STRUCTURAL FLEXIBILITY OF [M3(u3-L)(u-dppm)3]n+ TWIN-BOWL CLUSTERS. Kenneth W. Muir, Ljubica Manojlovic-Muir & Mark W. Hughes. Chemistry Department, Glasgow University, Glasgow G12 8QQ, U.K.
The coordinatively unsaturated cluster complexes [M3(u3-L)(u-dppm)3]n+ (n = 0-2: M = Pd, Pt; dppm = Ph2PCH2PPh2; L = CO, Hg, AuPh3, ReO3, SnX3 etc.) have proved useful as models for the chemistry of Pd and Pt surfaces and as homogeneous catalysts for some commercially important reactions (Puddephatt, Manojlovic-Muir & Muir, 1990).
A feature common to these complexes is the M3(u-dppm)3 building block in which both faces of the latitudinal M3P6 skeleton are encircled by an array of phenyl rings to form two bowl-shaped cavities sharing a common base. One of these cavities accommodates a u3-L ligand, while the other remains available for covalent binding of another ligand or for docking a small molecule or ion. Our previous crystallographic studies of the compounds obtained by addition reactions of [M3(u3-L)(u-dppm)3]n+ clusters have revealed a remarkable structural diversity, including the first examples of guest-host complexes in cluster chemistry (Manojlovic-Muir, Muir, Lloyd & Puddephatt, 1985). One of the main factors contributing to this diversity is the structural flexibility of the M3(u-dppm)3 core.
As part of our study of the molecular structures, bonding and guest-host recognition in these complexes and of their molecular organization in the solid state, we are investigating (i) conformational changes of the dppm ligands and (ii) their effect on the size and shape of the cavities of the M3(u-dppm)3 fragment in a series of twin-bowl [M3(u3-L)(u-dppm)3]n+ clusters.
Manojlovic-Muir, Lj, Muir, K.W., Lloyd, & Puddephatt, R.J. (1985). J. Chem. Soc., Chem. Commun., 536 - 537 and refs therein.
Puddephatt, R.J., Manojlovic-Muir, Lj., & Muir, K.W. (1990). Polyhedron, 9, 2767 - 2802.