Heteroleptic compound

Synthesis and structural chemistry of non-cyclopentadienyl organolanthanide complexes have been reviewed by Edelmann and Schumann et /.13,13a 24 Marques et al. have published a review on the chemistry of the lanthanide using pyrazolylborate ligands.36 Theoretical investigations on lanthanide alkyls have been published by Eisenstein et al. under the title Lanthanide complexes electronic structure and H—H, C-H, and Si-H bond activation from a DFT perspective.  

YCI3 + 3LiCH(SiMe3)2 -------- (Et20)3Li(M-CI)Y[CH(SiMe3)2]3 + 2LiCI 

Reaction of the neutral ligand l,4,7-trimethyl-l,4,7-triazacyclononane (Me3[9]aneN3) with LnCl3(THF)3 (Ln = Sc, Y) in acetonitrile afforded the novel trihalide complexes (Me3[9]aneN3)LnCl3. Subsequent alkylation with LiMe in 

As wUl be noted later, this state has a notably shorter lifetime than the 88 state [73]. 

As noted earlier, by extending the conjugation in the R groups and by introducing strongly %-accepting groups such as CN or Noj, the MLCT absorption can be tuned to extend well into the near IR of the spectrum, 400 - 1200 nm [67]. 

Two other series of heteroleptic compounds have been studied, namely, cis-Mo2(ArNCHNAr)2 (OjCRjj and MojjArNCHNArjjjOjCR), where Ar =/ -anisole. In these, the lowest energy MLCT occurs to the carboxylate ligand R = thienyl, bithienyl, and terthienyl, -C=C-Ph, /i-CgH CN, and C HjSCsCH (2-carboxylate-5-ethynylthienyl) [70]. 

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Properties of nickel poly(pyrazol-l-yl)borate complexes such as solubility, coordination geometry, etc., can be controlled by appropriate substituent groups on the pyrazol rings, in particular in the 3- and 5-positions. Typical complexes are those of octahedral C symmetry (192)°02-604 and tetrahedral species (193). In the former case, two different tris(pyrazolyl)borate ligands may be involved to give heteroleptic compounds.602,603 Substituents in the 5-position mainly provide protection of the BH group. Only few representative examples are discussed here. 

A second problem is the widespread occurrence of compounds in which several different anionic elements bond to the metal (heteroleptic compounds). Most inorganic compounds have homoleptic coordination, i.e. the cation is bonded to only one kind of anion, making the determination of the bond valence parameters relatively simple (Appendix 1). Flomoleptic coordination is much less common among the transition-metal complexes. As described in Appendix 1, bond valence parameters for a variety of transition metals to O, N, C, Cl, S, and P have been determined using heteroleptic systems although the values obtained are often less reliable than those obtained from homoleptic systems. 

Heteroleptic chromium aryl compounds, preparation and characterization, 5, 298 Heteroleptic compounds actinide complexes, 4, 193 lanthanide complexes, 4, 7... 

They have also demonstrated that reaction of Bal2 with only one molar equivalent of KTp in THF yields the heteroleptic compound [Tp BaI (THF) ], which upon drying under vacuum loses crystallinity and solvent to form the monosolvated species (n = 1). The mixed Tp -Bp (Bp = H2B(3,5-Me2pz)2) complex of Ba, BaTp Bp, may be prepared from [Tp BaI(THF) ] by addition of KBp to this species in THF. Caulton... 

The solid-state structure of the heteroleptic compound [Tp Bal (HMPA)2] is shown in Fig. 21.111 The steric bulk of the poly(pyrazolyl)bo-rate ligand is apparent in this figure, effectively blocking oligomerization from occurring. This is even more apparent in the bis(3,5-dimethylpoly (pyrazolyl)borate) complex Ba[HB(3,5-Me2pz)3]2 shown in Fig. 22, where two poly(3,5-dimethylpyrazolylborate) ligands have sterically saturated the coordination sphere of the barium center. The shortest intermolecular distance is 5.23 A.112... 

This class of heteroleptic compounds is of interest since several factors (M, ligands, net charge) can be modulated in order to obtain complexes with... 

Anionic species derived from 2,3,4,5-tetraethylhetereroles 11a, 11b and the metals Mg, Ca, Sr, and Ba have been prepared <2001ZFA1741> from corresponding 1-chloroderivatives 18 (E = As, Sb) by reaction with an excess of the appropriate metal in THE. Magnesium and calcium react under ultrasonic irradiation and heteroleptic compounds with structures analogous to 12 have been formed. Intermediates of biheterole type 3 can be isolated. 

Limited heteroleptic organoindium examples are known since they have a tendency to rearrange to form the more stable symmetrical derivatives. The preparation of the majority of the heteroleptic compounds has been investigated via (a) ligand redistribution (equation 7-8), (b) metathesis (equation 9), or (c) methane elimination (equation 10) ... 

Heteroleptic (see Heteroleptic Compound) alkylzinc thiolate and selenolate componnds present two major interests they can be nsed as models for metalloenzyme activity and as precursors for the formation of binary metal snlfides and selenides. " Furthermore, these compounds tend to... 

Some heteroleptic (see Heteroleptic Compound) alkylzinc amides have been prepared by addition reaction of dialkylzinc compounds (ZnR2) on l,4-di-tert-butyl-l,4-diaza-l,3-butadiene (t-BuN=CHCH=N-t-Bu). Extensive studies ... 

Homo- and heteroleptic (see Heteroleptic Compound) triorganozincates can also be prepared by reacting an... 

Owing to the significant lability within the target compounds, ligand exchange reactions are frequently observed. This is especially relevant for heteroleptic compounds, where complex solution equilibria complicate the isolation of pure species. As such, solution chemistry of the organometalhaUdes is discussed below. 

Grubbs Kinetics on heteroleptic compounds Sigma donation of phosphine directly related to initiation rates in heteroleptic compounds rates of phosphine reassociation not directly linked... 

Large metal ions such as thorium or uranium were also employed in order to combine a porphyrin, octaethylporphyrin (OEP), with a phthalocyanine (Pc) chromophore in face-to-face or double-decker orientation. and Th compounds could be electrogenerated in up to seven different oxidation states. The first two reductions occurred mainly on the Pc ring while the first two oxidations of the same heteroleptic compounds involved primarily orbitals of the porphyrin macrocycle. In contrast, the homoleptic (MP)2 and (MPc)2 derivatives undergo initial one-electron oxidations and reductions which are localized not at a single ring, but involve both macrocycles. ... 

Further reactions of iodo complexes 158 and 160 with KN(PPh2) in THF led to heteroleptic compounds [Ln(L30) N(PPh2) (THF)] (Ln = Eu (161), Yb (162)) [95]. An alternative reaction pathway (Scheme 59) started from the triva-lent ytterbium complex 156 which already contained both ligands L30 and the... 

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