title: Synthesis of a sterically bulky diphosphine synthon and Ru(ii) complexes of a cooperative tridentate enamide-diphosphine ligand platform.
abstract: In order to generate tridentate enamido diphosphine ligand platforms, we developed procedures for the preparation of tBu2PCH2CH2P(tBu)I, which involve low temperatures, pentane solvent and addition of 4 equiv. of tBuLi to Cl2PCH2CH2PCl2or 2 equiv. of tBuLi to known Cl(tBu)PCH2CH2P(tBu)Cl also at low temperatures in pentane; an alternate method involves the inverse addition of Cl(tBu)PCH2CH2P(tBu)Cl to 2 equiv. of tBuLi in pentane at 0 °C; all of these methods generate good yields of the tetraphosphine dimer (tBu2PCH2CH2P(tBu))2contaminated by small amounts of tBu2PCH2CH2PtBu2(dtbpe), which can be conveniently separated by sublimation. Subsequent oxidative cleavage of the P-P bond with I2or 1,2-diiodoethane results in the formation of the desired tBu2PCH2CH2P(tBu)I, which undergoes C-P bond formation when added to 1 equiv. of the lithium N-2,6-diisopropylphenylenamide of cyclopentylidene imine to generate the HNPP ligand precursor; this species exists as a tautomeric mixture of the corresponding enamine and imine, the ratio of which depends on workup conditions used. This enamine-imine mixture can be used directly to form Ru(ii) species either directly with heating to generate the five-coordinate (NPP)RuCl(CO) via loss of H2or by inclusion of 1 equiv. of KOtBu to generate (NPP)RuH(CO). X-ray crystallographic studies confirm that the geometry in the solid state matches the solution spectroscopic data. Subsequent studies of (NPP)RuH(CO) indicate that it reacts with benzaldehyde, benzyl alcohol, and H2in a cooperative manner to generate a series of hydride carbonyls that have been characterized fully by NMR spectroscopy and X-ray crystallography.
authors.affiliation: Department of Chemistry, The University of British Columbia, 2036 Main Mall, Vancouver, BC, CanadaV6T 1Z1. fryzuk@chem.ubc.ca.
authors.forename: Vincent T
authors.initials: VT
authors.lastname: Annibale
authors.affiliation: Department of Chemistry, The University of British Columbia, 2036 Main Mall, Vancouver, BC, CanadaV6T 1Z1. fryzuk@chem.ubc.ca.
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Ostapowicz
authors.affiliation: Department of Chemistry, The University of British Columbia, 2036 Main Mall, Vancouver, BC, CanadaV6T 1Z1. fryzuk@chem.ubc.ca.
authors.forename: Stefan
authors.initials: S
authors.lastname: Westhues
authors.affiliation: Department of Chemistry, The University of British Columbia, 2036 Main Mall, Vancouver, BC, CanadaV6T 1Z1. fryzuk@chem.ubc.ca.
authors.forename: Truman C
authors.initials: TC
authors.lastname: Wambach
authors.affiliation: Department of Chemistry, The University of British Columbia, 2036 Main Mall, Vancouver, BC, CanadaV6T 1Z1. fryzuk@chem.ubc.ca.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Fryzuk