Synthesis And Characterization Of Polymetallic Iron, Ruthenium And Osmium Complexes With Conjugated Bridges

Bimetallic organometallic compounds with d-conjugated bridges have recently attracted considerable attention, because of their unusual intrinsic chemical, physical, and material properties. A large number of interesting conjugated organometallic bimetallic complexes without metal-metal bonding have been reported, including those with Cx-bridged complexes LnM-Cx-M'Ln', CxHx-bridged complexes LnM-CxHx -MLn,C4H2-bridged complexes with M = C linkages such as [Mo] = CCH=CHC = [Mo]or complexes with M=C linkages such as [Nb]=C=CMe-CMe=C=C=[Nb] and 1, 3-bimetalated cyclobutenylidene^Ra) complexes.Despite the fact that a large number of conjugated bimetallic organometallic complexes have been reported, there are still very limited bimetallic complexes with conjugated hydrocarbon chains of odd numbers of carbon atoms linking two metal centers. The previous reported linkages are limited to €3- and €5. In this thesis, the synthesis, characterization, and properties of the first bimetallic complexes with CsHj-and CsH-bridges are described. X-ray diffraction studies show that the bridging CsH-ligand is symmetrically bound to the metals with a delocalized 7r-system.Bimetallic complexes with hydrocarbon chains containing only sp2-hybridized carbons are interesting because many conjugated organic materials (for examplepolyacetylenes) have only sp2 carbons in their backbones. However, only a few complexes with linear CXHX( X = 2,4 ,6 ) bridges have been reported. Thus it is of interest in the synthesis and properties of new conjugated dimeric and polymeric complexes with CXHX bridges. Here I present the synthesis and characterization of conjugated bimetallic complexes with linear CXHX (X = 5 , 4 ) bridges. The complexes are made from the surprisingly simple insertion reactions of HC=C-CH(OH)-C=CH or HC=C-C=CH with RuHCl(CO)(PPh3)3. Dimeric complexes bridged with CXHX where x is odd were unknown before this work. My synthetic route is the first method to prepare the CsHs-bridged complexes.All new compounds were characterized by elemental analysis and NMR spectroscopy. The main results are summarized as following:1. Activation of acetylene by [(n5-C5R5)ML2]+:Synthesis and characterization of bimetallic iron, ruthenium, and osmium complexesbridged with C5H and C5H2 ligands(1) Treatment of [(T|S-C5R5)M(L)2]BF4 (M = Fe, Ru, Os; R = Me, H; (L)2= dppe, (PPh3)2) with 0.45 equiv of HC=C-CH(OH)-OCH led to the formation of the first C5H2-bridged compounds [(n5-C5R5)(L)2M=C=C=CH-CH=C=M(L)2(Ti5-C5R5)](BF4)2(2) The CsH2-bridged compounds reacted with alumina to give the first C5H-bridged compounds [(r,5-C5R5)(L)2M=C=C=CH-C=C-M(L)2(Ti5-C5R5)]BF4.(3) The molecular structure of the conjugate C.sH-bridged complex [Cp(PPh3)2Ru=OC=CH-OC-Ru(PPh3)2Cp]BPh4 and [Cp(PPh3)2Os=C=C=CH-C=C-Os(PPh3)2Cp]BF4 has been confirmed by X-ray diffraction, which show that the bridging CjH ligand is symmetrically linked to M with a delocalized n-system.(4) The CsH2- and CsH-bridged compounds are intensely colored complexes. TheC5H-bridged complexes have intense blue color with strong absorption bands around 520-730 nm. It could be assigned to the electronic transition involving the M=C=C=CH-C=C-M unit. The C5H2-bridged complexes have intense purple color with strong absorption bands around 530 nm(for Ru-complex). It could be assigned to the electronic transition involving the Ru=C=C=:CH-CH=C=Ru unit.(5) It is interesting to note that the Cs-bridged complex [Cp*Re(NO)(PPh3)(u-C5)Mn(CO)2(C5Cl5)]BF4 was reported to be light-sensitive and decomposed in hours even in the dark, but the CsH-bridged complexes are stable species which can be stored under an inert atmosphere for months at room temperature.(6) The CsH-bridge is reactive and could be attacked by nucleophiles at the Y-carbon atom. Reaction of [(T|5-C5R5)(L)2Ru=C=C=CH-C=C-Ru(L)2(n5-C5R5)]BF4 with [CH2COCH3]" gen...