Redox‐Induced Coordination Isomerization of a Phosphoniobenzophospholide

Abstract

1-Triphenylphosphoniobenzo[c]phospholide 1 reacts with [M(CO)(5)Br] (M = Mn, Re) and [Mn(CO)(3)(naphthalene)][BF(4)] to give complexes cis-[M(CO)(4)(1)Br] (5 a,b) and [Mn(CO)(3)(1)][BF(4)] (6 a[BF(4)]), respectively, featuring eta(1)(P)- and eta(5)(pi)-coordination of the phosphole ring. The corresponding reactions with [M(2)(CO)(10)] proceed with conservation of the metal-metal bond and yield, depending on the reaction temperature, dinuclear complexes [M(2)(CO)(8)(1)] (M=Mn, 7 a) or [M(2)(CO)(6)(1)(2)] (M=Mn, Re, 8 a,b) with mu(2)-bridging eta(1)(P):eta(2)(Pdbond;C) coordination of the phosphole moiety. All complexes formed were characterized by spectroscopic data; 5 b, 6 a[BF(4)], and 8 a,b were characterized by X-ray diffraction studies as well. The structural and (31)P NMR data of the dinuclear manganese complex 8 a suggest that the interaction between the metal atoms and the eta(2)-bound Pdbond;C double bond moieties is dominated by the L-->M charge-transfer contribution; this hints at a very low back-donation ability of the central M(2)(CO)(6) fragment. Investigation of the reactions of the Mn complexes 6 a and 8 a with Mg or ferrocenium hexafluorophosphate ([Fc][PF(6)]), respectively, revealed that the chemically reversible mutual interconversion between both species was feasible. Likewise, oxidation of the rhenium complex 8 b with [Fc][PF(6)] gave spectroscopic evidence for the formation of a Re analogue of 6 a. Electrochemical studies suggested that the oxidation 8 a-->2 6 a involves two consecutive single-electron-transfer steps, the first of which is electrochemically reversible and produces a metastable radical cation that is detectable by ESR spectroscopy. The mutual interconversion between 6 a and 8 a represents the first case of a reversible coordination isomerization of a phosphaarene that is triggered by a redox process and might stimulate further studies directed at the use of dinuclear phosphaarene complexes in redox-catalysis.

Organometallic Complexes of Benzannelated Phospholyls: Synthesis and Characterization of Benzophospholyl and the First iso-Benzophospholyl Metal Complexes

“…The similarities between 19 and 33 are further manifested by their respective unit cell parameters, which are virtually identical. The molecular geometry of 33 also compares favorably with that of its recently reported ionic triphenylphosphonio derivative 34a10 Selected Distances (Å) and Angles (deg) for One of the Independent Molecules of 33 Mn(1)−C(1) 2.1555(16) C(1)−P(1)−C(3) 89.46(8) Mn(1)−C(3) 2.1693(16) C(1)−C(1A)−C(3A) 111.42(14) Mn(1)−C(1A) 2.2214(14) C(1A)−C(1)−P(1) 113.54(12) Mn(1)−C(3A) 2.2255(14) C(3A)−C(3)−P(1) 113.48(12) Mn(1)−P(1) 2.3696(5) C(3)−C(3A)−C(1A) 111.62(14) Mn(1)−C(10) 1.7885(17) Mn(1)−C(8) 1.7983(16) Mn(1)−C(9) 1.8032(17) P(1)−C(1) 1.7583(19) P(1)−C(3) 1.7594(18) C(1A)−C(1) 1.426(2) C(1A)−C(3A) 1.430(2) C(3)−C(3A) 1.424(2) …”

“…Complexes 32 and 33 are air and moisture sensitive, but are indefinitely stable under an inert atmosphere. The isolation of 33 is particularly important because it is the first metal complex of the hitherto unknown ligand 5 . The synthesis of 19 and 33 proves that 4 and 5 form π-complexes with manganese, in contrast to the behavior of 3 , for which only σ-complexes were obtained.…”

P–C, P–N, and M–N Bond Formation Processes in Reactions of Heterometallic Phosphinidene-Bridged MoMn and MoRe Complexes with Diazoalkanes and Organic Azides to Build Three- to Five-Membered Phosphametallacycles

“…This yields a 34-electron complex for which a single Mo–Re bond has to be proposed according to the 18 electron rule, which is in agreement with the Mo–Re distance of 3.1579(3) Å, very similar to the distance of 3.1745(6) Å measured in the parent compound 1a . We note that no other heterometallic complex with κ 1 :η 2 -bridging phosphaalkene ligands appears to have been crystallographically characterized so far, and the additional coordination of the oxygen atom to render a 6-electron donor μ-κ 2 :η 2 coordination mode is also unprecedented for a phosphaalkene ligand.…”

Synthesis of a Cobalt−Phospholyl Half-Sandwich Complex and Its Transformation into a Phosphacobaltocene

“…Taken together, these new data imply that functionalized phosphacobaltocenes may be quite accessible synthetic targets. Given their easy oxidation to phosphacobaltocenium salts, which are good candidates for new ligand platforms, further research into these and related cobalt complexes is in progress.…”