Tris -phosphine complex

All the reported methods suffer from drawbacks, being either multistep processes that are time-consuming or affording difficult-to-separate mixtures of bis- and tris(phosphane) complexes.13 Moreover, they usually require an excess of phosphane or the cumbersome preparation of sophisticated starting materials, ultimately leading to low overall yields. It is noteworthy that the tris(phosphine) complexes cannot be prepared by substitution of CO by phosphine in the well-known and easily prepared bis(phosphine) complexes.14... 

In the low-temperature region, the P-31 spectra of all of the solutions exhibited the doublet arising from the triphenylphosphine coordinated with rhodium. This doublet has a chemical-shift value of + 39.8 ppm (relative to 85% H3P04) and a coupling constant,/P Rh, of 155 Hz. As such, it arises undoubtedly from triphenylphosphine bound to rhodium in a trigonal bipyramidal complex, (Ph3P)3Rh(CO)H. None of the spectra showed any indication of the trans-bisphosphine complex that is formed by dissociation of the tris-phosphine complex. The equilibrium concentration of (Ph3P)2Rh(CO)H was too low for detection by NMR under all of the experimental conditions used in the present studies. 

In Figure 1, the observed reactions are indicated in the context of a proposed catalytic scheme for terminal hydroformy-lation. The reaction pathway involving the alkyl phosphine intermediate (VIII) is the most likely. Overall, the results of the NMR studies provide consistent explanations for the process parameters of selective hydroformylation, particularly of the low pressure continuous product flashoff process (.5,15). it was shown that, in contrast to prior indications (3), the tris-phosphine complex (I) is a remarkably stable and favored species in the presence of excess phosphine and H2. This complex (I) is postulated to have a key role in the reversible generation and... 

The mechanism of the oxidative addition of aryl bromides to the bis-P(o-tolyl)3 Pd(0) complex 3 was surprising [196]. It has been well established that aryl halides undergo oxidative addition to L2Pd fragments [197 -200] thus, one would expect oxidative addition of the aryl halide to occur directly to 3 and ligand dissociation and dimerization to occur subsequently. Instead, the addition of aryl halide to [Pd[P(o-tolyl)3]2] occurs after phosphine dissociation, as shown by an inverse first-order dependence of the reaction rate on phosphine concentration and the absence of any tris-phosphine complex in solution [196]. 

A further example of the tendency toward multiple substitution was observed upon treatment of Tp Rh(/ -C2H4)(L) (L = C2H4 (118), PMea (145)) with excess (five to six equivalents) PMc3, which affords the tris(phosphine) complex ( c -A-Tp )Rh(PMe3)3 (267), in which one pyrazole donor has been displaced in addition to the ancillary ligands. The identity of 267 was established crystallographically (Fig. 5), while variable temperature P H -NMR spectroscopic studies revealed thermal equilibration of the pyrazolyl groups, a process that could be frozen out at —80°C. ° ... 

The preparation of copper(i) trifluoroacetate and the formation of some phosphine and olefin complexes from it are described. Triphenylphosphine forms mono-, bis-, and tris-phosphine complexes, but evidence for co-ordination of four phosphine groups could be obtained only with bis(diphenyl-phosphino)ethane. The tris(triphenylphosphine)copper(i) trifluoroacetate is also formed by reduction of copper(ii) trifluoroacetate with triphenylphosphine in alcoholic solution. Cyclo-octa-1,5-diene forms 1 1 and 1 2 complexes with copper(i) trifluoroacetate, and cyclo-octatetraene forms a 1 2 complex for which the structure (155) is suggested. ... 

In the tris(phosphine) complexes [Table 1, part (ii)] the interbond angles involving the copper atom show smaller departures from ideal tetrahedral values than those in the bis(phosphine) complexes, and the Cu-P distances are rather longer. In [Cu(PMePh2)3(NOa)] (2) the trends in the Cu-P... 

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