Alkynyls bridging

Bis(cyclopentadienyl)zirconium(III) complexes alkynyl-bridged complexes, 4, 749 dinitrogen complexes, 4, 747 electrochemical reduction, 4, 745 phosphido-bridged complexes, 4, 750 Bis(cyclopentadienyl)zirconium(IV) complexes electrochemical reduction, 4, 745 with M-C r/)-bonds, 4, 895 with M-C r/i2-bonds, 4, 887 with M-C r/i3-bonds, 4, 884 with M-H bonds, 4, 878 with M-N bonds, 4, 910 with M-0 bonds, 4, 917 with M-P bonds, 4, 927 with M-S bonds, 4, 930 with M-Si bonds, 4, 925 non-functionalized metallocene halides, 4, 870 ring-functionalized metallocene halides, 4, 874 Bis(cyclopentadienyl)zirconium(III) halides, in organic synthesis, 4, 754... 

In the structure of Me2Ga(/x-C=C-Ph)2GaMe2 [Fig. 13.6.1(d)], each alkynyl bridge leans over toward one of the Ga centers. The organic ligand... 

Work on Ptn terpyridyl complexes has not been limited to just mononuclear systems. Yam and coworkers have also investigated complexes wherein two platinum centers are attached through alkynyl bridges more specifically they studied chromophores of the type f Hu. tpy )Ptf( =C)nI>tf Hu. tpy)]2+ (3.10) [65], These structures exhibit photoluminescence in both the solid state and in room temperature solutions, the latter assigned as 3CT in nature mixed with 3IL and 3LLCT character. 

Complexes containing alkynyl bridges are known. Some examples are Yb and Sm in [(MeCp)2Yb-C=C-CMe3]2 and the Sm analogue. The structure of the Sm compound shows it to be centrosymmetric dimer with two (MeCp)2Sm units connected by... 

Alkynyl-bridged dinuclear zirconocene(m) compounds such as 22-24 (and 30 below) exhibit dynamic behavior and rapidly exchange alkynyl ligands between the two metal centers, in a process that can be monitored by variable-temperature NMR.27,32... 

As we have noted in a previous section of this chapter, cumulenic resonance forms present one extreme description for dimetal complexes linked by all carbon bridges. They are frequently encountered in some oxidation state (mostly the dioxidised one) and also contribute to intermediate ones between the purely cumulenic and oligoynediyl or the cumulenic- and the alkynyl-bridged dicarbyne forms (see Schemes 6.6-6.8). Purely cumulenic wires are encountered in ot,a)-di- or -tetraferrocenyl substituted cumulenes, but no evidence other than a splitting of the ferrocenyl-based redox waves has been presented to support the presence of electronic interactions between the fer-rocenyl end groups across the cumulenic ligands. Based on the results of ex-... 

The reaction between disubstituted 1,3-diynes such as 5,5-dimethyl-1-tri-methylsilyl-l,3-hexadiyne with metallocenes M(t -C5H5)2 studied by Baumann et al yielded a complex with the intact diyne when M = Ti and a CT,7c-alkynyl-bridged dinuclear complex when M = Zr. These two types of compounds could be easily discriminated by the use of 7hc couplings observed between the terminal carbon atoms of the 1,3-diyne moiety and the protons either of the t-Bu or the SiMes group. 

The TPQ reduction potential shows a linear variation with pH of -60 mV/pH, indicating a 2e. 211 ET process, in contrast to the 2e, 3H ET observed with model compounds." Presumably the protein matrix or nearby Cu(II) stabilizes the deprotonated topaquinol. No copper electrochemistry was observed. It is not clear whether the copper potential is anomalously low or if it could not be measured due to weak electronic coupling with the phenyl-alkynyl bridge. 

The crystalline alkynyl-bridged dimers, [(MeBe NMe3)2(/r-C=CR)]2 (R = Me, t-Bu) are formed from 1 2 mixtures of [(RC=C)2Be-NMe3]2 and Me2Be-NMe3 in benzene or toluene at RT . The equilibrium between the MejN adducts ... 

For the time being, the best model system to exemplify the particular type of alkynyl bridging may be the aluminium compound (CH3)2AIC2CH3 which is dimeric both in the crystalline and in the gaseous state (39). The Av(CEC)-values known for this main group metal alkynyl system match nicely those listed in Table VII. 

Monomeric and Alkynyl Bridged Phthalocyaninato Element-14 Compounds. . 63... 

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