Reactivity of Electron-Deficient Benzoheterocycle Triosmium Clusters. 5. The Chemistry of Os₃(CO)₉(μ₃-η²-(C(9)−N)-5,6-benzoquinolyl)(μ-H) and Its Phosphine Derivative

Abstract

The reactivity of Os3(CO)9(μ3-η2-C13H8N)(μ-H) (1) is reported. The reaction of 1 with triphenyl phosphine gives Os3(CO)9(μ-η2-C13H8N)(μ-H)(PPh3) (2), in which the phosphine is bonded to the same osmium as the C(10) of the heterocyclic ring, isostructural with the quinoline analogue. Thermal or photochemical decarbonylation of 2 gives moderate yields of Os3(CO)8(μ3-η3-C13H8N)(μ-H)PPh3 (3), which has a σ−π-vinyl bonding mode with the C(9)−C(10) double bond and not the expected μ3-η2 electron-deficient bonding mode. The reactivity of 1 with hydride followed by protonation yields the electron-precise Os3(CO)9(μ3-η2-C13H9N)(μ-H)2 (4), and labeling experiments using D-/H+ indicate direct nucleophilic attack at C(9) by the deuteride followed by protonation at the metal core. The reaction of 1 with lithium isobutyrile nitrile followed by protonation gives Os3(CO)9(C13H9(4-(CH3)2CCN)N)(μ-H) (5), a result of nucleophilic addition across the 3,4 double bond. Reaction with n-butyllithium followed by protonation, on the other hand, gives three products, Os3(CO)9(μ3-η2-C13H8(9-C4H9)N)(μ-H)2 (6), the result of addition at the 9-position, Os3(CO)9(μ3-η2-C13H7(6-C4H9)N)(μ-H) (7), and Os3(CO)9(μ3-η2-C13H7(5-C4H9)N)(μ-H) (8), both the result of nucleophilic substitution for hydrogen. The solid-state structures of 3 and 8 are reported, and the mechanistic implications of these results for the synthetic methodology being developed for these electron-deficient clusters will be discussed.

Reaction of electron-deficient 6-methoxyquinolinate-substituted cluster [Os3(CO)9{μ3-η1,κ1-C9H5N(6-OMe)}(μ-H)] with PPh3: Thermally induced ligand isomerization, decarbonylation and orthometallation

“…In summary, the room temperature reaction between electron-deficient 1 and PPh3 affords the (R = H, Me) [27], but is quite different from those observed for its quinolinate [3,5] and 5,6benzoquinolinate analogs [8]. This study also confirms that a small change in the benzoheterocycle significantly affects the reactivity of the resultant phosphine adducts of these electron-deficient clusters towards phosphines.…”

“…Studies also showed that the nature of the heterocyclic ligands somehow influences the reactivity of the resultant phosphine adducts. For example, photolysis or thermolysis of these phosphine adducts usually leads to nonspecific decomposition or phosphine ligand dissociation to give the phosphine-free nona-and deca-carbonyl clusters [Os3(CO)9(μ3-η 1 ,κ 1 -L)(μ-H)] and [Os3(CO)10(μ-η 1 ,κ 1 -L)(μ-H)] [3,8]. However, an electron-precise σ-π vinyl complex was formed via carbonyl dissociation upon photolysis or thermolysis in the case of metallated 5,6benzoquinolate cluster as shown in Scheme 1 [8].…”

“…For example, photolysis or thermolysis of these phosphine adducts usually leads to nonspecific decomposition or phosphine ligand dissociation to give the phosphine-free nona-and deca-carbonyl clusters [Os3(CO)9(μ3-η 1 ,κ 1 -L)(μ-H)] and [Os3(CO)10(μ-η 1 ,κ 1 -L)(μ-H)] [3,8]. However, an electron-precise σ-π vinyl complex was formed via carbonyl dissociation upon photolysis or thermolysis in the case of metallated 5,6benzoquinolate cluster as shown in Scheme 1 [8]. As part of our studies on the reactivity of electron-deficient [Os3(CO)9(μ3-η 1 ,κ 1 -L)(μ-H)] with two electron donor ligands, we recently reported the reactions of benzothiazolate triosmium clusters [Os3(CO)9(µ3-η 1 ,κ 1 -C7H3NSR)(µ-H)] (R = H, Me) with PPh3 that led to the isolation of electron-precise adducts [Os3(CO)9(PPh3)(µ, 2 -C7H3NSR)(µ-H)] in which PPh3 ligand occupies an equatorial site at the carbon bound osmium.…”

A comparative study of the reactivity of unsaturated triosmium clusters [Os3(CO)8{μ3-Ph2PCH2P(Ph)C6H4}(μ-H)] and [Os3(CO)9{μ3-η2-C7H3(2-Me)NS}(μ-H)] with BuNC

“…On the other hand, the reactions of the electron-deficient benzoheterocyclic triosmium clusters of the type [Os 3 (CO) 9 (l-H)(l 3 -g 2 -L-H)] (L = quinoline, quinoxaline, benzimidazole, benzothiazole, benzoxazole) obtained from decarbonylation of the corresponding decacabonyls [Os 3 (CO) 10 (l-H)(l-g 2 -L-H)], with neutral nucleophiles such as phosphine and amines results in ligand addition at the metal core along with rearrangements whereas reactions with anionic nucleophiles such as hydride or carbanions results in attack at the carbocyclic ring [4][5][6][17][18][19][20]23] (Scheme 2).…”

Water-soluble benzoheterocycle triosmium clusters as potential inhibitors of telomerase enzyme

“…We have recently developed synthetic procedures for a class of benzoheterocycle triosmium clusters of general formula [(l-H)Os 3 (CO) 9 (L)(l 3 -g 2 -(Q-H))], where L = [P(C 6 H 4 SO 3 Na) 3 ] or [P(OCH 2 CH 2 NMe 3 I) 3 ] and Q = quinoline, 3-aminoquinoline, quinoxaline, phenanthridine [23][24][25][26][27][28][29][30] (Fig. 2).…”