Dimolybdenum Cyclopentadienyl Complexes with Bridging Chalcogenophosphinidene Ligands

Abstract

The reactions of the phosphinidene-bridged complex [Mo(2)Cp(2)(μ-PH)(η(6)-HMes*)(CO)(2)] (1), the arylphosphinidene complexes [Mo(2)Cp(2)(μ-κ(1):κ(1),η(6)-PMes*)(CO)(2)] (2), [Mo(2)Cp(2)(μ-κ(1):κ(1),η(4)-PMes*)(CO)(3)] (3), [Mo(2)Cp(2)(μ-κ(1):κ(1),η(4)-PMes*)(CO)(2)(CN(t)Bu)] (4), and the cyclopentadienylidene-phosphinidene complex [Mo(2)Cp(μ-κ(1):κ(1),η(5)-PC(5)H(4))(η(6)-HMes*)(CO)(2)] (5) toward different sources of chalcogen atoms were investigated (Mes* = 2,4,6-C(6)H(2)(t)Bu(3); Cp = η(5)-C(5)H(5)). 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 [Mo(2)Cp(2){μ-κ(2)(P,Z):κ(1)(P)-ZPH}(η(6)-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 [Mo(2)Cp(2)(μ-κ(2)(P,Z):κ(1)(P),η(6)-ZPMes*)(CO)(2)] for Z = O and S (P-O = 1.565(2) Å), along with small amounts of the dithiophosphorane complex [Mo(2)Cp(2)(μ-κ(2)(P,S):κ(1)(S'),η(6)-S(2)PMes*)(CO)(2)], in the reaction with sulfur. The η(4)-complexes 3 and 4 reacted with sulfur and gray selenium to give the corresponding derivatives [Mo(2)Cp(2)(μ-κ(2)(P,Z):κ(1)(P),η(4)-ZPMes*)(CO)(2)L] (L = CO, CN(t)Bu), 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 Mo(2)P plane. The cyclopentadienylidene compound 5 reacted with all chalcogens, and gave with good yields the chalcogenophosphinidene derivatives [Mo(2)Cp(μ-κ(2)(P,Z):κ(1)(P),η(5)-ZPC(5)H(4))(η(6)-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 [Mo(2)Cp(μ-κ(2)(P,S):κ(1)(S'),η(5)-S(2)PC(5)H(4))(η(6)-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-[Mo(2)Cp(2)(μ-κ(2)(P,S):κ(1)(P),η(4)-SPMes*)(CO)(3)].

Phosphinidene-bridged binuclear complexes

“…The above reaction seems to be a characteristic feature of asymmetric trigonal planar phosphinidene and Te) [111,74]. The main products obtained in all reactions were complexes of type 188 displaying three-membered MoPZ cycles (Scheme 92).…”

“…The main products obtained in all reactions were complexes of type 188 displaying three-membered MoPZ cycles (Scheme 92). The PC 5 H 4 complex proved to be very reactive in these reactions, and was able to add not just one, but up to two S atoms to give the dithiophosphorane complex 189, with full cleavage of one of the MoP bonds [111]. Interestingly, the last process could be reversed by just attempting chromatographic purification of this product on alumina at room temperature, which caused partial desulphurisation to regenerate the phosphinidene sulphide ligand.…”

Nucleophilic behaviour of dioxo- and thiooxophosphorane complexes [MoCp(CO)2{E,P-EP(O)(2,4,6-C6H2tBu3)}]−(E = O, S)

“…14 Similarly short PS lengths have been found previously for different S,P:P-bridged chalcogenophosphinidene Mo 2 complexes, a circumstance which we have linked to the involvement of the chalcogen atom in some (SP) bonding interaction within the MoPS ring of these molecules. 15 On the other hand, the MoP bond of 3 is neither expected to be much perturbed upon alkylation, and displays a value of 2.3963(6) Å, indicative of a strong single bond. A final structural feature deserved of comment is the distorted trigonal pyramidal environment around the P atom, derived from the fact that this atom remains placed almost in the same plane as the Mo, O3 and C11 atoms ((XPY) = 354 o ).…”

Heterometallic clusters derived from the unsaturated carbyne-bridged dimolybdenum complexes [Mo 2 (η 5 -C 5 H 5 ) 2 (μ-CPh) (μ-PCy 2 ) (CO) x ] (x = 1, 2)

“…The minor isomer displays a PCy 2 resonance at 223.8 ppm, a position almost identical to those of compounds 8b,c, and is thus assigned to the isomer syn. The major isomer of 8a, identified by a slightly more shielded 31 3 }]PF 6 a molecule proposed to be formed through initial attack of the gold electrophile to the Mo-P bond of the parent carbyne complex [8]. This exemplifies the great influence that subtle electronic and steric factors exert over the course of these cluster-building reactions.…”

“…In most cases, a change in the coordination mode of the carbyne ligand, from terminal to the  2 and  3 modes was observed. More recently we examined comparable reactions of the methoxycarbyne-bridged analogues of compounds 1 and 2, which indeed proved to be useful reagents to prepare different trinuclear and tetranuclear clusters [7,8]. As it will be shown below, complexes 1 and 2 are nucleophilic enough to react with different precursors of unsaturated metal fragments of type M(CO) x (M = W, Fe, Ru, Co), whereby different tri-and tetranuclear heterometallic clusters can be obtained, all having the benzylidyne ligand bound to three metal centres.…”