Coordination chemistry of aminoborylphosphanes. Crystal structure determinations of (iPr2N)2BP(H)SiPh3*Cr(CO)5 and iPr2N)2BP(H)>2SiMe2*W(CO)4

Article abstract of DOI:10.1016/S0022-328X(98)01181-4

The reactions of the aminoborylphosphanes, (ⁱPr2N)2BP(H)SiPh3 (1), <(ⁱPr2N)2BP(H)>2SiMe2 (2), and <(ⁱPr2N)2BP(H)Si(Me)2>2 (3) with M(CO)5*NMe3 or M(CO)4 (norbornadiene) (M = Cr, Mo, W) gave solid, crystalline adducts, thre

Full text of DOI:10.1016/S0022-328X(98)01181-4

Journal of Organometallic Chemistry 582 (1999) 25–31
Coordination chemistry of aminoborylphosphanes. Crystal structure
determinations of (iPr2N)2BP(H)SiPh3·Cr(CO)5 and
ꢀ
[(iPr2N)2BP(H)]2SiMe2·W(CO)4
Tuqiang Chen a, Jeffery Jackson a, Stephen A. Jasper a, E.N. Duesler a, H. No¨th b,1
Robert T. Paine a,*
,
a Department of Chemistry, Uni6ersity of New Mexico, Albuquerque, NM, USA
b Institut fu¨r Anorganische Chemie, Uni6ersita¨t Mu¨nchen, D-80333 Mu¨nchen, Germany
Received 22 August 1998
Abstract
The reactions of the aminoborylphosphanes, (iPr2N)2BP(H)SiPh3 (1), [(iPr2N)2BP(H)]2SiMe2 (2), and [(iPr2N)2BP(H)Si(Me)2]2
(3) with M(CO)5·NMe3 or M(CO)4 (norbornadiene) (M=Cr, Mo, W) gave solid, crystalline adducts, three of which have been
fully characterized. The molecular structures of (iPr2N)2BP(H)SiPh3·Cr(CO)5 (4) and [(iPr2N)2BP(H)]2SiMe2·W(CO)4 (5%) have
been determined by single crystal X-ray diffraction techniques. Ligand 1 acts as a monodentate s donor ligand while 2
coordinates as a chelating phosphane. © 1999 Elsevier Science S.A. All rights reserved.
Keywords: Aminoborylphosphanes; Metal carbonyls; Coordination complexes
metal carbonyl might act as protecting groups in cage
assembly reactions. In this report we describe the for-
mation of complexes with the phosphane (iPr2N)2-
BP(H)SiPh3 1, and the bis-phosphanes [(iPr2N)2BP-
(H)]2SiMe2 2 and [(iPr2N)2BP(H)Si(Me)2]2 3.
1. Introduction
Relatively few primary and secondary phosphanes or
bis-phosphanes containing inorganic substituents, e.g.
(XnE)PH2, (XnE)2PH, (XnE)(YmE%)PH and (XnE)P(H)-
(EYm)P(H)(XnE) (E=main group element, excluding
carbon; X=alkyl, aryl, halide, alkoxy, amino sub-
stituents) have been reported [1], and examples contain-
ing boryl substituents, until recently, have been
especially rare [2]. During efforts to develop synthetic
routes to new main group element cage molecules con-
taining boron and phosphorus atoms, we have found it
necessary to prepare a collection of new aminobo-
rylphosphanes [2–5]. Subsequently, it became of inter-
est to examine the coordination ability of some of these
compounds toward metal carbonyl fragments since the
2. Experimental
Standard inert atmosphere techniques were employed
in all syntheses and product manipulations. Solvents
were dried, deoxygenated, and distilled prior to use.
Mass spectra were obtained by using a Finnegan GC/
MS or from the Midwest Center for Mass Spectrome-
try, University of Nebraska. IR spectra were obtained
with a Mattson 2020 FTIR and NMR spectra were
recorded from Bruker WP–250 and JEOL GSX–400
spectrometers. All samples were sealed in 5 mm NMR
tubes containing a deuterated lock solvent and refer-
ences were set with external samples: Me4Si (1H, 13C),
ꢀ Dedicated to Professor Alan H. Cowley, in honor of his 65th
birthday.
* Corresponding author.
1 Also corresponding author.
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(98)01181-4

26
T. Chen et al. / Journal of Organometallic Chemistry 582 (1999) 25–31
H3PO4 (31P) and F3B·OEt2 (11B). Elemental analyses
were obtained at the UNM microanalysis facility.
mmol) and (NBD)W(CO)4 (0.28 g, 0.72 mmol) in 30 ml
hexane at 23°C for 1 day. The solvent volume was
reduced, and two crops of orange crystals were ob-
tained by cooling to −20°C: yield 0.194 g, 32%. Com-
plex 5¦ was prepared by combination of 2 (1.22 g, 2.24
mmol) and (NBD)Cr(CO)4 (0.58 g, 2.26 mmol) in 40 ml
of hexane at 23°C for 1 day. The resulting mixture was
reduced in volume and a yellow solid deposited which
was recrystallized from hexane at −20°C: yield 0.56 g,
35%. Compound 6 was obtained from an equimolar
combination of 3 with (NBD)Mo(CO)4 and purified as
described for 4.
2.1. Synthesis of ligands
The ligands 1–3 were prepared and purified in the
same general fashion, and the procedure for 1 is de-
scribed in detail here. The syntheses of 2 and 3 are
described in a paper outlining their utility in cage
building chemistry [5,6]. Equimolar amounts of
(iPr2N)2BP(H)Li·DME (DME=1,2-dimethoxyethane)
(1.16 g, 3.4 mmol) [3] and Ph3SiCl (1.0 g, 3.4 mmol)
were combined in 40 ml of hexane at 0°C and stirred at
0°C (1 h) and then at 23°C (6 h). Insoluble LiCl was
removed by filtration under nitrogen and the solvent
vacuum evaporated from the filtrate. The resulting col-
orless oil formed colorless crystals of 1 upon standing
at 23°C for several days: yield 1.7 g, 100%, m.p. 164–
167°C (dec.). Anal. Found: C, 71.04; H, 8.83; N, 5.57.
C30H44N2BPSi (502.54): C, 71.70; H, 9.21; N, 5.75. MS
(m/e, relative intensity): 211 (100%, B(NiPr2)2). IR spec-
trum (KBr, cm−1): 3054 (m), 2967 (s), 2930 (s), 2872
(s), 2326 (w, PH), 1464 (m), 1425 (s), 1364 (s), 1310 (s),
1221 (s), 1198 (s), 1107 (s), 1071 (s), 1001 (m), 907 (w),
822 (w), 740 (m), 652 (w), 527 (s), 492 (m). 31P-NMR
(C6D6): l −206.5 (1JPH=215 Hz). 11B{1H}-NMR
2.3. Characterization data for complexes
Complex 4. Anal. Found: C, 59.65; H, 6.46; N, 4.17.
C35H44N2BO5PSiCr (694.59): C, 60.52; H, 6.39; N, 4.03.
Mass spectrum (FAB) (m/e, intensity): 693–690 (6%,
M+), 259 (100%). IR spectrum (KBr, cm−1) (carbonyl
region): 2058 (m), 1975 (m), 1935 (s). 31P-NMR (C6D6):
l −170.9 (1JPH=275 Hz). 11B{1H}-NMR (C6D6): l
1
3
35.8. H-NMR (C6D6): l 0.89–1.20 (m, CH3, JHH$6
1
3
Hz, 24H), 2.83 (PH, JPH=276 Hz), 3.43 (CH, JHH
=
3
6.9 Hz, 2H), 3.81 (CH, JHH=6.9 Hz, 2H), 7.14–7.18
(m, Ph), 7.73–7.77 (m, Ph). 13C{1H}-NMR (C6D6): l
24.7, 24.9, 25.5, 26.6 (CH3), 50.23, 51.4, 51.5 (CH),
128.6, 130.7, 133.5 (2JP–C=7.7 Hz), 136.5 (Ph), 218.0
(CO, cis 2JPC=8.3 Hz), 222.4 (CO, trans 2JPC=6.0
Hz). Complex 5. IR spectrum (KBr, cm−1) (carbonyl
region): 2012 (w), 1892 (s), 1865 (s). 31P-NMR (C6D6):
1
3
(C6D6): l 40.1. H-NMR (C6D6): l 1.09 (CH3, JHH
=
1
6.9 Hz, 24H), 2.05 (PH, JPH=220 Hz, 1H), 3.71 (CH,
3JHH=6.9 Hz, 4H), 7.16–7.21 (m; Ph), 7.80–7.85 (m,
Ph). 13C{1H}-NMR (C6D6): l 24.6 (CH3), 49.1 (CH,
3JPC=3.1 Hz), 128.1 (Ph), 129.5 (Ph), 136.4 (Ph), 137.2
1
l −163. H-NMR (C6D6): l 0.20 (Me2Si, 6H), 1.86
2
(Ph, JPC=8.6 Hz). Characterization data for ligands 2
(NCH(CH3)2, 48H), 2.78 (CH, 8H). Complex 5%. 31P-
NMR (C6D6): l −195. Complex 5¦. 31P-NMR (C6D6):
l −136. Complex 6. IR spectrum (KBr, cm−1) (car-
bonyl region only): 2002 (m), 1886 (s), 1851 (s). 31P-
NMR (C6D6): l −190.5. 1H-NMR (C6D6): l 0.39
(SiMe2, 3JPH=3.2 Hz), 0.47 (SiMe2, 3JPH=6.3 Hz),
and 3 are available in the literature [5,6], and selected
NMR data are discussed in Section 3 along with data
for the complexes.
2.2. Formation of complexes
3
3
1.30 (CHCH3, JHH=6.9 Hz), 1.31 (CHCH3, JHH
6.8 Hz), 1.96, 3.04. 13C{1H}-NMR (C6D6): l −5.1
(SiMe2), −2.0 (SiMe2), 24.9 (CH(CH3)2 CP=70.3
=
Equimolar amounts of ligand 1 (1.71 g, 3.4 mmol)
and Cr(CO)5·NMe3 (0.87 g, 3.4 mmol) were combined
in 50 ml of hexane at 23°C and stirred overnight. The
yellow reaction mixture was filtered and the filtrate
concentrated to ca. 20 ml, or until some solid deposited.
The flask was then warmed to 40°C and cooled slowly
overnight. Pale yellow crystals of 4 deposited and were
collected. A second crop could be obtained by further
solution concentration: yield 1.4 g, 60%; m.p. 78–80°C
(dec.). Complex 5 was obtained by combination of 2
(1.22 g, 2.24 mmol) and (NBD)Mo(CO)4 (0.68 g, 2.3
mmol) (NBD=norbornadiene) in 40 ml hexane at
23°C for 1 day. The volatiles were removed, the result-
ing yellow solids redissolved in diethylether, and the
mixture filtered. The filtrate was reduced in volume and
cooled to −20°C, whereupon yellow crystals deposited.
Two crops were obtained: yield, 0.96 g, 57%. Complex
5% was synthesized by combination of 2 (0.40 g, 0.73
J
Hz), 48.6, 50.9 (CH), 212.9 (JCP=55.5 Hz), 216.0,
217.5, 217.7, 218.
2.4. Structure determinations
Suitable crystals of 4 and 5% were obtained from
hexane solutions at −10°C. Crystals were placed in
glass capillaries under nitrogen and sealed. The crystals
were centered on a Siemens R3m/V four-circle diffrac-
tometer and determinations of the crystal class, orienta-
tion matrix and accurate unit cell parameters were
made at 20°C. The crystal parameters and data collec-
tion details are summarized in Table 1. The intensity
˚
data were collected with Mo–Ka (u=0.71073 A)
monochromated radiation, a scintillation counter, and
pulse height analyzer. Intensities for three standard

T. Chen et al. / Journal of Organometallic Chemistry 582 (1999) 25–31
27
Table 2
reflections were monitored every 97 reflections. No
Atomic positional parameters (×104) for complex 4
crystal decay was detected. All calculations were per-
formed on the Siemens P3 structure solution system
using SHELXTL PLUS. Neutral atom scattering factors
and anomalous dispersion terms were used for all non-
hydrogen atoms. A small empirical adsorption correc-
tion based on psi scans was applied in each case. The
structures were solved by direct methods (4) and Patter-
son techniques (5%). Full matrix least-squares methods
were used in the refinements. Tables 2 and 3 contain
listings of the atom positional parameters and bond
distances, and angles are given in Table 4.
x
y
z
Cr
C(1)
O(1)
C(2)
O(2)
C(3)
O(3)
C(4)
O(4)
C(5)
O(5)
P
B
1486(1)
9528(1)
8825(10)
8386(9)
7968(11)
7022(8)
11007(10)
11832(7)
10132(9)
10467(9)
8936(8)
8585(8)
10435(2)
9384(9)
8707(6)
9330(7)
8572
9488(5)
1468(6)
1459(5)
1852(5)
2074(4)
1108(5)
878(4)
2395(5)
2937(4)
584(5)
10054(4)
8228(6)
8073(6)
8991(5)
9299(4)
8745(5)
8883(4)
8388(5)
8287(4)
7330(1)
6495(4)
6121(4)
6346(4)
5809(4)
6055(6)
4983(5)
6108(5)
5372(6)
6672(6)
6859(5)
6547(6)
7243(7)
5646(5)
5743(7)
5098(5)
7110(1)
8120(5)
8561(6)
8628(6)
8223(5)
7772(5)
7708(4)
5913(5)
5179(6)
4663(6)
4862(5)
5580(4)
6129(4)
6874(6)
7101(8)
7803(9)
8288(7)
8067(5)
7353(5)
41(3)
1431(1)
1777(5)
1242(3)
2485(3)
649(4)
−66(5)
683(5)
1278(6)
1181(7)
827(7)
3004(5)
3469(6)
3433(5)
2712(6)
3124(8)
3009(7)
1448(1)
895(5)
3. Results and discussion
N(1)
N(2)
C(6)
C(7)
C(8)
The equimolar combination of (iPr2N)2BP(H)-
Li·DME and Ph3SiCl in hexane gives the borylsi-
lylphosphane 1 as described in Eq. 1. Ligand 1 is
obtained in quantitative yield as a colorless oil that
slowly crystallizes upon standing at 23°C. Subsequent
equimolar combination of this ligand with
Cr(CO)5·NMe3 in hexane gives a yellow solution (Eq.
2) from which pale yellow crystals deposit.
9405(9)
8980(11)
9511(10)
7304(9)
C(9)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
Si
C(18)
C(19)
C(20)
C(21)
C(22)
C(23)
C(24)
C(25)
C(26)
C(27)
C(28)
C(29)
C(30)
C(31)
C(32)
C(33)
C(34)
C(35)
6701(10)
6672(10)
9849(11)
10861(11)
8850(11)
8720(11)
7518(16)
9614(15)
12563(2)
14325(8)
14852(8)
14302(9)
13324(10)
12722(10)
13252(8)
13117(8)
13199(10)
12942(11)
12603(10)
12493(10)
12763(7)
14066(9)
14704(11)
14610(12)
13898(11)
13255(10)
13340(8)
Table 1
Summary of X-ray diffraction data for complexes 4 and 5%
4
5%
392(5)
Formula
C35H44N2BO5PSiC C30H64N4B2O4P2S
−233(4)
−385(4)
105(4)
r
iW
Color
Colorless
Pale yellow
Crystal dimensions (mm)
Crystal system
Space group
0.18×0.21×0.46 0.56×0.46×0.20
763(4)
567(5)
396(6)
874(8)
Orthorhombic
Pna21
19.323(2)
10.572(1)
18.425(1)
90
Monoclinic
P21/c
13.533(2)
17.620(2)
17.908(2)
90
˚
a (A)
˚
b (A)
˚
1543(7)
1693(5)
1228(4)
2671(5)
3260(5)
3475(6)
3116(6)
2528(4)
2292(4)
c (A)
h (°)
i (°)
k (°)
90
90
96.91(1)
90
3
˚
V (A )
3763.7(6)
4
4239.2(9)
4
Z
Formula weight
694.6
1.226
840.35
1.317
Dcalc. (g cm−3
)
Absorption coefficient
(mm−1
F(000)
0.419
2.862
)
1464
1728
Temperature (K)
2q limit (°)
293
2–50
293
4–45
Indices
Scan type
9h, 9k, 9l
ꢀ
−h, 9k, 9l
ꢀ
Max/min transmission
No. collected reflections
No. observed reflections
0.950/0.887
6855
3278
(F\1.5|(F))
417
4.88
1.000/0.528
11320
3275
(F\4|(F))
388
(1)
(2)
Parameters refined
R (%)a
3.45
6.14
Rw (%)b
5.20
a R1=ꢀ(ꢁFoꢁ−ꢁFcꢁ)/ꢀꢁFoꢁ.
b Rw=[ꢀw(ꢁFoꢁ−ꢁFcꢁ)2/ꢀwFo
] .
1/2
2

28
T. Chen et al. / Journal of Organometallic Chemistry 582 (1999) 25–31
Both ligand 1 and the complex, [(iPr2N)2BP(H)-
Table 4
Selected bond distances and angles for complexes 4 and 5%
SiPh3]·Cr(CO)5 4, have been fully characterized. Ligand
1 does not display a parent ion in an electron impact
mass spectrum under the conditions employed; how-
ever, the parent ion is seen in a FAB MS. The IR
spectrum for 1 shows a weak wPH stretching frequency
at 2326 cm−1. In the complex this weak band disap-
4
5%
˚
Bond distances (A)
Cr–C(1)
1.85(1)
1.90(1)
1.89(1)
1.895(9)
1.884(9)
2.483(2)
W–C(1)
W–C(2)
W–C(3)
W–C(4)
2.02(1)
2.007(9)
1.90(1)
1.972(9)
Cr–C(2)
Cr–C(3)
Cr–C(4)
Cr–C(5)
Table 3
Atomic positional parameters (×104) for complex 5%
Cr–P
W–P(1)
W–P(2)
P(1)–B(1)
P(2)–B(2)
P(1)–Si
2.582(2)
2.578(2)
1.990(8)
2.016(8)
2.264(3)
2.262(3)
1.392(9)
1.45(1)
P–B
P–Si
2.013(9)
2.286(3)
x
y
z
W
P(1)
P(2)
3161(1)
1440(1)
3235(1)
2039(2)
4037(5)
2473(6)
5313(5)
2755(6)
282(7)
4386(6)
373(4)
−622(5)
5162(4)
4318(4)
3699(6)
2712(7)
4468(8)
2900(7)
2519(6)
1172(5)
−553(6)
−468(7)
−969(7)
1333(6)
1200(13)
1466(13)
1887(13)
1761(13)
1092(6)
−1123(7)
−2153(6)
−716(8)
−176(9)
−384(10)
5163(6)
5958(12)
5963(14)
5255(13)
4926(16)
6020(7)
8898(1)
8887(1)
7833(1)
8363(1)
2336(1)
2821(1)
3328(1)
3939(1)
3520(3)
1105(4)
1957(4)
1124(4)
2712(5)
3811(5)
3033(3)
2275(4)
4241(3)
3647(3)
3108(5)
1542(5)
2083(5)
1571(5)
4671(4)
4340(4)
3025(5)
2726(6)
3798(5)
3393(5)
4307(10)
4033(11)
3116(10)
2666(10)
2560(6)
3398(6)
2191(6)
1452(6)
1049(5)
1198(6)
4402(5)
3872(9)
4333(10)
5112(10)
5323(12)
4566(6)
4577(11)
4000(12)
5541(11)
5230(13)
2925(5)
2342(6)
2606(6)
3994(5)
4584(11)
4862(10)
4054(8)
P(2)–Si
B–N(1)
B–N(2)
1.43(1)
1.40(1)
B(1)–N(1)
B(1)–N(2)
B(2)–N(3)
B(2)–N(4)
Si
1.386(9)
1.451(9)
O(1)
O(2)
O(3)
O(4)
B(1)
B(2)
N(1)
N(2)
N(3)
N(4)
C(1)
C(2)
C(3)
C(4)
C(5)
10138(3)
7663(4)
8655(4)
10179(4)
9592(5)
7208(5)
10311(3)
9323(3)
7575(3)
6402(3)
9679(5)
8126(5)
8752(5)
9702(5)
9055(4)
7689(4)
10794(5)
11562(4)
10785(5)
10604(4)
10821(10)
11032(12)
11150(12)
11105(10)
8626(5)
8709(5)
8478(6)
9357(6)
8768(6)
10130(7)
8394(4)
8818(10)
8845(12)
8723(10)
8412(12)
7093(5)
7324(9)
7235(11)
7028(10)
6992(12)
6121(5)
6012(6)
6614(6)
5947(4)
6169(12)
6283(10)
5120(6)
Bond angles (°)
C(1)–Cr–P
176.3(4)
C(4)–W–P(2)
C(3)–W–P(1)
P(1)–W–P(2)
W–P(1)–B(1)
W–P(2)–B(2)
W–P(1)–Si
W–P(2)–Si
B(1)–P(1)–Si
B(2)–P(2)–Si
172.0(3)
170.0(3)
74.03(6)
133.9(3)
131.1(2)
93.37(8)
93.53(8)
122.4(3)
125.4(2)
Cr–P–B
Cr–P–Si
B–P–Si
118.5(3)
122.9(1)
113.7(3)
pears and a new band for the coordinated PH group is
not confidently identified. The IR spectrum does show
the expected three-band pattern in the wCO region with
C(6)
C(7)
C(8)
C(9)
absorptions centered at 2058, 1975 and 1935 cm−1
.
C(10)
C(11)
C(11%)
C(12)
C(12%)
C(13)
C(14)
C(15)
C(16)
C(17)
C(18)
C(19)
C(20)
C(20%)
C(21)
C(21%)
C(22)
C(23)
C(23%)
C(24)
C(24%)
C(25)
C(26)
C(27)
C(28)
C(29)
C(29%)
C(30)
The NMR spectra for 1 and 4 provide additional
definitive characterization data. The 31P{1H} spectra
for 1 and 4 each show a single resonance: 1, l −206.5;
4, l −170.9. The downfield shift upon coordination is
consistent with removal of electron density from the P
1
atom donor center. The values of JPH, 1, 215 Hz; 4,
275 Hz, also suggest some degree of phosphorus atom
rehybridization. The increase in JPH with coordination
suggests that more s character is directed to the P–H
bond in the complex, which in turn requires that the
P–Cr bond has more p orbital character. Similar trends
have been observed with coordination complexes of
diborylphosphanes [3,4] and some organophosphanes
1
[7]. The H-NMR spectra for 1 and 4 show a single
6972(14)
6965(16)
5865(15)
6447(17)
4580(6)
3733(8)
5336(8)
3618(8)
resonance assigned to the P–H group, each of which is
split into a doublet by one-bond P–H coupling. The
resonance in 1, l 2.05, is slightly upfield of that in the
complex 4, l 2.83. The H- and 13C{1H}-NMR spectra
1
i
show only one Pr CH3 and CH environment in the free
ligand, consistent with free B–N and/or C–N bond
rotation. The complex, on the other hand, displays at
least two distinguishable environments, suggesting that
bond rotation is now hindered. The 13C{1H}-NMR
3204(14)
3619(15)
3892(11)

T. Chen et al. / Journal of Organometallic Chemistry 582 (1999) 25–31
29
spectrum of 4 in the carbonyl region shows two reso-
nances, l 218.0 and 224.4, which are assigned to cis and
trans COs. Both display two-bond P–C coupling,
2JPC=8.3 and 6.0 Hz, respectively.
The structure of 4 was confirmed by single crystal
X-ray diffraction analysis. A view of the molecule is
shown in Fig. 1, and selected bond lengths and angles
appear in Table 4. The Cr atom has a distorted pseudo-
octahedral geometry while the P atom geometry more
closely approximates a trigonal pyramid rather than a
tetrahedron. This is evidenced by the fact that the three
heavy-atoms in the substituents, Cr(CO)5, Ph3Si and
B(NiPr2)2, are nearly coplanar with the central P atom,
as indicated by the sum of bond angles about the P
Fig. 2. Molecular sturcture and atom labeling scheme for
[(iPr2N)2BP(H)]2SiMe2·W(CO)4 5% (30% thermal ellipsoids).
˚
atom: 355.1°. The Cr–P bond distance, 2.483(2) A, is
similar to the value in P2(iPr2NB)2(tmpB)·Cr(CO)5,
˚
BP(H)]2SiMe2·Mo(CO)4 5, [(iPr2N)2BP(H)]2SiMe2·W-
(CO)4 5%, and [(iPr2N)2BP(H)]2SiMe2·Cr(CO)4 5¦ as
summarized in Eq. (3).
2.486(4) A [8], (tmp=2,2,6,6-tetramethylpiperidino)
but it is longer than the distances in Ph3P·Cr(CO)5,
˚
˚
2.422(1) A [9] and (tmpBPH)2·Cr(CO)5, 2.458(2) A [10].
Based upon these data and the IR CO frequencies, it
can be concluded that 1 is a modest s donor and a
poor p acceptor. This is further reflected by the short-
˚
ening of the trans Cr–C(O) bond distance, 1.85(11) A,
relative to the average cis Cr–C(O) bond distance,
˚
1.89(1) A. Within the ligand fragment, the B–P bond
˚
˚
length, 2.012(9) A, and the Si–P distance, 2.286(3) A,
are in the normal ranges for single bonds [11].
(3)
The syntheses for the ligands 2 and 3 follow similar
procedures to that described for 1, and full details can
be found in descriptions of other aspects of their chem-
istry [5,6]. Each ligand was allowed to react with
equimolar amounts of M(CO)4 (norbornadiene), M=
Cr, Mo, W, in an effort to obtain M(CO)4(PP) com-
plexes. In particular, ligand 2 combines in a 1:1 ratio
with (CO)4Cr(NBD), (CO)4Mo(NBD) or (CO)4W-
(NBD), forming pale yellow complexes [(iPr2N)2-
Only the MꢀMo species was obtained with reasonable
purity; however, the crystal quality was poor. Some
single crystals of the MꢀW species were obtained and
the X-ray crystal structure of this compound was deter-
mined. As seen in Fig. 2, the ligand bonds to the
W(CO)4 unit in a bidentate manner. The four-mem-
bered WPSiP chelate ring is slightly folded along the
W···Si vector and the BN2 planes are twisted so that
they are roughly perpendicular to the chelate ring. The
borylamine groups, (iPr2N)2B, are cis to each other
across the ring. The W–P bond lengths, W–P(1)
˚
2.582(2) and W–P(2) 2.578(2) A, are identical and
typical of W–P bond lengths in complexes containing
chelating diphosphanes. The average W–(CO) bond
˚
length, 1.97(1) A, is also typical of distances in W(CO)4
(LL) complexes. Similar to 4, the geometry at the
phosphorus atoms generated by the heavy atom groups
W(CO)4, SiMe2 and B(NiPr2)2 are relatively flat as
indicated by the sums of angles: P(1) 349.7 and P(2)
˚
350.0°. The average P–Si bond length, 2.263(3) A, is
typical of single bond distances in a variety of bo-
rylphosphanes [2–4]. Finally, the B–N bond lengths
fall into two groups as found in many diaminoborane
˚
fragments: 1.389(9) and 1.450(9) A. The shorter dis-
tances, B(1)–N(1) and B(2)–N(3) are positioned below
the WPSiP ring and the two longer distances, B(1)–
N(2) and B(2)–N(4) are above the ring.
Fig. 1. Molecular structure and atom labeling scheme for
(iPr2N)2BP(H)SiPH3·Cr(CO)5, 4 (30% thermal ellipsoids).

30
T. Chen et al. / Journal of Organometallic Chemistry 582 (1999) 25–31
The 31P{1H}-NMR spectrum of ligand 2 consists of
a single resonance centered at l −186.1. The proton-
coupled spectrum displays first-order doublet,
ordination of the ligand with the inequivalence gener-
ated by the presence of meso and rac isomers of the
chelated phosphane. The 13C{1H}-NMR data are also
consistent with this conclusion, and together they
support the bidentate structure proposed in Eq. 4.
Attempts to obtain a data set for the X-ray structure
determination of 6 have been frustrated thus far by
an inability to obtain adequate single crystals.
a
1JPH=213 Hz. The 31P{1H}-NMR spectra for 5, 5%
and 5¦ contain major singlet resonances centered at l
−136, −163 and −195, respectively. In addition,
each spectrum contains several weak signals that may
belong to impurities, or perhaps diastereomers. The
coordination shifts (l complex—l (free ligand)) are:
+50, +23 and −9 ppm, respectively. These shifts
are comparable to those reported for a series of
di(tertiaryphosphine) M(CO)4 complexes that also
contain four-membered chelate rings [12,13]. The pro-
ton-coupled 31P-NMR spectra of the complexes show
interesting variations. The W complex 5% displays a
doublet pattern with 1JPH=287 Hz, while the Cr
complex 5¦ shows a ‘pseudo triplet’ pattern with peak
spacings of ca. 280 Hz. The Mo complex produces a
complex second order pattern that is not fully repro-
duced in all detail with an AA%XX% spin system simu-
4. Conclusion
The borylphosphane ligands 1–3 provide a new
class of s donor phosphanes that are shown to
form monodentate and bidentate complexes on
M(CO)5 and M(CO)4 fragments. The coordination
chemistry provides a means to protect fragile primary
and secondary borylphosphane ligands that are useful
in ring and cage construction chemistry. That utility
will be expanded upon in future reports from our
group.
lation.
A
complete interpretation of the P–H
coupling details and the differences between the com-
plexes will require further study of these complexes,
as well as related new derivatives.
Ligand 3 produces a pale yellow crystalline solid 6
when combined with Mo(CO)4(NBD), as shown in
Eq. 4. The complex displays three carbonyl stretching
frequencies at 2002, 1886, and 1851 cm−1. The fourth
band expected for a cis-M(CO)4L2 complex is not
resolved. The NMR spectra for 6 is diagnostic of its
structure. The 31P{1H}-NMR spectrum displays a sin-
5. Supplementary material available
Crystallographic data for the structural analyses have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC No. 108008 for Compound 4 and
108009 for Compound 5%. Copies of this information
may be obtained free of charge from the Director,
CCDC, 12 Union Road, Cambridge, CB2 1EZ UK
(Fax: +44-1223-336-033; e-mail: deposite@ccdc.com.
ac.uk or www: http://www.ccdc.com.ac.uk).
gle resonance centered at l −190.5, and restoration
1
of proton coupling reveals a doublet pattern, JPH
=
278 Hz.
Acknowledgements
Financial support for this work was provided by
the National Science Foundation, Grant CHE-
8503550.
(4)
This resonance is downfield of the resonance for the
1
free ligand, 3, l −212.3, JPH=213 Hz, and the in-
References
1
creased JPH value in 6 is consistent with increased s
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1
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T. Chen et al. / Journal of Organometallic Chemistry 582 (1999) 25–31
31
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