligand is pointing more or less straight up (away from the C(33)-N(1)-O(1) face), while the other phenyl ring in the BINO ligand lies more or less beneath the Mo=N bond. The C(1)−C(2)−C(22)−C(17) dihedral angle is 65°, which is approximately what has been found in several W(6+) complexes that contain the parent binaphtholate ligand. − 2 A Chem 3D view of Mo(N-2,6-C 6 H 3 Me 2 )(CHCMe 2 Ph)(3,3‘-diphenyl-2,2‘-diolate-1,1‘-dinaphthyl)(THF) ( 2b ‘).…”
Section: Resultsmentioning
confidence: 53%
“…A significant fact is that the neophylidene ligand has the anti configuration in which the Mo 17) dihedral angle is 65°, which is approximately what has been found in several W(6+) complexes that contain the parent binaphtholate ligand. [20][21][22] Proton NMR spectra of 2b′ in toluene-d 8 show two alkylidene H R resonances at low temperatures (Figure 3). The most downfield singlet (13.4 ppm) is assigned to anti-2b′ (J CH ) 144 Hz), while that at 13.2 ppm is assigned to syn-2b′.…”
Section: Synthesis Of Binaphtholate and Biphenolatementioning
Several racemic or enantiomerically pure complexes of the general
type Mo(CHR)(NR‘)(O2R‘‘) that contain binaphtholate or biphenolate
(O2R‘‘) ligands have been prepared and employed
to
ring open several achiral, racemic, or enantiomerically pure
norbornenes and norbornadienes. A bimodal
molecular weight distribution sometimes results from polymerization of
an enantiomerically pure monomer
with a racemic initiator as a consequence of a different rate of chain
growth from enantiomeric metal
centers. The analogous polymerization of an enantiomerically pure
monomer with an enantiomerically
pure initiator yields only a single polymer chain, as expected.
Evaluation of the cis content of the
resulting
polymers suggests that cis polymer results from
polymerization via syn alkylidene propagating
species
and that accessibility of the anti rotamer on the
polymerization time scale is determined by a subtle
combination of steric bulk in the biphenoxide and imido ligands.
All cis polymers were found to be highly
isotactic. The X-ray structures of two catalytically active
species are also described. One is a THF adduct
of 3,3‘-diphenyl-2,2‘-diolate-1,1‘-dinaphthyl (anti rotamer)
while the other is a base-free syn species that
contains the
6,6‘-dimethyl-3,3‘,5,5‘-tetra-tert-butyl-1,1‘-biphenyl-2,2‘-diolate
ligand.
“…One phenyl ring on the BINO ligand is pointing more or less straight up (away from the C(33)-N(1)-O(1) face), while the other phenyl ring in the BINO ligand lies more or less beneath the Mo=N bond. The C(1)−C(2)−C(22)−C(17) dihedral angle is 65°, which is approximately what has been found in several W(6+) complexes that contain the parent binaphtholate ligand. − 2 A Chem 3D view of Mo(N-2,6-C 6 H 3 Me 2 )(CHCMe 2 Ph)(3,3‘-diphenyl-2,2‘-diolate-1,1‘-dinaphthyl)(THF) ( 2b ‘).…”
Section: Resultsmentioning
confidence: 53%
“…A significant fact is that the neophylidene ligand has the anti configuration in which the Mo 17) dihedral angle is 65°, which is approximately what has been found in several W(6+) complexes that contain the parent binaphtholate ligand. [20][21][22] Proton NMR spectra of 2b′ in toluene-d 8 show two alkylidene H R resonances at low temperatures (Figure 3). The most downfield singlet (13.4 ppm) is assigned to anti-2b′ (J CH ) 144 Hz), while that at 13.2 ppm is assigned to syn-2b′.…”
Section: Synthesis Of Binaphtholate and Biphenolatementioning
Several racemic or enantiomerically pure complexes of the general
type Mo(CHR)(NR‘)(O2R‘‘) that contain binaphtholate or biphenolate
(O2R‘‘) ligands have been prepared and employed
to
ring open several achiral, racemic, or enantiomerically pure
norbornenes and norbornadienes. A bimodal
molecular weight distribution sometimes results from polymerization of
an enantiomerically pure monomer
with a racemic initiator as a consequence of a different rate of chain
growth from enantiomeric metal
centers. The analogous polymerization of an enantiomerically pure
monomer with an enantiomerically
pure initiator yields only a single polymer chain, as expected.
Evaluation of the cis content of the
resulting
polymers suggests that cis polymer results from
polymerization via syn alkylidene propagating
species
and that accessibility of the anti rotamer on the
polymerization time scale is determined by a subtle
combination of steric bulk in the biphenoxide and imido ligands.
All cis polymers were found to be highly
isotactic. The X-ray structures of two catalytically active
species are also described. One is a THF adduct
of 3,3‘-diphenyl-2,2‘-diolate-1,1‘-dinaphthyl (anti rotamer)
while the other is a base-free syn species that
contains the
6,6‘-dimethyl-3,3‘,5,5‘-tetra-tert-butyl-1,1‘-biphenyl-2,2‘-diolate
ligand.
“…Although other examples of organometallic early transition metal complexes containing hydrogen-bonding ligands are known, , these acetylene complexes are unusual, because the tungsten is in a high formal oxidation state, the hydrogen-bonding functionality possesses a low p K a , and the organometallic functional group is prone to protonolysis. d 2 tungsten diphenylacetylene complexes hydrolyze to produce stilbenes in protic media. , Molecular weights of the analytically pure free acids 1 in benzene solution are determined (by the Signer method 48 ) to be between the mono- and dinuclear forms. This is in sharp contrast to the oxo free acid analogs which exist only as dimers in benzene solution .…”
Section: Resultsmentioning
confidence: 99%
“…Our interests in metal-mediated hydrogen-bonding interactions began with the inadvertent discovery of several members of a now extensive class of chelating phenol−phenolate Brønstead acids of tungsten oxo and arylimido complexes. − It became clear that these complexes were unique both in the accessability of a broad range of isoelectronic, isostructural analogs of the tungsten template and in the variability of the hydrogen bond strength of the Brønstead acid. Our long term goal in this project is to utilize the control of hydrogen bond strength available in this class of molecules in the rational assembly of inorganic/organic hybrid materials.…”
Reactions between
W(η2-Ph2C2)Cl4
and salicylic acid derivatives generate analytically pure
free acids of formula
W(η2-Ph2C2)Cl3(Hsal-R)
(1) in high yields (Hsal = a salicylate
monoanion). The products exist as hydrogen-bonded dimers in the
solid state. The acid
functionality on one molecule hydrogen bonds to one of the
cis-chloride ligands of an adjacent
complex at a 3.03 Å distance. The more electron-rich tungsten
center renders these acetylene
complexes less acidic than their oxo and arylimido analogs. As a
result,
W(η2-Ph2C2)Cl3(Hsal) exhibits partial dimerization in solution and have relatively
weak hydrogen bonds to
nitrogen- and oxygen-containing organic molecules. Among a range
of possible phenol−phenoxide complexes of the
W(η2-Ph2C2)Cl3
subunit, only the ether adduct of the catecholate,
W(η2-Ph2C2)Cl3(Hcat···OEt2)
(2), has been isolated and structurally characterized.
The weaker
hydrogen bond strength of larger chelating bis(phenolates)
evidently destabilize the phenol−phenoxide structures in favor of simple chelating bis(phenoxides).
The salicylate free acids
form various supramolecular complexes in solution and the solid state,
including [W(η2-Ph2C2)Cl3(Hsal)]4(18-crown-6)
(5), one of a family of tetranuclear systems organized
around
hydrogen bonding to an 18-crown-6 template. This structure is
characterized by π-stacking
of the Hsal ligands between confacial free acid complexes and the
steric screening of the
two non-hydrogen-bonded 18-crown-6 oxygens by pairs of antarafacial
W(Ph2C2) units.
“…The present paper studies the complex formation and extraction of vanadium(V) with 2,3-dihydroxynaphthalene (DHN) and iodonitrotetrazolium chloride (INT). Complexes also form when reacting DHN with W [8], Fe [9], Ti [10] and Mo [11,12]. mol/dm 3 .…”
Abstract:The formation of a new ternary ion-associate complex of vanadium(V) with 2,3-dihydroxynaphthalene and iodonitrotetrazolium chloride with a composition ratio of 1:2:1 is reported. The complex is quantitatively extracted from water into chloroform. The molar absorptivity (ε) of the extract at λ max =340 nm is 2.5 × 10 4 dm 3 /mol cm, and Beer's law is obeyed for concentrations ranging from 0.1 to 0.9 μg/cm 3 V(V). The following constants are determined: the extraction constant, the association constant, the distribution constant, and the recovery factor. The effects of foreign ions and reagents are studied. A selective and sensitive method is developed for determination of vanadium in steels.
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