Borato complexes

M[TpRR ] complexes (M = Li, Na, Cs, R4N+) may also be obtained by the reactions of the monoprotonated derivative H[TpRR ] with MOH (lb). Both the M[TpRR] and M[BpRR] complexes are useful starting materials for the preparation of poly(pyrazolyl)borato complexes of both the transition and main group metals. 

M[pzTp](H20) (M = Na, K) have been determined by x-ray diffraction (30). In contrast to the discrete monomeric structures of the tris (pyrazolyl)hydroborato complexes Tl[TpRR ], K[TpBut2], and Cs[TpBut2] described earlier, the hydrated tetrakis(pyrazolyl)borato complexes M[PzTp](H20) (M = Na, K) exhibit an interesting polymeric-type structure, a portion of which is illustrated in Fig. 14. In each case, the cations occupy two different crystallographic sites, and the cation in one of the sites is coordinated to two pyrazolyl groups in a rr-type fashion. 

Smaller degrees of non-coplanarity are not uncommon in poly(pyrazolyl)borato complexes, e.g., [TpMe2]2Mg. 

Group III Donors. Boron donor ligands. The unusual tris(pyrazolyl)borato-complex [RuL3(CO)2X] [X = Cl, Br, or I L = (16a)] has been prepared ... 

Figure 5.4 Reaction of the silsesquioxane-borato complex PhN(H)Me2 [(c-C5H,),SUO,3]B(QF5)3 (5) with [Cp2Zr(CH2Ph)2] to afford well-defined cationic species 7-9. (Redrawn from Duchateau et al. [15].)...

Figure 8.2. Silver tris(pyrazolyl)borato complexes.

Cyclopentadienyl, Indenyl, and Poly(pyrazolyl)borato Complexes... 

The last series of tungsten complexes that have been electrochemically studied belong to the 3,5-dimethylpyrazolyl-borato complexes of the type shown in Scheme 7-7. Also in this case, they exhibit the one-electron oxidation of the ferrocenyl centre and the one-electron reduction of the molybdenum fragment [55], The relevant redox potentials are summarized in Table 7-13. 

The six-coordinate, coordinatively unsaturated nitrosyl tris(3,5-dimethylpyrazolyl)borato complexes [Mo(NO) HB(3,5-Me2pyz)3)XY], where X = Y = Cl or I X = Cl or I, Y = OR, OAr, NHR, NHAr, etc) are redox active, undergoing a one-electron reduction to form the paramagnetic monoanionic species [Mo(NO) HB(3,5-Me2pyz)3XY] . The neutral precursor formally contains a metal atom having a 16-electron configuration, whereas the metal in the reduced species has a 17-electron configuration. 

The relative orientations of these groups in the dicarbonyl [Mo(CX))2(NO)L"] are similar but have no apparent steric consequences. It is not possible to make a direct structural comparison with phenolate complexes of other tris(pyrazolyl)borato complexes, but this strong orientational effect is absent in the formally isoelectronic anilido species [Mo(NO) HB(3,5-Me2pyz)3)I(NHC R-p)] (R = Me or OMe)4. Certainly other work has indicated that orientational effects can have a pronounced effect on reduction potentials in these systems. ... 

L = CNBu ) to 95 5 (L = P(p-tolyl)3). Several chelate bis(benzotriazolyl)borato complexes of rhodium carbonyl were obtained. ... 

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