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A synthetic and mechanistic study is reported on ligand substitution and other reactions of six-coordinate ruthenium(II) carbonyl complexes containing tridentate PhP(CH 2 CH 2 CH 2 PCy 2 ) 2 (Cyttp). Carbonylation of cis-mer -Ru(OSO 2 CF 3 ) 2 (CO)(Cyttp) ( 1 ) affords [ cis-mer -Ru(OSO 2 CF 3 )(CO) 2 (Cyttp)]O 3 SCF 3 ( 2 (O 3 SCF 3 )) and, on longer reaction times, [ cis-mer -Ru(solvent)(CO) 2 (Cyttp)](O 3 SCF 3 ) 2 (solvent = acetone, THF, methanol). 2 (O 3 SCF 3 ) reacts with each of NaF, LiCl, LiBr, NaI, and LiHBEt 3 to yield [ cis-mer -RuX(CO) 2 (Cyttp)] + (X = F ( 3 ), Cl ( 4 ), Br ( 5 ), I ( 6 ), H ( 7 )), isolated as 3 – 7 (BPh 4 ). These conversions proceed with high stereospecificity to afford only a single isomer of the product that is assigned a structure in which the Ph group of Cyttp points toward the CO trans to X ( anti when X = F, Cl, Br, or I; syn when X = H). Treatment of 2 (O 3 SCF 3 ) with NaOMe and CO generates the methoxycarbonyl complex [ cis-mer -Ru(CO 2 Me)(CO) 2 (Cyttp)] + ( 8 ), whereas addition of excess n -BuLi to 2 (O 3 SCF 3 ) in THF under CO affords mer -Ru(CO) 2 (Cyttp) ( 9 ). The two 13 C isotopomers [ cis-mer -Ru(OSO 2 CF 3 )(CO)( 13 CO)(Cyttp)]O 3 SCF 3 ( 2 ′(O 3 SCF 3 ): 13 CO trans to P C ; 2 ″(O 3 SCF 3 ): 13 CO cis to all P donors) were synthesized by appropriate adaptations of known transformations and used in mechanistic studies of reactions with each of LiHBEt 3 , NaOMe/CO, and n -BuLi. Whereas LiHBEt 3 reacts with 2 ′(O 3 SCF 3 ) and 2 ″(O 3 SCF 3 ) to replace triflate by hydride without any scrambling of the carbonyl ligands, the corresponding reactions of NaOMe–CO are more complex. The methoxide combines with the CO cis to triflate in 2 , and the resultant methoxycarbonyl ligand ends up positioned trans to the incoming CO in 8 . A mechanism is proposed for this transformation. Finally, treatment of either 2 ′(O 3 SCF 3 ) or 2 ″(O 3 SCF 3 ) with an excess of n -BuLi leads to the formation of the same two ruthenium(0) isomers of mer- Ru(CO)( 13 CO)(Cyttp). These products represent, to our knowledge, the first example of a syn–anti pair of isomers of a five-coordinate metal complex. |
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