Unusual hydrolysis reactions of cis-bis((2,2'-biphenylylene)phosphochloridite ester)tetracarbonylmolybdenum(0)

The hydrolysis of cis-Mo(CO) 4 (2,2'-C 1 2 H 8 O 2 PCl) 2 (1) in the presence of excess triethylamine and water yields [(C 2 H 5 ) 3 NH] 2 [cis-Mo(CO) 4 (2,2'-C 1 2 H 8 O 2 PO) 2 ] (2). This complex is in equilibrium with [(C 2 H 5 ) 3 NH][cis-Mo(CO)4(2,2'-C 1 2 H 8 O 2 PO)(2,2'-C 1 2 H 8 O 2 POH)] (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 x 10 - 3 for the reaction. Fitting the variable-temperature 3 1 P{ 1 H} NMR spectra of a CD 2 Cl 2 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 3R*R* diastereomer crystallizes in the noncentrosymmetric P2 1 2 1 2 1 space group, but the 3R*S* diastereomer crystallizes in the centrosymmetric P2 1 /c space group. The most interesting feature of the structures of 3R*R* and 3R*S* is the strong, intramolecular hydrogen bonding between the 2,2'-C 1 2 H 8 O 2 -POH and 2,2'-C 1 2 H 8 O 2 PO - ligands that result in short O-O distances in both enantiomers (2.520(6) A in 3R*R* and 2.373(11) A in 3R*S*). The hydrogen bonding in both diastereomers is asymmetric, in contrast to previous speculation in the literature.