Organo–platinum–iron complexes containing one bridging Ph 2 PCH 2 PPh 2 ligand. Crystal structures of [(OC) 3 Fe(µ-dppm)(µ-CO)Pt(PPh 3 )], [(OC) 2 Fe(µ-dppm){µ-C(O)C 2 H 2 }Pt(PPh 3 )], and [(OC) 3 Fe(µ-dppm)(µ-CMeCH 2 )Pt(PPh 3 )][BF 4 ]
1988; Royal Society of Chemistry; Issue: 3 Linguagem: Inglês
10.1039/dt9880000741
ISSN2050-5671
AutoresXavier L. R. Fontaine, Grant B. Jacobsen, Bernard L. Shaw, Mark Thornton‐Pett,
Tópico(s)Metal-Catalyzed Oxygenation Mechanisms
ResumoTreatment of [Fe(CO)4(dppm-P)](dppm = Ph2PCH2PPh2) with [Pt(trans-PhCHCHPh)(PPh3)2] gave the bimetallic [(OC)3Fe(µ-dppm)(µ-CO)Pt(PPh3)](1) in 75% isolated yield. Complex (1) was also prepared by the sodium tetrahydroborate reduction of [(OC)3Fe(µ-dppm)(µ-CO)PtCl2] in the presence of PPh3. Its structure was established by X-ray crystallography: the crystals are triclinic, space group P, with a= 1 177.3(2), b= 1 198.4(1), c= 1 776.5(1) pm, α= 103.34(1), β= 107.81(1), γ= 91.76(1)°, and Z= 2; final R factor 0.0257 for 5 422 observed reflections. The structure shows that one of the carbonyl ligands is almost symmetrically bridging the Fe–Pt bond. Protonation of complex (1) with HBF4·OEt2 gave the hydride [(OC)4Fe(µ-dppm)PtH(PPh3)][BF4](4), 1H n.m.r. studies of which indicated the hydride ligand to be terminal on platinum. Ethyne reacted with (1) at 20 °C to give the complex [(OC)2Fe(µ-dppm){µ-C(O)C2H2}Pt(PPh3)](5), the structure of which was established by X-ray crystallography: the crystals are orthorhombic, space group Pbca, with a= 1 898.9(4), b= 1 828.3(3), c= 2 414.4(5) pm, and Z= 8; R 0.0381 for 4 163 observed reflections. The molecule contains a dimetallacyclopentenone ring in which the ethylenic bond is η2-bound to iron, so that the C(O)C2H2 moiety is σ-co-ordinated to platinum and η3-co-ordinated to iron. Unsymmetrical alkynes (MeCCH, PhCCH, 4-MeC6H4CCH, MeNHCH2CCH, HOMe2CCCH, and MeCO2CCH) also reacted with complex (1), at 80 °C, to give complexes of type [(OC)2Fe(µ-dppm){µ-C(O)CRCH}Pt(PPh3)]. At 20 °C, MeCCH and 4-MeC6H4CCH reacted with (1) to give isolable complexes of type [(OC)2Fe(µ-dppm){µ-C(O)CHCR}Pt(PPh3)] which isomerised in solution, at rates dependent on the steric bulk of R, to complexes of type [(OC)2Fe(µ-dppm){µ-C(O)CRCH}Pt(PPh3)]. The mechanism of the alkyne-insertion reactions appears to involve an intermediate containing a monodentate dppm ligand co-ordinated to iron, formed by opening of the five-membered [graphic omitted]t ring in (1). Protonation of the alkyne complexes breaks the alkyne–CO link to give µ-vinyl cations of type [(OC)3Fe(µ-dppm)(µ-CRCH2)Pt(PPh3)]+(R = H, Me, or C6H4Me-4). The structure of [(OC)3Fe(µ-dppm)(µ-CMeCH2)Pt(PPh3)][BF4](16) has also been established by X-ray crystallography: the crystals are monoclinic, space group Cc, with a= 2 321.3(3), b= 1 091.2(2), c= 1 962.6(2) pm, β= 98.48(1)°, and Z= 4, R 0.0460 for 3 615 observed reflections. The structure shows that the µ-CMeCH2 moiety is σ-co-ordinated to platinum and η2-co-ordinated to iron. Treatment of complex (1) with MeO2CCCCO2Me displaced the PPh3 ligand to give [(OC)4Fe(µ-dppm)Pt(MeO2CCCCO2Me)](19). The complex [(OC)3Fe(µ-dppm)(µ-SO2)Pt(PPh3)](20) was formed in high yield when SO2 was bubbled through a dichloromethane solution of (1). In addition, analogues of many of the above complexes have been prepared with (Ph2P)2CCH2.
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