Mononuclear eight-coordinate

The synthesis and the X-ray single crystal studies of the dimeric heteroleptic eight-coordinate complexes [Eu(02CPh)(Tp)2]2 and [Eu(C>2CPh)2(Tp)]2 as also the structure of the known mononuclear eight-coordinated derivatives [Eu(acac)(Tp)2] and [Eu-(0C(Ph)CHC(Ph)0)(Tp)2] have been reported. The molecular parameters of these compounds have been related to the Ln3+ ionic radius.630... 

In the solid state the stereochemistry of copper(I) in its mononuclear complexes, as determined by X-ray crystallography (Figure 4.1), is dominated by four coordination. A significant number of three- and two-coordinate complexes are known, very few five-coordinate complexes exist and six coordination (or above) is unknown. This contrasts with the predominance of six coordination in the chemistry of copper(II) (see Section 53.4.2) and the absence of two or three coordination in the solid state, and with the formation of a significant number of seven- and eight-coordinate geometries.47,48... 

The reaction products of 2,2 -bipyrimidine (bpm), P-diketones, and lanthanide ions demonstrated the diverse nuclearity and dimensionality. As stated in the last section, dinuclear eight-coordinate [Ln2(P-diketonate)6(bpm)] could be formed [78, 79]. Zucchi et al. [26a] reacted Nd(N03)3 with bpm to afford the mononuclear nine-coordinate adduct [Nd(N03)3(bpm)(Me0H)2], while reactions of hydrated NdCb and various P-diketonates in the presence of bpm gave the binuclear nine-coordinate compounds [ Nd(L )3(THF) 2([JL-bpm)] (see Figure 2.46) and [ Nd(L )3(MeOH) 2([r-bpm)]-bpm (see Figure 2.47) and the one-dimensional coordination polymer [Nd(L )3(p,-bpm)-MeOH]oo (4-MeOH) (see Figures 2.48 and 2.49). Other groups have also reported the one-dimensional arrays [Ln(L )3(p.-bpm)]co (Ln = Eu [80], Gd, and Nd [75]. 

Mononuclear [Yb(02CCCl3)3.(terpy).MeOH] contains coordinated methanol and two uniden-tate carboxylates and one bidentate carboxylate affording eight coordinate ytterbium and [Ln(02CCCl3)3 (terpy) (H2O)] (Ln = La-Nd) are dimeric with nine-coordinate lanthanides. A compound [Lu(02CCCl3)3 (terpy) (H2O)] contains both the foregoing geometries. 

Mononuclear dialkylcarbamato complexes M(02CNRo) ( =4,5) are eight coordinate, as demonstrated for Nb C CNEt and Ta V(02CNEt2)s.329 The niobium compound is dodecahedral with four bidentate ligands while the tantalum example is essentially square antiprismatic with three bi- and two monodentate ligands (as seen previously in Nbv(02CNMe2)5327). 

Similarly the THF adduct [(tht)(C5Me5)2Sm(/i-02Ci6Hio)Sm(C5Me5)2(thf)] is either four- or eight-coordinated. Similar geometry is found in the mononuclear complex [(C5Me5)2Sm(OC4H8C5Me5)(thl)]. ... 

The molar ratio of coordinating carboxylate to RE(III) is usually noted as carboxylate/RE. rare earth formates are polymeric from La to Lu when carboxylate/RE = 3. They become mononuclear when carboxylate/RE increases from 3 to 6 or 8, where the metal centers are eight-coordinated either by 4 unidentate() ) and 2 bidentate( ) formates, or by 8 unidentate( ) formates. 4 ... 

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