Russell M. Thompson

Complexes of functionalised phosphine ligands. Part 1. Complexes of FeIII, CoIII, NiII and ReV with tridentate Schiff bases having PNO, NNO and NNS donor sets. Crystal structures of 2-(Ph2PC6H4NCH)C6H4OH and [Co{2-(Ph2PC6H4CHN)C6H4O}2][PF6]

The Schiff bases 2-[Ph2P(CH2)nNCH]C6H4OH (n= 3, HL1 or 2 HL2), 2-(RCHN)C6H3(OH)X-4 (R = 2-Ph2PC6H4, X = H HL3; R = 2-C5H4N, X = H HL4; R = 2-C5H4N, X = Cl HL5) were synthesised from the appropriate amine and aldehyde. On deprotonation these all functioned as tridentate monoanionic ligands to give complexes [FeL2]+ and [CoL2]+ with FeIII and CoIII and neutral complexes of stoichiometry NiL2 with NiII. The iron complexes were examined by Mossbauer spectroscopy which indicated the presence of two iron sites in [FeL12]+ with a spin-state equilibrium dependent on both temperature and the counter ion. The complex [FeL32]+ showed a single iron site, again with a spin state dependent on counter ion and temperature. The crystal structures of HL3 and [CoL32]+ have been determined. The distortions in free HL3 predispose it for co-ordination in a fac geometry to the Co with cis-PPh2 groups, and the changes occurring on co-ordination are discussed in detail. Reaction of RCHO (R = 2-Ph2PC6H4 or 2-C5H4N) with 2-aminobenzenethiol gave stable thiazoles R[graphic omitted]-2 which did not ring open to give tridentate ligands even on reaction with base and/or metal ions.

Development of new technetium cores containing technetium—nitrogen multiple bonds. Synthesis and characterization of some diazenido-, hydrazido- and imido- complexes of technetium

Abstract The syntheses of several novel diazenido-, hydrazido- and imido- complexes of technetium are described. These precursors which contain technetium—nitrogen multiple bonds are derived directly from the appropriate organohydrazine or amine in good yield. Some of the chemistry has been extended to the metastable isotope 99mTc (γ, t 1 2 = 6 h) in highly dilute aqueous media to give single species in high radiochemical purity. These preparations are applicable to the synthesis of new technetium radiopharmaceuticals and should provide for the development of a whole new range of technetium-based diagnostic agents in nuclear medicine.

The preparation and substitution chemistry of the cationic bis(hydrazido(2−))rhenium(VII) complex [ReCl2(NNMePh)2(PPh3)][BPh4]. The crystal and molecular structures of [Re(NNMePh)2(S2CNMe2)2][BPh4] and [ReOCl(NNMePh)(PPh3)2][PF6]2

Abstract Reaction of [ReOCl3(PPh3)2] with MePhNNH2 in boiling methanol gives the orange five-coordinate bis(hydrazido) cation [ReCl2(NNMePh)2(PPh3)][BPh4] (1). Attempted recrystallization of 1 as its [PF6]− salt led unexpectedly to the brown crystalline oxo-hydrazido dication [ReOCl(NNMePh)(PPh3)2][PF6]2 (2). The structure of 2 was determined as five-coordinate with the oxo- and hydrazido-moieties in the equatorial plane of a trigonal bipyramid, and with the mutually trans-phosphine ligands occupying the axial sites. Complex 1 is a versatile starting material and reacts with the sodium dithiocarbamates (NaS2CNR2, R = Me and Et) to give the red-crystalline bis(hydrazido)-bis-(dithio-carbamato) cations [Re(NNMePh)2(S2CNR2)2][BPh4] [R = Me (3) and R = Et (4)]. The structure of 3 was determined as pseudo-octahedral with linear, mutually cis-NNMePh groups and cis-chelating dithiocarbamato ligands. Reaction of 1 with the sterically hindered thiol 2,6-dichlorobenzene thiol (DCTH) gives the orange cationic bis(hydrazido)-bis(thiolato) complex [Re(NNMePh)2(DCT)2(PPh3)][BPh4] (5). Reaction of the imido precursor [ReCl3(NPh)(PPh3)2] with excess MePhNNH2 gives the yellow imido-hydrazido cation [ReCl2(NPh)(NNMePh)(PPh3)][BPh4] (6). Complexes 1, 2 and 6 contain the formally isoelectronic cores [Re(NNR2)2]3+, [ReO(NNR2)]3+ and [Re(NPh)(NNR2)]3+.

Technetium diazenido complexes. Part 1. Syntheses and structures of [TcCl(NNC6H4Cl-4)2(PPh3)2] and [TcCl(NNPh)(Ph2PCH2CH2PPh2)2][PF6]·H2O

Reaction of [NBu4][TcOCl4] with monosubstituted organohydrazines RNHNH2(R = aryl) in methanol leads to red solutions of technetium diazenido species. These species may be derivatised with the monotertiary phosphine PPh3 to give the khaki to orange bis(diazenido) complexes [TcCl(NNR)2(PPh3)2](R = Ph 1, C6H4Cl-4 2 or C6H4Me-4 3) and the lime-green monodiazenido complex [TcCl2(NNC6H4NO2-4)(PPh3)2]4. These triphenylphosphine derivatives are also easily prepared directly from [NH4][TcO4]. An X-ray crystal structure of one of the bis(diazenido) complexes [TcCl(NNC6H4Cl-4)2(PPh3)2] shows the Tc to be trigonal bipyramidal with axial PPh3 ligands. Derivatisation of the red technetium diazenido containing solutions with the bidentate ditertiary phosphine ligand Ph2PCH2CH2PPh2(dppe) gives the orange cationic complexes [TcCl(NNR)(dppe)2]+(R = Ph 5, C6H4Cl-4 6 or C6H4NO2-4 7) isolated as hexafluorophosphate or tetraphenylborate salts in good yield. These cationic monodiazenido complexes may also be prepared by substitution reactions of complexes 1–4 with dppe, or directly from [NH4][TcO4]. X-Ray structure details for 5: monoclinic, space group C2/c with Z= 4 in a unit cell of dimensions a= 23.808(5), b= 13.830(3), c= 17.452(4)A, β= 92.53(2)°. Complex 5 has slightly distorted trans octahedral geometry with two co-ordinated dppe ligands surrounding both axial phenyldiazenido and chloride ligands. The angle at the α nitrogen Tc–N(1)–N(2) is 163(2)° with Tc–N(1) 1.917(19) and N(1)–N(2) 1.25(4)A. The phenyldiazenido(1–) ligand therefore bonds formally as a singly bent three-electron donor giving complex 5 an overall valence electron count of eighteen. A most important development of this work is that these technetium complexes are directly accessible from ammonium pertechnetate [NH4][TcO4], the chemical form of technetium used in preparation of radiopharmaceuticals.

Mono- and bis-diazenido complexes of rhenium(III) containing bidentate ditertiary phosphine ligands. The crystal and molecular structures of [Re(NNC6H4Me-4)2(Ph2PCH2CH2PPh2)2][PF6]·2dmf, [Re(NNC6H4Cl-4)2(Me2PCH2CH2PMe2)2][PF6] and [ReCl(NNC6H4Me-4)(Me2PCH2CH2PMe2)2][PF6]

Reaction of the ReIII bis-diazenido starting materials [ReCl(NNC6H4X-4)2(PPh3)2](X = Cl 1 or Me 2) with excess dppe (Ph2PCH2CH2PPh2) in methanol–toluene under reflux gave the novel orange-brown, formally 20-electron ReIII bis-diazenido cations [Re(NNC6H4X-4)2(dppe)2]+(X = Cl or Me) in good yield by addition of a suitable anion to the cooled reaction mixture. Reaction of 1 and 2 with the more reducing dmpe (Me2PCH2CH2PMe2) ligand gave the formally 20-electron bis-diazenido cation [Re(NNC6H4X-4)2(dmpe)2]+ for X = Cl but the 18-electron mono-diazenido cation [ReCl(NNC6H4X-4)(dmpe)2]+ for X = Me. The structures of complexes [Re(NNC6H4Me-4)2(dppe)2][PF6]·2dmf (dmf = dimethylformamide)5, [Re(NNC6H4Cl-4)2(dmpe)2][PF6]6 and [ReCl(NNC6H4Me-4)(dmpe)2][PF6]7 have been determined: 5, triclinic, space group P, a= 13.046(3), b= 13.250(3), c= 12.233(4)A, α= 110.74(2), β= 95.86(2), γ= 115.83(2)°, Z= 1, R= 0.040; 6 monoclinic, space group P21/c, a= 8.992(2), b= 21.947(2), c= 18.982(2)A, β= 91.45(1)°, Z= 4, R= 0.056; 7 orthorhombic, space group Pnma, a= 19.298(2), b= 11.327(2), c= 13.960(2)A, α=β=γ= 90°, Z= 4, R= 0.042. All three complexes have pseudo-octahedral co-ordination with four P donors in a planar equatorial array. The M–N–N angle of the diazenide ligands is found to be dependent on the steric requirements of the diphosphine ligands, the smaller dmpe ligand permitting the M–N–N angles in 6 to decrease to 147.3(5) and 149.0(4)° compared to values of around 162.7(2)° for the dppe complex 5. Reaction of [NH4][ReO4] with the arylhydrazine hydrochloride 4-MeC6H4NHNH2·HCl in CH2Cl2 in the presence of SiMe3Cl and pyridine (py) gave the new hydrazide [ReCl3{NN(SiMe3)C6H4Me-4}2(py)]. Subsequent reaction with PPh3 in MeOH gave the ReIII diazenide [Re(OMe)(NNC6H4Me-4)2(PPh3)2], and overall this provides a route for the synthesis of Re diazenides directly from perrhenate.

Synthesis and characterization of some novel pentagonal bipyramidal 2,6-diacetylpyridine bis(benzoylhydrazone) (DAPBH2) complexes of Rhenium(III) and molybdenum crystal and molecular structure of [ReCl(DAPB)(PPh3)]. An investigation of the Mössbauer spectroscopy of [FeIICl2(DAPBH2)]·H2O and [FeIIICl(DAP-Me-B)(H2O)] ☆

Abstract Reaction of [ReCl3(MeCN)(PPh3)2] with the planar pentadentate diacetylpyridinebis(benzoylhydrazone) ligands DAPBH2 and DAP-Me-BH2 and triethylamine in isopropanol under reflux gave the dark brown seven-coordinate complexes [ReCl(L)PPh3], containing the doubly deprotonated pentadentate ligand [L = DAPB(2−)(1); L = DAP-Me-B(2−) (2)]. Complex 1 has been characterized by crystallography. The central rhenium atom in 1 is seven-coordinate, with pentagonal bipyramidal geometry with the axial positions being occupied by the chloride ion and the triphenylphosphine ligand. The DAPB coordinates in a pentadentate manner in the equatorial plane of the complex and the five donor atoms of the doubly deprotonated DAPB(2−) ligand form an approximately planar pentagon. The rhenium atom is slightly displaced out of the ligand plane towards the phosphorus atom. Reaction of 2 with Ag[BF4] in CH2Cl2 at room temperature gave a black complex of stoichiometry [Re(DAP-Me-B)(PPh3)][BF4] (3). Reaction of [MoCl4(MeCN)2] with DAP-Me-BH2 and Et3N in dry CH2Cl2 under reflux gave deep green [MoCl2(DAP-MeB2)] (4), formulated as a seven-coordinate molybdenum(II) complex containing the doubly deprotonated pentadenate DAP-MeBH2 ligand in the equatorial plane of the complex. The Mossbauer spectra of the complexes [FeCl2(DAPBH2)]·H2O (5) and [FeCl(DAPMe-B)(H2O)] (6) were investigated as a function of temperature. The spectrum of 5 was consistent with high-spin seven-coordinate iron(II) and 6 was shown to contain two distinct iron(III) sites; possible structures are discussed.

A d4-thiolato–dinitrogen complex. The synthesis and crystal structure of [Re(N2)(SC6H2-2,4,6-Pri3)3(PPh3)]

[ReH7(PPh3)2] or [ReH5(PPh3)3] reacted with L [L = 2,4,6-triisopropylthiophenol (Htipt) or HSC6h2-2,6-Pri2,4-Br (Hdipbt)] in toluene, under dinitrogen, to give [Re(N2)(tipt)3(PPh3)] and [Re(N2)(dipbt)3(PPh3)], respectively in good yield, and under similar conditions 2,6-dimethyithiophenol (Hdmt) or 2,6-dimethoxythiophenol (Hdmot) gave [Re(dmt)3(PPh3)] and [Re(dmot)3(PPh3)] respectively; the complex [Re(dmt)3(PPh3)(PPh2H)] was also isolated from the same reaction with Hdmt.

The synthesis and reactivity of a new technetium(III) precursor. The crystal structures of [TcCl3(MeCN){P(C6H4Me-3)3}2] and [Tc(bipy)3]2+ (bipy=2,2'-bipyridine)

The reduction of [TcCl4(PPh3)2] with zinc metal in acetonitrile in the presence of triphenylphosphine gives the orange crystalline technetium(III) complex [TcCl3(MeCN)(PPh3)2]1 in good yield. Suitable crystals of 1 were grown, but the crystal structure could not be determined satisfactorily due to pseudo-symmetry in the crystal lattice. To overcome this problem the crystal and molecular structure of the tri-m-tolylphosphine analogue [TcCl3(MeCN){P(C6H4Me-3)3}2]1a was determined. Crystals of 1a are triclinic, space group P with Z= 2 in a unit cell of dimensions a= 10.157(2), b= 10.302(2), c= 22.073(2)A, α= 87.27(2), β= 86.66(1) and γ= 66.87(1)°. The structure was refined based on 5636 reflections converging to R= 0.039. Complex 1a exhibits a distorted pseudo-octahedral geometry with two trans P(C6H4Me-3)3 groups, three meridionally disposed chloride groups, and a linear terminally N-bound acetonitrile ligand. The reaction of 1 with the aromatic imines 2,2′-bipyridine (bipy), 1,10-phenanthroline (phen), and 2,2′:6′2″-terpyridine (terpy) gives the blue-black technetium(II) dicationic complexes [Tc(bipy)3]2+, [Tc(phen)3]2+ and [Tc(terpy)2]2+ isolated as their [BPh4]– or [PF6]– salts. The crystal and molecular structure of one of these novel technetium(II) complexes, [Tc(bipy)3][PF6]22a, has been determined. Crystals of 2a are trigonal, space group Pc1 (no. 165) with Z= 2 in a unit cell of dimensions a= 10.847(2) and c= 16.299(3)A. The structure was refined based on 414 unique reflections converging to R= 0.0525. The monomeric complex 2a exhibits exact D3 symmetry with the Tc–N bonds [2.077(10)A] equivalent by symmetry. The electrochemical behaviour of complexes 1, 2 and 3 has been investigated.

Hydrazide, diazenide and nitride complexes as olefin metathesis or ROMP procatalysts

Abstract The complexes [MCl 4 (NNR 2 )] (M=Mo, W; R 2 = MePh, Ph 2 ), [MoCl(NNR 2 ) 2 (PPh 3 ) 2 ] + , [ReCl(NNAr) 2 (PPh 3 ) 2 ] (Ar=4-substituted phenyl), [ReCl 3 (NNR 2 ) 2 py] (R 2 =Ph 2 , PhMe) and [ReNCl 2 (PMe 2 Ph) 3 ] form efficient catalysts for metathesis and ring-opening metathesis polymerisation on activation with alkylating agents such as EtAlCl 2 . These show activities comparable with other reported systems and stereochemical selectivity for the ROMP reaction of norbomene. Possible reaction mechanisms are discussed.

Technetium diazenido-complexes. Part 2. Substitution chemistry of [TcCl(NNC6H4Cl-4)2(PPh3)2] and the synthesis of technetium diazenido-complexes directly from [NH4][TcO4]

The bis(diazenido)technetium(III) complex [TcCl(NNR)2(PPh3)2](R = C6H4Cl-4) reacted with bidentate ligands L with loss of one diazenide ligand to give [Tc(NNR)L2(PPh3)](L = S2CNR2) and [TcCl(NNR)L(PPh3)2](HL = maltol) in high yield. With dianionic tetradentate ligands L′ complexes of the type cis-[Tc(NNR)L′(PPh3)][L′= dianion of N,N′-bis(salicylidene)ethane-1,2-diamine (salen), S(CH2)2NMe(CH2)2NMe(CH2)2S or O2S(CH2)2NMe(CH2)2NMe(CH2)2SO2] were obtained. The crystal structure of the complex with L′= salen has been determined. It shows pseudo-octahedral co-ordination about the Tc with the NNR and PPh3 ligands cis. Direct reaction of [TcO4]– with arylhydrazine hydrochlorides generated a diazenide species in situ which reacts with S2CNR2 to give [TcCl(NNR)2(S2CNR2)2] and 2,2′-bipyridine (bipy) to give [TcCl(NNR)(bipy)2]+ isolated as a BPh4– salt.