Synthesis and reactions of trigonal-bipyramidal rhenium and technetium complexes with a tripodal, tetradentate NS3 ligand

Abstract

Abstract Neutral, trigonal-bipyramidal complexes of technetium and rhenium with the tripodal, tetradentate ligand 2,2′,2″-nitrilotris(ethanethiol), N(CH2CH2SH)3 (H31) have been synthesized and characterized. The technetium complex [99Tc(1) (PPh3)] (2) can be obtained by reduction of K99TcO4 with PPh3 in the presence of H31 or by substitution reaction starting from [99TcCl3(PPh3)2(NCMe)]. The trigonal-bipyramidal complex 2, C24H27NPS3Tc, crystallizes in the monoclinic space group P21/c with a=8.906(2), b=25.804(6), c=11.061(4) A , β=108.42(2)° and Z=4 . Rhenium complexes [Re(1) (PR3)] (3) (PR3 = PPh3 (3a, PMe2Ph (3b), PMePH2 (3c), P(n-Bu)3 (3d), P(OEt)3 3e)) have been obtained in analogy to the technetium derivative 2 by reduction of NH4ReO4 with phosphines PR3 in the presence of H31. Complex 3a, C24H27NPReS3, crystallizes in the monoclinic space group P21/n with a=10.855(3), b=16.707(4), c=15.441(5) A , β=92.62(2)° and Z=4. Rhenium complexes containing an isocyanideco-ligand [Re(1) (CNR)] (5) (R=CH2COOMe (5a), t-Bu (5b), Ph (5c), CH2CH2NC4H8O (5d), CH2COOEt (5e)) aan be prepared by substitution of the phosphine ligand in 3 for an isocyanide or by reaction of the isocyanide complexes [ReCl3(PPh3)2(CNR)] (4) (R=CH2COOMe (4a), t-Bu (4b), Ph (4c), CH2CH2NC4H8O (4d)) with H31. The crystal structure of complex 4b has been determined. 4b crystallizes with one molecule of CH2Cl2 per formula unit. Crystals of 4b·CH2Cl2, C42H41Cl5NP2Re, are monoclinic, space group P21/c with a=12.868(3), b=20.454(7), c=16.378(9) A , β=104.71(4)° and Z=4. The substitution reaction starting with complexes of type 3 gives the best yields in the preparation of complexes of type 5. Two complexes of the type [Re(1) (CNR)] were characterized by X-ray crystallography. Crystals of 5a, C10H17N2O2ReS3, are monoclinic, space group P21/c with a=7.827(4), b=13.866(3), c=13.627(6) A , β=93.19(7)° and Z=4. Crystals of 5b, C11H21N2ReS3, are monoclinic, space group P21/c with a=12.084(2), b=11.915(2), c=12.244(3) A , β=114.31(2)° and Z=4. Treatment of 5e with LiOH leads to ester hydrolysis and yields the complex [Re(1) (CNCH2COOH)] (6) while reaction of 5d–5e in the two-phase system toluene/conc. hydrochloric acid gives the carbonyl complex [Re(1) (CO)] (7) which was characterized by X-ray crystallography. Crystals of 7, C7H12NOReS3, are triclinic, space group P 1 with a=7.924(2), b=10.467(3), c=13.556(2) A , α=96.61(2), β=90.47(2), γ=101.68(2)° and Z=4 (2 molecules of 7 per asymmetric unit).