Trigonal-prismatic and octahedral hexaruthenium boride clusters: molecular structures of [N(PPh3)2][Ru6H2(CO)18B], [Ru6(CO)17B{AuP(C6H4Me-2)3}], [Ru6H(CO)16B{Au(PPh3)}2] and [Ru6(CO)16B{Au(PPh3)}3]

Abstract

The reaction of the [N(PPh,),] + salt of [Ru,(CO),(B,H,)] -with [Ru,(CO),,(NCMe),] yielded both the octahedral [Ru,(CO),,B] -I and trigonal-prismatic [RU,H,(CO),,B] -2 boride cluster anions. This result indicates that the choice of the trigonal-prismatic versus octahedral cage is not determined by the size of the interstitial atom. The salt [ N (PPh,),] [Ru,H,(CO),,B] has been structurally characterised. The reactions of anions 1 and 2 with [AuCI(PPh,)], [AuCI{P(C,H,Me-z),}], [{(Ph,P)Au},O] [BF,] and [{(Z-MeC,H,),PAU},O] [BF,] have been studied and the distribution of the products [Ru,(CO),,B(Au( PR,)}], starting cluster has been examined. The trigold derivatives are best prepared by treating the octahedral anion 1 with [{(Ph,P)Au},O] +. Single-crystal X-ray crystallography has confirmed that each of the gold(i) phosphine derivatives has an octahedral Ru,B core. [RU6H(CO)16B{AU(PR3)}2] and [~U6(co)16B{AU(PR3)}3] as a function Of R (Ph or Z-MeC,H,) and Of the Transition-metal clusters which encapsulate p-block atoms '-' are well documented but carbide clusters predominate. '-, In terms of regular, closed polyhedra, a hexametallic framework is typically either an octahedron (86 valence electrons) or, less often, a trigonal prism (90 valence electrons). In cobalt and rhodium chemistry the trigonal-prismatic cluster carbide is repre~ented.~.~-" However, within the Group 8 triad, the trend observed for hexametallic clusters incorporating p-block elements has tended to suggest that a first-row atom (B,,,12-15 C,'-3 N4,') prefers to reside within an octahedral M, cage, while the trigonal-prismatic cage is observed when the interstitial atom is a larger p-block atom, e.g. p h o s p h ~r u s . ~, ' ~* ' Recently, we published preliminary information regarding the reaction of [N(PPh,),][Ru,(CO),(B,H,)] with [RU,(CO)~ o(N-CMe),]. Significantly, this reaction gives both the octahedral boride cluster [RU,(CO)~ 7B]-1 13,19 and the trigonalprismatic cluster [Ru,H,(CO),,B)-2. We now present a full report of this work, and describe reactions of anions 1 and 2 with the gold(1) phosphines [AuCI(PR3)] and [{(R,P)Au],O][BF,] (R = Ph or 2-MeC6H4), all of which lead to hexaruthenium boride derivatives with octahedral cluster cores. ExperimentalGeneral Data.-Fourier-transform NMR spectra were recorded on a Bruker WM 250 or AM 400 spectrometer; 'H shifts are reported with respect to 6 0 for SiMe,, 'B with respect to 6 0 for F,B-OEt, and 31P with respect to 6 0 for H3PO4. All spectral data listed in the Experimental section are recorded at 298 K. All downfield chemical shifts are positive. Infrared spectra were recorded on a Perkin Elmer FT 1710 spectrophotometer, FAB (fast atom bombardment) and FIB (fast ion bombardment) mass spectra on Kratos instruments with 3nitrobenzyl alcohol as matrix.

Gold–Heterometal Interactions and Bonds

“…Heptanuclear clusters with Au-Fe [160,306,[370][371][372][373]394], Au-Ru [264,319,328,[374][375][376][377][378][379][380][381][382][383][384][385][386][387][388][389][390] and Au-Os bonds [327,[391][392][393] have also been reported. Most common structures are based on C-centered [160,306,374,375] or B-centered [376][377][378][379] [160], (b) (Ph 3 P)AuOs 6 (m 6 -P)(CO) 18 253 [391], (c) [(Et 3 P)Au] 2 Fe 5 (m 6 -C)(CO) 14 254 [370], (d) (dppm)Au 2 Os 4 Ru(h 6 -C 6 H 6 )(CO) 12 [379].…”

“…Most common structures are based on C-centered [160,306,374,375] or B-centered [376][377][378][379] [160], (b) (Ph 3 P)AuOs 6 (m 6 -P)(CO) 18 253 [391], (c) [(Et 3 P)Au] 2 Fe 5 (m 6 -C)(CO) 14 254 [370], (d) (dppm)Au 2 Os 4 Ru(h 6 -C 6 H 6 )(CO) 12 [379]. A gold atom edge-bridged to an Ru-Ru bond in B-centered BRu 6 and cis-BRh 2 Ru 4 cores were found in some compounds [378,380,381] or in the cluster (Ph 3 P)AuRu 6 (m 6 -C)(mSePh)(CO) 15 252 [Au-Ru 2.7253(6)/2.8515(6) Å] [382]. In contrast, compound (Ph 3 P) AuOs 6 (m 6 -P)(CO) 18 (Figure 4.39c) [370].…”

“…The gold atoms of a diphosphinesupported Au-Au bond can span adjacent Ru-Ru bonds [384,396,399], as in [PhCH 2 N(CH 2 PPh 2 ) 2 ]Au 2 Ru 6 (m 6 -C)(CO) 16 271 [397], while in the anion of [NEt 4 ] [{(dppm)Au 2 }MoFe 5 (m 6 -C)(CO) 17 ] 151 [160] an Fe-Fe edge is bridged by one gold atom, whereas the other Au is directly attached to the molybdenum center. Finally, one gold atom of a (R 3 P)Au-Au(PR 3 ) system is m 3 -capping, while the other one bridges an Ru-Ru bond of the same triangular Ru 3 face in [(Et 3 P)Au] 2 Ru 5 W(m 6 -C) (CO) 17 272 [395], or both are m 3 -capping adjacent Ru 3 faces in the related [(Ph 3 P) Au] 2 Ru 6 (m 6 -B)(m-H)(CO) 16 273 [380].…”

“…Clusters with nuclearity higher than eight are more common for ruthenium [369,380,399,403,404] and osmium [399,[405][406][407][408][409][410][411][412][413][414]. They include species based on a M 10 tetracapped C-centered octahedron.…”

“…In (dppm)Au 2 Ru 10 (m 6 -C)(CO) 24 279 the Au atoms cap two adjacent, vertex sharing, triangular Ru 3 faces [369]. Ruthenium clusters based on B-centered octahedral frameworks with two adjacent trigonal faces capped by a gold atom and an additional Ru-Ru bond bridged by a third gold atom are known [380,404], for example, [(Ph 3 P)Au] 3 Ru 6 (m 6 -B)(CO) 16 280 [380]. The structures of some other clusters containing Au 2 Os 7 [407,408], Au 2 Os 8 [409,410], Au 2 Os 9 [411], Au 4 Os 6 [412] and Au 4 Os 10 [414] cores, as well as of some trimetallic species with Au 2 Os 6 Ru 2 [399] and AuRu 3 Pt 3 Ru 3 [403] frameworks, have also been reported.…”