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
Houston Byrd
Jeremiah D. Harden
Jennifer M. Butler
Michael J. Jablonsky
Gary M. Gray
10.1021/om030411z.s001
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.
2003-10-13 00:00:00
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