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Dimolybdenum Cyclopentadienyl Complexes with Bridging Chalcogenophosphinidene Ligands

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journal contribution
posted on 16.07.2012, 00:00 by Belén Alvarez, M. Angeles Alvarez, Inmaculada Amor, M. Esther García, Daniel García-Vivó, Jaime Suárez, Miguel A. Ruiz
The reactions of the phosphinidene-bridged complex [Mo2Cp2(μ-PH)­(η6-HMes*)­(CO)2] (1), the arylphosphinidene complexes [Mo2Cp2(μ-κ116-PMes*)­(CO)2] (2), [Mo2Cp2(μ-κ114-PMes*)­(CO)3] (3), [Mo2Cp2(μ-κ114-PMes*)­(CO)2(CNtBu)] (4), and the cyclopentadienylidene-phosphinidene complex [Mo2Cp­(μ-κ115-PC5H4)­(η6-HMes*)­(CO)2] (5) toward different sources of chalcogen atoms were investigated (Mes* = 2,4,6-C6H2tBu3; Cp = η5-C5H5). The bare elements were appropriate sources in all cases except for oxygen, in which case dimethyldioxirane gave the best results. Complex 1 reacted with the mentioned chalcogen sources at low temperature, to give the corresponding chalcogenophosphinidene derivatives [Mo2Cp2{μ-κ2P,Z1P-ZPH}­(η6-HMes*)­(CO)2] (Z = O, S, Se, Te; P–Se = 2.199(2) Å). The arylphosphinidene complex 2 was the least reactive substrate and gave only chalcogenophosphinidene derivatives [Mo2Cp2(μ-κ2P,Z1P6-ZPMes*)­(CO)2] for Z = O and S (P–O = 1.565(2) Å), along with small amounts of the dithiophosphorane complex [Mo2Cp2(μ-κ2P,S1S′6-S2PMes*)­(CO)2], in the reaction with sulfur. The η4-complexes 3 and 4 reacted with sulfur and gray selenium to give the corresponding derivatives [Mo2Cp2(μ-κ2P,Z1P4-ZPMes*)­(CO)2L] (L = CO, CNtBu), obtained respectively as syn (Z = Se; P–Se = 2.190(1) Å for L = CO) or a mixture of syn and anti isomers (Z = S; P–S = 2.034(1)–2.043(1) Å), with these diastereoisomers differing in the relative positioning of the chalcogen atom and the terminal ligand at the metallocene fragment, relative to the Mo2P plane. The cyclopentadienylidene compound 5 reacted with all chalcogens, and gave with good yields the chalcogenophosphinidene derivatives [Mo2Cp­(μ-κ2P,Z1P5-ZPC5H4)­(η6-HMes*)­(CO)2] (Z = S, Se, Te), these displaying in solution equilibrium mixtures of the corresponding cis and trans isomers differing in the relative positioning of the cyclopentadienylic rings with respect to the MoPZ plane in each case. The sulfur derivative reacted with excess sulfur to give the dithiophosphorane complex [Mo2Cp­(μ-κ2P,S1S′5-S2PC5H4)­(η6-HMes*)­(CO)2] (P–S = 2.023(4) and 2.027(4) Å). The structural and spectroscopic data for all chalcogenophosphinidene complexes suggested the presence of a significant π­(P–Z) bonding interaction within the corresponding MoPZ rings, also supported by Density Functional Theory calculations on the thiophosphinidene complex syn-[Mo2Cp2(μ-κ2P,S1P4-SPMes*)­(CO)3].