Synthesis of the Reagent [Na][Pt(PEt3)2(η5-7-CB10H11)] and Preparation of the Platinacarborane Complexes [PtX(PEt3)2(η5-7-CB10H11)] (X = H, Au(PPh3), Cu(PPh3), HgPh)
Abstract:The salt
[Na][Pt(PEt3)2(η5-7-CB10H11)]
(1a) has been prepared. Protonation affords the hydrido
complex [PtH(PEt3)2(η5-7-CB10H11)]
(2) while reactions with [AuCl(PPh3)],
[CuCl(PPh3)]4, and [HgClPh] yield the
dimetal
compounds
[PtM(PEt3)2(PPh3)(η5-7-CB10H11)]
(3a, M = Au; 3b, M = Cu) and
[PtHgPh(PEt3)2(η5-7-CB10H11)]
(3c), respectively. The salt
[N(PPh3)2][Pt(CO)(PPh3)(η5-7-CB10H11)]
(4) has also been obtained. Single-crystal
X-ray diffraction studies have been made on 2 and
3a−c. Complexes 2,
3a, and 3c have si… Show more
“…Consequently their metal complexes also carry a higher negative charge, a property resulting in reactivity towards various electrophiles, which leads to functionalization at the carborane cage 2. Moreover, cationic metal–ligand fragments react to give bimetallic species 3. 4 We have recently expanded our studies to non‐icosahedral metal–monocarborane complexes with the rhenacarborane ion 1 2− (Scheme ) 5.…”
Building butterflies: A carborane‐supported {ReIrAu2} butterfly has been assembled by stepwise addition of iridium and then gold to a rhenium‐monocarborane complex (see picture green=BH, orange=B, black=CPh). The method of preparation has considerable potential for the synthesis of other new heteropolymetallic species.
“…Consequently their metal complexes also carry a higher negative charge, a property resulting in reactivity towards various electrophiles, which leads to functionalization at the carborane cage 2. Moreover, cationic metal–ligand fragments react to give bimetallic species 3. 4 We have recently expanded our studies to non‐icosahedral metal–monocarborane complexes with the rhenacarborane ion 1 2− (Scheme ) 5.…”
Building butterflies: A carborane‐supported {ReIrAu2} butterfly has been assembled by stepwise addition of iridium and then gold to a rhenium‐monocarborane complex (see picture green=BH, orange=B, black=CPh). The method of preparation has considerable potential for the synthesis of other new heteropolymetallic species.
“…Several years ago during a preliminary investigation of the rhenacarborane Cs[Re(CO) 3 ( η 5 -7,8-C 2 B 9 H 11 )] ( 1 ), first synthesized by Hawthorne and Andrews, it came as some surprise to us that there was no propensity for this salt to react either with strong acids (HBF 4 ·Et 2 O, HCl(Et 2 O), CF 3 CO 2 H) or with sources of the fragment [Au(PPh 3 )] + . Failure of [Au(PPh 3 )] + to afford a Re−Au species was especially surprising, as the gold reagent reacts with several other anionic metallacarboranes to form metal−metal bonds . However, recently the monocarbon rhenacarborane [N(PPh 3 ) 2 ] 2 [Re(CO) 3 ( η 5 -7-CB 10 H 11 )] has been used as an effective precursor to novel bimetallic complexes with Re−Pt, Re−Pd, Re−Rh, and Re−Ir bonds, and this has prompted us to reexamine the reactivity of compound 1 .…”
The rhenacarborane salt Cs[Re(CO)3(η
5-7,8-C2B9H11)] (1) has been synthesized in excellent
yield using a new procedure. Treatment of CH2Cl2 solutions of 1 with [RuCl2(PPh3)3] yields
the exo-closo complex [Re(CO)3(η
5-2,3,10-(μ-H)3-exo-{RuCl(PPh3)2}-7,8-C2B9H8)] (2a). In this
molecule a [RuCl(PPh3)2]+ moiety is exopolyhedrally bound via three B−H⇀Ru bonds to a
closo-3,1,2-ReC2B9 system. An X-ray diffraction study revealed that one of these agostic
interactions utilizes a β-B−H bond in the coordinating
face of the cage, while the
source of the remaining two B−H⇀Ru bonds is in the B5 belt. The anion of salt 1 also binds
exopolyhedral [Rh(PPh3)2]+ and [Rh{Fe(η-C5H4PPh2)2}]+ fragments in the complexes [Re(CO)3(η
5-5,10-(μ-H)2-exo-(RhL2)-7,8-C2B9H9)] (L2 = (PPh3)2 (3a), {Fe(η-C5H4PPh2)2} (3b)).
Reaction of 1 with the salts [M(CO)2(THF)(η-C5H5)][BF4] (M = Fe, Ru) and [Fe(CO)2(THF)(η-C5Me5)][BF4] gives the complexes [Re(CO)3(η
5-n-(μ-H)-exo-{M(CO)2(η-C5R5)}-7,8-C2B9H10)]
(M = Fe, R = H, n = 10 (4a); M = Ru, R = H, n = 10 (4b); M = Fe, R = Me, n = 10 (4c), 9
(4d)) with isomers 4c and 4d formed as an inseparable mixture. An X-ray structural study
on 4b revealed that there was no Re−Ru bond and that an exo-[Ru(CO)2(η-C5H5)]+ fragment
is bound to the rhenacarboranyl anion by a single unsupported B−H⇀Ru interaction with
an unusually long B−Ru distance (2.695(13) Å). The compounds [ReM(μ-10-H-η
5-7,8-C2B9H10)(CO)3(PPh3)] (M = Cu (5a), Ag (5b)) were isolated from the reaction of 1 with sources of the
fragments [M(PPh3)]+ (M = Cu, Ag). X-ray structure determinations of both species 5 revealed
the presence of direct Re−M (M = Cu, Ag) connectivities bridged by carborane β-B−H⇀M
interactions. In solution the complexes 5 are highly dynamic on the NMR time scale, even
at low (−90 °C) temperatures.
“…In solution the molecule evidently undergoes dynamic behavior, since even when measured at −80 °C the 1 H NMR spectrum did not reveal a signal for the B−H⇀Cu group. This is not unusual even when such bonds are present 10a. It is well-established that metal−ligand groups exopolyhedrally attached to icosahedral carborane frameworks by B−H⇀M linkages can undergo exchange mechanisms involving equilibria between tautomers and these processes are fast on the NMR time scale. , The Cu(PPh 3 ) moiety in 6a is held in place by the B(4)−Cu bond; therefore, the likely fluxional process would be a restricted one in which the B−H⇀Cu linkage exchanges between B(8)H(8) and B(9)H(9) vertexes on either side in the same pentagonal layer. 12a,d In the 1 H NMR spectrum the B(3)−H(3)⇀Ru(2) group displays a diagnostic quartet at δ −9.61 ( J (BH) = 50 Hz) 5 and a doublet resonance for μ -H(23) is seen at δ −18.31 ( J (PH) = 13 Hz) .…”
Section: Resultsmentioning
confidence: 85%
“…Interestingly, theB(8)−H(8) group partakes in a B(8)−H(8)⇀Cu three-center−two-electron bond with the copper atom (B(8)−Cu = 2.365(8) Å, H(8)−Cu = 2.20(5) Å). Such linkages are well-established for molecules where a B−H⇀Cu interaction supplements a direct bond between the copper and another metal atom M which is a vertex in a closo -3,1,2-MC 2 B 9 system. , However, 6a is unique in having the copper atom σ-bonded to a boron vertex in the η 5 -coordinated belt of the carborane framework and also forming a B−H⇀Cu linkage with a boron atom in the upper pentagonal B 5 layer of the cage. 2 Structure of [Ru 3 ( μ -Η)(CO) 7 (PPh 3 ){ η 5 -10-Cu(PPh 3 )-7-CB 10 H 10 }] ( 6a ), showing the crystallographic labeling scheme.…”
Section: Resultsmentioning
confidence: 99%
“…As discussed elsewhere, , for gold only one such orbital is energetically suitable for bonding, whereas for copper, and evidently for silver also, all three are accessible for bond formation. This property is well-illustrated by the two molecules [PtM(PEt 3 ) 2 (PPh 3 )( η 5 -7-CB 10 H 11 )] (M = Cu, Au); in the copper species the Pt−Cu bond is supported by two exopolyhedral B−H⇀Cu linkages, whereas in the gold complex 6c the Pt−Au bond stands alone 10b…”
In thf (tetrahydrofuran) at reflux temperatures the compounds [Ru 3 (CO) 12 ] and [NHMe 3 ]-[nido-7-CB 10 H 13 ] give the anionic triruthenium complex [Ru 3 (CO) 8 (η 5 -7-CB 10 H 11 )] -, characterized as its [PPh 4 ] + salt (4a). Protonation of [NHMe 3 ][Ru 3 (CO) 8 (η 5 -7-CB 10 H 11 )] (4b) with HBF 4 ‚ Et 2 O yields the hydrido cluster complex [Ru 3 (µ-H)(CO) 8 (η 5 -7-CB 10 H 11 )] (5), the structure of which has been determined by X-ray diffraction. The molecule has a triangle of ruthenium atoms. One ruthenium atom is ligated by the η 5 -7-CB 10 H 11 cage system and carries two CO groups, while the other two ruthenium atoms each carry three CO molecules with a hydrido ligand bridging the metal-metal bond which joins them. In addition, these two metal atoms are linked to the cage through two exopolyhedral B-HFRu bonds. These are formed using boron atoms lying in sites with respect to the carbon in the open CBBBB face of the nido-CB 10 H 11 fragment ligating the Ru(CO) 2 group. Treatment of 4b in thf with [CuCl(PPh 3 ) 3 ] in the presence of TlPF 6 , or with Ag[BF 4 ] and PPh 3 , affords the bimetallic complexes [Ru 3 (µ-H)(CO) 7 (PPh 3 ){η 5 -10-M(PPh 3 )-7-CB 10 H 10 }] (M ) Cu (6a), Ag (6b)), respectively. The structure of 6a was established by X-ray diffraction. A triangle of ruthenium atoms is formed by Ru-(CO) 2 , Ru(CO) 3 , and Ru(CO) 2 (PPh 3 ) units. This triangle is bridged by a nido-10-Cu(PPh 3 )-7-CB 10 H 10 fragment, the open CBBBB face of which is η 5 -coordinated to the Ru(CO) 2 group.The two boron atoms lying in the -sites in the CBBBB ring coordinated to the Ru(CO) 2 moiety form exopolyhedral B-H F Ru and B-CufRu linkages, respectively, to the Ru-(CO) 2 (PPh 3 ) and Ru(CO) 3 groups, which have their Ru-Ru bond bridged by a hydrido ligand. A novel feature of the structure is a three-center-two-electron B-HFCu bond involving the B(2) site in the nido-10-Cu(PPh 3 )-7-CB 10 H 10 cage system. The reaction between 4b and [AuCl(PPh 3 )] gives [Ru 3 (µ-H)(CO) 8 {η 5 -10-Au(PPh 3 )-7-CB 10 H 10 }] (6c), the structure of which was also determined by X-ray crystallography. It is similar to that of 6a, except there is no exopolyhedral B-HFAu bond supplementing the B(10)-AufRu and Au-P bonds.
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