Sulfur-bonded thiophenes in organometallic rhenium complexes and adsorption of isocyanides on gold

Robertson, Mitchell
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Sulfur-coordinated benzo (b) thiophene ([eta][superscript]1 (S)-BT) complexes Cp[superscript]'(CO)[subscript]2Re(BT) (Cp[superscript]'=C[subscript]5H[subscript]5 or C[subscript]5Me[subscript]5) and [Cp[superscript]'(CO)[subscript]2Re] ([eta][superscript]2:[eta][superscript]1(S)-[mu][subscript]2-BT)[Re(CO)[subscript]2Cp[superscript]''] (Cp[superscript]'=Cp[superscript]''=C[subscript]5H[subscript]5; Cp[superscript]'=Cp[superscript]''=C[subscript]5Me[subscript]5; Cp[superscript]'=Cp, Cp[superscript]''=C[subscript]5Me[subscript]5) complexes were synthesized. The bimetallic compounds contain a bridging BT ligand in which one metal is [eta][superscript]1(S)-bonded to the BT and another metal is 2,3-[eta][superscript]2 bonded to the C2-C3 olefin bond of the BT. Infrared, [superscript]1H NMR, and [superscript]13C NMR data indicate that this dual metal coordination enhances the sulfur-donating ability of the BT and strengthens the Re-olefin bond. The bimetallic complexes are protonated with one equivalent of CF[subscript]3SO[subscript]3H exclusively at the Re atom that is [eta][superscript]1(S) bonded to the BT;Sulfur-coordinated thiophene complexes of the type [Cp(NO)PPh[subscript]3)Re([eta][superscript]1(S)-Th)) BF[subscript]4 (Th = thiophene (T), 2,5-Me[subscript]2T, BT, 2-MeBT) were also synthesized. A proton can be abstracted from the coordinated thiophenes with base to give the neutral thienyl (Tyl) and benzothienyl (BTyl) complexes. The 2-Tyl and 3-BTyl complexes react with CF[subscript]3SO[subscript]3H to protonate the C3 carbon of the ligand to give the 2-thienylcarbene (Cp(NO)(PPh[subscript]3)Re (2-(Tylcarbene)) O[subscript]3SCF[subscript]3 and 2-benzothienylcarbene (Cp(NO)(PPh[subscript]3)Re (2-(BTylcarbene)) O[subscript]3SCF[subscript]3 complexes;The adsorption of isocyanides (phenylisocyanide, t-butyl-isocyanide, and 1,4-phenylene diisocyanide) on gold powder was studied using DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy). The isocyanides were adsorbed on the gold powder through the isocyanide group from methanol solution, and the [nu](NC) frequency typically shifted 50-60 cm[superscript]-1 higher than in the free isocyanides. The intensity of the [nu](NC) frequency reached an asymptotic value with increasing amounts of isocyanide used in the methanol solution; a finite amount of isocyanide was adsorbing to the gold surface. The [nu](NC) frequency of the phenylisocyanide and t-butylisocyanide in the model Au(1) complexes (isocyanide)AuCl shifts about 100 cm[superscript]-1 higher, indicating that the isocyanides are not bound to a formally Au(1) species on the surface.

Chemistry, Inorganic chemistry