Tetramethyl complexes

A similar mechanism was proposed, based on analogous kinetic behavior, for Pt(IV) tetramethyl complexes with isonitrile ligands (47). Isonitrile dissociation preceded the release of ethane. 

My own credentials are mixed. On the credit side is a refusal to predict concerted rrans-addition less impressive is a clear explanation of facile free radical loss from titanium tetramethyl complexes, shortly before evidence began to accu-mulate that such species decompose by internal or mutual abstraction. 

The binuclear tetramethyl complex [TiMe2(THF)(/x-NAr)]2 [Ar = w-C6H4-P(3,5-(CF3)2C6H3)2] can be prepared by methylation of the chloro parent compound with LiMe in Et20 at 0 °C (Scheme 77) and is stabilized by two imido bridges. The molecular structure of this complex has been determined by X-ray diffraction methods and shows that each Ti atom occupies the center of a trigonal bipyramid.152... 

From diromium(II) chloride, the yellow tetramethyl complex [Li2[Cr(CH3)4(THF)2]]2 may be prepared [99, 100] it has a magnetic moment of 0 5 B.M. Finally, there is evidence that treatment of CrCl3(THF)3 with vinylmagnesium chloride forms an unstable vinyl-Cr complex [100a]. 

Hydroc rbylComplexes. Stable homoleptic and heteroleptic thorium hydrocarbyl complexes have been synthesized. Two common homoleptic species are [Li-TMEDA]2 Th(CH2). ] [92366-18-2] (19), where TMEDA = tetramethyl ethylenediarnine, and Th(CH2CgH ) [54008-63-8] (20). 

AGE965, 86AGE1099, 880M2316). Species /x-h h -(2-benzyl-l,3,4,5-tetramethyl-2,3-dihydro-l,3-diborolyl)(i7 -allyl)(i7" -l,5-hexadiene)dinickel and /x-i7 i7 -[2-(2,4,6-trimethylbenzyl)-l,3,4,5-tetramethyl-2,3-dihydro-l,3-diborolyl](i7 -allyl)(i7" -l,5-hexadiene)dinickel serve as representative tripledecker complexes (01ZN(B)73). 

Europium, tris(2,2,6,6-tetramethyl-3,5-heptanedione-quinuclidine)-stereochemistry, 1, 81 Europium complexes... 

Note 1. The alternative fusion name (see 2-Carb-35.2) is 2,2,2, 2 -tetramethyl-4,4, 5,5 -tetra-hydro-(2,3,4,5-tetradeoxy-P-D-fructopyranoso)[2,3-d 4,5-d ]bis[l,3]dioxole this is clearly less desirable on grounds of complexity. 

Complex I is formed if l,4-difluoro-2,3,5,6-tetramethyl-l,4-diboracyclohexa-2,5-diene and Ni(CO>4 are condensed with dry, degassed toluene into a tube on a vacuum line. When the tube is allowed to warm to RT for 30 min, the complex can be trapped as yellow crystals at — 30 C when all volatile material is pumped off. The sandwich... 

In methylcyclohexane 2,3-diethyl-l,4,5,5-tetramethyl-lH-l,5,2-azasilaborole reacts with Ni or Fe atoms at - 130°C in an apparatus for metal vaporization to give sandwich complexes ... 

Perhaps chemists will be able to mimic nature without duplicating the iron-sulfur-molybdenum structure. For example, a zirconium complex with tetramethyl cyclopentadiene can bind dinitrogen in a manner that breaks the NON bond, as shown below. Treatment with hydrogen gas results in formation of small amounts of ammonia. Although the yields are too low to make this a viable commercial process, researchers hope to make the process more efficient through chemical modifications and changes in conditions. 

A stopped flow technique coupled with spectrophotometric analysis of the iron (II) complex formed has been used to investigate - the reactions of some organic complexes of iron(III) with the ion Fe ". The iron(III) was complexed with 1,10-phenanthroline, various substituted 1,10-phenanthrolines (5-methyl-, 5-nitro-, 5-chloro-, 5-phenyl-, 5,6-dimethyl-, 4,7-diphenyl-, and 3,4,7,8-tetramethyl-) and 2,2 -dipyridine, 4,4 -dimethyl-2,2 -dipyridine, and 2,2, 2"-tripyridine. The wavelengths used for the analysis lay in the region 500-552 m/i. 

The crystal structures of a number of diphosphine disulphides (121) and (122) show a remarkable constancy in the bond lengths. Two types of molecule are observed in the crystal of the tetramethyl compound (121, X = Y = Me). The crystal structure of triphenylphosphine oxide (P—C 176 pm, P—O 164 pm) varies little from that observed in the uranium oxide complexes, and does not confirm P—O bond lengthening in complexes, as indicated by vp=.o (see Section 3C). 

This section deals with the most important control experiments to be considered when molecular complexes or NPs want to be proved as true catalysts. But in some cases both types of catalysts can be present in the same reaction. For example, in the ring opening polymerisation of l,l,3,3-tetramethyl-l,3-disilacyclobutane catalysed photo-chemically by Pt(acac)2, the co-existence of both homogeneous and colloidal catalytic species has been proved, giving each of them different type of polymers [10]. 

In contrast to the dihalogens, there are only a few spectral studies of complex formation of halocarbon acceptors in solution. Indeed, the appearance of new absorption bands is observed in the tetrabromomethane solutions with diazabicyclooctene [49,50] and with halide anions [5]. The formation of tetrachloromethane complexes with aromatic donors has been suggested without definitive spectral characterization [51,52]. Moreover, recent spectral measurements of the intermolecular interactions of CBr4 or CHBr3 with alkyl-, amino- and methoxy-substituted benzenes and polycyclic aromatic donors reveal the appearance of new absorption bands only in the case of the strongest donors, viz. Act = 380 nm with tetramethyl-p-phenylendiamine (TMPD) and Act = 300 nm with 9,10-dimethoxy-l,4 5,8-... 

Imines, either acyclic or macrocyclic but invariably multidentate, have a rich coordination chemistry that has been investigated at length. The 7r-accepting ability of imine donors results in the stabilization of lower oxidation states relative to their saturated amine analogs, and there exist many air-stable divalent imine complexes of Co, in contrast to amine relatives. The hexa-methyl-diene (52) has been the most intensively studied ligand of this class, particularly when complexed with Co. In addition, Co complexes of the dimethyl (53),295,296 tetramethyl (54),297 pentamethyl (55)298 and octamethyl (56)299 macrocyclic dienes are also known. In the presence of... 

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