Mixed-metal cluster synthesis: [Re(CO)3(μ-S2NC7H4)]2 as a precursor for tri- and tetranuclear 2-mercaptobenzothiolato capped clusters

Abstract

a b s t r a c tThe readily prepared [Re 2 (CO) 6 (l-S 2 NC 7 H 4 ) 2 ] (1) reacts with Group 8 trimetallic carbonyl clusters to yield new mixed-metal tri-and tetranuclear clusters. With [Os 3 (CO) 10 (NCMe) 2 ] at 80°C the tetranuclear mixed-metal cluster [Os 3 Re(CO) 13 (l 3 -C 7 H 4 NS 2 )] (2) is the only isolated product. With Ru 3 (CO) 12 products are dependent upon the reaction temperature. At 80°C, a mixture of tetranuclear mixed-metal [Ru 3 Re(-CO) 13 (l 3 -C 7 H 4 NS 2 )] (5) and the triruthenium complex [Ru 3 (CO) 9 (l-H)(l 3 -C 7 H 4 NS 2 )] (4) results, while at 110°C a second tetranuclear mixed-metal cluster, [Re 2 Ru 2 (CO) 12 (l 4 -S)(l-C 7 H 4 NS)(l-C 7 H 4 NS 2 )] (3), resulting from carbon-sulfur bond scission, is the major product. Reaction of 1 With Fe 3 (CO) 12 at 80°C furnishes the trinuclear mixed-metal cluster [Fe 2 Re(CO) 8 (l-CO) 2 (l 3 -C 7 H 4 NS 2 )] (6). The reactivity of 6 has been probed with the aim of identifying any metal-based selectivity for carbonyl substitution. Addition of PPh 3 in presence of Me 3 NO at 25°C gives both the mono-and bis(phosphine)-substituted derivatives [Os 3 Re(CO) 12 (PPh 3 )(l 3 -C 7 H 4 NS 2 )] (7) and [Os 3 Re(CO) 11 (PPh 3 ) 2 (l 3 -C 7 H 4 NS 2 )] (8). In 7 the PPh 3 ligand occupies an axial site on wingtip osmium, while in 8 one PPh 3 ligand is equatorially coordinated to wingtip osmium and the other is bonded to a hinge osmium. New complexes have been characterized by a combination of spectroscopic data and single crystal X-ray diffraction studies.

Investigation on the reactivity of tetranuclear Group 7/8 mixed-metal clusters toward triphenylphosphine

“…It coordinates with rhenium using one of the ring nitrogen while bridges the hinge osmium atoms using the sulfur. The Os-Os [Os(1)-Os(3) 2.8596(3), Os(1)-Os(2) 2.8650(3) and Os(2)-Os 32.7626(4) Å], Os-Re [Re(1)-Os 3) 2.9249(3and Re(1)-Os 2) 2.9307(3 15and Os(3)-S(1) 2.3979 16Å] bond distances are within the expected range and similar to those reported for related clusters [12,13] The mono-phosphine substituted cluster 3 has been characterized structurally together with spectroscopic methods. The solid-state molecular structure of 3 is depicted in Fig.…”

“…But in these butterfly clusters, the carbonyls axially bonded to the hinge metals on their convex side had been removed by the bridging sulfur ligand. This factor together with the butterfly arrangement of the metal core makes enough space in these clusters for a phosphine ligand to be axially bound to the wingtip Group 8 metal on their convex side as observed in ReOs3(CO)12(PPh3)(µ3-mbt) (mbtH = 2-mercatobenzothiazole) [12] (Chart 1).…”

“…Heterometallic systems may also combine the catalytic features of different metals to give novel reactivity that is inaccessible by homometallic systems [7]. We have reported systematic synthesis of a number of mixed-metal carbonyl clusters containing heterocyclic thiolate ligand(s) in the past few years [8][9][10][11][12][13][14][15][16]. For example, the Group 7/8 mixed-metal clusters of the general formula MM′3(CO)13(µ3-L) [M = Mn, Re; M′ = Os, Ru;…”

“…L-H = nitrogen containing heterocyclic thiol] can be readily obtained from the direct reaction between M′3(CO) x (x = 0, 2) and M2(CO)6(µ-L)2 in moderate to good yield (Scheme 1). The metallic core of these mixed-metal clusters forms a butterfly skeleton where the Group 7 metal (Mn or Re) always occupies a wingtip position [10][11][12][13][14][15][16]. The heterocyclic thiolate ligand is facially located on the convex side of the butterfly core that contains the Group 7 metal, but recent studies showed that it can also be shifted to the other face of the convex side by heating as shown in Scheme 1 [16].…”

“…Clusters having a butterfly arrangement of metal atoms are considered intermediate between tetrahedral and square-planar clusters [17,18] which have been studied as intermediates in homogeneous catalytic processes [18,19], and also considered as a model for chemisorption of small molecules [20]. Although the MM′3(CO)13(µ3-L) type butterfly clusters are relatively easy to prepare, studies on their reactivity toward various substrates has been almost neglected [12,13]. Tertiary phosphines (PR3) are an important class of ligands in organometallic chemistry as their steric and electronic properties can easily be tuned in a systematic and predictable way over a very wide range by varying the R group(s) and they are also capable of stabilizing an exceptionally wide variety of metal complexes.…”