Site‐Selectivity in the Protonation and Related Reactions of Chalcogenophosphinidene‐Bridged Dimolybdenum Cyclopentadienyl Complexes. Issue 10 (16th December 2013)

• Record Type: Journal Article
• Authors: Alvarez, Belén; Alvarez, M. Angeles; Amor, Inmaculada; García, M. Esther; García‐Vivó, Daniel; Suárez, Jaime; Ruiz, Miguel A.
• Other Names: Caporali Maria sponsoringEditor.
• Is Part Of: European journal of inorganic chemistry. Issue 10(2014)
• Page Start: 1706
• Page End: 1718
• Publication Date: 2013-12-16
• Subjects: Metallocenes -- Molybdenum -- P ligands -- Arene ligands -- Chalcogenophosphinidene ligands; Chemistry, Inorganic -- Periodicals; Organometallic chemistry -- Periodicals; Bioinorganic chemistry -- Periodicals; Solid state chemistry -- Periodicals; 546
• DOI: 10.1002/ejic.201301292
• Languages: English
• ISSNs: 1434-1948

Abstract

Abstract: Reactions of the chalcogenophosphinidene‐bridged complexes syn ‐[Mo2 Cp2 (μ‐κ 2 P, Z :κ 1 P, η 4 ‐ZPMes*)(CO)2 L] (L = CO, CN t Bu; Z = O, S, Se), anti ‐[Mo2 Cp2 (μ‐κ 2 P, S :κ 1 P, η 4 ‐SPMes*)(CO)2 L] (L = CO, CN t Bu) and [Mo2 Cp2 {μ‐κ 2 P, Z :κ 1 P ‐ZPH}(η 6 ‐HMes*)(CO)2 ] (Z = S, Se, Te) towards sources of H +, Me +, and AuP( p Tol)3 + cations were investigated (Mes* = 2, 4, 6‐C6 H2 t Bu3 ; Cp = η 5 ‐C5 H5 ). The latter two electrophiles invariably added to the chalcogen atom to give corresponding derivatives [Mo2 Cp2 {μ‐κ 2 P, Z :κ 1 P, η 4 ‐Mes*PZ(CH3 )}(CO)3 ]BX4 [X = F, Z = O, S, Se; P–S 2.144(1) Å when Z = S and X = Ar′ = 3, 5‐C6 H3 (CF3 )2 ], [Mo2 Cp2 {μ‐κ 2 P, Z :κ 1 P, η 4 ‐Mes*PZ(CH3 )}(CN t Bu)(CO)2 ]BF4 (Z = S, Se), and [AuMo2 Cp2 (μ3 ‐κ 1 S :κ 2 P, S :κ 1 P, η 4 ‐SPMes*){P( p Tol)3 }(CO)3 ]PF6 [P–S 2.113(2), S–Au 2.320(2) Å]. Even when syn and anti isomers of the neutral precursor were used, the corresponding products were invariably characterized by their syn conformation (Z atom close to L ligand). Besides this, methylated derivatives of the chalcogenophosphinidene complexes bearing the formula [Mo2 Cp2 {μ‐κ 2 P, Z :κ 1 P ‐HPZ(Me)}(η 6 ‐HMes*)(CO)2 ](CF3 SO3 ) (Z = S, Se, Te), were found in solution to exist as an equilibrium of corresponding cis and trans isomers differing, in each case, in the relative positioning of the Cp rings with respect to the MoPZ plane. In contrast to the above results, the protonation of all these compounds was quite sensitive to the particular chalcogenophosphinidene ligand and conformation of the complex. Protonation of the HPZ‐bridged complexes led to complex mixtures of products that could not be isolated or properly characterized. In contrast, the aryl‐bearing substrates reacted selectively to give corresponding complexes [Mo2 Cp2 {μ‐κ 2 P, Z :κ 1 P, η 5 ‐ZP(C6 H3 t Bu3 )}(CO)3 ]BX4 (Z = S, X = F; P–S 2.032(2) Å when X = Ar′; Z = Se, X = F) and [Mo2 Cp2 {μ‐κ 2 P, Z :κ 1 P, η 5 ‐ZP(C6 H3 t Bu3 )}(CN t Bu)(CO)2 ]BAr′4 (Z = S, Se). The reaction of anti ‐[Mo2 Cp2 (μ‐κ 2 P, S :κ 1 P, η 4 ‐SPMes*)(CO)3 ] with HBF4 · OEt2 at 213 K initially gave unstable intermediate anti ‐[Mo2 Cp2 {μ‐κ 2 P, S :κ 1 P, η 4 ‐Mes*PS(H)}(CO)3 ]BF4, which then rapidly converted at room temperature to the conventional isomer with the S atom close to the metallocene‐bound carbonyl ligand ( syn isomer). This transformation is in agreement with Density Functional Theory calculations for neutral thiophosphinidene complexes; electrophilic attack at the sulfur atom, which is both an orbital‐ and charge‐favoured event, affords products that are more stable than those resulting from protonation at the metal sites. All these protonation reactions eventually result in an endo addition of H + to the C 6 atom of the Mes* ring with concomitant η 4 →η 5 haptotropic shift of the resulting HMes* group. This conversion involves an easy H migration from S to the C 6 atom, computed to take place with a low activation barrier of about 70 kJ/mol. Abstract : Chalcogenophosphinidene‐bridged complexes reacted readily with electrophilic reagents at the chalcogen site to give P‐ and Z‐bound thiolophosphide‐like derivatives of the type [L n Mo‐RPZ( E )‐MoCp(CO)2 ] + {E = Me, Au[P( p Tol)3 ]}. When E = H and R = aryl, these derivatives rapidly rearranged by chalcogen‐to‐carbon(aryl) migration affording chalcogenophosphinidene derivatives with η 5 ‐bound aryl rings.