OConnell, D;Patterson, JC;Spalding, TR;Ferguson, G;Gallagher, JF;Li, YW;Kennedy, JD;Macias, R;ThorntonPett, M;Holub, J

1996

August

J. Chem. Soc., Dalton Trans.

Conformational polymorphism and fluxional behaviour of M(PR(3))(2) units in closo-twelve-atom metallaheteroboranes with MX(2)B(9) (X=C or As) and MZB(10) cages (Z=S, Se or Te)

Validated

WOS: 21 ()

NUCLEAR MAGNETIC-RESONANCE EXO-NIDO-PHOSPHINERHODACARBORANES MOLECULAR-STRUCTURES CRYSTAL-STRUCTURES CHEMISTRY METALLACARBORANES PALLADIUM COMPLEXES CATALYSIS REARRANGEMENTS

3323

3333

The compounds [3,3-(PEt(3))(2)-closo-3,1,2-PtAs2B9H9] 1 and [2,2-(PMe(2)Ph)(2)-closo-2,1-PtSB10H10] 2 were synthesised and characterised by NMR spectroscopy and X-ray crystallography. Crystals of 1 exhibit conformational polymorphism with five conformers of the Pt(PEt(3))(2) unit above the As2B3 face; those of 2 contain single conformers. The free energy of the barrier to rotation of the Pt(PMe(2)Ph)(2) unit above the SB10 cage ligand in 2 has been determined in chloroform solution and is compared with data from other platinum and palladium metallaheteroboranes containing C2B9H11, As2B9H9, SeB10H10 and TeB10H10 ligands. A mechanism for the rotation of M(PR(3))(2) units above heteroborane ligand faces is suggested. It involves shifting the M(PR(3))(2) unit via eta(n)-bonded species (n < 5) with a concomitant twisting of the M(PR(3))(2) unit about an axis passing approximately through the metal atom and the antipodal B atom.

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