A NEW METHOD OF CREATING COORDINATIVE UNSATURATION - SYNTHESIS AND REACTIONS OF A REACTIVE IRIDIUM(I) COMPLEX )(PPH(2)CH(2)C(BU(T))=N-N=C(BU(T))CH(2)PPH(2))]PF6 - CRYSTAL-STRUCTURES OF )(PPH(2)CH(2)C(BU(T))=N-N=C(BU(T))CH(2)PPH(2))]PF6 (L=MEO(2)CC-CCO(2)ME OR COCH=CHCONME)

Treatment of [IrCl(CO)(2)(H(2)NC(6)H(4)Me-p)] with the azine diphosphi ne PPh(2)CH(2)(Bu(t))=N-N=C(Bu(t))CH(2)PPh(2) 1 in benzene gave the co -ordinatively saturated (18e) octahedral iridium(III) hydride l)(CO)(P Ph(2)CH=C(Bu(t))-N-N=C(Bu(t))CH(2)PPh(2)}] 3 in which the P,N,P-terden tate diphosphine ligand had lost a hydrogen to give an ene-hydrazone b ackbone. On dissolution in methanol or ethanol, complex 3 immediately dissolved to give the isomeric but co-ordinatively unsaturated (16e) i ridium(I) complex (CO){PPh(2)CH(2)C(BUt)=N-N=C(Bu(t))CH(2)PPh(2)}]Cl 4 a in which the P,N,P-terdentate ligand backbone contained an azine moi ety. Complex 4a was readily converted to the corresponding PF6 salt 4b . On dissolution in dichloromethane or benzene 4a rapidly gave back 3. Treatment of 4b with acetylenes or olefins gave adducts {PPh(2)CH(2)C (Bu(t))=N-N=C(Bu(t))CH(2)PPh(2)}L]PF6 in which L=MeO(2)CC=CCO(2)Me 5a, HC=CCO(2)Me 5b, MeN(O=C)CH=CHCO 8a, trans-MeO(2)CCH=CHCO(2)Me 8b, tra ns-EtO(2)CCH=CHCO(2)Et 8c; C2H4 8d or CH2=C-CH2 8e,8f. Proton NMR stud ies on the ethene adduct showed that the ethene ligand was rotating at ca. 20 degrees C. but at -40 degrees C rotation had stopped. Allene g ives a mixture of two isomeric adducts 8e and 8f. Complex 4b reacted w ith PhC=CH in a different fashion to give the phenylacetylide hydride ){PPh(2)CH(2)C(Bu(t))=N-N=C(Bu(t))CH(2)PPh(2)}]PF6 6 which isomerised on heating to C(Bu(t))=N-N=C(Bu(t))=N-N=C(Bu(t))CH(2)PPh(2)}]PF6 7. Tr eatment of 4b with EtO(2)CN=NCO(2)Et gave an adduct ))-N-N=C(Bu(t))CH( 2)PPh(2)}(EtO(2)CNHNCO(2)Et)]PF6 9 in which the diphosphine backbone h ad been deprotonated and the diethyl azocarboxylate protonated. Treatm ent of 4b with carbon monoxide gave the dicarbonyliridium complex {PPh (2)CH(2)C(Bu(t))=N-N=C(Bu(t))-CH(2)PPh(2)}]PF6 10. Treatment of 4b wit h dihydrogen gave a dihydridoiridium(III) adduct 11 in which the terde ntate P,N,P diphosphine was in the fac arrangement. In solution 11 slo wly isomerised over several hours to give a dihydride in which the ter dentate P,N,P diphosphine was in the mer arrangement, i.e. the structu re of the dihydride was 12. Complex 46 underwent other types of ox dat ive-addition reactions, ie. with formic acid it gave the hydride O{PPh (2)CH(2)C(Bu(t))=N-N=C(Bu(t))CH(2)PPh(2)}]PF6 13, with methyl iodide t he mer-methyliridium(III) adduct 14 and with bromine the mer-iridium(I II) dibromide 15. The crystal structures of 5a and 8a were determined.