P-31 NMR and X-ray crystallographic study of atropisomerism in cis-tetracarbonylmolybdenum(0) and cis-dichloroplatinum (II) complexes of (+/-)-6,6 '-[[1,1 '-biphenyl]-2,2 '-diylbis(oxy)]bis(dibenzo[d,f]-1,3,2] dioxaphosphepin) and (+/-)-6,6 '-[[1,1 '-binaphthyl]-2,2 '-diylbis(oxy)]bis(dibenzo[d,f][1,3,2]dioxaphosphepin) ligands
M. Hariharasarma et al., P-31 NMR and X-ray crystallographic study of atropisomerism in cis-tetracarbonylmolybdenum(0) and cis-dichloroplatinum (II) complexes of (+/-)-6,6 '-[[1,1 '-biphenyl]-2,2 '-diylbis(oxy)]bis(dibenzo[d,f]-1,3,2] dioxaphosphepin) and (+/-)-6,6 '-[[1,1 '-binaphthyl]-2,2 '-diylbis(oxy)]bis(dibenzo[d,f][1,3,2]dioxaphosphepin) ligands, ORGANOMETAL, 18(14), 1999, pp. 2593-2600
Both cis-tetracarbonylmolybdenum(0) and cis-dichloroplatinum(II) complexes
of {(+/-)-6,6'-[[1,1'-biphenyl]-2,2'-diylbis(oxy)]bis(dibenzo [d,f][1,3,2]d
ioxaphosphepin)}, 1, and {(+/-)-6,6'-[[1,1'-binaphthyl]-2,2'-diylbis(oxy)]b
is(dibenzo[d,f][1,3,2]dioxaphosphepin)} 2, have been prepared. Atropisomeri
sm of the ligands in these complexes has been investigated by variable-temp
erature P-31{H-1} NMR spectroscopy. These studies demonstrate that all thre
e diastereomers are pre sent in solutions of the cis-tetracarbonylmolybdenu
m(0) complexes of both ligands in the slow exchange region, although the di
stribution of the diastereomers is strongly dependent on the nature of the
ligand. The conformations proposed for the major complexes in solution are
consistent with the solid-state conformations of the complexes, as determin
ed by X-ray crystallography. Only two species are present in solutions of t
he cis-dichloroplatinum(II) complexes, and surprisingly, both appear to hav
e the R*R*S*(S*S*R*) configuration. The different conformations of the R*R*
S*(S*S*R*) disatereomers may arise from different interplanar angles of the
biaryl group in the nine-membered chelate ring.