10.1021/om030411z.s001
Houston Byrd
Houston
Byrd
Jeremiah D. Harden
Jeremiah D.
Harden
Jennifer M. Butler
Jennifer M.
Butler
Michael J. Jablonsky
Michael
J. Jablonsky
Gary M. Gray
Gary M.
Gray
Nucleophilic Displacement Reactions of
<i>cis</i>-Bis((2,2‘-biphenylylene)phosphochloridite
ester)tetracarbonylmolybdenum(0). The First Example of
an Unusual Hydrolysis Reaction Yielding
Unsymmetrically Substituted Products
American Chemical Society
2003
nucleophilic displacement reactions
ligand
RX
NMR studies
Unusual Hydrolysis Reaction Yielding Unsymmetrically Substituted Products Ligands
diastereomer
solution
dioxaphosphepin
PO
Mo
conformation
Pr n H 2
nucleophilic substitution reactions
NH
chloride
disubstituted complexes cis
XR
hydrolysis
SC
bulkier biaryl groups
OMe
PXR
nucleophile
Nucleophilic Displacement Reactions
NPr n
2003-10-13 00:00:00
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Nucleophilic_Displacement_Reactions_of_i_cis_i_Bis_2_2_biphenylylene_phosphochloridite_ester_tetracarbonylmolybdenum_0_The_First_Example_of_an_Unusual_Hydrolysis_Reaction_Yielding_Unsymmetrically_Substituted_Products/3361561
Ligands containing groups derived from bis(aryl)diols are widely used in asymmetric
catalysis; however, few studies of the conformations of these ligands in transition-metal
complexes have been reported. In this paper, the nucleophilic displacement reactions of <i>cis</i>-Mo(CO)<sub>4</sub>(2,2‘-C<sub>12</sub>H<sub>8</sub>O<sub>2</sub>PCl)<sub>2</sub> (<b>1</b>) have been used to prepare a variety of complexes with [1,3,2]dioxaphosphepin ligands, and the conformations of these ligands have been studied by NMR
spectroscopy and X-ray crystallography. The nucleophilic substitution reactions yield both
the expected disubstituted complexes <i>cis</i>-Mo(CO)<sub>4</sub>(2,2‘-C<sub>12</sub>H<sub>8</sub>O<sub>2</sub>PXR)<sub>2</sub> (XR = NPr<sup>n</sup> (<b>2</b>), OMe
(<b>4</b>), SC<sub>6</sub>H<sub>4</sub>-4-Me (<b>6</b>)) and the unexpected hydrolysis products [R‘<sub>3</sub>NH][<i>cis</i>-Mo(CO)<sub>4</sub>(2,2‘-C<sub>12</sub>H<sub>8</sub>O<sub>2</sub>PO)(2,2‘-C<sub>12</sub>H<sub>8</sub>O<sub>2</sub>PXR)] (R‘<sub>3</sub> = Pr<sup>n</sup>H<sub>2</sub>, XR = NPr<sup>n</sup>, <b>3</b>; R‘<sub>3</sub> = Et<sub>3</sub>; XR = OMe, <b>5</b>). NMR
studies have demonstrated that the hydrolysis product is the major product when more than
a minute amount of water is present, even in the presence of a large excess of the
nucleophiles. This reaction is complete in approximately 90 min at 25 °C. A very surprising
feature of this reaction is that substitution of one chloride in <b>1 </b>by the RX<sup>-</sup> nucleophile greatly
enhances the rate of substitution of the second chloride either by water or by another RX<sup>-</sup>
nucleophile. NMR studies of the [1,3,2]dioxaphosphepin complexes in chloroform-<i>d</i> solution
suggest that the <i>R</i>* and <i>S*</i> enantiomers of the ligands interconvert via a low-energy pathway.
Crystal structures of the complexes demonstrate that both the <i>R</i>*<i>S</i>* diastereomer (<b>1</b>) and
racemic mixtures of the <i>R</i>*<i>R</i>* and <i>S</i>*<i>S</i>* diastereomers (<b>2</b>−<b>4</b>) are observed in the solid state.
These results suggest that bulkier biaryl groups are needed to prevent the racemization of
the [1,3,2]dioxaphosphepin ligands in solution.