Unusual Hydrolysis Reactions of cis-Bis((2,2‘-biphenylylene)phosphochloridite ester)tetracarbonylmolybdenum(0)

• Published in: Organometallics 2004-06, Vol.23 (13), p.3239-3245
• Main Authors: Byrd, Houston, Harden, Jeremiah D, Butler, Jennifer M, Jablonsky, Michael J, Gray, Gary M
• Format: Article
• Language: English
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/om049851w

The hydrolysis of cis-Mo(CO)4(2,2‘-C12H8O2PCl)2 (1) in the presence of excess triethylamine and water yields [(C2H5)3NH]2[cis-Mo(CO)4(2,2‘-C12H8O2PO)2] (2). This complex is in equilibrium with [(C2H5)3NH][cis-Mo(CO)4(2,2‘-C12H8O2PO)(2,2‘-C12H8O2POH)] (3) and free triethylamine in solution. The hydrolysis of 1 with a stoichiometric amount of triethylamine and water yields only 3. A Scatchard plot for the reaction of 3 and triethylamine to form 2 at 25 °C gives an equilibrium constant of 5.8 × 10-3 for the reaction. Fitting the variable-temperature 31P{1H} NMR spectra of a CD2Cl2 solution of 3 and 0.5 equiv of triethylamine using the gNMR program gives an activation energy of 47.4 kJ/mol for the reaction. The diastereomers of 3 crystallize with very different morphologies, allowing the X-ray crystal structures of both enantiomers to be determined. The 3 R * R * diastereomer crystallizes in the noncentrosymmetric P212121 space group, but the 3 R * S * diastereomer crystallizes in the centrosymmetric P21/c space group. The most interesting feature of the structures of 3 R * R * and 3 R * S * is the strong, intramolecular hydrogen bonding between the 2,2‘-C12H8O2POH and 2,2‘-C12H8O2PO- ligands that result in short O−O distances in both enantiomers (2.520(6) Å in 3 R * R * and 2.373(11) Å in 3 R * S *). The hydrogen bonding in both diastereomers is asymmetric, in contrast to previous speculation in the literature.