Coordination Complexes of Tetrakis(trifluoroacetato)dimolybdenum. A Solution ¹H, ¹⁹F, and ³¹P Nuclear Magnetic Resonance and Infrared Spectroscopic Study

New coordination complexes of the type Mo₂(O₂CCF₃)₄(L)₂ where L is Me₃P, Me₂PhP, MePh₂P, Ph₃P, Et₃P, (c-Hx)₃P (c-Hx = cyclohexyl), (t-Bu)₃P, (Me₃Si)₃P, Me₃PO, and quinuclidine have been prepared. These complexes fall into two classes, viz., class I or class II. Class I complexes are formed with MePh₂P, Ph₃P, (c-Hx)₃P, (f-Bu)₃P, (Me₃Si)₃P, Me₃PO, and quinuclidine. Solution infrared and ¹⁹F NMR studies show that these complexes are of the classical type (axial coordination) as shown by X-ray crystallography for L = pyridine, some years ago. Solution ^3IP{¹H} NMR spectroscopy of these phosphine adducts indicates that they are extensively dissociated in CDC1₃. Class II complexes (L = Me₃P, Me₂PhP, or Et₃P) exist in solution (CDC1₃) with bidentate and monodentate trifluoroacetate groups as determined by infrared and ₁₉F NMR spectroscopy. At least two isomers are present as shown by ³¹P{¹H} and ¹H{³¹P} NMR spectroscopy. Some bidentate phosphine complexes are also described.