Tridentate chelate π-bonded complexes of rhodium(I), iridium(I), and iridium(III) and chelate σ-bonded complexes of nickel(II), palladium(II), and platinum(II) formed by intramolecular hydrogen abstraction reactions

2,2′-Bis(o-diphenylphosphino)bibenzyl, o-Ph₂PC₆H₄CH₂CH₂C₆H₄PPh₂-o (bdpbz), is dehydrogenated by various rhodium complexes to give the planar rhodium(I) complex

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, from which the ligand, 2,2′-bis(o-diphenylphosphino)-trans-stilbene (bdpps) can be displaced by treatment with sodium cyanide. The stilbene forms stable chelate olefin complexes with planar rhodium(I) and iridium(I) and with octahedral iridium(III). On reaction with halide complexes of nickel(II), palladium(II) or platinum(II), the stilbene ligands

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(R = Ph or o-CH₃C₆H₄) lose a vinyl proton in the form of hydrogen chloride to give chelate, planar σ-vinyls of general formula =CHC₆H₄PR₂-o) (M = Ni, Pd, Pt; X = Cl, Br, I) of high thermal stability; analogous methyl derivatives =CHC₆H₄PR₂-o) are obtained from Pt(CH₃)₂(COD) (COD = 1,5-cyclooctadiene) and the stilbene ligands. The bibenzyl also forms chelate σ-benzyls HCH₂C₆H₄PPh₂-o) (M = Pd, Pt; X = Cl, Br, I). The ¹H NMR spectra of the o-tolyl methyl groups in the compounds =CHC₆H₄PR₂-o) (M = Ni, Pd, Pt; R = o-CH₃C₆H₄) vary with temperature, probably as a consequence of interconversion of enantiomers arising from restricted rotation about the M---P and M---C bonds. Possible mechanisms for the dehydrogenation reactions are briefly discussed.     

Study of homogenous hydrogenation of acetylene compounds withpara-hydrogen and Pd(0) and Pt(0) complexes byin situ NMR spectroscopy

η² -C₆₀Pd(PPh₃)₂, η² -C₆₀Pt(PPh₃)₂ and C₂H₄Pt(PPh₃)₂ have been used as catalysts for homogeneous hydrogenation of acetylene compounds enriched in para-hydrogen (p-H₂). The study of the processes has been carried out byin situ NMR spectroscopy. It has been concluded that the nature of the substrate affects the intensity and patterns of polarization signals.     

The Synthesis by Decarboxylation Reactions and Crystal Structures of 1, n–Bis(diphenylphosphino)alkane(pentafluorophenyl)‐platinum(II) Complexes

Decarboxylation reactions between the complexes cis–[PtCl₂L] (L = 1, n–bis(diphenylphosphino)–ethane (n = 2, dppe), –propane (n = 3, dppp) or –butane (n = 4, dppb)) and thallium(I) pentafluorobenzoate in pyridine give cis–[PtCl(C₆F₅)L] and cis–[Pt(C₆F₅)₂L] complexes in high yields with short reaction times. X–ray crystal structures of cis–[PtCl(C₆F₅)(dppe)] · 0.5 C₅H₅N, cis–[PtCl(C₆F₅)(dppp)], cis–[PtCl(C₆F₅)(dppb)] · C₃H₆O, cis–[Pt(C₆F₅)₂L] (L = dppe, dppp and dppb) and the reactants cis–[PtCl₂(dppp)] (as a CH₂Cl₂ solvate) and cis–[PtCl₂(dppb)] show monomeric structures with chelating diphosphine ligands in all cases rather than dimers with bridging diphosphines. ³¹P NMR data are consistent with these structures in solution.     

The Synthesis of Mono- and Bi-Metallic Platinum(II) and/or (IV) Complexes Containing the Ligand Bis(diphenylphosphino) Methylamine

Complexes of the type [Pt R₂ (dppma-PP′)] (R─Me, Et, Ph, CH₂Ph, C₆H₄ Me-p, C₆H₄OMe-2, CH₂CMe₃, 1-naphthyl, C₆H₄Me-o, dppma = Ph₂PNMe PPh₂) have been prepared from [PtCl₂, (dppma-PP′)] and the corresponding alkyl-lithium or Grignard reagents. Equilibrium constants, k, for the conversion of [PtR₂ (dppma-PP′)] into cis-[PtR₂(dppma-P)₂] with dppma were studied using ³¹P NMR spectroscopy at room temperature. Equilibrium is rapidly established for R─C₆H₄-Me-o, at 20°C. Complex of the type cis-[PtR₂ (dppma-P)₂] was isolated R─C₆H₄ Me-o. The complexes [PtMe₂(dppma-P)₂] and [Pt(o-methoxyphenyl)₂(dppma-P)₂] were prepared, but unfortunately decomposed once isolated, the only evidence for its formation being from ³¹P-{¹H} NMZR spectroscopy. The o-tolyl or 1-naphthyl complexes exist as syn-anti mixtures in solution, due to restricted rotation around the platinum aryl bonds. Treatment of several complexes of the type [PtR₂(dppma-PP′)] with MeI gives [PtR₂Me(I)(dppma-PP′)] with trans addition of MeI. Treatment of [PtR₂(dppma-PP′)] with HCl gives [Pt Cl (R) (dppma-PP′)] for R─C₆H₂Me₃-2,4,6, C₆H₄-CH₃-2, C₆H₄-Me-4, Me, 1-naphthyl. The ¹H, ³¹P NMR parameters for these complexes are discussed. Attempted preparation of complexes of the type [PtR₂ (dppma-P)₂M] (R─C₆H₄-Me-2, Me CN-C₆H₄-Me-4); M─Pd, Pt, Au,) are reported.     

Platinum(II) complexes containing the 3,3-dimethylglutarimidate ligand

Reaction of cis-[PtCl₂(PPh₃)₂] with excess 3,3-dimethylglutarimide (dmgH) and sodium chloride in refluxing methanol gives the mono-imidate complex cis-[PtCl(dmg)(PPh₃)₂], which was structurally characterized. The plane of the imidate ligand is approximately perpendicular to the platinum coordination plane which, coupled with restricted rotation about the Pt–N bond, results in inequivalent methyl groups and CH₂ protons of the dmg ligand in the room temperature ¹H NMR spectrum. These observations were corroborated by a theoretical study using density functional theory methods. The analogous bromide complex cis-[PtBr(dmg)(PPh₃)₂] can be prepared by replacing NaCl with NaBr in the reaction mixture.     

Platinum(II) Mixed Ligand Complexes with Thiourea Derivatives,Dimethyl Sulphoxide and Chloride: Syntheses,Molecular Structures,and ESCA Data

The platinum(II) mixed ligand complexes [PtCl(L^1‐6)(dmso)] with six differently substituted thiourea derivatives HL, R₂NC(S)NHC(O)R′ (R = Et, R′ = p‐O₂N‐Ph: HL¹; R = Ph, R′ = p‐O₂N‐Ph: HL²; R = R′ = Ph: HL³; R = Et, R′ = o‐Cl‐Ph: HL⁴; R₂N = EtOC(O)N(CH₂CH₂)₂N, R′ = Ph: HL⁵) and Et₂NC(S)N=CNH‐1‐Naph (HL⁶), as well as the bis(benzoylthioureato‐κO, κS)‐platinum(II) complexes [Pt(L^{1, 2})₂] have been synthesized and characterized by elemental analysis, IR, FAB(+)‐MS, ¹H‐NMR, ¹³C‐NMR, as well as X‐ray structure analysis ([PtCl(L¹)(dmso)] and [PtCl(L^{3, 4})(dmso)]) and ESCA ([PtCl(L^{1, 2})(dmso)] and [Pt(L^{1, 2})₂]). The mixed ligand complexes [PtCl(L)(dmso)] have a nearly square‐planar coordination at the platinum atoms. After deprotonation, the thiourea derivatives coordinate bidentately via O and S, DMSO bonds monodentately to the Pt^II atom via S atom in a cis arrangement with respect to the thiocarbonyl sulphur atom. The Pt—S‐bonds to the DMSO are significant shorter than those to the thiocarbonyl‐S atom. In comparison with the unsubstituted case, electron withdrawing substituents at the phenyl group of the benzoyl moiety of the thioureate (p‐NO₂, o‐Cl) cause a significant elongation of the Pt—S(dmso)‐bond trans arranged to the benzoyl‐O—Pt‐bond. The ESCA data confirm the found coordination and bonding conditions. The Pt 4f_7/2 electron binding energies of the complexes [PtCl(L^{1, 2})(dmso)] are higher than those of the bis(benzoylthioureato)‐complexes [Pt(L^{1, 2})₂]. This may indicate a withdrawal of electron density from platinum(II) caused by the DMSO ligands.     

New platinum complexes with carbodiphosphorane as pincer ligand via ortho phenyl metallation

The platinum complex [Pt(η³-C₈H₁₁)(C₆H₄PPh₂CPPh₃)] (2) is a halve side o-phenyl insertion product resulting from the reaction of C(PPh₃)₂ and [I₂Pt(cod)] and is unstable in halogenated hydrocarbons. In a slow reaction 2 abstracts HCl from CH₂Cl₂, CHCl₃ or CDCl₃ (DCl) and converts the η³-C₈H₁₁ ligand into cod which is replaced by Cl⁻. Simultaneously, a second insertion of the Pt atom into an o-phenyl CH bond occurs under movement of the o-phenyl proton to the ylidic carbon atom resulting in the C,C,C-pincer complex [ClPt{CH(PC₆H₄Ph₂)₂}] (3). Surprisingly, crystals of the unusual carbonyl complex [(CO)Pt{C(PC₆H₄Ph₂)₂}] (5) were obtained upon attempts to replace Cl⁻ in 3 by PPh₃ in CHCl₃ solution. Instead, an intermediate was identified by ³¹P NMR spectroscopy in which the coordinated CH group is replaced by PPh₃; however, no crystals could be obtained. From the resulting oily material after some month crystals of 5 separated. We suggest, that hydrolysis of an intermediate CCl₂ ligand (from CHCl₃) to CO via a leaking stopcock has taken place. The compounds are characterized by X-ray analyses, ³¹P NMR, and IR spectroscopy.     

Hydridocyanoalkyl complexes of platinum(II). Insertion of olefins into the PtH bond

The preparation and spectroscopic properties are described of some platinum(II) complexes having a hydride ligand cis or trans to an sp³ carbon, viz. trans-PtH(YCN)(PPh₃)₂ and cis-PtH(YCN)(LL) with YCN = C₂H₄CN, n-C₃H₆CN, o-CH₂C₆H₄CN and LL = bis(diphenylphosphino)-ethene or -ethane. The complexes trans-PtH(YCN)(PPh₃)₂ can add a fifth ligand in solution; the resulting five-coordinate complex was observed by ³¹P NMR in the case of PtH(C₃H₆CN)(PPh₃)₃. Insertion of olefin (ethen, 1-cyanoethene, norbornadiene, allen) into the PtH bond of the trans-hydrido complexes occurs to give cis-dialkyl complexes, but the cis-hydrido complexes are unreactive. The mechanism of insertion is discussed in terms of the kinetics and the geometries of reactants and products.     

Coordination modes of 2-hydroxynicotinic acid in second- and third-row transition metal complexes

The new Pd(II), Pt(II), Re(V), Mo(VI) and W(VI) complexes of 2-hydroxynicotinic acid (H₂nicO), trans-[PdCl(HnicO)(PPh₃)₂]·0.75CH₃CN (1), K[PdCl(HnicO)₂]·H₂O (2), [Pd(HnicO)₂(bipy)] (3), cis-[PtCl(HnicO)(PPh₃)₂]·0.75CH₃OH·0.5H₂O (4), [PtCl(HnicO)(bipy)] (5), cis-[ReOI₂(HnicO)(PPh₃)] (6), Na₂[Mo₂O₆(HnicO)₂]·5H₂O (7), Na₂[Mo₄O₁₂(HnicO)₂]·2H₂O (8) and Na₂[W₂O₆(HnicO)₂]·5H₂O (9) have been prepared. The crystal structures of 1 and 4, were determined by X-ray diffraction and show the HnicO⁻ ligand coordinated to palladium or platinum through the nitrogen atom only. Infrared, Raman, ¹H and ¹³C{¹H} NMR spectroscopic data for the complexes are presented and are in agreement with the crystallographic results.     

A novel reaction producing the rhodium(I) complexes with π-coordinated tetraphenylborate anion, (π-PhBPh3). X-ray study of [Rh(PPh3)2(π-PhBPh3)]

Treating the complexes [Rh(TFA)(PPh₃)₂], [Rh(HFA)(PPh₃)₂], and [Rh(TFA)(Cod)] (TFA - trifluoroacetylacetonate, HFA - hexafluoroacetylacetonate, Cod - 1,5 cyclooctadiene) with an excess of NaBPh₄ in acetonitrile yields the rhodium(I) complexes with coordinated [BPh₄]⁻ anion, [Rh(PPh₃)₂(π-PhBPh₃)] · 2MeCN (I) and [Rh(Cod)(π-PhBPh₃)] (II). The reactions present a new example of β-diketonate ligand replacement. The ¹H, ³¹P, and ¹¹B NMR spectra of I and II are discussed. [Rh(PPh₃)₂(π-PhBPh₃)] has been characterized by single crystal X-ray analysis.     

Phosphine σ-sydnonyl complexes of Ni,Pd, and Pt

3-R"-4-Bromosydnones 1 (R" = Me) and 2 (R" = Ph) react with complexes Ì(PR₃)_n (M = Ni, Pd, Pt) to form mononuclear phosphine -sydnonyl d⁸-complexes of trans-configuration MBr(3-R"-sydnon-4-yl)(PR₃)₂: 3, 4 (Ì = Ni, R" = Ph); 5 (M = Pd, R" = Me); 6a (M = Pd, R" = Ph); 7 (M = Pt, R" = Ph). In the reaction of bromosydnone 2 with Pd(PPh₃)₄, the cis-complex PdBr(3-Ph-sydnon-4-yl)(PPh₃)₂ (6b) is formed initially; 6b rearranges in solution to give trans-complex 6a. On heating in THF, complex 6a is converted into the binuclear [PdBr(3-phenylsydnon-4-yl)(PPh₃)]₂ complex (8). The reaction of 4-chloromercurio-3-phenylsydnone (10) with Ni(PEt₃)₄, Pd(PPh₃)₄, and Pt(PPh₃)₄ gives mononuclear NiCl(3-phenylsydnon-4-yl)(PEt₃)₂ complex (11), binuclear [PdCl(3-phenylsydnon-4-yl) (PPh₃)]₂ complex (14), and cis- and trans-bimetallic PtCl(3-phenylsydnon-4-ylmercurio)(PPh₃)₂ complexes 15a and 15b, respectively. UV irradiation of 15a and 15b in a benzene solution induces redox demercuration to yield the PtCl(3-phenylsydnon-4-ylcarbonyl)(PPh₃)₂ complex (16). In carbonylation of complexes 3, 6, and 7, CO insertion into the M--C bond occurred to form the corresponding acyl derivatives MBr(3-phenylsydnon-4-ylcarbonyl)(PR₃)₂ (17--19).     

Coordination behaviour of the multidentate Schiff base 2,6-bis(2-hydroxyphenyliminomethyl)pyridine towards the fac-[Re(CO)3] and [ReO] cores

The seven-coordinate rhenium(III) complex cation [Re^III(dhp)(PPh₃)₂]⁺ was isolated as the iodide salt from the reaction of cis-[Re^vO₂I(PPh₃)₂] with 2,6-bis(2-hydroxyphenyliminomethyl)pyridine (H₂dhp) in ethanol. In the complex fac-[Re(CO)₃(H₂dhp)Br], prepared from [Re(CO)₅Br] and H₂dhp in toluene, the H₂dhp ligand acts as a neutral bidentate N,N-donor chelate. The complexes were characterized by elemental analysis, infrared and ¹H NMR spectroscopy and X-ray crystallography.     

A novel cis-push–pull effect in cycloruthenated azobenzene thiocarbonyl-containing complexes: crystal and molecular structures of [RuX(CS)(η-C,N-C6H4N=NPh)(PPh3)2](X=Cl, I)

Treatment of [RuHCl(CS)(PPh₃)₃] with Hg(o-C₆H₄N=NC₆H₅)₂ affords [RuCl(CS)(η²C,N-o-C₆H₄N=NC₆H₅)(PPh₃)₂] (1) in good yield, where the cyclometallated azobenzene ligand coordinates through an ortho-C and one azo-N to give a five-membered chelate ring. Reaction of 1 with AgNO₃ followed by NaBr or NaI affords the chloride-exchanged products [RuX(CO)(η²C,N-o-C₆H₄N=NC₆H₅)(PPh₃)₂] (2, 3), whereas reaction of 1 with AgOC(O)Me or NaS₂CNEt₂·2H₂O gives the halide mono-phosphine-substituted complexes [Ru(CS)(LL)(η²C,N-o-C₆H₄NNC₆H₅)(PPh₃)] (4, 5). In the solid-state structures of 1 and 3 there are significant changes in the bond lengths for the cyclometallated azobenzene ligand are observed relative to free azobenzene. These are discussed, with the aid of spectroscopic and crystallographic data, in terms of a cis-push–pull effect.     

Heterobimetallische phosphanido-verbrückte Zweikern-Komplexe - Synthese von cis-rac-[(η-C5H4R)2Zr{μ-PH(2,4,6−iPr3C6H2)}2M(CO)4] (RMe,MCr,Mo; RH,MMo)

Heterobimetallic Phosphanido-bridged Dinuclear Complexes - Syntheses of cis-rac-[(η-C₅H₄R)₂Zr{μ-PH(2,4,6-ⁱPr₃C₆H₂)}₂M(CO)₄] (R?Me, M?Cr, Mo; R?H, M?Mo) The zirconocene bisphosphanido complexes [(η-C₅H₄R)₂Zr{PH(2,4,6-ⁱPr₃C₆H₂)}₂] (R?Me, H) react with [(NBD)M(CO)₄] (NBD?norbornadiene, M?Cr, Mo) to give only one diastereomer of the phosphanido-bridged heterobimetallic dinuclear complexes cis-rac-[(η-C₅H₄R)₂Zr{μ-PH(2,4,6-ⁱPr₃C₆H₂)}₂M(CO)₄] [R?Me, M?Cr ( 1 ), Mo ( 2 ); R?H, M?Mo ( 3 )]. However, no reaction was observed between [(η-C₅H₅)₂Zr{PH(2,4,6-^tBu₃ C₆H₂)}₂] and [Pt(PPh₃)₄]. 1—3 were characterised spectroscopically. For 1—3 , the presence of the racemic isomer was shown by NMR spectroscopy. No reaction was observed at room temperature for 3 and CS₂, (NO)BF₄, Me₃NO or PH(2,4,6-Me₃C₆H₂)₂. With Et₂AlH or PhC?CH decomposition of 3 was observed.     

On the reactivity of platina‐β‐diketones: a straightforward synthesis of trans‐acetylchlorobis(phosphine)platinum(II) complexes and their reactivity

The platina‐β‐diketone [Pt₂{(COMe)₂H}₂(µ‐Cl)₂] ( 1 ) was found to react with monodentate phosphines to yield acetyl(chloro)platinum(II) complexes trans‐[Pt(COMe)Cl(PR₃)₂] (PR₃ = PPh₃, 2a ; P(4‐FC₆H₄)₃, 2b ; PMePh₂, 2c ; PMe₂Ph, 2d ; P(n‐Bu)₃, 2e ; P(o‐tol)₃, 2f ; P(m‐tol)₃, 2g ; P(p‐tol)₃, 2h ). In the reaction with P(o‐tol)₃ the methyl(carbonyl)platinum(II) complex [Pt(Me)Cl(CO){P(o‐tol)₃}] ( 3a ) was found to be an intermediate. On the other hand, treating 1 with P(C₆F₅)₃ led to the formation of [Pt(Me)Cl(CO){P(C₆F₅)₃}] ( 3b ), even in excess of the phosphine. Phosphine ligands with a lower donor capability in complexes 2 and the arsine ligand in trans‐[Pt(COMe)Cl(AsPh₃)₂] ( 2i ) proved to be subject to substitution by stronger donating phosphine ligands, thus forming complexes trans‐[Pt(COMe)Cl(L)L′] (L/L′ = AsPh₃/PPh₃, 4a ; PPh₃/P(n‐Bu)₃, 4b ) and cis‐[Pt(COMe)Cl(dppe)] ( 4c ). Furthermore, in boiling benzene, complexes 2a – 2c and 2i underwent decarbonylation yielding quantitatively methyl(chloro)platinum(II) complexes trans‐[Pt(Me)Cl(L)₂] (L = PPh₃, 5a ; P(4‐FC₆H₄)₃, 5b ; PMePh₂, 5c ; AsPh₃, 5d ). The identities of all complexes were confirmed by ¹H, ¹³C and ³¹P NMR spectroscopy. Single‐crystal X‐ray diffraction analyses of 2a ·2CHCl₃, 2f and 5b showed that the platinum atom is square‐planar coordinated by two phosphine ligands (PPh₃, 2a ; P(o‐tol)₃, 2f ; P(4F‐C₆H₄)₃, 5b ) in mutual trans position as well as by an acetyl ligand ( 2a, 2f ) and a methyl ligand ( 5b ), respectively, trans to a chloro ligand. Single‐crystal X‐ray diffraction analysis of 3b exhibited a square‐planar platinum complex with the two π‐acceptor ligands CO and P(C₆F₅)₃ in mutual cis position (configuration index: SP‐4‐3). Copyright © 2005 John Wiley & Sons, Ltd.     

The reaction of diaryl derivatives of bis(triphenylphosphine)platinum(II) with [60]fullerene as a route to the platinum complex η2-C60Pt(PPh3)2

The reaction ofcis-Ar₂Pt(PPh₃)₂ (Ar=p-MeC₆H₄ (1a) and Ar=Ph (1b)) with [60]fullerene in toluene afforded the metal-fullerene complex η²-C₆₀Pt(PPh₃)₂ (2), which was isolated in the crystalline state. The reductive elimination between C₆₀ and1a or1b also resulted in the formation of biaryls (p-MeC₆H₄)₂ and Ph−Ph. The composition and structure of the compounds were established by¹H and³¹P NMR spectroscopy, electronic absorption spectroscopy, and elemental analysis. The homolytic phosphorylation of2 was additionally studied by the ESR method.     

PLATINUM(II) COMPLEXES OF P(III) CYCLOPHOSPHAMIDE DERIVATIVES

Abstract

The syntheses of the P(III) analogues of cyclophosphamide, isophosphamide and triphosphamide are reported. These compounds (4–6, respectively) polymerize easily at room temperature but are sufficiently stable in solution to react with Cl₂Pt(NCPh)₂, forming cis-Cl₂Pt(4)₂, cis-Cl₂Pt(5)₂ and cis-Cl₂Pt(6)₂ (complexes 9–11, respectively). Complex 10 can also be made by condensing cis-Cl₂Pt[ClPN(CH₂CH₂Cl)CH₂CH₂CHO]₂ with ClCH₂CH₂NH₂, while an alternate route to 9 and 11 is afforded by the condensation of cis-Cl₂Pt[Cl₂PN(CH₂CH₂Cl)₂]₂ with H₂NCH₂CH₂CH₂OH and ClCH₂CH₂NHCH₂CH₂CH₂OH, respectively. Complexes 9–11 exist in two diastereomeric configurations and these can be separated in the cases of 9 and 11 by column chromatography. ³¹P NMR spectral data for the complexes are discussed and the results of NCl antitumor screening are presented.     

Rhodium complexes of 1,3-diaryltriazenes: Usual coordination, N-H bond activation and, N-N and C-N bond cleavage

Reaction of 1,3-diaryltriazenes (R-C₆H₄-NN-(NH)-C₆H₄-R, R = OCH₃, CH₃, H, Cl, NO₂ at the para position) with [Rh(PPh₃)₃Cl] in ethanol in the presence of a base (NEt₃) affords a family of yellow complexes (1-R) containing a PPh₃, two de-protonated triazenes coordinated as bidentate N,N-donors, and an aryl (C₆H₄-R) fragment coordinated in the η¹-fashion. A similar reaction in toluene yields a group of reddish-orange complexes (2-R) containing a PPh₃, two N,N-coordinated triazenes, and a chloride. Structures of the 1-CH₃ and 2-CH₃ complexes have been determined by X-ray crystallography. All the 1-R and 2-R complexes are diamagnetic, and show characteristic ¹H NMR signals and intense MLCT transitions in the visible region. The 1-R and 2-R complexes also fluoresce in the visible region under ambient condition while excited at around 400 nm. Cyclic voltammetry on these complexes shows a Rh(III)-Rh(IV) oxidation (within 0.76-1.68 vs. SCE), followed by an oxidation of the coordinated triazene ligand (except the R = NO₂ complexes). An irreversible reduction of the coordinated triazene is also observed for all the complexes below −0.96 V vs. SCE. In the 1-R and 2-R complexes potential of the Rh(III)-Rh(IV) oxidation correlates linearly with the electron-withdrawing nature of the para-substituent (R).     

Reactivity of a functionalized trisamido ligand with Zr(NMe2)4 and GaMe3

NMR study of the reactivity of multifunctional ligand cis,cis-C₆H₉(NHCH₂C₆H₄-o-PPh₂)₃ (1) with GaMe₃ and Zr(NMe₂)₄ was carried out, yielding [cis,cis-(κ^N-NHCH₂C₆H₄-o-PPh₂)(κ^N-NCH₂C₆H₄-o-PPh₂)₂C₆H₉]GaMe (2) and [cis,cis-(NCH₂C₆H₄-o-PPh₂)₃C₆H₉]Ga₂Me₃ (3), and [cis,cis-(NCH₂C₆H₄-o-PPh₂)₃C₆H₉]Zr(NMe₂) (4), respectively. The spectral properties of 2 and 3 are very similar to that observed for the equivalent aluminum species already reported, but form at a much slower rate which allows for the observation of a GaMe₃⋅1 adduct. Species 4 undergoes coordination/displacement of one of the phosphine arms, which was observed using both NMR spectroscopy and DFT analyses.     

Oxidative addition of boron–boron, boron–chlorine and boron–bromine bonds to platinum(0)

The synthesis and spectroscopic characterisation of the new diborane(4) compounds B₂(1,2-O₂C₆Cl₄)₂ and B₂(1,2-O₂C₆Br₄)₂ are reported together with the diborane(4) bis-amine adduct [B₂(calix)(NHMe₂)₂] (calix=Bu^tcalix[4]arene). B–B bond oxidative addition reactions between the platinum(0) compound [Pt(PPh₃)₂(η-C₂H₄)] and the diborane(4) compounds B₂(1,2-S₂C₆H₄)₂, B₂(1,2-O₂C₆Cl₄)₂ and B₂(1,2-O₂C₆Br₄)₂ are also described which result in the platinum(II) bis-boryl complexes cis-[Pt(PPh₃)₂{B(1,2-S₂C₆H₄)}₂], cis-[Pt(PPh₃)₂{B(1,2-O₂C₆Cl₄)}₂] and cis-[Pt(PPh₃)₂{B(1,2-O₂C₆Br₄)}₂] respectively, the former two having been characterised by X-ray crystallography. In addition, the platinum complex [Pt(PPh₃)₂(η-C₂H₄)] reacts with XB(1,2-O₂C₆H₄) (X=Cl, Br) affording the mono-boryl complexes trans-[PtX(PPh₃)₂{B(1,2-O₂C₆H₄)}] as a result of oxidative addition of the B–X bonds to the Pt(0) centre; the chloro derivative has been characterised by X-ray crystallography.