Complex with Diboron

We beheve that reaHzation of these unique reactions is attributed to the structural features of the phenylene-bridged PSiP-pincer ligand, which enables facile structural change to trigonal bipyramidal-like geometry around palladium as seen in 50 and 51 because of its strain in square planar geometry. It is conceivable that such stmctural effect would facilitate interaction and reaction of the metal catalyst with other substrates, leading to the development of new types of transformations. 

Morales-Morales, D. and Jensen, C.M. (2007) The Chemistry of Pincer Compounds, Elsevier. 

Stobart, S.R., Grundy, S.L., and Joslin, F.L. (1990) Process for catalytic hydro-formylation. US Patent 4,950,798. 

For other examples of synthesis and utilization of phenylene-bridged PSiP-pincer complexes, see Korshin, E.E., Leitus, G., Shimon, L.J.W., Konstantinovski, L, and Milstein, D. (2008) Inorg. Chem., 47, 7177-7189. 

Aresta, M. (ed.) (2010) Carbon Dioxide as Chemical Feedstock, Wiley-VCH Verlag GmbH, Weinheim. 

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In contrast, reaction of ligand 72 with 4,4 -biphenyldiboronic acid has been successful and diboronate 73 is obtained in yields of 33%. This complex acts as a receptor for the paraquat dication forming a 1 1 complex with an association constant of 320 in acetone. The intermolecular forces responsible for the complexation are ion-dipole stabilization between the dative N B dipoles and the two cationic centers in paraquat, attractive tz-tz interactions between... 

Compounds 167-171 outlined in Fig. 43 form another series of diboronic acids that form complexes with mono- and disaccharides. In these cases the asymmetrical immobilization of chromophoric functional groups, e.g., aromatic rings in 167-170 or Fe -complexation with the related boronate 171, can be analyzed by circular dichroism measurements [256-262]. 

Diboration of alkene is catalyzed by Pt(0),42,48-51 Rh(i),52-57 Au(i),52 and Ag(i)58 complexes. Phosphine-free platinum complexes such as Pt(dba)2 and Pt(cod)2 are efficient catalysts for diboration of alkene, whereas those with phosphine ligands show much lower catalytic activities (Equations (3) and (4)).48,49 A PtCl2(cod) complex, which may be readily reduced to Pt(0) species with diboron, also catalyzes the addition of bis(catecholato)diboron to alkenes.42 Platinum-catalyzed diboration has so far been limited to terminal alkenes and strained cyclic alkenes. 

Bis(carbodiimido) complexes, with bis-Cp Ti(IV), 4, 583 Bis(catecholato)diboron, alkyne additions, 10, 727—728 Biscorroles, in organometallic synthesis, 1, 71—72 Bis(cyclodiyne) clusters, trirutheniums and triosmiums, 6, 772 Bis(cyclooctadienyl) chromium complexes, characteristics,... 

The diboronic acids 23 and 24 form rigid cyclic complexes with chiral monosaccharides and disaccharides this is the origin of the CD observations. The induced chirality upon formation of rigid, chiral complexes was monitored by CD spectroscopy, and this rigidification process can be utilized in the design of spectroscopic... 

The similar Ir-catalyzed direct borylation of benzene with diboron was recently reported experimentally [52] and its full catalytic cycle was theoretically investigated with the DFT(B3LYP) method [53]. In this reaction, the iridium(III) complex, Ir(bpy)(Beg)3 (bpy=2,2 -bipyridine eg=ethyleneglycolate),is an active... 

As in the case of the Negishi reaction, quinolinyl moiety can be incorporated in the Suzuki reaction either by using substituted quinoline halides or by the use of quinolinylborane complexes. Quinolinylborane reagents can be generally prepared in situ by the Miyuara reaction. Treatment of quinoline bromides or iodides with diboron compounds in the presence of palladium catalyst provides quinolinylboranes in good yields. Subsequent reaction with aryl bromides affords the corresponding substituted quinolines. On the... 

B.iii.c. ttsns-ArPd(OAc)L2 Complexes (L = PPh ). Irani-ArPd(OAc)(PPh3)2 complexes are reagents for the transmetallation step in Suzuki cross-coupling when acetate ions are added as a base. Indeed, Ishiyama and co-workers have reported that trans-ArPd(OAc)(PPh3)2 complexes, formed by substitution of bromide by acetate in trans-ArPdBr(PPh3)2 (see Sect. undergo transmetallation reactions with diboronic esters... 

Diphenyl-3,3 -diboronic acid 41 forms T.l complexes with cellobiose, maltose and lactose (but not sucrose), giving exiton coupling in c.d. spectroscopy owing to the immobilisation of the two phenyl rings of 41 in a chiral form. " 2... 

Tsukagoshi, K. and Shinkai, S. (1991) Specific complexation with mono- and disaccharides that can be detected by circular dichroism, J. Org. Chem., 56, 4089-4091 Shiomi, Y., Saisho, M., Tsukagoshi, K., and Shinkai, S. (1993) Specific complexation of glucose with a diphenylmethane-3,3 -diboronic acid derivative, J. Chem, Soc, Perkin Trans. 7, 2111-2117. 

The complexation of aldoses with cholesterol-derived boronic acids has been reviewed, and the changes in UV absorption and fluorescence intensity of a stilbene-type boronic acid on complexation with aldoses, especially D-fructose, have been studied with a view to their use in sugar-detection. Similar work has been carried out with diboronic acids derived from biphenyl and a -functionalized diaza-18-C-6 crown ether.A carbohydrate boronic acid derivative with liquid crystal properties referred to in Chapter 6, and further reports on boronate esters are noted in Chapter 17. 

In addition to considering solubility, a minimisation of the pen-hydrogens should reduce sterie crowding within the binding pocket and, as demonstrated with D-glucose and D-galactose, increase the relative stability of complexes formed with diboronic aeid sensors. 

Mizuno prepared similar complexes with cobalt (II) and bipyridine (bpy) diboronic acid 239. The diboronic acid saccharide complex can be used to control the chirality of the cobalt (II) bipyridine complex. The system is then converted to the substitution-inactive cobalt (III) and the boronic acids removed using silver nitrate to give [Co (bpy)3]. ... 

Sakaki. In fact, the product from the oxidative addition is a saturated hexacoordinated Pd(IV) complex which would require creation of a vacant site in order to enable the coordination of an alkene. The activation ofB2cat2 by [Pd(II)(NHC)Br] resulted more favorably through o-bond metathesis providing [Pd(NHC)(Bcat)] andBrBcat (Scheme 17B) with 3.4 kcal/mol above the reactants (Scheme 17B). Alternatively, the dicationic complex [Pd(II)(NHC)] could form a very stable o-complex with B2cat2, with 32.9 kcal/mol below the two isolated reagents, which promoted the oxidative addition of the diboron (Scheme 17C). 

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