Consuelo Fortuño

Synthesis, molecular structure (M = Pd, X = OH) and reactivity of trinuclear asymmetric complexes [(C6F5)2Pt(µ-PPh2)2M(µ-X)2Pt(PPh3)2](M = Pd or Pt; X = Cl or OH)

The tetranuclear complexes [NBu4]2[(C6F5)2Pt(µ-PPh2)2M(µ-CI)2M(µ-PPh2)2Pt(C6F5)2](M = Pd or Pt) reacted with AgCIO4 and cis-[PtCl2(PPh3)2] in dichloromethane–acetone affording the neutral homo- or hetero-metallic asymmetric species [(C6F5)2Pt(µ-PPh2)2M(µ-CI)2Pt(PPh3)2]1 and 2. Treatment of their CH2CI2 solutions with KOH in methanol rendered the corresponding µ-hydroxo derivatives 3 and 4 which reacted with HX′(X′= Cl, Br, SPh, NHC6H4Me-p or PPh2) to afford [(C6F5)2Pt(µ-PPh2)2M(µ-X)(µ-X′)Pt(PPh3)2](X = X′= Cl 1, 2; Br 5, 6; SPh 7, 8; X = OH, X′= NHC6H4Me-p9, 10; X = OH, X′= PPh211, 12). The structure of 3 has been determined by single-crystal X-ray diffraction.

Unsymmetrical platinum(II) phosphido derivatives: oxidation and reductive coupling processes involving platinum(III) complexes as intermediates.

Reaction of the trinuclear [NBu 4] 2[(R F) 2Pt(mu-PPh 2) 2Pt(mu-PPh 2) 2Pt(R F) 2] ( 1, R F = C 6F 5) with HCl results in the formation of the unusual anionic hexanuclear derivative [NBu 4] 2[{(R F) 2Pt(mu-PPh 2) 2Pt(mu-PPh 2) 2Pt(mu-Cl)} 2] ( 4, 96 e (-) skeleton) through the cleavage of two Pt-C 6F 5 bonds. The reaction of 4 with Tl(acac) yields the trinuclear [NBu 4][(R F) 2Pt(mu-PPh 2) 2Pt(mu-PPh 2) 2Pt(acac)] ( 5, 48 e (-) skeleton), which is oxidized by Ag (+) to form the trinuclear compound [(R F) 2Pt(mu-PPh 2) 2Pt(mu-PPh 2) 2Pt(acac)][ClO 4] ( 6, 46 e (-) skeleton) in mixed oxidation state Pt(III)-Pt(III)-Pt(II), which displays a Pt-Pt bond. The reduction of 6 by [NBu 4][BH 4] gives back 5. The treatment of 6 with Br (-) (1:1 molar ratio) at room temperature gives a mixture of the isomers [(PPh 2R F)(R F)Pt(mu-PPh 2)(mu-Br)Pt(mu-PPh 2) 2Pt(acac)], having Br trans to R F ( 7a) or Br cis to R F ( 7b), which are the result of PPh 2/C 6F 5 reductive coupling. The treatment of 5 with I 2 (1:1 molar ratio) yields the hexanuclear [{(PPh 2R F)(R F)Pt(mu-PPh 2)(mu-I)Pt(mu-PPh 2) 2Pt(mu-I)} 2] ( 8, 96 e (-) skeleton), which is easily transformed into the trinuclear compound [(PPh 2R F)(R F)Pt(mu-PPh 2)(mu-I)Pt(mu-PPh 2) 2Pt(I)(PPh 3)] ( 9, 48 e (-) skeleton). Reaction of [(R F) 2Pt(mu-PPh 2) 2Pt(mu-PPh 2) 2Pt(NCMe) 2] ( 10) with I 2 at 213 K for short reaction times gives the trinuclear platinum derivative [(R F) 2Pt(mu-PPh 2) 2Pt(mu-PPh 2) 2Pt(I) 2] ( 11, 46e skeleton) in mixed oxidation state Pt(III)-Pt(III)-Pt(II) and with a Pt-Pt bond, while the reaction at room temperature and longer reactions times gives 8. The structures of the complexes have been established by multinuclear NMR spectroscopy. In particular, the (195)Pt NMR analysis, carried out also by (19)F- (195)Pt heteronuclear multiple-quantum coherence, revealed an unprecedented shielding of the (195)Pt nuclei upon passing from Pt(II) to Pt(III). The X-ray diffraction structures of complexes 4, 5, 6, 9, and 11 have been studied. A detailed study of the relationship between the complexes has been carried out.

Synthesis and reactivity of the unsaturated trinuclear phosphanido complex [(C6F5)2Pt(μ-PPh2)2Pt(μ-PPh2)2Pt(PPh3)].

The reaction of [NBu(4)][(C(6)F(5))(2)Pt(μ-PPh(2))(2)Pt(μ-PPh(2))(2)Pt(O,O-acac)] (48 VEC) with [HPPh(3)][ClO(4)] gives the 46 VEC unsaturated [(C(6)F(5))(2)Pt(1)(μ-PPh(2))(2)Pt(2)(μ-PPh(2))(2)Pt(3)(PPh(3))](Pt(2)-Pt(3)) (1), a trinuclear compound endowed with a Pt-Pt bond. This compound displays amphiphilic behavior and reacts easily with nucleophiles L, yielding the saturated complexes [(C(6)F(5))(2)Pt(II)(μ-PPh(2))(2)Pt(II)(μ-PPh(2))(2)Pt(II)(PPh(3))L] [L = PPh(3) (2), py (3)]. The reaction with the electrophile [Ag(OClO(3))PPh(3)] affords the adduct 1·AgPPh(3), which evolves, even at low temperature, to a mixture in which [(C(6)F(5))(2)Pt(III)(μ-PPh(2))(2)Pt(III)(μ-PPh(2))(2)Pt(II)(PPh(3))(2)](2+)(Pt(III)-Pt(III)) and 2 (plus silver metal) are present. The nucleophilic nature of 1 is also demonstrated through its reaction with cis-[Pt(C(6)F(5))(2)(THF)(2)], which results in the formation of [Pt(4)(μ-PPh(2))(4)(C(6)F(5))(4)(PPh(3))] (4). The structure and NMR features indicate that 1 can be better considered as a Pt(II)-Pt(III)-Pt(I) complex instead of a Pt(II)-Pt(II)-Pt(II) derivative. Theoretical calculations (density functional theory) on similar model compounds are in agreement with the assigned oxidation states of the metal centers. The strong intermetallic interactions resulting in a Pt(2)-Pt(3) metal-metal bond and the respective bonding mechanism were verified by employing a multitude of computational techniques (natural bond order analysis, the Laplacian of the electron density, and localized orbital locator profiles).

Synthesis of neutral and cationic pentafluorophenylpalladium(I) derivatives. Insertion versus coordination of isocyanides in binuclear palladium(I) complexes

Abstract Reaction between PdX(C6F5)(dpm)2 (dpm = bis(diphenylphosphino)methane; X = Cl, Br, I, CNO or C6F5) and Pd2(dba)3CHCl3 (dba = dibenzylideneacetone) gives, the pentafluorophenyl palladium(I) derivatives [XPd(μ-dpm)2Pd(C6F5)]. Treatment of [ClPd(μ-dpm)2Pd(C6F5)] with an excess of the ligand L, and in the presence of NaBPh4 gives the cationic complexes [LPd(μ-dpm)2Pd(C6F5)]BPh4 (L = PPh3, P(OPh)3, pyridine or tetrahydrothiophene (tht)). Reaction with isocyanides RNC leads to three different types of compounds: (a) products with the isocyanide groups inserted into the PdPd bond [(μ-RNC){;XPd(μ-dpm)2Pd(C6F5)};] (X = C6F5; R = p-tolyl; X = Cl, R = p-tolyl or Cy); (b) cationic complexes with terminal isocyanides [(RNC)Pd(μ-dpm)2Pd(C6F5)]X (X = Cl; R = t-Bu; X = BPh4, R = p-tolyl, Cy or t-Bu) and (c) complexes which contain both bridging and terminal isocyanides, [(μ-RNC){;(RNC)Pd(μ-dpm)2Pd(C6F5};BPh4] (R = p-tolyl or cyclohexyl). Addition of NaBPh4 to solutions of complexes of type a (X = Cl) results in deinsertion of the isocyanide to give complexes of type b. IR spectroscopy reveals that [(μ-CyNC){;ClPd(μ-dpm)2Pd(C6F5)};] isomerizes in CH2Cl2 to give [(CyNC)Pd(μ-dpm)2pd(C6F5)]Cl, which upon recrystallization regenerates the former complex, showing that in this case the insertion-deinsertion process is reversible.

Synthesis and characterization of [NBu4][Pt3(µ-PPh2)2(C6F5)5]: an anionic cluster containing an unusual µ3-PPh2 bridging system

[NBu4]2[Pt2(µ-PPh2)2(C6F5)4] reacts with cis-[Pt(C6F5)2(thf)2](1:2 molar ratio) yielding [NBu4][Pt3(µ-PPh2)2(C6F5)5] which contains unusual µ3-PPh(1,2-η2-Ph)-κ3P phosphido and semi-bridging C6F5 ligands and two Pt–Pt bonds of length 2.899(1) and 2.772(1)A.

Acetylenes attached to poly(pentafluorophenyl)platinum(II) moieties. Syntheses and molecular structures of cis-[Pt(C6F5)2(PhCCPh)2] and [NBun4][Pt(C6F5)3(PhCCPh)]

The complexes cis-[Pt(C6F5)2(RCCR)2](R = Et 1a or Ph 1b) have been prepared by treating cis-[Pt(C6F5)2(thf)2](thf = tetrahydrofuran) with the appropriate alkyne. They undergo facile ligand exchange with either cis-[Pt(C6F5)2(thf)2] or [NBun4]2[Pt(C6F5)4] giving rise respectively to neutral cis-[Pt(C6F5)2(thf)(RCCR)]2 or anionic [NBun4][Pt(C6F5)3(PhCCPh)]7b mono(η2-alkyne) derivatives. A series of mono(η2-alkyne) complexes of formulae cis-[Pt(C6F5)2L(RCCR)](L = pyridine 3a, 3b; PPh34a; SbPh35b; or CO 6a, 6b) and [N(PPh3)2][Pt(C6F5)3(EtCCEt)]7a has also been prepared. None of these complexes except 7b shows ν(CC) absorptions in their IR spectra. The molecular structures of complexes 1b and 7b have been established by X-ray diffraction studies: 1b, monoclinic, space group C2/c, a= 19.177(4), b= 8.4971(4), c= 19.790(3)A, β= 103.297(14)° and Z= 4 (C2 symmetry imposed); 7b, monoclinic, space group P21/c, a= 10.5179(9), b= 17.5834(20), c= 25.369(5)A, β= 99.376(11)° and Z= 4. Parameters within the acetylene moiety of 1b suggest that the platinum→alkyne π-back bonding is minimal.

Pentafluorophenyl complexes of palladium and platinum containing chelating, unidentate, or bridging Ph2PCH2PPh2 ligands

The reactions of cis-[M(C6F5)2(thf)2], trans-[M(C6F5)2(tht)2], and [M2(µ-Cl)2(C6F5)2(tht)2](M = Pd or Pt, thf = tetrahydrofuran, tht = tetrahydrothiophene) with dppm (Ph2PCH2PPh2) in molar ratios M : dppm = 1 : 1 and 1 : 2 have been studied. Pentafluorophenyl complexes containing dppm acting as endobidentate (chelate), unidentate, or exobidentate (bridging homo- or hetero-metal centres) have been obtained and characterized by i.r. and 31P n.m.r. spectroscopy.

Synthesis of heterobimetallic complexes containing cobalt–platinum or rhodium–platinum dative bonds. Molecular structure of [(η5-C5H5)(CO)2Rh→Pt(C6F5)2(CO)]

The complexes [(η5-C5R5)(CO)LM→Pt(C6F5)2(CO)](R = H or Me; M = Co or Rh; L = CO or PPh3) have been obtained by reacting the bases [M(η5-C5R5)(CO)L] with cis-[Pt(C6F5)2(CO)(thf)](thf = tetrahydrofuran). Their structures are discussed on the basis of 1H, 19F, and 31P n.m.r. and i.r. data. The molecular structure of the complex [(η5-C5H5)(CO)2Rh→Pt(C6F5)2(CO)] has been determined by an X-ray diffraction study: orthorhombic, space group P212121 with a= 7.632 1(10), b= 16.415 1(17), c= 16.520 0(43)A, Z= 4; R= 0.027, R′= 0.028 for 3 676 reflections with I 3σ(I) having 2 < 2θ < 60°. The structure shows that the basic (η5-C5H5)(CO)2Rh group is co-ordinated to the Pt(C6F5)2(CO) moiety forming a binuclear complex with an unbridged Rh–Pt bond of length 2.750(1)A. Platinum is in an almost square-planar environment with the C6F5 groups mutually cis. The 19F n.m.r. spectra of the complexes reveal fluxional behaviour leading to equivalence of the two C6F5 groups. The reaction of [(η5-C5R5)(CO)2Rh→Pt(C6F5)2(CO)](R = H or Me) with PPh3 yields [Rh(η5-C5R5)(CO)2] and cis-[Pt(C6F5)2(CO)(PPh3)]; reacting [(η5-C5H5)(CO)2Rh→Pt(C6F5)2(CO)] with bis(diphenylphosphino)methane (dppm) gives [Rh(η5-C5H5)(CO)2] and [Pt(C6F5)2(dppm)].

Addition of Nucleophiles to Phosphanido Derivatives of Pt(III): Formation of P–C, P–N, and P–O Bonds

The reactivity of the dinuclear platinum(III) derivative [(R(F))2Pt(III)(μ-PPh2)2Pt(III)(R(F))2](Pt-Pt) (R(F) = C6F5) (1) toward OH(-), N3(-), and NCO(-) was studied. The coordination of these nucleophiles to a metal center evolves with reductive coupling or reductive elimination between a bridging diphenylphosphanido group and OH(-), N3(-), and NCO(-) or C6F5 groups and formation of P-O, P-N, or P-C bonds. The addition of OH(-) to 1 evolves with a reductive coupling with the incoming ligand, formation of a P-O bond, and the synthesis of [NBu4]2[(R(F))2Pt(II)(μ-OPPh2)(μ-PPh2)Pt(II)(R(F))2] (3). The addition of N3(-) takes place through two ways: (a) formation of the P-N bond and reductive elimination of PPh2N3 yielding [NBu4]2[(R(F))2Pt(II)(μ-N3)(μ-PPh2)Pt(II)(R(F))2] (4a) and (b) formation of the P-C bond and reductive coupling with one of the C6F5 groups yielding [NBu4][(R(F))2Pt(II)(μ-N3)(μ-PPh2)Pt(II)(R(F))(PPh2R(F))] (4b). Analogous behavior was shown in the addition of NCO(-) to 1 which afforded [NBu4]2[(R(F))2Pt(II)(μ-NCO)(μ-PPh2)Pt(II)(R(F))2] (5a) and [NBu4][(R(F))2Pt(II)(μ-NCO)(μ-PPh2)Pt(II)(R(F))(PPh2R(F))] (5b). In the reaction of the trinuclear complex [(R(F))2Pt(III)(μ-PPh2)2Pt(III)(μ-PPh2)2Pt(II)(R(F))2](Pt(III)-Pt(III)) (2) with OH(-) or N3(-), the coordination of the nucleophile takes place selectively at the central platinum(III) center, and the PPh2/OH(-) or PPh2/N3(-) reductive coupling yields the trinuclear [NBu4]2[(R(F))2Pt(II)(μ-Ph2PO)(μ-PPh2)Pt(II)(μ-PPh2)2Pt(II)(R(F))2] (6) and [NBu4][(R(F))2Pt(1)(μ3-Ph2PNPPh2)(μ-PPh2)Pt(2)(μ-PPh2)Pt(3)(R(F))2](Pt(2)-Pt(3)) (7). Complex 7 is fluxional in solution, and an equilibrium consisting of Pt-Pt bond migration was ascertained by (31)P EXSY experiments.

Insertion reactions of 1,4-diisocyanobenzene in binuclear Pd(I) complexes

Reactions between XPd(μ-dmp)2PdX′ (X = X′ = Cl, Br, I, NCO, SCN, N3 or C6F5; X = C6F5, X′ = Cl, Br, I, NCO) with 1,4-diisocyanobenzene lead to the tetranuclear complexes [(μ,μ′-CNC6H4NC){XPd(μ-dpm)2PdX′}2], where both ends of the diisocyanide are inserted in a metalmetal bond. The cationic derivatives [(μ,μ′-CNC6H4NC){(RNC)Pd(μ-dpm)2(CNR)}2](BPh4)4 and [(μ,μ′-CNC6H4NC){(RNC)Pd(μ-dpm)2Pd(C6F5)}2] (BPh4)2 (R = p-Tol, Cy, or tBu) are obtained by reacting [(μ,μ′-CNC6H4NC){ClPd(μ-dpm)2PdX}2] (X= Cl or C6F5) with RNC in the presence of NaBPh4. Treatment of [(μ,μ′-CNC6H4NC){ClPd(μ-dpm)2Pd(C6F5)}]2 with NaBPh4 causes the di-insertion and subsequent coordination of the isocyanide, yielding [(C6F5)Pd(CN-C6H4NC) Pd(μ-dpm)2Pd(C6F5)](BPh4)2.