Lewis bases adduct

The diketonates can form Lewis base adducts such as 5-coordinate Pd[P(o-tolyl)3](CF3COCHCOCF3)2 (Figure 3.25), though with acetylacetone square planar adducts of the type M(acac)2(PR3)2 are usually obtained, where the diketone is monodentate O-bonded [63]. 

No homoleptic tetramethyl has been made, though PtMe - and Lewis base adducts PtMe4L2 (L = PMe2Ph, 1/2 bipy etc.) can be made. 

Trialkyls are only known as Lewis base adducts. Reaction of Au2Br6 with methyllithium at 70°C affords an unstable AuMe3 (which is probably AuMe3Br ), but stable phosphine adducts AuMe3PR3 (R, e.g. Me, Ph) can be made [169]. 

A conventional synthesis may be used for the triaryl obtained as a Lewis base adduct... 

These compounds form an interesting contrast to the Lewis base adducts of silyl-metal carbonyls (Section II,C,4), where silicon is thought to be present in a cation. 

When stannylenes are allowed to react with nucleophiles Y the attack of the electron donor proceeds stereospecifically and orthogonal to the SnXX -plane. This can be demonstrated by the Lewis base-adducts of the stannylenes which exclusively exhibit structures of type A or B, depending on the number of nucleophiles present. 

The interaction between catalyst and diazo compound may be initialized by electrophilic attack of the catalyst metal at the diazo carbon, with simultaneous or subsequent loss of N2, whereupon a metal-carbene complex (415) or the product of carbene insertion into a metal/ligand bond (416) or its ionic equivalent (417) are formed. This is outlined in a simplified manner in Scheme 43, which does not speculate on the kinetics of such a sequence, nor on the possible interconversion of 415 and 416/417 or the primarily formed Lewis acid — Lewis base adducts. 

Lewis base adducts of bis (dialky Idithiocarbamato) compounds... 

Table 5 Metallocenes of calcium, strontium, and barium and their Lewis base adducts...

Syntheses and Structures of R3M (R = Alkyl, Aryl, Alkynyl) and Lewis Base Adducts 288... 

Bu3Si(OH2)] [H-CBuMesBBrg] 106, which can be rationalized in two canonical forms, namely a Lewis acid-Lewis base adduct of the silylium ion and water, and, alternatively, a protonated silanol (Scheme 18).264... 

Notably, the reaction of an isomeric mixture of l,l-(Me3Si)2(NH)2 470 and l,2-(Me3Si)2(NH)2 471 with /-Bu2A1C1 (in the absence of alkali metals) affords the fully characterized Lewis acid-Lewis base adducts /-Bu2A1CF NH2NHSiMe3 472 and N2H(SiMe3)3 473, respectively.430... 

Metal Complexes of Stable Carbenes compounds best described as Lewis acid-Lewis base adducts. 

The structures, relative stabilities, and relative Lowry-Bronsted acidities of carboranes and boranes as well as related anions, Lewis base adducts, and heteroelement analogs are rationalized primarily on the basis of rudimentary coordination numbers. The principal factors, in decreasing order of importance, are (a) the various deltahedra and deltahedral fragments, (b) the placement of bridge and endohydrogens, (c) the placement of carbon and other heteroelements, and d) the resulting coordination number of boron. 

In 1971, a note 164) was published favoring the hypothesis that the carboranes, boranes, their isoelectronic anions, Lewis base adducts, and heteroatom-substituted analogs should be viewed as constructed about the vertices of either the most spherical series of triangular-faceted polyhedra (deltahedra) found to be characteristic of the dicarba-cZoao-carboranes (Fig. 1) or, with one lone exception, fragments of the series of deltahedra produced by the successive removal of the highest coordinated vertices that sequentially define the nido and arachno classes. This position was in conflict with the then prevalent shibboleth that all nido and arachno compounds [except B5H9 (I-N5)] had or would prove to have icosahedral fragment structures. 

The IV-A15- or III-Al5-type structures for BsHgiLB would also be ideal precursors for a di-Lewis base adduct since the structure of BbH9(P(CH3)3)2 has one of the Lewis base units on the apex 127) and one on the base. 

Studies are under way to determine the structures of the C2BeHjo (V-N8 or X-N8) Lewis base adducts, i.e., C2BeHio LB. The structural antecedent (V-N8) would favor VI-A18, but V-A18 should be more stable, i.e., satisfying one carbon and one endohydrogen more completely without compromising the 55-bridge hydrogen. 

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