Influence of sterically demanding groups on the structure and stability in the solid and solution state of (acylpyrazolonate)bis(phosphine)copper(I) derivatives

Abstract

New neutral derivatives [Cu(L)(PR 3) 2] (LH=1-phenyl-3-methyl-4-R 1(CO)-pyrazol-5-one, in detail L 1H, R 1=C 6H 5; L 2H, R 1=CH 3; L 3H, R 1=CF 3; L 4H, R 1=C 6H 11; L 5H, R 1=C 6H 5CH 2; L 6H, R 1=(C 6H 5) 2CH; R=C 6H 5, p-CH 3C 6H 4, C 6H 5CH 2 or C 6H 11) and [Cu(L) 2] (L=L 4, L 5 and L 6) have been synthesised and characterised by analytical and spectroscopic techniques. The X-ray crystal and molecular structures of [Cu(L 1)(PCy 3) 2], [Cu(L 5)(PPh 3) 2] and [Cu(L 6)(PPh 3) 2] have been resolved, in which the copper atom is found in a strongly distorted tetrahedral CuO 2P 2 environment. The interbond angles PCuP, PCuO and OCuO are strongly influenced by the steric properties of PR 3 and also to a lesser degree by the 4-acyl moiety of the L donor. [Cu(L)(PR 3) 2] derivatives undergo partial dissociation in chloroform solution through breaking of CuP and, when R=Cy, also of CuO bonds. [Cu(L 4)(PPh 3) 2] reacts with 1-methylimidazolin-2-thione (Hmimt), with 1,10-phenanthroline (Phen), with 2,9-dimethyl-1,10-phenanthroline (Cupr) and with bis(diphenylphosphino)propane (DPPP), yielding the mixed-ligand compounds [Cu(PPh 3)(Hmimt) 3](L 4), [Cu(L 4)(PPh 3)(Phen)], [Cu(Cupr) 2](L 4) and [Cu(DPPP) 2](L 4), respectively.