SYNTHESIS AND REACTIONS OF TRIGONAL-BIPYRAMIDAL RHENIUM AND TECHNETIUM COMPLEXES WITH A TRIPODAL, TETRADENTATE NS3 LIGAND

Neutral, trigonal-bipyramidal complexes of technetium and rhenium with the tripodal, tetradentate ligand 2,2',2''-nitrilotris (ethanethiol), N(CH2CH2SH)(3) (H(3)1) have been synthesized and characterized. The t echnetium complex [Tc-99(1)(PPh(3))] (2) can be obtained by reduction of (KTcO4)-Tc-99 with PPh(3) in the presence of H(3)1 or by substituti on reaction starting from [(TcCl3)-Tc-99(PPh(3))(2)(NCMe)]. The trigon al-bipyramidal complex 2, C24H27NPS3Tc, crystallizes in the monoclinic space group P2(1)/c with a = 8.906(2), b = 25.804(6), c = 11.061(4) A ngstrom, beta = 108.42(2)degrees and Z = 4. Rhenium complexes [Re(1)(P R(3))] (3) (PR(3) = PPh(3) (3a), PMe(2)Ph (3b), PMePh(2) (3c), P(n-Bu) (3) (3d), P(OEt)(3) (3e)) have been obtained in analogy to the technet ium derivative 2 by reduction of NH4ReO4 with phosphines PR(3) in the presence of H(3)1. Complex 3a, C24H27NPReS3, crystallizes in the monoc linic space group P2(1)/n with a = 10.855(3), b = 16.707(4), c = 15.44 1(5) Angstrom, beta = 92.62(2)degrees and Z = 4. Rhenium complexes con taining an isocyanide co-ligand [Re(1)(CNR)] (5) (R = CH(2)COOMe (5a), t-Bu (5b), Ph (5c), CH2CH2NC4H8O (5d), CH(2)COOEt (5e)) can be prepar ed by substitution of the phosphine ligand in 3 for an isocyanide or b y reaction of the isocyanide complexes [ReCl3(PPh(3))(2)(CNR)] (4) (R = CH(2)COOMe (4a), t-Bu (4b), Ph (4c), CH2CH2NC4H8O (4d)) with H(3)1. The crystal structure of complex 4b has been determined. 4b crystalliz es with one molecule of CH2Cl2 per formula unit. Crystals of 4b . CH2C l2, C42H41Cl5NP2Re, are monoclinic, space group P2(1)/c with a = 12.86 8(3), b = 20.454(7), c = 16.378(9) Angstrom, beta = 104.71(4)degrees a nd Z = 4. The substitution reaction starting with complexes of type 3 gives the best yields in the preparation of complexes of type 5. Two c omplexes of the type [Re(1)(CNR)] were characterized by X-ray crystall ography. Crystals of 5a, C10H17N2O2ReS3, are monoclinic, space group P 2(1)/c with a = 7.827(4), b = 13.866(3), c = 13.627(6) Angstrom, beta = 93.19(7)degrees and Z = 4. Crystals of 5b, C11H21N2ReS3, are monocli nic, space group P2(1)/c with a = 12.084(2), b = 11.915(2), c = 12.244 (3) Angstrom, beta = 114.31(2)degrees and Z = 4. Treatment of 5e with LiOH leads to ester hydrolysis and yields the complex [Re(1)(CNCH2COOH )] (6) while reaction of 5b-5e in the two-phase system toluene/conc. h ydrochloric acid gives the carbonyl complex [Re(1)(CO)] (7) which was characterized by X-ray crystallography. Crystals of 7, C7H12NOReS3, ar e triclinic, space group <P(1)over bar> with a = 7.924(2), b = 10.467( 3), c = 13.556(2) Angstrom, alpha = 96.61(2), beta = 90.47(2), gamma = 101.68(2)degrees and Z = 4 (2 molecules of 7 per asymmetric unit).