CAPPING CALIXARENES WITH METALLODIPHOSPHINE FRAGMENTS - TOWARDS INTRACAVITY REACTIONS

The co-ordinative properties of four disubstituted 5,11,17,23-tetra-te rt-butyl-25,27-di-RCH2O-26,28- bis(diphenylphosphinomethoxy)calix[4] a renes [R = C(O)NEt2L1, C(O)OEt L-2, (R)-C(O)NHCH(Me)Ph L-3 or CH2OMe L -4] have been investigated. Compound L-1 reacted with [Au(thf)(SC4H8)] BF4 (thf = tetrahydrofuran, SC4H8 = tetrahydrothiophene) and AgBF4 to yield the chelate complexes [AuL1]BF4 1 and [AgL1]BF4 2, respectively. Reaction of L-1 with trans-[PtH(Cl)(PPh3)(2)] resulted in quantitativ e formation of trans-[PtH(Cl)L1] 3 in which the platinum hydrogen bond is partially encapsulated within the calixarene cavity. The structura lly related cationic complexes [PtH(PPh3)L-1]BF4 (L-i = L-1 4, L-3 5 o r L-4 6), having a PPh3 ligand trans to the hydride ligand, were obtai ned in high yield by treating trans-[PtH(thf)(PPh3)(2)]BF4 with diphos phine L-i. Abstraction of the chloride ion from 3 with AgBF4 gave [PtH (L-1)IBF4 7, a. complex in which the calixarene behaves as a tridentat e P2Oamide ligand and in which the metal plane caps one end of the cal ixarene tunnel. Reaction of 7 with PPh3 resulted in substitution of th e co-ordinated amide to form 4, while reaction with 4,4'-bipyridine ga ve the binuclear complex [(L-1)HPt(4,4'-bipy)PtH(L-1)I[BF4](2) 8. Reac tion of trans-[PtH(Cl)(PPh3)(2)] with L-i resulted in a mixture of com plexes of general formula [PtH(PPh3)L-1]Cl (type A) and [PtH(Cl)L-1] ( type B). The A:B ratio depends on the co-ordinating ability of the R g roups, since these act as internal solvent molecules in promoting PPh3 substitution. For R groups containing strong donors, e.g. as in L-1 a nd L-2, complexes of type B are favoured; with L-4 the reaction leads selectively to [PtH(PPh3)L-4]Cl, no B-type complex being formed. In at least one case (L-3) it was shown that complexes of type A may be con verted into the B type. Reaction of 7 with dimethyl acetylenedicarboxy late gave the insertion product trans-P,P'-[Pt(MeO2CC=CHCO2Me)L-1]BF4 where the two amides compete for coordination. Complex 7 reacted insta ntaneously with tetracyanoethylene (tcne) to yield the platinum(o) com plex [Pt(tcne)L1] for which NMR spectra suggest fast flipping of the c oordination plane between amides. In contrast to [Pt(MeO2CC=CHCO2Me)L- 1]BF4, strong tridentate P2O co-ordination abounds in the rhodium carb onyl complexes [Rh(CO)L-1]BF, (L-i = L-1 or L-3) Obtained from [Rh(CO) (2)(thf)(2)]BF4 and the corresponding diphosphines.