Trimerization complexes

An X-ray crystal-structure determination (370) revealed that mixed, nickel coordination exists in the trimeric complex, [Ni(S2CPh)2]3. The trimeric structure is similar to that found (371) in [Pd(PhCS2>]. The structure contains one molecule of type A linked centrosymmetrically through short Ni-S bridges to two molecules of type B, the three molecules being closely parallel (XXVII). Bonamico and co-workers (372)... 

Sulfur dioxide and carbon disulfide react with bis(bulky phosphine)platinum complexes to give monomeric trigonal planar [Pt(PR3)2(S02)] and trimeric complexes such as [Pt3(/u-S02)(PR3)2] and [Pt3(/i-CS2)(PR3)2] where R = Cy or But70 71... 

The cloned opiate receptors expressed in homogeneous cell lines associate with guanine nucleotide binding (G) proteins which couple the receptors to cellular effector systems. G proteins consist of hetero-trimeric complexes of a, fj and y subunits [66]. Multiple subtypes of each subunit have been identified and cloned. In particular, three subtypes of Gi have been cloned that are approximately 90% identical in amino acid sequence. Furthermore, two splice forms of G0 have been identified. 

In contrast with formation of three types of bpz-substituted RU3 cluster species, reactions of 2 with pyq induced isolation of monomer 45 and trimer 46 containing 6>rf/ 6>-metallated pyq depending on the reaction conditions [30]. Reduction of the 3+ trimeric complex 46 by addition of aqueous hydrazine gave neutral species 46a. Oxidation of 46a by addition of two equivalents of ferrocenium hexaflu-orophosphate afforded 2+ intercluster heterovalent complex46b containing two Ru30(0Ac)6(py)2II,III,m and one Ru30(OAc)5(py)2II,m,n moieties. 

As shown in Fig. 7, the electronic spectrum of 2+ intercluster heterovalent trimeric complex 46b includes IC absorption envelopes characteristic of both [RU3O]0 and [Ru30]+ moieties, which are only slightly perturbed compared with those in the corresponding neutral (46a) and 3+ complexes (46). Three reversible redox waves occur at +0.89, —0.29, and —1.57V in the CV... 

Binding of substrates to exportins is regulated in a converse manner to importins. Exportins bind their cargoes preferentially in the nucleus, forming a trimeric cargo exportin Ran GTP complex [142]. This trimeric complex is then transferred to the cytoplasm where Ran GTP is converted to Ran GDP. This results in Ran s dissociation from the complex, allowing the exportin to release its substrate, re-enter the nucleus, and to start the next export cycle. 

G-proteins can be found membrane bound or free in the cytosol. The membrane bound proteins are trimeric complexes of a, [3 and y subunits. The [3 and y subunits may... 

Table 10 Fragment ion abundance ratios in the MS spectra of Cu(II)-bound trimer complexes...

Kay Severin s group has previously investigated the preparation of dynamic combinatorial libraries of metallo-macrocycles for use as sensors for Li+ at physiologically relevant conditions [59]. For example, they have found that ligand 62 and metal complexes 63 undergo a self-assembly process to yield the trimeric complexes depicted in Scheme 4.15 [60]. Mixtures of 64 and... 

The observations reported above on the alkylation of the trimeric complex species, [Ni Ni(NH2CH2CH2S)2 2]+2, have an important bearing on the reaction of the neutral complex, [Ni(NH2CH2CH2S)2]. When [Ni(NH2CH2-CH2S) 2] is treated with alkyl halides, the trimeric complex forms in solution and can be isolated if the reaction is interrupted. The appearance of this species as a stable intermediate indicates that the alkylation reaction of [Ni(NH2CH2CH2S)2] proceeds in a stepwise fashion (Equations 10 to 13). 

A trimeric complex has also been the subject of a detailed study.709 The mole ratio [Cr] [OH] was found to be 4 3 the degree of polymerization was assessed, by freezing point depression, to be three. A triangular structure, as shown in (157), was suggested on the basis of magnetic studies. 

Other possible compounds may be formed including mixed-valent1566 and hydroxy-bridged trimeric complexes of type [Pt3(ju-0H)3(NH3)6](N03)31567 and [Pt3( -0H)3(NH3)6](S04)3-6H20.1568... 

Stepwise addition of halogens to the trimeric complex, [Au C(OMe)= NMe ]3 produced (155) three complexes Au3 C(OMe)=NMe 3X ] (n = 2,4,6) by consecutive oxidation of the three gold(I) centers. Binuclear gold(I) ylide complexes, however, underwent (56) consecutive oxidative addition of X2 to give formal gold(II) and finally gold(III) products [Eq. (49)]. Crystal structure (188) and spectroscopic (56. 189, 190) data have... 

Avery active form of Ni(0) is generated from bis-7r-allylnickel (12) and Ni(cod)2 (13) in the absence of phosphine ligand, and is often called naked Ni(0). Three butadienes coordinate to naked Ni(0) and the 18-electron trimeric complex 10 is... 

Additional work by the Forster group, making use of transient emission spectroscopy, probed the rate of photoinduced electron transfer between metal centers within a novel trimeric complex [Os(II)(bpy)2(bpe)2 ] [Os(II) (bpy)2Cl]2 4+, where bpy is 2,2/-bipyridyl and bpe is fra s-l,2-bis-(4-pyridyl) ethylene. Transient emission experiments on the trimer, and on [Os(bpy)2(bpe)2]2+ in which the [Os(bpy)2Cl]+ quenching moieties are absent, reveal that the rate of photoinduced electron transfer (PET) across the bpe bridge is 1.3 0.1 x 108s-1. The electron transfer is believed to be from the peripheral Os(II)Cl metal centers to the [Os(bpy)2(bpe)2]2+ chro-mophore. Comparison to rate constants for reduction of monolayers at a Pt electrode reveals that the photoinduced process is significantly faster [39]. 

Dimeric and Trimeric Complexes with Bridging Sulfurs. 233... 

---