Dibromobis complex

Nickel salts form coordination compounds with many ligands. Dibromobis(tri- -butylphosphine)nickel(Il) [15242-92-9], [( -C4H2)3P]2NiBr2, dicyanoammineaquanickel(11), Ni(NH3)(H20)(CN)2, and bromonitrosobis(triphenylphosphine)nickel(Il) [14586-72-2], are complexes used for syntheses in preparative organonickel chemistry. 

Di- x-bromobis[diethylenethioureatellurium(II)] dibromide, 35 294-295 Dibromobis(phosphine)nickel(Il) complex, bond length changes in spin state transition, 32 6... 

Alkylation of dibromobis(triethylphosphine)nickel(II) has been conducted stepwise using arylmagnesium bromide and methyllithium, leading to unsymmetrical /ra/7.y-aryl(methyl)nickel complex 5 [24], which further reacts with l,2-bis(dimethyl-phosphino)ethane (dmpe) to give ra-aryl(methyl)nickel complex 6 (eq (15)) [25]. 

Werner prepared cis- and tazns-dibromobis(l, 2-ethanediamine)cobalt(III) bromide by reacting the carbonato bromide with concentrated hydrobromic acid.2 In the cold, the cis isomer resulted the trans isomer was obtained by heating the mixture. The reaction proceeds via ds-aquabromobis(l, 2-ethanedi-amine)cobalt(III) dibromide which can be isolated by this route. In our hands, the preparations, as originally described, are not reproducible. The reaction times and yields are variable, depending too critically on the conditions for one not intuitively skilled in the art to consistently obtain the desired cis or trans form. However, the syntheses described here for the cis and trans dibromo complexes and based on this reaction are reproducible if one adheres closely to the procedures. 

Transition-metal induced [1,2]-rearrangement is also available to obtain phosphaalkyne 39. Dichlorophosphaethene 2a was allowed to react with an equivalent amount of tetrakis(triphenylphosphine)palladium(0) to afford phosphaalkyne 39 through intermediates (Scheme 21) [37]. The rearrangement process takes place in the reaction of dibromophosphaethene 2b with a small amount (0.2 equiv.) of dibromobis(triphenylphosphine)nickel(II) in the presence of zinc and tetraethylammonium iodide through the generation of a nick-el(0) intermediate [38]. Complex 43 was isolated in the reaction of 2a and tetrakis(triethylphosphine)platinum(0) which could afford phosphaalkyne 39 [27,28,39]. 

F are2 Perspective drawing of the complex dibromobis acetylacetone)-manganese ny... 

Other preparative methods have been reported. cis-Dibromobis(l,2-ethane-diamine )cobalt(III) bromide is obtained in reasonable yield by evaporating a neutral aqueous solution of the trans isomer to dryness. The reaction between ds-diazidobis(l,2-ethanediamine)cobalt(III) perchlorate and hydrobromic acid proceeds rapidly and quantitatively at ambient temperature, largely with retention of the cis configuration to yield the dibromo bromide. The diazido starting complex can be made within 1 hour in greater than 90% yield. 

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