Fluorophosphine ligands

Knowing all these facts, especially the difficult access to fluorophosphines and the poor donating abilities of phosphorus trifluoride (5, 6), we decided to use another approach, which readily led to a number of coordination compounds with fluorophosphine ligands—namely, the fluorination of chlorophosphines already coordinated to the transition metal, where the 3s electrons of phosphorus are blocked by the complex formation. There was no reaction between elemental nickel and phosphorus trifluoride, even under extreme conditions, whereas the exchange of carbon monoxide in nickel carbonyl upon interaction with phosphorus trifluoride proceeded very slowly and even after 100 hours interaction did not lead to a well defined product (5,6). 

Phosphorus-phosphorus coupling constants ( 7pMpO octahedral complexes containing fluorophosphine ligands... 

Mixed phosphine-fluorophosphine (160, 247, 164, 173, 174), phos-phite-fluorophosphine (174), tertiary amine-fluorophosphine (174), carbonyl-fluorophosphine (160, 173, 56, 58, 59), tertiary arsine-fluoro-phosphine (174,175), and stibine-fluorophosphine complexes are readily formed directly from the appropriate fluorophosphine-metal complex. Only in the case of carbon monoxide, chlorophosphines, and phosphites is it possible to completely displace all the fluorophosphine ligands from the metal. Some typical examples are quoted below ... 

Rearrangements.—Boron trifluoride catalyses the rearrangement of unco-ordinated trimethyl phosphite to dimethyl methylphosphonate, but reacts quite differently with co-ordinated phosphite to give complexes with fluorophosphine ligands. ... 

Observations have been made which support coordination of the dialkyl-amino fluorophosphine ligands to the transition metal through phosphorus, rather than through nitrogen, whereas in the reaction of (CH )2NPp2 with some boron acceptor molecules coordination both through phosphorus or nitrogen was observed (1). 

Organic derivatives of phosphorus trichloride—i.e., chlorophosphines of the types RPC12 or R2PC1—had never been fluorinated. We assumed the hitherto unknown fluorophosphines to be possibly interesting ligands in coordination chemistry. Such expectations were supported by earlier observations of Chatt (5, 6) and Wilkinson (32), who found that the parent compound phosphorus trifluoride as a ligand in certain coordination compounds with platinum or nickel behaved very much like carbon monoxide. 

In our study of the fluorination of coordinated chlorophosphine ligands (23), we started out with tetrakis(trichlorophosphine)nickel-(0), which could previously be converted into tetrakis(trifluorophosphine)nickel-(0) by displacement of the coordinated phosphorus trichloride with excess phosphorus trifluoride in a sealed tube (32). The limitations of this method, requiring the use of phosphorus trifluoride, a low boiling gas, under pressure, and involving the mechanical separation of the fluorophosphine complex from phosphorus trichloride, are obvious, and the yield was low. A straightforward method for the synthesis of this interesting compound was found in the fluorination of the coordinated phosphorus trichloride with potassium fluorosulfinate ... 

Fluorophosphine-boranes have been prepared and the relative donor abilities of the phosphine ligands have been reported 58>. 

Photoelectron spectra have been reported for [RhH(PF3)4] and some related tri-fluorophosphine species.120 Comparison with related carbonyl complexes suggests similar 7t-acceptor properties for CO and PF3 ligands. Studies have shown that the activity of the hydrogenation catalyst [RhH(CO)2(PPh3)3], which decreases with time, can be regenerated using weak u.v.-visible irradiation.121... 

Fluorophosphines are tervalent phosphorus compounds containing phosphorus-fluorine bonds and they often show markedly different chemical behavior compared with other halogenophosphines. This article is mainly concerned with recent advances in the chemistry of derivatives of PF 3 of the type PF3 X , with particular reference to (a) synthesis of new structural types, (6) the role of fluorophosphines as ligands, particularly in transition metal complexes, and (c) nuclear magnetic resonance (NMR) studies. 

The ease of substitution of metal-fluorophosphine complexes has also been related to the a-donor and 7r-acceptor characteristics of the substituting ligand (152), since only ligands of high 7T-acceptor ability (e.g., CO, phosphites) can completely displace the coordinated fluorophos-phines, whereas tertiary amines, phosphines, arsines, and stibines usually form partially substituted products (see Section IX, 6). 

Fewer data are available on fluorophosphine complexes of metals in higher oxidation states. In Pt(II) complexes 241, 242) Sp occurs at higher field than the free ligand, whereas the behavior in Rh(I) complexes 242, 250) is more variable. 

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