Organometallics
Article
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39.6 [d, JRhP = 153 Hz; 2PPh3]. LRMS (MALDI+/DCTB): m/z 595
cm−1): ν 2567 vs (BH), 2520 vs (BH), 2493 vs (BH), 2466 vs (BH),
1982 vs (CO), 1632 m, 1479 m, 1434 m, 1262 m, 1161 m, 1092 m,
1006 m, 935 m, 935 m, 877 m, 829 m, 800 m, 746 m, 692 vs, 577 w,
[M − (PPh3) − H]+. Isotope envelopes match those calculated from
the known isotopic abundances of the constituent elements.
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Synthesis of Ethylene-Ligated closo-Rhodathioboranes 13−
15. As a general procedure, 100 mg of the corresponding
hydridorhodathiaborane [8,8,8-(PPh3)2H-9-(L)-nido-8,7-RhSB9H9],
where L= 2-Me-NC5H4 (3), 3- Me-NC5H4 (4), 4-Me-NC5H4 (5),
was dissolved in 20 mL of CH2Cl2 in a Schlenk tube. After three
freeze−thaw cycles, a balloon containing ethylene was attached to the
Schlenk tube, and the rhodathiaborane solution was exposed to the
gas. The system was stirred at room temperature. After a variable
length of time, the reaction mixture was concentrated by solvent
evaporation under vacuum, and hexane was added to produce an
orange-red precipitate, which was washed several times with hexane.
The solid was crystallized from CH2Cl2/hexane to isolate the
respective ethylene ligated clusters [1,1-(η2-C2H4)(PPh3)-3-(L)-closo-
1,2-RhSB9H8].
525 vs. H NMR (300 MHz, CD2Cl2, 300 K): δ 9.41 (d, 1H, 2-CH3-
NC5H4), 8.04 (d, 1H, 2-CH3-NC5H4), 7.62 (t, 2H, 2-CH3-NC5H4),
7.50−7.05 (15H, PPh3), 3.02 (m, 3H, 2-CH3-NC5H4). 31P{1H} NMR
(121 MHz, CD2Cl2, 300 K): δ 37.7 (d, 1JRhP = 133 Hz; PPh3). LRMS
(MALDI+/DCTB): m/z 596 [M − (CO)]+. Isotope envelopes match
those calculated from the known isotopic abundances of the
constituent elements.
[1,1-(PPh3)(CO)-3-(3-Me-NC5H4)-closo-1,2-RhSB9H8] (18). The re-
action was carried out with 150 mg (0.174 mmol) of 4, and stirring
under an atmosphere of CO was maintained for 2 h. Yield: 97.0 mg,
0.156 mmol, 90%. Anal. Calcd for C25H30B9NOPRhS·CH2Cl2: C,
44.06; H, 4.55; N, 1.98; S, 4.52. Found: C, 44.41; H, 4.42; N, 1.76; S,
4.32. IR (ATR, cm−1): ν 2563 vs (BH), 2519 vs (BH), 2494 vs (BH),
2464 vs (BH), 1974 vs (CO), 1619 m, 1478 m, 1433 m, 1180 m, 1093
m, 1005 m, 939 m, 742 m, 684 vs, 524 v. 1H NMR (300 MHz,
CD2Cl2, 300 K): δ 8.90 (d, 2H, 3-CH3-NC5H4), 8.01 (d, 1H, 3-CH3-
NC5H4), 7.58 (t, 1H, 3-CH3-NC5H4), 7.34−7.28 (15H, PPh3), 2.40
(m, 3H, 3-CH3-NC5H4). 31P{1H} NMR (121 MHz, CD2Cl2, 300 K):
δ 37.9 (d, 1J RhP = 136 Hz; PPh3). LRMS (MALDI+/DCTB): m/z 596
[M − (CO)]+. Isotope envelopes match those calculated from the
known isotopic abundances of the constituent elements.
[1,1-(PPh3)(η2-C2H4)-3-(2-Me-NC5H4)-closo-1,2-RhSB9H8] (13). The
reaction was carried out with 100 mg (0.116 mmol) of 3, and the
solution was exposed to an ethylene atmosphere for 2 h. Yield: 62 mg,
0.099 mmol, 86%. Anal. Calcd for C26H34B9NPRhS: C, 50.06; H, 5.49;
N, 2.5; S, 5.14. Found: C, 50.26; H, 5.63; N, 2.32; S, 5.01. IR (ATR,
cm−1): ν 2528 vs (BH), 2507 vs (BH), 2497 vs (BH), 2472 vs (BH),
2452 vs (BH), 1618 w, 1476 s, 1451 w, 1430 s, 1260 m, 1151 m, 1087
s, 1010 m, 946 m, 748 m, 692 s, 526 s, 492 m, 456 m (Rh-C2H4), 418
m (Rh-C2H4), 325 w (RhP). 1H NMR (300 MHz, CD2Cl2, 300 K): δ
9.45 (m, 2H, 2-CH3-NC5H5), 8.07 (m, 2H, 2-Me-NC5H5), 7.70−7.01
(15H, PPh3), 3.05 (s, 3H, 2-CH3-NC5H5), 2.16 (m, 2H, C2H4), 1.99
(m, 2H, C2H4). 31P{1H} NMR (121 MHz, CD2Cl2, 300 K): δ 34.19
[1,1-(PPh3)(CO)-3-(4-Me-NC5H4)-closo-1,2-RhSB9H8] (19). The re-
action was carried out with 30 mg (0.035 mmol) of 5, and stirring
under an atmosphere of CO was maintained for 8 h. Yield: 20.0 mg,
0.032 mmol, 91%. Anal. Calcd for C25H30B9NOPRhS·CH2Cl2: C,
44.06; H, 4.55; N, 1.98; S, 4.52. Found: C, 44.51; H, 4.43; N, 1.73; S,
4.02. IR (ATR, cm−1): ν 2567 vs (BH), 2523 vs (BH), 2501 vs (BH),
2465 vs (BH), 1993 vs (CO), 1978 vs (CO), 1632 m, 1479 m, 1452 w,
[d, JRhP = 134 Hz, PPh3]. LRMS (MALDI+/DCTB): m/z 595 [M −
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(C2H4) − H]+. Isotope envelopes match those calculated from the
known isotopic abundances of the constituent elements.
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1434 m, 1163 m, 1092 s, 1006 m, 935 m, 746 s, 692 vs, 525 vs H
[1,1-(PPh3)(η2-C2H4)-3-(3-Me-NC5H4)-closo-1,2-RhSB9H8] (14). The
reaction was carried out with 100 mg (0.116 mmol) of 4, and the
solution was exposed to an ethylene atmosphere for 4 h. Yield: 60 mg,
0.096 mmol, 83%. Anal. Calcd for C26H34B9NPRhS: C, 50.06; H, 5.49;
N, 2.5; S, 5.14. Found: C, 50.46; H, 5.66; N, 2.30; S, 5.08.IR (ATR,
cm−1): ν 2529 vs (BH), 2505 vs (BH), 2499 vs (BH), 2476 vs (BH),
2453 vs (BH), 1616 w, 1479 s, 1450 w, 1432 s, 1261 m, 1152 m, 1089
s, 1010 m, 947 m, 747 m, 692 s, 525 s, 491 m, 455 m (Rh-C2H4), 417
m (Rh-C2H4), 326 w (RhP). 1H NMR (300 MHz, CD2Cl2, 300 K): δ
9.14 (m, 2H, 3-CH3-NC5H4), 8.44 (m, 1H, 3-CH3-NC5H4), 8.10 (m,
1H, 3-CH3-NC5H4), 7.70−7.03 (15H, PPh3), 2.52 (s, 3H, 3-CH3-
NC5H4), 2.28 (m, 2H,C2H4), 2.05 (m, 2H, C2H4). 31P{1H} NMR
(121 MHz, CD2Cl2, 300 K): δ 40.3 [d, 1JRhP = 137 Hz, PPh3]. LRMS
(MALDI+/DCTB): m/z 595 [M − (C2H4) − H]+. Isotope envelopes
match those calculated from the known isotopic abundances of the
constituent elements.
NMR (300 MHz, CD2Cl2, 300 K): δ 8.97 (m, 2H, 4-CH3-NC5H4),
7.46 (m, 2H, 4-CH3-NC5H4), 7.36−7.27 (15H, PPh3), 2.65 (s, 3H, 4-
CH3-NC5H4). 31P{1H} NMR (121 MHz, CD2Cl2, 300 K): δ 37.9 (d,
1J
= 132 Hz; PPh3). LRMS (MALDI+/DCTB): m/z 596 [M −
RhP
(CO)]+. Isotope envelopes match those calculated from the known
isotopic abundances of the constituent elements.
Reactions with Carbon Monoxide: Characterization of
Intermediates. Carbon monoxide was bubbled for several minutes
(3−9 min) through a CD2Cl2 solution of the corresponding nido-
hydridorhodathiaborane 2−5 in a 5 mm NMR tube at room
temperature. The sample was subsequently cooled to −50 °C in an
isopropyl alcohol bath and transferred to an NMR spectrometer in
which the temperature of the probe was set to −50 °C. The system
was studied at different temperatures, allowing the identification of the
different intermediates that form before hydrogen loss occurs to yield
the CO ligated closo clusters 16−19 described above. The following
are the NMR data for the reaction mixtures that contain the labile new
species. Spectra can be seen in the main text as well the Supporting
Information of this paper.
[1,1-(PPh3)(η2-C2H4)-3-(4-Me-NC5H4)-closo-1,2-RhSB9H8] (15). The
reaction was carried out with 100 mg (0.116 mmol) of 5, and the
solution was exposed to an ethylene atmosphere for 12 h. Yield: 54
mg, 0.087 mmol, 75%. Anal. Calcd for C26H34B9NPRhS·CH2Cl2: C,
45.76; H, 5.12; N, 1.98; S, 4.52. Found: C, 45.91; H, 4.98; N, 1.69; S,
4.07. IR (ATR, cm−1): ν 2549 vs (BH), 2517 vs (BH), 2482 vs (BH),
2470 vs (BH), 1630 s, 1478 m, 1451 w, 1433 s, 1256 w, 1161 m, 1090
s, 1005 s, 936 m, 743 s, 693 vs, 525 vs, 491 s, 457 m (Rh-C2H4), 424 m
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Reaction of 2 with CO. Nine minutes of CO bubbling. H{11B}
NMR (500 MHz, CD2Cl2, 223 K): δ +9.27 to +7.06 (aromatics,
NC5H5, PPh3), +3.92 (s, BH), +3.41 (s, BH), +1.86 (s, BH), +0.28 (s,
BH), −1.66 (low intensity br s, BH), −2.93 (s, BHB), −4.56 (s, BHB),
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−10.96 (low intensity apparent t, JRhH = 20.4 Hz, RhH), −11.25 (d,
1JRhH = 22.1 Hz, 1H). There are also resonances corresponding to 2,
which is in solution as a minor species. 31P{1H} NMR (202 MHz,
CD2Cl2, 203 K): δ +38.9 (d, 1JRhP = 131 Hz, compound 16), +36.6 (d,
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(Rh-C2H4), 339 w (RhP). H NMR (300 MHz, CD2Cl2, 300 K): δ
9.14 (m, 2H, 4-CH3-NC5H4), 7.53 (m, 2H, 4-CH3-NC5H4), 7.70−7.01
(15H, PPh3), 2.71 (s, 3H, 4-CH3-NC5H4), 2.26 (m, 2H, C2H4), 2.06
(m, 2H, C2H4). 31P{1H} NMR (121 MHz, CD2Cl2, 300 K): δ 40.3 [d,
1JRhP = 137 Hz, PPh3]. LRMS (MALDI+/DCTB): m/z 596 [M −
(C2H4)]+. Isotope envelopes match those calculated from the known
isotopic abundances of the constituent elements.
CO-Ligated closo-Rhodathiaboranes 17−19. The procedure
was the same as that for ethylene, but using a CO-filled balloon.
[1,1-(PPh3)(CO)-3-(2-Me-NC5H4)-closo-1,2-RhSB9H8] (17). The re-
action was carried out with 60 mg (0.070 mmol) of 3 with stirring
under an atmosphere of CO for 2 h. Yield: 37.6 mg, 0.0604 mmol,
87%. Anal. Calcd for C25H30B9NOPRhS·CH2Cl2: C, 44.06; H, 4.55; N,
1.98; S, 4.52. Found: C, 44.09; H, 4.53; N, 1.83; S, 4.27. IR (ATR,
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1JRhP = 125.2 Hz), +35.2 (d, JRhP = 99.4 Hz), +29.5 (d, JRhP = 121.9
Hz), +28.6 (OPPh3), −7.9 (PPh3); the resonances exhibit a
1:2.94:11.30:1.60:0.77:14.04 relative intensity ratio, respectively.
[1H−31P]-HMBC (500 MHz, CD2Cl2, 203 K) {ordered as (δH, δP)
correlation}: (−10.96, +29.5), (−11.35, +35.2); as expected, all the 31P
resonances exhibit correlations with aromatic signals.
Reaction of 3 with CO. Three minutes of CO bubbling. 11B-{1H}
NMR (160 MHz; CD2Cl2, 273 K): δ +12.8 (s, minor species) +8.2 (d,
1JBH = 118 Hz, major species), +5.8 (minor species), +3.6 (d, 1JBH = 72
Hz, major), −2.1 (minor species), −4.4 (minor species), −9.2 (d, 1JBH
= 137 Hz, minor species), −13.5 (major species), −12.5 (minor
O
dx.doi.org/10.1021/om500374g | Organometallics XXXX, XXX, XXX−XXX