Master of Science (MS)
Semester of Degree Completion
Richard L. Keiter
The synthesis of cis-(OC)4M(PPh2H)L (M=Cr,Mo,W; L=PPh3,PPh2Et,PPhEt2,PEt3) can be achieved by treating (OC)5MPPh2H with potassium tert-butoxide in the presence of L. […] The products are easily isolated and are not contaminated with trans isomers. Obtained as a minor product is [(OC)4MPPh2]2.
The reaction of (OC)5WPPh2H with potassium tert-butoxide generates [(OC)5WPPh2]- which reacts with (OC)5WPPh2H to give [(OC)5WPPh2W(CO)5]-, [(OC)5WPPh2W(CO)4PPh2H]- and [(OC)4W PPh2]2=. We envision the following scheme to account for the observed results. […]
Both [(OC)5WPPh2W(CO)4PPh2H]- and [(OC)5WPPh2W(CO)5]- were isolated as PPN+ salts. The latter complex is very stable in a variety of solvents over a long period of time and is not sensitive to oxygen. The former complex is air stable but slowly decomposes in solution. The dianion [(OC)4WPPh2]2= was isolated as the K+ salt. This anion is extremely air sensitive and is oxidized by molecular oxygen to [(OC)4WPPh2]2.
The complexes were characterized by 31P nmr and IR spectroscopy. 31P chemical shifts of the anions are upfield from the reference H3PO4 while that of the oxidized product is far downfield. Thus the chemical shift is diagnostic for the presence or absence of a metal-metal bond in these systems.
Madigan, Matthew J., "Cis Labilization: A Study of the Reactions of Group 6 Pentacarbonyl Phosphido Anions" (1981). Masters Theses. 2976.