The synthesis and characterization of early high-late low oxidation state mixed metal organometallic compounds.

Abstract

Mixed metal organometallic complexes with oxide co-ligands may serve as useful models for platinum metal catalysts on early transition metal oxide supports. Reaction of the electronically unsaturated hydride containing cluster [H2Os3(CO)10] with [W(C≡CPh)(O) 2(Cp*)] afforded the mu-oxo, mu-hydrido, mu-vinylidene cluster [Os3W(mu-H)(mu-eta1-C=CHPh)(CO)10(O)(mu-O)(Cp*)] 1 via a process involving acetylide and oxide coordination to the Os 3 framework and transfer of a hydride ligand to the unsaturated hydrocarbyl. Under thermal conditions, cluster 1 undergoes smooth decarbonylation concomitant with the formation of a novel mu3-oxo ligand to afford [Os3W(mu-H)(trans-mu-eta1-C=CHPh)(CO) 9(O)(Cp*)(mu3-O)] 2. Under photolysis, 2 isomerizes in high yield to a second mu3-oxo, mu-vinylidene complex [Os3W(mu-H)(cis-mu-eta1-C=CHPh)(CO) 9(O)(Cp*)(mu3-O)] 3. Under photolytic conditions, the mu-hydrido ligand of 1 is transferred over to the mu-vinylidene ligand resulting in the formation of a mu-eta1,eta2-vinyl ligand in [Os 3W(CO)10(O)(mu-eta1,eta2-CH=CHPh{ W-Os})(mu-O)(Cp*)] 4. Cluster 4 reacts under photolytic conditions with dihydrogen gas in a non-regioselective manner to produce two clusters, [Os3W(mu-H)(anti-mu-eta 1-CHCH2Ph)(CO)9(O)(Cp*)(mu3-O)] 5 and [Os3W(mu-H)(gauche-mu-eta 1-CHCH2Ph)(CO)9(O)(Cp*)(mu3-O)] 6, bearing a mu3-oxo ligand and a mu-alkylidene organic fragment. The complexes 1, 4, 5 and 6 resemble species proposed as intermediates on hydrogenation catalysts. A rational next step in such a catalyzed reduction process would be the elimination of the organic fragment from the metal framework. However in this study no evidence supporting such chemical behavior was observed. Nevertheless interesting clusters bearing no hydrocarbyl fragments were isolated from a related experiment. Thermolysis of 4 led to the isolation of two clusters, [Os 3W(mu-H)(CO)9(mu-O)2(Cp*)] 9 and [Os3W(CO)8(mu-O)2(Cp*)]2 12, without hydrocarbyl units. The metal framework of 12 consists of a rare Os6 rhombic raft and a packing diagram suggested the presence of a layered W(O)2|Os6|W(O)2 lattice. This reaction also led to the isolation of an additional four clusters demonstrating various bonding modes for both the [W(O)2(Cp*)] fragment and the vinyl ligand on a Os3 skeleton. As suggested by TLC analysis and infrared spectroscopy, the first complex formed upon thermolysis of 4 is [Os3W(CO)9(mu-O)2(mu-eta 1,eta2-CH=CHPh{W-Os})(Cp*)] 7 which further isomerizes to [Os3W(CO)9(mu-O) 2(mu-eta1,eta2-CH=CHPh{ Os···Os})(Cp*)] 8. The reaction of 8 with carbon monoxide liberated during previous reaction steps led to the isolation of [Os3W(CO)10(O)(mu-eta 1,eta2-CH=CHPh{Os-Os})(mu-O)(Cp*)] 10 which also reacts with one molecule of carbon monoxide to provide [Os3W(eta1-CH=CHPh)(CO)11(O)(mu-O)(Cp*)] 11.