Synthesis and Properties of IrRe₂(μ-H)₂(CO)₉(η⁵-C₉H₇)

Abstract

The slow addition of Re(2)(&mgr;-H)(2)(CO)(8) to a solution of Ir(CO)(eta(2)-C(8)H(14))(eta(5)-C(9)H(7)) in hexane at reflux provides IrRe(2)(&mgr;-H)(2)(CO)(9)(eta(5)-C(9)H(7)) (1) in 80% yield. The molecular structure of 1 shows an IrRe(2) triangle incorporating one Ir(CO)(eta(5)-C(9)H(7)) and two Re(CO)(4) fragments. The strongly different Ir-Re distances suggest that one hydride ligand bridges one Ir-Re edge and the other hydride bridges the Re-Re edge. Low-temperature (1)H and (13)C NMR spectra are consistent with this structure; at higher temperatures a dynamic process involving migration of one hydride ligand between the two Ir-Re edges is observed. Cluster 1 is readily deprotonated with KOH/EtOH, and the resulting anion has been isolated as the PPN salt, [PPN][IrRe(2)(&mgr;-H)(CO)(9)(eta(5)-C(9)H(7))] (2). Both the (1)H and low temperature (13)C NMR spectra of 2 are consistent with a structure in which the remaining hydride ligand bridges the Re-Re edge. Variable-temperature (13)C NMR spectra indicate that 2 undergoes CO scrambling localized on the Ir-Re edges. The reaction of 1 with PPh(3) leads to IrRe(2)(&mgr;-H)(2)(CO)(8)(PPh(3))(eta(5)-C(9)H(7)) (3), which contains the phosphine on a rhenium atom, as well as to cluster fragmentation.

Directed Synthesis of the Triangular Mixed-Metal Cluster H2RhRe2Cp*(CO)9: Ligand Fluxionality and Facile Cluster Fragmentation in the Presence of CO, Halogenated Solvents, and Thiols

“…4 exhibits a scalene RhRe 2 architecture, and the metal−metal bond distances range from 2.8962(5) Å (Re(2)−Rh(1)) to 3.1202(4) Å (Re(1)−Re(2)). Despite the fact that few structurally characterized RhRe 2 clusters exist, our data are in agreement with those Rh−Re and Re−Re bond distances in RhRe 2 (μ-PPh 2 )(CO) 10 (PPh 3 ). , While the two hydrides were not located during data refinement, their locations are readily assigned to the Rh(1)−Re(1) and Re(1)−Re(2) vectors on the basis of hydride-induced structural trends found in H 2 Re 2 Ir(η 5 -ind)(CO) 9 and other polynuclear clusters . Here the two hydrides are assumed to span the two longest metal−metal bonds, namely the Rh(1)−Re(1) and Re(1)−Re(2) vectors.…”

“…The new clusters 4 − 6 were obtained by following the general procedure outlined by Shapley in his synthesis of H 2 Re 2 Ir(η 5 -ind)(CO) 9 . Here the slow addition of a hexane solution of 1 to a refluxing hexane solution containing 2 eliminates the premature decomposition of 1 , which has limited stability at elevated temperature, and allows for maximum conversion to the desired product 4 .…”

“…The former hydride appears as a doublet ( J Rh−H = 26 Hz) and is consistent with a hydride that spans one of the Rh−Re bonds in the product, with the remaining hydride singlet at δ −16.04 readily assigned to the Re−Re bond in 4 . The magnitude of the J Rh−H coupling constant matches those values reported for a series of RhH(PPh 3 )(SiR 3 )X derivatives and several PtRh 2 clusters. , The locus of two hydrides in 4 is analogous to that formulated for the hydrides in the iridium derivative H 2 Re 2 Ir(η 5 -ind)(CO) 9 . Examination of 4 by ESI mass spectrometry failed to yield a molecular ion for the cluster and instead gave m / e peaks for the sodiated fragmentation products [Cp*RhRe(CO) n +Na] + (where n = 2−4).…”

“…Accordingly, a major prerequisite in any mechanistic study dealing with ligand activation at a heterometallic cluster involves the ready availability of the starting cluster in amounts that will facilitate the associated spectroscopic, physical, and kinetic analyses. Our interest in the title heterometallic cluster H 2 RhRe 2 Cp*(CO) 9 stems, in part, from the earlier report by Shapley and co-workers on the indenyl-substituted cluster H 2 Re 2 Ir(η 5 -ind)(CO) 9 , which may be prepared in 80% yield from H 2 Re 2 (CO) 8 and Ir(CO)(η 2 -coe)(η 5 -ind) as shown in eq . The dinuclear compound H 2 Re 2 (CO) 8 is a suitable precursor for the directed synthesis of MRe 2 clusters because it is easily prepared in 0.2−0.4 g amounts from Re 2 (CO) 10 and it is reactive in cluster aggregation scenarios due to its intrinsic unsaturation, features utilized by others for the construction of triangular PtRe 2 and IrRe 2 clusters as well as polynuclear rhenium clusters. , Instead of using H 2 Re 2 Ir(η 5 -ind)(CO) 9 in our diphosphine ligand activation studies, we wanted to prepare the unknown H 2 RhRe 2 Cp*(CO) 9 derivative and utilize the presence of the 103 Rh nucleus (100% natural abundance and I = 1 / 2 ) to assist with the NMR interpretation of the reaction products.…”

Phosphinoborane-induced fragmentation of the unsaturated hydride H2Re2(CO)8: X-ray structure of HRe(CO)4(κB,P-Ph2PCH2CH2BR2) (where BR2 = 9-borabicyclo[3.3.1]nonanyl) and DFT Evaluation of hydride versus CO coordination by the ancillary borane

“…The starting dimer H 2 Re 2 (CO) 8 was prepared from Re 2 (CO) 10 and H 2 according to the procedure of Shapley, [17] while the phosphinoborane Ph 2 PCH 2 CH 2 BR 2 (2) was synthesized from vinyldiphenylphosphine and the 9-borabicyclo[3.3.1]nonane dimer, (9-BBN) 2 , according to the modification outlined by Tilley [14]. Re 2 (CO) 10 was purchased from Pressure Chemical Co.; the chemicals vinyldiphenylphosphine and (9-BBN) 2 were obtained from Aldrich Chemical Co., and these reagents were used as received.…”