Aristides Christofides

Xylyl isocyanide platinum and palladium complexes

Abstract Bis(cycloocta-1,5-diene)platinum reacts with isopropyl isocyanide to give the trinuclear complex [Pt 3 (CNPr i ) 6 ]. A related palladium compound was prepared by treating either [Pd(dba) 2 ] or [Pd 2 (dba) 2 CHCl 3 ] with 2,6-dimethylphenyl isocyanide. Reactions of the cluster [Pt 3 (CNC 6 H 3 -2,6-Me 2 ) 6 ] and its presumed palladium analogue with the olefins (NC) 2 C:C(CN) 2 , F 2 C:CFCl and (CN) 2 C:C(CF 3 ) 2 , give the compounds [M(olefin)(CNC 6 H 3 -2,6-Me 2 ) 2 ] (M  Pt, Pd) in which the metals are η 2 -bonded to the coordinated olefins. The compound [Pd 3 (CNC 6 H 3 -2,6-Me 2 ) 6 ] reacts with F 2 C:CFBr and with F 2 C:CFCl to give the trans complexes [Pd(X)(C 2 F 3 )(CNC 6 H 3 -2,6-Me 2 ) 2 ] (X  Br, Cl). Similar compounds [M(L)-(CNC 6 H 3 -2,6-Me 2 ) 2 ] (M  Pt, Pd), (L  MeO 2 CHC:CHCO 2 Me, OOCH: CHCOO) have also been prepared, and characterised. Two platinum complexes [Pt(CH:NC 6 H 3 -2,6-Me 2 )(SiMePh 2 )(CNC 6 H 3 -2,6-Me 2 ) 2 ] and [Pt 2 (μ-(PhC) 2 CO)(CNC 6 H 3 -2,6-Me 2 ) 4 ] hav been synthesized by treating the complex [Pt 3 (CNC 6 H 3 -2,6-Me 2 ) 6 ] with HSiMePh 2 and cyclopropenone, respectively. NMR and IR data for the new species are reported and discussed.

Fulvene—platinum complexes: X-ray crystal structure of [Pt(η2-C5H4CPh2)(PPh3)2]

Summary Bis(cycloocta-l,5-diene)platinum reacts with 2,3,4,5-tetraphenylfulvene to afford the complex [Pt( η 2 -CH 2 =C 5 Ph 4 )(cod)] (cod = C 8 H 12 ) in which the metal atom is coordinated to the exo -cyclic double bond of the fulvene. Related compounds [Pt( η 2 -CH 2 =C 5 Ph 4 )L 2 ] (L = PPh 3 , PMePh 2 , PMe 2 Ph, AsPh 3 or CNBu t ) have also been prepared and characterised. Reaction of the complexes [Pt-(C 2 H 4 ) 2 (L)] (L = P(cyclo-C 6 H 11 ) 3 , PPh 3 or AsPh 3 ) with 2,3,4,5-tetraphenylfulvene yields the compounds [Pt(C 2 H 4 )( η 2 -CH 2 =C 5 Ph 4 )(L)]. NMR data for the new species are reported and discussed. 6,6-Diphenylfulvene reacts with [Pt(cod) 2 ] and PPh 3 (1/2 mol ratio) to give the complex [Pt( η 2 -C 5 H 4 CPh 2 )-(PPh 3 ) 2 ] in which the metal atom is bonded to carbon atoms C(2) and C(3) of the fulvene ring. This was established by an X-ray diffraction study. Crystals are monoclinic, space group P2 1 / n , with Z = 4 in a unit cell of dimensions a = 13.761(4), b = 21.653(13), c = 17.395(6) A, β = 104.46(2)°. The structure has been solved and refined to R = 0.064 ( R ′ = 0.064) for 3139 independent diffracted intensities measured at room temperature. The platinum atom is in a trigonal environment formed by the two ligated phosphorus atoms and the C−C bond of the fulvene which is elongated to 1.52(3) A. The C 5 fulvene ring is planar, and makes an angle of 108° with the coordination plane around the platinum. In this plane the metal atom is slightly asymmetrically bonded with Pt−C 2.15(2) and 2.24(2) A, and Pt−P 2.280(6) and 2.301(6) A.

Reduction-oxidation properties of organo-transition metal complexes. Part 33. Ligand-vs. metal-based oxidation of cyano-bridged catecholatoruthenium–manganese carbonyl compounds: the X-ray crystal structure of cis-[(dppe)(Et3P)(OC)2Mn(µ-CN)Ru(CO)2(PPh3)(o-O2C6Cl4)]·CH2Cl2

The reactions of cis- or trans-[Mn(CN)(CO)2{P(OPh)3}(dppm)](dppm = Ph2PCH2PPh2) or cis-[Mn(CN)(CO)2(PEt3)(dppe)](dppe = Ph2PCH2CH2PPh2) with [{Ru(CO)2)(PPh3)(µ-o-O2C6Cl4)}2] give the heterobinuclear complexes cis- and trans-[(dppm){(PhO)3P}(OC)2Mn(µ-CN)Ru(CO)2(PPh3)(o-O2C6Cl4)]5 and 6 and cis-[(dppe)(Et3P)(OC)2Mn(µ-CN)Ru(CO)2(PPh3)(o-O2C6Cl4)]7. The X-ray crystal structure of 7 shows approximately octahedrally co-ordinated ruthenium and manganese centres linked by a µ-CN ligand C-bonded to Mn and N-bonded to Ru, the Ru–N–C–Mn system is slightly non-linear, with angles at C and N of 174.8(5) and 171.4(4)°, despite the formal sp hybridisation at these atoms. Complexes 5–7 undergo two sequential one-electron oxidations at a platinum electrode in CH2Cl2. Treatment with 1 equivalent of [NO][PF6] gives the monocations cis- and trans-[(dppm){(PhO)3P}(OC)2Mn(µ-CN)Ru(CO)2(PPh3)(o-O2C6Cl4)]+5+ and 6+ and cis-[(dppe)(Et3P)(OC)2Mn(µ-CN)Ru(CO)2(PPh3)(o-O2C6Cl4)]+7+ the voltammetry and IR and ESR spectra of which show electron removal from the catecholate ligand. The reaction of [{Ru(CO)2(PPh3)(µ-o-O2C6Cl4)}2] with trans-[Mn(CN)(CO)2{P(OPh)3}(dppm)]+ also gave 6+ but the analogus reaction with trans-[Mn(CN)(CO)2(PEt3)(dppe)]+ gave 7+. In both cases, intramolecular electron transfer from the O,O-chelate to MnII follows cyanide-bridge formation; in the second case this is accompanied by trans–cis isomerisation at the resulting manganese(I) centre. Subsequent oxidation of 5+–7+ occurs at the manganese(II) centre and is accompanied by cis–trans isomerisation. The reaction of the more electron-rich manganese(I) donor trans-[Mn(CN)(CO)(dppm)2] with [{Ru(CO)2(PPh3)(µ-o-O2C6Cl4)}2] gives trans-[(dppm)2(OC)Mn(µ-CN)Ru(CO)2(PPh3)(o-O2C6Cl4)]8 which also undergoes two one-electron oxidations. In this case, however, oxidation at MnI precedes that at the catecholate ligand; the manganese(II)-containing monocation 8+ is synthesised from 8 and [N2C6H4F-p]+ or directly from [{Ru(CO)2(PPh3)(µ-o-O2C6Cl4)}2] and trans-[Mn(CN)(CO)(dppm)2]+. Changes in v(CN)bridge appear to be diagnostic of oxidation at the C- or N-bonded centre of the binuclear complexes.

Reactions of dimethyldivinylsilane, dimethyldivinyltin and allyltrimethyltin with diethylene (tertiary) phosphine)platinum complexes

Abstract The compounds [Pt(C2H4)2(PR3)] [PR3 = P-tBu2Me, P(C6H11)3, PPh3] react dimethyldivinylsilane or dimethyldivinyltin to give chelate complexes [Pt{(CH2CH)2MMe2} (PR3)] (M = Si or Sn). allyltrimethyltin reacts with various diethylene (tertiary phosphine)platinum compounds with cleavage of the allyl group to afford complexes [Pt(SnMe3)(η3-C3H5)(PR2)]. The NMR spectra (13C, 1H and 31P) of the new compounds have been recorded, and the data are discussed in terms of the structures proposed.

Heteropolynuclear complexes containing multiple redox sites: Cyanometal ligand derivatives of the triazenido-bridged dirhodium fragment

Abstract The reactions of [Rh 2 (CO) 4 (μ-RNNNR) 2 ] (R= p -tolyl) with cyanometal ligands such as trans -[Mn(CN)(CO) 2 {P(OEt) 3 } (dppm)l, [Mn(CN)(NO)(PPh 3 )(η-C 5 H 4 Me)], and [Re(CN)(CO) 3 (4,4′-dimethyl-2,2′-bipyridyl)] give heteropolynuclear complexes containing multiple redox sites.

Spin delocalisation and the geometry of redox-active cyanomanganesecarbonyl ligands in heteropolynuclear complexes of rhodium(I)

The reactions of trans-[Mn(CN)(CO)(dppm)2](dppm = Ph2PCH2PPh2) and cis- or trans-[Mn(CN)(CO)2(PR3)(L–L)][R = OEt or OPh, L–L = dppm; R = Et, L–L = dppe (Ph2PCH2CH2PPh2)] with [{Rh(µ-Cl)(CO)2}2] give the heterobinuclear complexes [trans-(dppm)2(OC)Mn(µ-CN)Rh(CO)2Cl] and [(L–L)(R3P)(OC)2Mn(µ-CN)Rh(CO)2Cl] respectively. Cyclic voltammetry shows that each complex undergoes oxidation at the manganese centre; chemical oxidation of [trans-(dppm)2(OC)Mn(µ-CN)Rh(CO)2Cl] gives [trans-(dppm)2(OC)Mn(µ-CN)Rh(CO)2Cl]+ which may also be prepared from trans-[Mn(CN)(CO)(dppm)2]+ and [{Rh(µ-Cl)(CO)2}2]. The crystal structures of the redox pair [trans-(dppm)2(OC)Mn(µ-CN)Rh(CO)2Cl]z(Z= 0 or +1) show that substantial changes in geometry resulting from oxidation are limited to the vicinity of the manganese atoms (e.g. mean Mn–P increases from 2.284 to 2.352 A). These changes are similar to those observed for the free cyanomanganese complexes trans-[Mn(CN)(CO)(dppm)2]z(Z= 0 or +1) and indicate that the singly occupied molecular orbital in the radical cation is largely composed of the Mn dπ orbital in the MnP4 plane. Changes in geometry in the Mn(µ-CN)Rh(CO)2Cl unit are very small. Treatment of [cis-(L–L)(R3P)(OC)2Mn(µ-CN)Rh(CO)2Cl] or [trans-(L–L)(R3P)(OC)2Mn(µ-CN)Rh(CO)2Cl] with TIPF6 in the presence of [Mn(CN)(CO)2(PR3)(L–L)] gives the heterotrinuclear cations [{(L–L)(R3P)(OC)2Mn(µ-CN)}2Rh(CO)2]+; the crystal structure of one, [{trans-(dppm)[(EtO)3P](OC)2Mn(µ-CN)}2Rh(CO)2], shows the two cyanomanganese ligands cis-co-ordinated to the rhodium centre. Cyclic, differential-pulse, and square-wave voltammetry of [{trans-(dppm)(R3P)(OC)2Mn(µ-CN)}2Rh(CO)2]+(R = OEt or OPh) show two closely spaced oxidation waves; the small separation (ca. 80–90 mV) suggests weak interaction between the two cyanomanganese ligands in the mixed-valence dication [{trans-(dppm)(R3P)(OC)2Mn(µ-CN)}2Rh(CO)2]2+(R = OEt or OPh). The results provide evidence for the dependence of spin delocalisation from MnII to RhI on the geometry of the ancillary ligands bound to manganese.

Triazenide-bridged dirhodium complexes containing redox-active cyanomanganese ligands

The complex [Rh2(CO)4(µ-RN3R)2]1 reacted with the cyanomanganese ligands cis-[Mn(CN)(CO)2(L–L)][L–L = Ph2PCH2PPh2(dppm), L = P(OEt)32 or P(OPh)33; L–L = Ph2PCH2CH2PPh2(dppe), L = PEt34] in n-hexane under reflux, or with trans-[Mn(CN)(CO)2L(L–L)][L–L = dppm, L = P(OEt)38 or P(OPh)39] or [Mn(CN)(NO)L(cp′)][L = P(OPh)312 or PPh313, cp′=η-C5H4Me], in CH2Cl2 in the presence of ONMe3, giving [Rh2{(µ-NC)MnLx}(CO)3(µ-RN3R)2]{Lx=cis-(CO)2[P(OEt)3](dppm)5, cis-(CO)2[P(OPh)3](dppm)6, cis-(CO)2(PEt3)(dppe)7, trans-(CO)2[P(OEt)3](dppm)10, trans-(CO)2[P(OPh)3](dppm)11, (NO)[P(OPh)3](cp′)14 or (NO)(PPh3)(cp′)15}. The tricarbonyls underwent one-electron oxidation at a platinum-disc electrode and reacted with [Fe(cp)2][PF6](cp =η-C5H5) in CH2Cl2 to give the corresponding paramagnetic complexes 5+–7+, 10+, 11+, 14+ and 15+ which contain [Rh2]3+ cores. The addition of compounds 2 or 8 to 5+ or 10+, or of 3 or 9 to 6+ or 11+, resulted in further carbonyl substitution to give the dicarbonyl complexes [Rh2{(µ-NC)MnLx}2(CO)2(µ-RN3R)2]+16+–21+ which reacted with [Fe(cp)2][PF6] in the presence of chloride ion to give the diamagnetic [Rh2]4+-containing cations [Rh2Cl{(µ-NC)MnLx}2(CO)2(µ-RN3R)2]+22+–24+. The ESR spectra of the paramagnetic [Rh2]3+-containing cations, and the effects of varying the cyanomanganese ligand on the order in which the redox-active sites (Rh2 and Mn) of the tri- and tetra-metallic complexes are oxidised, are discussed.

Cyanomanganese-(I) and -(II) carbonyls as redox-active donor ligands: the synthesis of novel paramagnetic heterobinuclear complexes

The cyanomanganese complexes trans-[Mn(CN)(CO)(dppm)2]z(z= 0, 1+)(dppm = Ph2PCH2PPh2), cis-[Mn(CN)(CO)2L(L–L)], and trans-[Mn(CN)(CO)2L(L–L)]z(z= 0, 1+) have been used as ligands in the synthesis of redox-active heterobinuclear complexes such as [L(L–L)(CO)2Mn(µ-CN)Ru(CO)2(PPh3)(o-O2C6Cl4)]z(z= 0, 1+) and [(dppm)2(CO)Mn(µ-CN)RhCl(CO)2]z(z= 0, 1+).

Synthesis of platinum complexes of 2-methyl-2,4,6-tris(trifluoromethyl)pyran. X-Ray crystal structure of (cyclo-octa-1,5-diene)[2-methyl-2,4,6-tris(trifluoromethyl)pyran]platinum

Bis(cyclo-octa-1,5-diene)platinum reacts with 2-methyl-2,4,6-tris(trifluoromethyl)pyran to afford the complex [Pt{η2-[graphic omitted](CF3)Me}(cod)]. Fluorine-19, 1H, and 13C n.m.r. spectroscopy showed that the pyran ligand was η2-co-ordinated to platinum. In order to define the structure rigorously an X-ray diffraction study was carried out at 218 K. Crystals are triclinic, space group P, Z= 2, in a unit cell with lattice parameters a= 10.136(12), b= 9.062(11), c= 11.455(9)A, α= 93.22(8), β= 106.23(8), and γ= 109.32(9)°. The structure was refined to R 0.056 (R′ 0.057) for 4 832 independent reflections with 2.9 ⩽ 2θ⩽ 50°(Mo-KαX-radiation). The X-ray structure determination confirmed that the pyran ligand is η2-co-ordinated to the platinum atom. Moreover, the linkage is such that the platinum atom is attached to the CC double bond having the C(Me)(CF3) substituent. The pyran ring is essentially planar with the three CF3 substituents bent away from this plane to the far side from the platinum, while the Me substituent projects from the plane on the near side to the metal atom. Reaction of [Pt{[graphic omitted](CF3)Me}(cod)] with PPh3 affords [Pt{[graphic omitted](CF3)Me}(PPh3)2]. Related complexes [Pt{[graphic omitted](CF3)Me}L2](L = CNBut or CNC6H3Me2-2,6) are obtained by reacting 2-methyl-2,4,6-tris(trifluoromethyl)pyran with the triplatinum compounds [Pt3(CNR)6]. Reaction between the pyran and [Pt(C2H4)2(PPh3)] yields [Pt{[graphic omitted](CF3)Me}(C2H4)(PPh3)]. Fluorine-19 and 13C n.m.r. studies reveal that the η2 mode of attachment of the pyran to the platinum is similar to that established for the cyclo-octa-1,5-diene analogue. In contrast, 2-methyl-2,4,6-tris(trifluoromethyl) pyran reacts with [Rh(acac)(C2H4)2](acac = acetylacetonate, pentane-2,4-dionate) to give [Rh(acac){η4-[graphic omitted](CF3)Me}].