By the refluxing of an acetonitrile solution of [Pd(OAc)2]3 and primary amines 4-XC6H4CH2NH2 (F, Cl, NO2, OMe), 3,5-X2C6H3CH2NH2 (X = OMe), or PhCH2CH2NH2 (Pd:amine = 1:1) and subsequent addition of excess NaBr, the corresponding orthometalated complexes [Pd{C6H3(CH2NH2)-2,X-5}(μ-Br)]2, [Pd{C6H3(CH2NH2)-2,(OMe)2-4,6}(μ-Br)]2, or [Pd{C6H3(CH2NH2)-2}(μ-Br)]2 are obtained. Alternatively, the hydrochloride of 4-XC6H4CH2NH2 (X = F, NO2) can also be used to prepare the corresponding [Pd{C6H3(CH2NH2)-2,X-5}(μ-Cl)]2 complexes. These results show that primary benzylamines can be orthometalated even if the substituents are electron-withdrawing groups and that 2-(phenyl)ethylamine can be orthometalated in spite of the six-membered ring that it forms. These reactions occur via intermediate complexes [Pd(OAc)2L2], which react with [Pd(OAc)2]3 to give the dimeric species [Pd(OAc)(μ-OAc)L]2 (L = amine), from which in turn the orthometalated complexes are formed. Each of these steps has been studied, and both types of intermediates have been isolated for all the amines. PPh3 reacts with the orthometalated complexes to give the corresponding products of the bridge splitting. The crystal structures of [Pd(OAc)(μ-OAc)L]2 (L = 4-O2NC6H4CH2NH2) and [Pd{C6H4(CH2CH2NH2)-2}Br(PPh3)] have been determined by X-ray diffraction.

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By refluxing a mixture of (S)-a-methyl-4-nitrobenzylamine and Pd(O,CMe), (1 : 1 ) in acetone, complexes (S,S)-[{Pd[C,H3(CH(Me)NH,}-2-NO,-5](p-X)},] (X = MeCO, l a or CI 1 b) are obtained. Complex 1 b can also be obtained by treating ( S ) -a-methyl-4-nitrobenzylamine hydrochloride with Pd(O,CMe), (1 : 1) in acetone. These complexes are the first orthometallated complexes containing a primary amine with an electron-withdrawing group in the benzene ring. Complex l a reacted with an excess of NaBr or Nal to give (S,S)-[{Pd[C,H3{CH(Me)NH,}-2-N0,-5](p-X)},] (X = Br l c or I I d ) . Triphenylphosphine reacted with 1 b or l c to give (S)-[Pd{C,H,[CH(Me)NH2]-2-NO,-5}X(PPh,)] (X = CI 2a or Br 2b). The reaction of complex 1 b with AgCIO, (1 :1) and an excess of pyridine (py) gave (S)-[Pd{C,H,[CH(Me)NH,]-2-NO2-5}(py),]CIO, 3. Complex l c reacted with 3 equivalents of

The crystal structures and variable-temperature NMR spectra of (CO)4FeP(o-tolyl)3, (CO)4FeAs(o-tolyl)3, (CO)4FeP-(o-tolyl)2CH2Ph, and (CO)4Fe(o-tolyl)2PP(o-tolyl)2 (la-d) are reported. In the solid state, complexes la-c contain the phosphine in an axial position of the trigonal bipyramid; complex Id is equatorially substituted in the solid state but exists as an axial/equatorial mixture in solution. All complexes exhibit P-C restricted rotation, which in the case of la may be linked to axial/equatorial CO exchange.

Variable temperature N M R studies have established equilibrium constants and/or activation parameters for the exoz -exo3 equilibrium in the series M(o-tolyl), ( M = P, As), X M (o-tolyl), ( M = P, X = 0, S, Se; M = As, X = 0, S) and [MeM(o-tolyl),]"+ ( n = 0, M = Si; n = 1, M = P, As). The crystal structure of OAs(o-tolyl),H,O is reported. Molecular mechanics studies of P(o-tolyl), reproduce correctly the ground state ~X O , conformation and provide an analysis of the lowest energy two-ring flip exchange mechanism.t If a regular pyramid is constructed from the lp, 0, S, Se or Me as the apex and the three puru ring carbons as the base, a proximal (exo) substituent will point away from the base, while a distal (endo) substituent will point towards the base.