Ligand triply

In an ever increasing number of compounds tolylidyne ligands triply-bridge a triangle of metal atoms, one of which is tungsten and the other two may or may not involve the same element. Thus two types of core structure are possible fM2W(y3-CR)l (Class A) or [M1M2W(y3-CR)] (Class B). Two methods are available for the synthesis of clusters of Class A. viz... 

The binary borohydride species Zr( III 11)4 and U(BH4)4 have been investigated by quantum mechanical techniques and, for the zirconium case, also by gas-phase electron diffraction. All confirm that these simple molecules have a staggered conformation of borohydride ligands.15 In a related study, the hafnium analog Hf(BH4)4 has also been analyzed and is essentially isostructural.16 These studies show the molecules to possess tetrahedral symmetry with all of the BH4 ligands triply (i.e., if) bridging. Photoelectron spectra [He(i)] of the half and bent metallocene complexes Zr(7]S-CsHs)(BH4)4, M(7]S-CsHs)2(BH4)2 (M = Zr, Hf), and Ta(7]S-CsHs)2(BH4) have been determined.17... 

Structure of 157 consists of a Fe2Mo triangle with a C(H) = C(Ph)C(Ph)=C ligand triply bridging the Fe2Mo face. 

Herberhold reported activation of water with Re2(CO)io. The reaction proceeded at 200°C to give a tetranuclear complex [Re(CO)3( X -OH)]4 (23) in quantitative yield, and evolution of dihydrogen and CO was observed (Eq. 6.13) [21]. Complex 23 has a pseudo-cubane structure without metal-metal bonds in which the Re(CO)3 groups are linked by triply-bridging OH ligands. Also in this case, no presumed intermediate hydrido(hydroxo) species was detected. 

Few Ni4 complexes with a cubane-like structure and four triply bridging //3-l,l,l-N3 ligands symmetrically bound to three Ni11 ions have been discovered (886),2135,2156 but magnetic data are only reported in the case of [Ni4(dmb)4(EtOH)4(//3-l,l,l-N3)4] (dbm = dibenzoylmethane).2135,2136 Its magnetic behavior was well reproduced by a model with a single 7 = +11.9cm 1. 

There has been considerable interest in the study of multinuclear metal complexes with bridging sulfide ligands.381 The first examples of triangulo palladium(II) are the complexes containing substituted 2,2 -bipyridine and triply bridging sulfide ligands, namely [Pd3(diimine)3(M3-S)2][C104]2382... 

Triply bridging carbonates between three zinc centers have been identified in nine different X-ray structures deposited in the CSD 458,461,465-467 For example, a binuclear ft-OH zinc complex with a tetradentate /V-donor ligand absorbs atmospheric carbon dioxide to a triply bridged carbonate.468 Examples are also known where the metal atoms are in varying coordination environments. The complex cation [Zn3(bipyridine)6(/U3-C03)(H20)2]4+ contains one penta- and two hexacoordinate zinc centers.469 A tetrapodal compartmental ligand forms a tetrameric complex with zinc that contains the carbonate bridging between three of the four zinc centers.470... 

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