Trifluorophosphine structure

IR spectra, 22 177-179 Raman spectra, 22 178, 179 triazole and triazolate complexes, 32 180 trifluoride, structure, 27 90, 91, 92, 95, 97 trifluorophosphine complexes cyclopentadienyl, 29 103 hexakis anion, 29 53-54 [Ni4(0CH3)4(acac)4(CH3OH4)l, 43 323 Nitramide, reaction mechanisms, 22 138, 139 acid catalysis, 22 139... 

Structural and/or spectroscopic investigations have shown that the local symmetries around the metal atoms in the M(PF3)4 (189,215), M(PF3)5(2), and M(PF3)6 compounds are Td, D3h, and Oh, respectively. Unfortunately theoretical studies on trifluorophosphine complexes are confined to CNDO/2 calculations on Ni(PF3)4, Fe(PF3)5, and Cr(PF3)6 (251). In view of the discussion of relaxation effects and basis set dependences presented in Section II the CNDO/2 results (Table XXVI) should be used only as a qualitative guide to spectral assignment. 

The question of the molecular structure of the adducts of tetraborane(8) has now been resolved 144>. The boron-11 nmr spectra of the carbon monoxide and trifluorophosphine adducts have been analyzed 140> in terms of the 2112 topological geometry 141> proposed by Dupont and Schaeffer 142>. The dimethylaminodifluorophosphine adduct of tetra-borane(8) 143> which was prepared by the following reaction is stable at room temperature. 

Fig. 23. The solid state structure of the trifluorophosphine adduct of bis(2,4-dimethylpentadienyl)-titanium. The corresponding vanadium compound is isomorphous (Ref. 256)...

No structural data are available for the pentakis(trifluorophosphine) complexes [M(PF3)5] (M = Fe, Ru, Os), which almost certainly have trigonal-bipyramidal structures. Detailed 19F and 31P NMR studies indicate clearly that these molecules are fluxional even at temperatures as low as — 160°C and the barrier to intramolecular ligand exchange between equatorial and axial positions of the trigonal bipyramid is less than 20 kJ/mol (251). Figure 3 shows the temperature-dependent 19F NMR spectrum of [Ru(PF3)5], which is typical for all the MPS... 

Several other tetranuclear complexes containing different metals have been obtained from the reaction between metal carbonyl and metal trifluorophosphine complexes (method E) or by intermolecular ligand-exchange reactions (method F) between tetranuclear complexes. The following structures have been proposed on the basis of 19F NMR and mass spectroscopic studies. 

Thus when the >73-l,l-dimethylallyltris(trifluorophosphine) complexes of cobalt or rhodium are gently warmed a rearrangement to the 73-l,2-isomer occurs (56, 295). The postulated mechanism involves a diene-metal hydride intermediate (Scheme 9). The small PF3 ligand can also be added directly to coordinatively unsaturated 3-allylic systems or to chloro-bridged structures (method H). 

An important paper describes the formation of the metal-metal bonded dirhodium tetracarboxylate trifluorophosphine complex [Rh2(OCOCH3)4(PF3)2] made directly from the dirhodium tetraacetate complex by direct addition of PF3 to the formally metal-metal triple bond. The structure was determined by a single-crystal X-ray study, and has been compared with other [Rh2(OAc)4X2] systems (X = py, Et2NH, CO, and P(OR)3). 

The molecular structure of trifluorophosphine has been the subject of several papers and considerable differences in bond length and bond angles have been reported. The very early work by Brockway et al. 33, 258) gave r(P-F) = 1.52 A, 0(FPF) = 104°, and more recently Hersh (13i) found r(P-F) = 1.537 0.04 A, 0(FPF) = 98.2° 0.6°. In neither case, however, were these data consistent with microwave studies [113, 208, 209). 

Force constant calculations for Ni(PF3)4 (190, 326) indicate that K(P-F) is similar to that in free trifluorophosphine and the metal-phosphorus force constant (about 2.4 mdyne/A), is only in the range expected for a single bond. Very recently, structural data for Ni(PF3)4 have become available from electron diffraction studies (la, 279a) (Section IX,C) and the phosphorus-fluorine bond length (1.561 ... 

A novel trifluorophosphine-tris(difluoroboryl)borane complex B4F3 PF3 (m.p. 55°C, b.p. 74°C) is formed by reacting the high-tempera-ture species boron monofluoride with PF3 on a cold surface (316). The crystal structure has recently been determined by X-ray diffraction and is shown in Fig. 7 (74). 

The structure of the red liquid complex (XXII), bis(p.-difiuorophos-phino)hexakis(trifluorophosphine) dicobalt has been confirmed by its characteristic F NMR spectrum which exhibits two doublets (from coupling with phosphorus) of relative intensity 9 2 (170). The chemical... 

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