No abstract

The reaction of long chain alkenes with CO and aniline in the presence of palladium complexes of 1,2-bis-(ditertbutylphosphinomethyl)benzene produces amides with high linear selectivity, with much higher rates and catalyst stability when 2-naphthol and sodium or potassium iodide are added. Unsaturated esters including methyl 10-undecenoate from castor oil give α,ω-ester amides, whilst reactions in THF give N-phenylpyrrolidine.

Several SPANphos ligands based on a spirobichroman backbone, introduced as a putative trans ligand, form compounds of the type [Rh(nbd)(SPANphos)]BF(4) () in which both norbornadiene and SPANphos act as cis chelating ligands. The cyclooctadiene rhodium chloride derivatives form bimetallic complexes. Crystal structures for several of these compounds and free ligands are reported. Semiemperical AM1 and DFT calculations show that spirobichroman can assume several conformations, some of which are suitable for the formation of cis chelating SPANphos. All calculations on SPANphos complexes of PdCl(2), PtCl(2) and Rh(CO)Cl show that the trans complex is more stable by 4-10 kcal mol(-1). The cis conformation is enforced by the cis chelating norbornadiene ligand.

A catalyst system based on palladium-1,2-bis-(di-tert-butylphosphinomethyl)benzene (BDTBPMB) shows good activity for the methoxycarbonylation of strongly activated aryl chlorides, like 4-chloromethylbenzoate or 4-chlorocyanobenzene. Surprisingly, the use of less activated aryl chlorides, like 4-chloroacetophenone, leads to the formation of dimethyl terephthalate amongst other products arising from organic reactions of methoxide ion and/or CO. Less nucleophilic alcohols such as 2,2,2-trifluoroethanol promote the formation of carbonylation products even from 4-chloroacetophenone and chlorobenzene. Labelling studies involving CD3OH, CD3OD or 13CO give information on the origin of many of the products.

Catalysts prepared in situ from 1,2-(Bu t 2 PCH 2 ) 2 C 6 H 4 (DTBPMB) and [RhCl(CO) 2 ] 2 catalyse the carbonylation of methanol in the presence of MeI at rates (4.12 and 8.90 × 10 −4 mol dm −3 s −1 at 150 and 180 • C respectively) faster than those in the absence of added phosphine, although they decompose to [RhI 2 (CO) 2 ] − over time. HPIR studies suggest that MeI adds to [Rh(DTBPMB)X(CO)] (X = Cl or I), which have been isolated and fully characterised, to give [Rh(DTBPMB)MeI 2 (CO)]. [Rh(DTBPMB)MeI 2 (CO)] reacts with CO to give [Rh(DTBPMB)(C(O)Me)I 2 (CO)], but that methanol promotes decomposition to [RhI 2 (CO) 2 ] − and [1,2-(MeBu t 2 PCH 2 ) 2 C 6 H 4 )][I 3 ] 2 , which has been isolated and characterised. HPNMR studies show that [Rh(DTBPMB)Cl(CO)] reacts with CO to give [Rh(DTBPMB)Cl(CO) 2 ], which is square pyramidal with an apical Cl.