Reactivity of Silyl-Substituted Iron–Platinum Hydride Complexes toward Unsaturated Molecules: 4. Insertion of Fluorinated Aromatic Alkynes into the Platinum–Hydride Bond. Synthesis and Reactivity of Heterobimetallic Dimetallacylopentenone, Dimetallacyclobutene, μ-Vinylidene, and μ 2 -σ-Alkenyl Complexes

Insertion of p-FC6H4C=CH, p-CF3C6H4C=CH, and m-CF3C6H4C=CH into the Pt-H bond of [(OC)(3)Fe{Si(OMe)(3)}(mu-dppm)Pt(H)(PPh3)] (1a) yields first the sigma-alkenyl complexes [(OC)(3)Fe{mu-Si(OMe)(2)(OMe)}(mu-dppm)Pt(ArC=CH2)] (2a, Ar = C6H4F-p; 2d, C6H4CF3-p; 2e, C6H4CF3-m), which react in a second step with the liberated PPh3 ligand to afford the structurally characterized mu-vinylidene complexes [(OC)(3)Fe(mu-dppm){mu-C=C(H)C6H4F-p}Pt(PPh3)] (3a) and [(OC)(3)Fe(mu-dppm){mu-C=C(H)C6H4R}Pt(PPh3)] (3d, R = p-CF3; 3e, R = m-CF3). In contrast, treatment of la with o-FC6H4C=CH produces first [(OC)(3)Fe{mu-Si(OMe)(2)(OMe)}(mu-dppm)Pt(o-FC6H4C=CH2)] (2b), which evolves to the dimetallacyclopentenone complex [(OC)(2)Fe(mu-dppm){mu-C(=O)C(H)=C(C6H4F-o)}Pt(PPh3)] (4b'). The latter slowly rearranges to the structurally characterized thermodynamic isomer [(OC)(2)Fe(mu-dppm){mu-C(=O)C-(C6H4F-o)=C(H)}Pt(PPh3)] (4b). Treatment of la with 2,4-F2C6H3C=CH produces via transient alkenyl complex 2c an isomeric mixture of [(OC)(3)F(mu-dppm){mu-C=C(H)C6H3F2-2,4}Pt(PPh3)] (3c), [(OC)(2)F(mu-dppm){mu-C(=O)C(H)=C(C6H3F2-2,4))Pt(PPh3)] (4c'), and [(OC)(2)Fe(mu-dppm){mu-C(=O)C(C6H3F2-2,4)=C(H)}Pt(PPh3)] (4c). Alternatively, 4b,c and [(OC)(2)Fe(mu-dppm){mu-C(=O)C(Ar)=C(H)}Pt(PPh3)] (4a, Ar = C6H4F-p, 4d, Ar = C6H4CF3-p) were obtained by reaction of [(OC)(3)Fe(mu-dppm)(mu-C=O)Pt(PPh3)] with the respective terminal alicyne. Upon reaction of 1a, [(OC)(3)Fe(Si(OMe)(3)}(mu-dppa)Pt(H)(PPh3)] (1b; dppa = bis(diphenylphosphino)amine), and [(OC)(3)Fe{Si(OMe)(3)}(mu-dppm)Pt(H)(PMePh2)](1c) with o-F3CC6H4C=CH, the dimetallacyclobutenes [(OC)(3)Fe(mu-PPh2XPPh2){mu-C(C6H4CF3-o)C=C(H)}Pt(PPh2R)] (5a, X = CH2, R = Ph; 5b, X = NH, R = Ph; Sc, X = CH2, R = Me) are formed as the sole products. Complexes 5 result also from the reaction of [(OC)(3)Fe(mu-Ph2PXPPh2)(mu-C=O)Pt(PPh3)] (X = CH2, NH) with o-trifluorophenylacetylene. NMR studies at variable temperatures reveal that dimetallacydobutenes 5 are in equilibrium with dimetallacydopentenones [(OC)(2)Fe(mu-Ph2PXPPh2){mu-C(=O)C(C6H4CF3-o)=C(H)}Pt(PPh2R)] (4e, X = CH2, R = Ph; 4f, X = NH, R = Ph; 4g, X = CH2, R = Me). Addition of HBF4 to 5 leads to formation of the Fe-sigma:mu(2)-alkenyl salts [(OC)(3)Fe(mu-Ph2PXPPh2){mu-C(C6H4CF3-o)=CH2}Pt(PPh3)[BF4] (6a, X = CH, 6b, X = NH). Protonation of 4 gives the isomeric Pt-sigma:mu(2)-alkenyl salts [(OC)(3)Fe(mu-dppm){mu-CH2=C(Ar)}Pt(PPh3)][BF4] (7) together with small amounts of the Fe-sigma:mu(2)-alkenyl salts [(OC)(3)Fe(mu-dppm){mu-C(Ar)=CH2}Pt(PPh3)][BF4] (Ar = mu-C6H4CF3, p-C6H4F, 2,4-C6H3F2). Protonation of the vinylidene complexes [(OC)(3)Fe(mu-dppm){mu-C=C(H)Ar}Pt(PPh3)] (3; Ar = p-C6H4CF3, Ph, p-C6H4CH3) with HBF4 occurs exclusively at the alpha-position of the vinylidene unit to produce a mixture of the isomeric sigma-alkenyl salts cis-[(OC)(3)Fe(mu-dppm){mu-C(H)=C(H)Ar}Pt(PPh3)] [BF4] (8-cis) and trans-[(OC)(3)Fe(mu-dppm){mu-C(H)=C(H)Ar}Pt(PPh3)][BF4] (8-trans).