Platinum(IV) complexes containing monodentate sulfonamide ligands, fac-(dppbz)PtMe(3)(NHSO(2)R) (dppbz = o-bis(diphenylphosphino)benzene; R = p-C(6)H(4)(CH2)(3)CH(3) (1a), p-C(6)H(4)CH(3) (1b), CH(3) (1c)), have been synthesized and characterized, and their thermal reactivity has been explored. Compounds 1a-c undergo competitive C-N and C-C reductive elimination upon thermolysis to form N-methylsulfonamides and ethane, respectively. Selectivity for either C-N or C-C bond formation can be achieved by altering the reaction conditions. Good yields of the C-N-coupled products were observed when the thermolyses of 1a-c were conducted in benzene-d(6). In contrast, exclusive C-C reductive elimination occurred upon themolysis of 1a,b in nitrobenzene-d(5). When the thermolyses of 1a were performed in the presence of sulfonamide anion NHSO2R- in benzene-d(6), ethane elimination was completely inhibited and C-N reductive elimination products were formed in high yield. Mechanistic studies support a two-step reaction pathway involving initial dissociation of NHSO(2)R(-) from the platinum center, followed by nucleophilic attack of this anion on a methyl group of the resulting five-coordinate platinum(IV) cation to form MeNHSO(2)R and (dppbz)PtMe(2). C-C reductive elimination to form ethane occurs directly from the five-coordinate Pt(IV) cation.
The new homoleptic rare earth compound [Y(C(SiHMe(2))(3))(3)] () is prepared in 82% yield by salt metathesis of YCl(3) and 3 equivalents of [KC(SiHMe(2))(3)] (); two beta-agostic Y(H-Si) interactions are observed for each C(SiHMe(2))(3) ligand in , giving six agostic interactions per yttrium(iii) center.
Optically active C 3 -symmetric monoanionic ligands are uncommon in organometallic chemistry. Here we describe the synthesis of readily prepared tris(4S-isopropyl-2-oxazolinyl)phenylborate [To P ] and fluxional, zwitterionic four-and five-coordinate iridium(I) compounds [Ir(To P )-(η 4 -C 8 H 12 )] ( 4) and [Ir(To P )(CO) 2 ] (5). The highly fluxional nature of 4 and 5 makes structural assignment difficult, and the interaction between the iridium(I) center and the [To P ] ligand is established by solid-state and solution 15 N NMR methods that permit the direct comparison between solution and solid-state structures. Although iridium cyclooctadiene 4 is a mixture of four-and five-coordinate species, the dicarbonyl 5 is only the five-coordinate isomer. The addition of electrophiles MeOTf and MeI provides the oxazoline N-methylated product rather than the iridium methyl oxidative addition product. N-Methylation was unequivocally proven by through-bond coupling observed in 1 H-15 N HMBC experiments.
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