Palladium fluxionality

The types of compounds formed by gold(I) and gold(III) often differ from those of other metals due to the constraints imposed by coordination number and electron count at the metal. Thus, for example, whereas 7r-bonded cyclopentadienyl complexes of palladium and platinum are numerous (336), and a copper(I) species of this type is known (337), cyclopentadienyl complexes of univalent (94, 96, 97) and trivalent (228) gold have invariably been found to be fluxional behavior, similar to that in dicyclopentadienylmercury, was involved (228). 

Finally in this section, the platinum complex BpP rihr -CgH OMe) (186) and related bis(pyrazolyl)methane complex salts [(H2Cpz2)M(r 1 r 2-CgHi2OMe)]PF6 (M = Pd 189.PF6, Pt 190.PF6) have been obtained from [M (ri1 ri2-C8FIi2OMe)Cl]2 and NaBp, or H2Cpz2/NFl4PF6, respectively (Scheme 15, Section III.B.l).73 The palladium analogue of 186 has proven inaccessible. These complexes all exhibit fluxionality, ascribed to inversion of the EN2M boat (E = B, C). 

The first palladium alkenyls, pzTpPd C,N-C(Cl) CHCMe2NMe2 (484)144 and the 3-oxo-hexenyl complex 493,160 were obtained systematically by halide displacement and dimer cleavage (Scheme 36). In common with alkyl and aryl systems (462—479, Section III.C.3), the pzTp ligand was in each case concluded to adopt a -coordination mode in solution, on the basis of (i) spectroscopic data, (ii) literature precedent, and (iii) the assumption that the Pd(II) centers in these complexes were too electron rich to permit coordination of the third pyrazole no solid-state data were reported. Both materials are fluxional in solution, and for 484 the slow-exchange limit was attained at —30 °C, with equilibration of the pyrazolyl environments becoming rapid at 79 °C, though the fast exchange limit... 

Fluxional behaviour, 73-allyl palladium complexes, 8, 371 Formamidinates, in chromium complexes, 5, 355 Formates, with Ru and Os half-sandwiches, 6, 483... 

Resolution of the racemic 7-/i-tolyldinaphtho[2,l-4 T,2 -optically active palladium complexes (with O.Sequiv of dimeric optically active di-p.-chlorobis (4)-2-[T(dimethylamino)-ethyl]phenyl-(7,M dipalladium(n)) 29 is a rare example of a reaction giving a product with CN 4 (Equation 6). The diastereomeric mixture thus produced could not be separated by fractional recrystallization from a variety of solvents or by column chromatography, because the optically active 7-A-tolyldinaphtho[2,l-4 l, 2 -palladium complex 48. Also the complex prepared from enantiomerically pure R-(-)-stibole 16 racemizes due to fluxionality (NMR estimated at elevated temperatures) <2001TL441, 2003YZ577>. 

Chemical shifts have been reported for [Me3CCH2HgX] 203) (see Table XII), tr-allylic derivatives (see Table XIII), o-cyclopentadienyl derivatives (see Table XIV), and miscellaneous compounds (see Table XV). In the case of fluxional a-cyclopentadienyl derivatives, it has been shown that chemical shifts can be used to differentiate between fluxional o-cyclopentadienyl derivatives and w-cyclopentadienyl derivatives 103). The NMR spectrum of [Sb(cyclopropyl)s] has only two carbon resonances, showing that the molecule is fluxional (56) and the NMR spectrum of the naturally occurring organometallic compound, 5 -deoxyadenosylcobalamin, has been reported (65). For a number of norbornane and allylic derivatives of palladium and platinum, a number of linear relationships have been found between chemical shifts of various carbon atoms. It was suggested that a term due to paramagnetic shielding by the metal was dominant 52b). 

R565 Y. Tsuji and Y. Obora, Structure and Fluxional Behavior of Platinum and Palladium Complexes Having M-Si or M-Sn (M=Pt or Pd) Inter-Element Linkages , J. Organomet. Chem., 2000, 611, 343 R566 V. V. Turov and R. Leboda, H-NMR Spectroscopy of Adsorbed Molecules and Free Surface Energy of Carbon Adsorbents , Chem. Phys. Carbon, 2001, 27, 67... 

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