Main Group Pyrazolates - the X-Ray Structures of [Al(η2-But2pz)3], [SnMe3(η1-Ph2pz)] and [GePh3(η1-But2pz)] (R2pz = 3,5-Disubstituted Pyrazolate)

Article abstract of DOI:10.1071/CH99068

From metathesis reactions between AlCl3, SnMe3Cl, or GePh3Br and the appropriate potassium 3,5-disubstituted pyrazolate [K(R2pz)] the complexes [Al(Bu^t2pz)3], [SnMe3(Ph2pz)], [SnMe3(Bu^t2pz)], and [GePh3(Bu^t2pz)] have been obtained. The X-ray structure of [Al(Bu^t2pz)3] shows the complex to be monomeric with η²-pyrazolate groups, in a quasi-trigonal prismatic array: the first monomeric homoleptic tris(pyrazolato) complex of any element. X-Ray structures of [SnMe3(Ph2pz)] and [GePh3(Bu^t2pz)] reveal mononuclear species with distorted tetrahedral stereochemistries and η¹-pyrazolate groups. Comparisons of spectroscopic data between [SnMe3(Ph2pz)] and [SnMe3(Bu^t2pz)] suggest the latter is also four-coordinate with an η¹-Bu^t2pz ligand.

Full text of DOI:10.1071/CH99068

C S I R O P U B L I S H I N G
Australian Journal
of Chemistry
Volume 52, 1999
© CSIRO Australia 1999
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Aust. J. Chem., 1999, 52, 733–739
.
Main Group Pyrazolates—the X-Ray Structures
2
1
of [Al( -But pz)3], [SnMe3( -Ph2pz)] and
2
[GePh3( -But pz)] (R2pz = 3,5-Disubstituted
1
2
Pyrazolate)†
Glen B. Deacon,A Ewan E. Delbridge,A Craig M. Forsyth,A
Peter C. Junk,B Brian W. Skelton C and Allan H. White C
A
Department of Chemistry, Monash University, Clayton, Vic. 3168.
Department of Chemistry, James Cook University, Townsville, Qld. 4811.
Department of Chemistry, The University of Western Australia, Nedlands, W.A. 6907.
B
C
From metathesis reactions between AlCl3, SnMe3Cl, or GePh3Br and the appropriate potassium
3,5-disubstituted pyrazolate [K(R2pz)] the complexes [Al(But pz)3], [SnMe3(Ph2pz)], [SnMe3(But pz)],
2
2
and [GePh3(But pz)] have been obtained. The X-ray structure of [Al(But pz)3] shows the complex to be
2
2
monomeric with 2-pyrazolate groups, in a quasi-trigonal prismatic array: the rst monomeric homoleptic
tris(pyrazolato) complex of any element. X-Ray structures of [SnMe3(Ph2pz)] and [GePh3(But pz)]
2
reveal mononuclear species with distorted tetrahedral stereochemistries and 1-pyrazolate groups.
Comparisons of spectroscopic data between [SnMe3(Ph2pz)] and [SnMe3(But pz)] suggest the latter is
2
also four-coordinate with an 1-But pz ligand.
2
Introduction
Prior to 1997, the crystallographically established
[GePh3(But pz)] together with the X-ray struc-
2
tures of the aluminium complex, [SnMe3(Ph2pz)],
and the germanium complex. Interest in the alu-
minium complex arose from an inability to pre-
5
modes for coordination1
of pyrazolate ions were (i)
1
1
2
-
:
1, (ii)
and (iii)
(chelating). The rst
pare monomeric homoleptic Ln( 2-R2pz)3 complexes
2
is commonly observed for d-block metals but known
for f-block, the second is best known for precious
metals, though the ubiquitous pyrazolylborates can
be regarded as such, and the third was restricted
to f-block elements for some 16 years following its
somewhat fortuitous discovery.6 Since 1997, the sit-
uation has been dramatically transformed with the
which invariably crystallize with coligands, e.g. [Ln(
-
But pz)3(thf)2] 15 and [Ln( 2-Ph2pz)3(thf)3],16 owing
2
to the large size of Ln3+
.
The small Al3+
ion was considered to o er better prospects for
the formation of a neutral monomeric homolep-
tic tris( 2-pyrazolato) metal complex.
The sole
crystallographically characterized aluminium pyrazol-
17
(initially surprising) observation of 2-coordination
ate hitherto recorded is [AlMe2( -pz)]2
which
1-pyrazolate ligands. Several structures
have been proposed for triorganotin(IV) pyrazol-
10
1
for both d-block and main group elements,7
and
has
-
:
2
the rst homoleptic pyrazolate complexes (viz. Ti(
-
7
8
1
Me2pz)4 and Ta( 2-Me2pz)3( 1-Me2pz)2 (Me2pz =
ates, e.g. polymeric with
-
:
1-bridging18 and
:
1-ligands,19 but X-ray valida-
1
3,5-dimethylpyrazolate)). Furthermore, ve new modes
dimeric with
-
14
of pyrazolate coordination have been observed.9,11
tion is lacking. However, 1-(N)-coordination has
been crystallographically established in a complex with
the rather more esoteric ligand 3-dimethylarsino-4,5-
di(methoxycarbonyl)pyrazolate.20 A few organogerma-
nium pyrazolates are known (e.g. [GeMe3(Me2pz)]),21
2
2
Thus
-
:
coordination11 with the pyrazolate group
normal to the metal
1
1
5
1
2
1
allel with
-
-
:
bonding,1
(to K+),9
1
3
(to Ag+),12
-
sive 5-pyrazolate (i.e. 5-1,2-diazacyclopentadienyl)
but none with the bulky But pz ligand, and no
2
coordination (to Ru2+
)
structure has been determined. Thus the derivative
This burgeoning development has led us to extend
our interests from lanthanoid pyrazolates to the struc-
[GePh3(But pz)] was chosen to provide an organoger-
2
manium pyrazolate that could be crystallized for
X-ray examination. Recently, a remarkable cationic
tural chemistry of main group pyrazolates.
We
2
now report the preparations of [Al(But pz)3] (But pz
germanium(II) trichlorogermate(II) complex [GeII2( -
2
1
= 3,5-di-t-butylpyrazolate), [SnMe3(R2pz)] (R2pz =
3,5-disubstitued pyrazolate, R = But or Ph) and
:
1-Me2pz)3] [GeIICl3] has been prepared and its
structure obtained.22
† Dedicated to Professor M. N. Bochkarev on the occasion of his 60th birthday.
Manuscript received 7 June 1999 ᭧ CSIRO 1999
0004-9425/99/080733$ 05.00
10.1071/CH98068

734
G. B. Deacon et al.
Results and Discussion
in the less condensed vapour state at an elevated
temperature. Moreover, the dinuclear ions have only
one Ph2pz group, suggesting they result from a process
which eliminates a Ph2pz ligand. A thermally induced
cyclometallation (3) provides a possible explanation:
Preparations and Properties
Air- and moisture-sensitive tris(3,5-di-t-butylpyr-
azolato)aluminium (1), 3,5-diphenylpyrazolatotri-
methyltin (2), 3,5-di-t-butylpyrazolatotrimethyltin (3),
and 3,5-di-t-butylpyrazolatotriphenylgermanium (4)
were obtained by metathesis reactions (1) and (2):
The 1H n.m.r. spectrum of (4) shows two But
resonances, consistent with the inequivalent But pz
Microanalysis of aluminium 3,5-di-t-butylpyrazolate (1)
indicated that the complex was obtained unsolvated
from tetrahydrofuran, by contrast with the isolation of
2
substituents of the 1-bonded monomer established
crystallographically (below). On warming, the peaks
coalesce and then sharpen to give, at 328 K, a
But resonance of similar form to that exhibited by
solvent-complexed [Ln(But pz)3(thf)2] 15 for the larger
2
lanthanoid ions. The highest peak in the mass spec-
trum was assignable to the monomeric [Al(But pz)3]+
[SnMe3(But pz)] at room temperature. Plausibly an
2
2
ion. The absence of any (NH) infrared absorption
was consistent with pyrazolate formation and elimi-
nated the possibility of an [Al(But pz)3(But pzH)n]
exchange process rendering the nitrogens equivalent is
inhibited for (4) by the smaller size of germanium than
tin and by the bulkier substituents (Ph > Me) on germa-
nium. An intermolecular exchange process involving
2
2
complex. The 27Al n.m.r. chemical shift ( 0 0),
coincidentally corresponding to that of the standard
(Al(H2O)63+), lies in the normal range (from 46 to 40
ppm) for octahedral aluminium(III) complexes.23 This
is consistent with the observed formal six-coordination
determined by X-ray crystallography (below), though
the stereochemistry is far from the octahedral norm.
The organotin pyrazolates [SnMe3(R2pz)] (R = Ph
or But) (2) and (3) each show features attibutable24
1
1
-
:
coordination and displacement of But pz
2
(Scheme 1) seems more likely to be adversely a ected
by steric factors than an intramolecular exchange
via an 2-bonded species, or unimolecular ionization
(which could even be aided by increased crowding in
[MR3(But pz)]).
2
1
to as(Sn–C) and s(Sn–C) at c. 540 and 515 cm
respectively in both their infrared and Raman spec-
tra. In agreement with this assignment, the former
absorption was more intense in the infrared and the
latter in the Raman spectrum. This rules out a
polymeric structure with planar SnMe3 units bridged
1
by
-
:
1-pyrazolate groups, but is consistent with a
X-Ray Crystal Structures
four-coordinate monomer with unidentate R2pz groups
and tetrahedral SnC3N stereochemistry as observed
for solid [SnMe3(Ph2pz)] from the following X-ray
study. In addition, the magnitude of the 2J(Sn–Me)
coupling constants are as expected25,26 for tetrahe-
dral [SnMe3X] complexes, whilst 119Sn n.m.r. chemical
shifts are in the range for monomeric [SnMe3NR2]
compounds.23,25 The tin complexes and the germanium
compound (4) show monomer parent ions in their elec-
tron impact mass spectra, but, surprisingly in view of
the monomeric solid-state structure, [SnMe3(Ph2pz)]
also gives [Sn2Me5(Ph2pz) H]+ and [Sn2Me3(Ph2pz)
H]+ ions which have signi cant intensity. It is unlikely
Atomic coordinates for the structures of (1), (2)
and (4) are given in Table 1, whilst the structures are
displayed in Figs 1–3 with selected bond lengths in
Tables 2–4.
(i) [Al(But pz)3] (1)
2
Tris(3,5-di-t-butylpyrazolato)aluminium(III) (1) has
a monomeric structure with three chelating pyrazolate
ligands and formal six-coordination for aluminium. The
combination of the small ionic radius of the metal27 and
the bulkiest 3,5-disubstituted pyrazolate available to us
has enabled the isolation of the rst neutral homoleptic
tris(pyrazolato) complex of any element. It is thus
consistent with the isolation of homoleptic tetrakis(
that [SnMe3(Ph2pz)] monomers from the solid state
2
1
:
1-Ph2pz groups
-
would give species linked by
-

Main Group Pyrazolates
735
pyrazolato) complexes of the larger Ti4+ 7,28
,
and con-
inclusive of one complete/independent ligand about
the aluminium, constitutes the asymetric unit of the
structure. The two Al–N distances do not di er
non-trivially (also true of N(1)–Al–N(10) and N(2)–Al–
N(20)) so that the molecular symmetry, particularly
that local to the aluminium, is a good approximation
to 62m or D3h. The arrangement of the six nitrogen
atoms lies much nearer the trigonal prismatic rather
than the octahedral extreme, consistent with the small
ligand ‘bite’.30 The two parallel triangular faces of the
trigonal prism exhibit a torsional deformation so that
the N(1)–N(2) bond (corresponding to a longitudinal
edge) makes an angle of 10 1(5) to the normal of the
triangular faces. The centres of the N–N bonds are
coplanar with aluminium with a (necessarily) regular
triangular arrangement about the metal which lies
0 058(4) A out of the C3N2 ligand plane.
trasts formation of [Ln( 2-R2pz)3L2] complexes by the
much larger lanthanoid ions.15,16 The sole structurally
characterized homoleptic tris(pyrazolato)lanthanoid(III)
complex attains a higher coordination number by dimer-
2
ization, viz. [Nd( 2-But pz)2( -
:
2-But pz)]2.29 The
2
2
molecule lies disposed with the aluminium on a site of
crystallographic 3 symmetry; one-third of the molecule,
Table 1. Non-hydrogen positional and equivalent isotropic
displacement parameters for [Al( 2-But2pz)3] (1),
[SnMe3(Ph2pz)] (2) and [GePh3(But2pz)] (4)
Complex Atom
x
y
z
Ueq (A2)
(1)
Al
2/3
1/3
0 8800(1) 0 0134(3)
0 9463(2) 0 017(1)
0 8135(2) 0 016(1)
0 9853(2) 0 015(1)
0 8793(2) 0 019(2)
0 7734(2) 0 016(2)
1 1251(2) 0 019(2)
1 1975(3) 0 028(3)
1 1847(3) 0 029(3)
1 1329(3) 0 032(3)
0 6340(2) 0 019(2)
0 5583(3) 0 025(3)
0 5797(3) 0 032(3)
0 6219(3) 0 036(3)
N(1)
N(2)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
C(9)
0 5381(2)
0 5306(2)
0 4468(2)
0 3790(2)
0 4352(2)
0 4274(2)
0 5332(3)
0 3561(3)
0 3727(3)
0 4023(2)
0 4784(3)
0 2175(2)
0 2294(2)
0 1328(2)
0 0895(2)
0 1522(2)
0 0985(2)
0 1473(3)
0 1372(3)
0 0233(3)
0 1391(2)
0 2390(3)
0 0431(3)
0 1159(4)
C(10) 0 4078(3)
C(11) 0 2881(3)
(2)
Sn
0 63116(5)
0 5358(5)
0 5906(5)
0 4226(6)
0 4062(6)
0 5134(6)
0 53869(3)
0 6445(3)
0 6762(4)
0 6884(4)
0 7476(5)
0 7391(4)
0 6695(5)
0 6632(6)
0 6477(7)
0 6412(7)
0 6485(6)
0 6638(5)
0 7875(4)
0 7664(5)
0 8141(6)
0 8821(6)
0 9041(5)
0 8577(5)
0 4871(6)
0 5985(5)
0 4528(5)
0 59825(2) 0 0497(3)
0 5577(2) 0 045(3)
0 5076(2) 0 045(3)
0 5684(3) 0 044(4)
0 5230(3) 0 045(4)
0 4865(3) 0 039(4)
0 6204(3) 0 051(4)
0 6769(3) 0 069(6)
0 7251(4) 0 100(8)
0 7162(5) 0 107(8)
0 6593(4) 0 088(7)
0 6121(3) 0 059(5)
0 4335(3) 0 045(4)
0 3986(3) 0 063(5)
0 3477(3) 0 077(6)
0 3289(3) 0 083(6)
0 3616(3) 0 072(5)
0 4136(3) 0 059(5)
0 5282(4) 0 081(6)
0 6670(4) 0 079(6)
0 6304(5) 0 083(6)
N(1)
N(2)
C(1)
C(2)
C(3)
C(11) 0 3406(6)
C(12) 0 3897(7)
C(13) 0 308(1)
C(14) 0 178(1)
C(15) 0 1275(8)
C(16) 0 2083(7)
C(31) 0 5446(6)
C(32) 0 6524(7)
C(33) 0 6783(8)
C(34) 0 6015(9)
C(35) 0 4993(9)
C(36) 0 4688(7)
C(111) 0 7363(9)
C(121) 0 7397(9)
C(131) 0 4874(9)
(4)
Ge
0 77475(4)
0 7103(4)
0 8280(4)
0 5945(5)
0 6372(4)
0 7819(5)
0 4463(5)
0 4919(5)
0 3181(6)
0 3740(6)
0 8756(5)
1 0262(8)
0 19346(3)
0 3651(3)
0 4306(3)
0 4445(3)
0 5627(3)
0 5508(3)
0 4077(4)
0 3169(5)
0 3495(5)
0 5267(5)
0 6507(4)
0 5969(5)
0 7088(4)
0 7538(5)
0 1587(3)
0 0615(4)
0 0340(4)
0 1036(4)
0 1989(4)
0 2270(4)
0 0756(3)
0 0160(4)
0 1109(4)
0 1153(4)
0 0237(4)
0 0710(4)
0 1744(3)
0 2608(4)
0 2436(4)
0 1384(4)
0 0547(4)
0 0716(4)
0 12669(1) 0 0195(2)
0 1274(1) 0 021(1)
0 1035(1) 0 022(1)
0 1446(1) 0 022(2)
0 1300(1) 0 023(2)
0 1049(1) 0 023(2)
0 1727(1) 0 027(2)
0 2117(1) 0 034(2)
0 1412(2) 0 036(2)
0 1951(2) 0 040(3)
0 0797(1) 0 027(2)
0 0470(2) 0 052(3)
0 0428(2) 0 046(3)
0 1138(2) 0 040(3)
0 0699(1) 0 022(2)
0 0411(1) 0 029(2)
0 0008(1) 0 036(2)
0 0107(1) 0 036(2)
0 0185(1) 0 035(2)
0 0584(1) 0 029(2)
0 1286(1) 0 023(2)
0 1629(1) 0 026(2)
0 1611(1) 0 030(2)
0 1250(2) 0 035(2)
0 0908(1) 0 034(2)
0 0923(1) 0 028(2)
0 1797(1) 0 022(2)
0 2153(1) 0 029(2)
0 2532(1) 0 035(2)
0 2550(1) 0 034(2)
0 2190(1) 0 033(2)
0 1814(1) 0 028(2)
N(1)
N(2)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
C(9)
C(10) 0 7655(7)
C(11) 0 9237(7)
C(111) 0 8930(5)
C(112) 0 8458(6)
C(113) 0 9325(6)
C(114) 1 0677(6)
C(115) 1 1186(6)
C(116) 1 0323(5)
C(121) 0 5941(4)
C(122) 0 5888(5)
C(123) 0 4736(5)
C(124) 0 3632(5)
C(125) 0 3652(5)
C(126) 0 4815(5)
C(131) 0 9185(4)
C(132) 0 9243(5)
C(133) 1 0263(6)
C(134) 1 1247(5)
C(135) 1 1250(6)
C(136) 1 0224(5)
Fig. 1. Molecular projection of [Al(But2pz)3] (1): (a) down;
(b) normal to the (quasi-)3 molecular axis showing 50% thermal
ellipsoids for the non-hydrogen atoms, with hydrogen atoms
having arbitrary radii of 0 1 A.

736
G. B. Deacon et al.
The Al–N distances (Table 2) are somewhat shorter
bonding. The largest N–Al–N angle is 131 6(1) ,
cf. the tris(triazenido)aluminium(III) complexes where
angles in the range 145–163 are observed, the di er-
ence being attributable to the adoption of essentially
trigonal prismatic stereochemistry in (1). Because of
(c. 0 05 A) than those of other six-coordinate
aluminium amides, viz. tris(1,3-disubstituted tri-
azenido)aluminium(III) complexes31 and tris(di(2-pyri-
dyl)amido)aluminium(III),32 perhaps re ecting less
crowding about the aluminium in (1). Terminal
Al–N(amide) bonds in four-coordinate complexes aver-
age 1 80 A,33 and addition of the di erence27 between
the ionic radii of six- and four-coordinate Al3+ gives
a value of 1 94 A, midway between values for (1)
and those of the triazenide31 and di(2-pyridyl)amide
complexes.32 The Al–N bond distances in (1) are com-
parable with those found in four-coordinate [AlMe2( -
pz)]2.17 This demonstrates that any lengthening of
the Al–N distances, because of the increased coor-
dination number in (1), is o set by terminal Al–N
the small size of the aluminium, the 2-pyrazolate
2
bite angle (43 18(9) ) is larger than those of [Ti(
-
Me2pz)4] (38–41 )28 and much larger than is found in
[Ln( 2-R2pz)3L2] complexes (31–35 )15,16,34 as well as
[Ln( 2-But pz)4] (c. 34 ).13
2
Fig. 3. Molecular projection of [GePh3(But2pz)] (4).
Fig. 2. Molecular projection of [SnMe3(Ph2pz)] (2).
Table 2. Selected geometries in [Al(But2pz)3] (1)
Distances (A)
1 903(2) Al–N(2)
1 776
Angles (degrees)
Al–N(1)
Al–cenA
1 911(2)
N(1)–Al–N(100)
N(1)–Al–N(2 )
N(2)–Al–N(200)
107 7(1)
117 3(1)
107 7(1)
N(1)–Al–N(2)
N(1)–Al–N(200)
43 18(9)
131 6(1)
A
cen = centre of the N(1)–N(2) bond.
Table 3. Selected geometries in [SnMe3(Ph2pz)] (2)
Angles (degrees)
Distances (A)
Sn–N(1)
Sn–C(111)
Sn–C(131)
2 102(5)
2 072(9)
2 117(9)
Sn
N(2)A
Sn–C(121)
2 950(5)
2 119(9)
N(1)–Sn
N(2)B
24 3(4)
103 9(3)
113 6(4)
113 3(4)
134 5(4)
N(1)–Sn–C(111)
N(1)–Sn–C(131)
C(111)–Sn–C(121)
Sn–N(1)–N(2)
102 2(3)
106 3(6)
115 6(4)
115 7(4)
N(1)–Sn–C(121)
C(111)–Sn–C(131)
C(121)–Sn–C(131)
Sn–N(1)–C(1)
A
B
Non-bonding separation.
Non-bonding to tin.
Table 4. Selected geometries in [GePh3(But2pz)] (4)
Angles (degrees)
Distances (A)
Ge–N(1)
Ge–C(111)
Ge–C(131)
1 909(3)
1 945(3)
1 948(3)
Ge
N(2)A
Ge–C(121)
2 656(3)
1 952(3)
N(1)–Ge
N(2)B
29 9(1)
114 0(1)
106 5(2)
112 0(2)
142 4(2)
N(1)–Ge–C(111)
N(1)–Ge–C(131)
C(111)–Ge–C(131)
Ge–N(1)–N(2)
109 4(1)
105 2(1)
109 7(2)
106 5(2)
N(1)–Ge–C(121)
C(111)–Ge–C(121)
C(121)–Ge–C(131)
Ge–N(1)–C(1)
A
B
Non-bonding separation.
Non-bonding to germanium.

Main Group Pyrazolates
737
(ii) [SnMe3(Ph2pz)] (2) and [GePh3(But pz)] (4)
(thf, dme, toluene and light petroleum—b.p. 60–70 C) were
dried and deoxygenated by re uxing over blue sodium ben-
zophenone ketyl under puri ed nitrogen. Tetraethylene glycol
dimethyl ether was added to the light petroleum to dissolve
the benzophenone ketyl. Solvents were distilled directly into
storage asks equipped with Te on taps and stored under
nitrogen. Elemental analyses (C, H, N) were performed by The
Campbell Microanalytical Laboratory, Chemistry Department,
University of Otago, Dunedin, New Zealand. I.r. spectra were
obtained as Nujol mulls with a Perkin Elmer 1600 FTIR instru-
ment. Raman data were obtained with a Renishaw Ramascope,
near-infrared diode laser operating at 780 nm for samples (solid
2
Both complexes have monomeric structures devoid of
crystallographic symmetry with a distorted tetrahedral
arrangement of one nitrogen and three carbon donor
atoms about the metal (Figs 2 and 3). The pyrazolate lig-
ands are 1-(N)-bonded, as observed in the trisubstituted
pyrazolato complex [SnMe3(Me2As(MeO2C)2C3N2)],20
but this latter complex has additional weak inter-
and intra-molecular Sn–O interactions. The M N(2)
separations are 0 75 (Ge) and 0 85 A (Sn) longer
or liquid) sealed in glass capillaries, and were recorded for the
than the M–N(1) bond distances, cf.
0 2 A for the
1
range 1100–100 cm
. The n.m.r. spectra were recorded on
most unsymmetrical 2-R2pz binding,9 so that N(2)
is not regarded as attached to Sn (Ge). Although
N(2) is closer to Ge or Sn than the sum of the
corresponding van der Waals radii (3 4 (Ge), 3 6
A (Sn)),36 their proximity is solely due to the N–N
connectivity of the pyrazolate ions. The non-bonded
status of N(2) is even more evident from bond angle
considerations. Thus, Ge–N(1)–N(2) (106 5(2) ), Ge–
N(1)–C(1) (142 4(2) ), Sn–N(1)–N(2) (115 7(4) ) and
Sn–N(1)–C(3) (142 4(2) ) angles are totally di er-
ent from those of complexes with 2-coordination,
e.g. for (1) Al–N(1)–N(2) 68 6(1) and Al–N(1)–C(1)
either Bruker AC200 or AM300 spectrometers, and data were
referenced to either the residual protonated solvent signals
(C4D8O 1H 1 74, C6D6 1H 7 15 or C7D8 1H 2 09) or a
solution of an external standard (Al(NO3)3, 0 67 M (aq), 27Al
= 0 0; SnMe4, neat, 119Sn = 0 0). Mass spectra (e.i.) were
obtained with a VG Trio-1 GC mass spectrometer; a sample
probe designed for air-sensitive materials was used. Only the
most intense peak of a cluster with the correct isotope pattern
is given. The vapour pressure of (3) was determined under
5
dynamic vacuum (>10 Torr) by monitoring rate of mass loss
(using a Cahn C1000 electrobalance).39 GePh3Br was obtained
from Research Organic and Inorganic Chemicals. SnMe3Cl
and AlCl3 were purchased from Aldrich, and the latter was
sublimed under vacuum before use. Pyrazole syntheses have
been described previously.40
176 2(2) , and, for [Er(But pz)4] , Er–N–N 70–75
2
and Er–N–C 168–172 .13 Furthermore, the pseudo
‘bite’ angles of (2) and (4) (Tables 3 and 4) are
less than 30 , whereas, even for large Ln3+ ions,
the ‘bite’ angles for 2-R2pz–Ln binding are 31–35
(‘bite’ angles decrease with increased Mn+ size, see
above). Both the Sn–C (average 2 10 A) and Sn–N
(2 102(5) A) distances are shorter than those found in
[SnMe3(Me2As(MeO2C)2C3N2)], consistent with the
observation of Sn–O interactions additional to four-
coordination in the latter and with the absence of
Tris( 2-3,5-di-t-butylpyrazolato)aluminium(III) (1)
3,5-Di-t-butylpyrazole (1 22 g, 6 8 mmol) was treated with
a thf solution (30 ml) of potassium hydride (0 27 g, 6 8 mmol)
at room temperature. Gas evolution was observed and a slightly
pale yellow solution formed. AlCl3 (0 30 g, 2 3 mmol) was
slowly added causing formation of a white precipitate. The
reaction mixture was stirred for 12 h after which time the thf
was removed under vacuum yielding an o -white solid which
was extracted with light petroleum (50 ml). Concentration
and cooling ( 20 C) yielded large colourless crystals of (1)
(yield 94%), m.p. 182–184 C (Found: C, 70 6; H, 10 5; N,
14 0.
C33H57AlN6 requires C, 70 2; H, 10 2; N, 14 9%).
M
N(2) binding in (2). The Sn–N distance is close
I.r. absorption: 1526m, 1507s, 1484m, 1417w, 1364s, 1325m,
1253s, 1233s, 1205m, 1112w, 1070w, 1028m, 1001w, 986vs,
to that (2 114 A) of four-coordinate tris(2-methyl-
2-phenylpropyl)(1,2,4-triazol-1-yl)tin,37 but the Sn–C
distances of (2) also average some 0 06 A shorter
than those of the 2-methyl-2-phenylpropyl species.
In (4), the Ge–C and Ge–N distances are closely
comparable with those of four-coordinate 1,4-diphenyl-
1,4-bis(trimethylgermyl)tetrazene.38 It is thus clear
from the relatively short M–N and M–C distances in
1
926w, 824w, 798vs, 718m cm
.
1H n.m.r. (C4D8O) 1 17,
s, 54H, But; 5 94 s, 3H, H 4. 27Al n.m.r. (C7D8) 0 0. Mass
spectrum: m/z 564 (35%, M+), 549 (15, (M Me)+), 385 (50,
(M L)+), 369 (50, (M
57 (90, C4H9+).
L
Me)+), 165 (100, (LH Me)+),
(
1-3,5-Diphenylpyrazolato)trimethyltin(IV) (2)
3,5-Diphenylpyrazole (1 10 g, 5 0 mmol) was treated with
(2) and (4) that there are no M
N(2) interactions.
a diethyl ether solution (30 ml) of potassium hydride (0 20 g,
5 0 mmol) at room temperature. Gas evolution was observed
and a pale yellow solution formed. SnMe3Cl (1 19 g, 5 0 mmol)
was added causing formation of a white precipitate. The reac-
tion mixture was stirred for 12 h after which time the diethyl
ether was removed under vacuum yielding a white solid which
was extracted with toluene (50 ml). The toluene solution
was concentrated and cooled to 20 C and a orded large
colourless crystals of (2) (yield 74%), m.p. 95–97 C (Found:
The similarity of the Sn–C stretching frequencies,
119Sn n.m.r. chemical shifts and 117,119Sn–H cou-
pling constants of (3) to those of (2) indicates that
[SnMe3(But pz)] has four-coordination for tin and a
2
unidentate 3,5-di-t-butylpyrazolate ligand.
Experimental
The compounds described here are air- and moisture-
sensitive. All manipulations were carried out under puri ed
(BASF R3/11 oxygen removal catalyst and activated 4A molec-
ular sieves) nitrogen or argon using standard Schlenk techniques
or in a Miller Howe or Vacuum Atmospheres dry box. Solvents
C, 56 7; H, 5 5; N, 7 3.
H, 5 3; N, 7 3%). I.r. absorption: 3102w, 1602w, 1541w,
1513w, 1320vw, 1295w, 1272m, 1190m, 1155w, 1120s, 1072s,
1024m, 1002w, 986m, 957m, 918m, 846w, 821m, 774s, 763vs,
708w, 697vs, 682vs, 669w, 550w, 541m, 517w, 438m cm
C18H20N2Sn requires C, 56 4;
1
.
In the triazenido complex [SnMe3(1,3-(But3Si)2N3)], where a weak Sn
Sn–N bond, the di erence is 0 35 A.35
N interaction is proposed in addition to the main

738
G. B. Deacon et al.
Raman lines (solid sample): 1029w, 1002s, 985w, 957m, 848w,
Mo K radiation, 0 71073 A) yielding N tot re ections after
integration (‘DENZO-SMN’) which merged to N unique data
(Rint 0 039). No absorption correction was applied. The
structure was solved by direct methods and expanded using
Fourier techniques. The non-hydrogen atoms were re ned by
full matrix least squares on F (’teXsan’), with anisotropic
displacement parameters. Hydrogen atoms were located in the
di erence-Fourier map and re ned isotropically. The weighting
scheme was based on counting statistics (w = 2(Fo) 1).
For (2), room-temperature single-counter/four-circle di rac-
tometer (Enraf–Nonius CAD4) data sets were measured on
768w, 708w, 668mw, 618mw, 543m, 518vs, 438m, 413m, 349w,
1
271w, 244w, 202m, 181m, 165m cm
2
Sn
.
1H n.m.r. (C4D8O)
2
0 49, s, JH,
60 Hz, JH,
63 Hz, 9H, Me; 6 67,
Sn
117
119
s, 1H, H 4; 7 35, m, 6H, m- and p-H; 7 66, s, 4H, o-H;
119Sn n.m.r. (0 06 M in PhMe/10% C6D6) 87 7 (
28
1/2
Hz). Mass spectrum: m/z 531 (10%, ((Sn2Me5Ph2pz) H)+),
501 (10, ((Sn2Me3Ph2pz) H)+), 384 (50, M+), 369 (85,
(
(
120Sn)(M Me)+), 354 (10, (120Sn)(M 2Me)+), 339 (80,
120Sn)(M 3Me)+), 220 (35, (Ph2pzH)+), 191 (100,
(C15H11)+), 165 (55, (120SnMe3)+), 150 (15, (120SnMe2)+),
135 (30, (120SnMe)+), 120 (10, 120Sn+).
a
capillary-mounted specimen (2 / scan mode; graphite
monochromatized radiation, 0 71073 A; temperature c. 296
K). For (4), a sphere of data was measured at c. 153 K on a
Bruker AXS CCD area detector di ractometer (monochromatic
Mo K radiation, 0 71073 A) using the proprietary software
SMART/SAINT. Both data sets yielded N tot re ections which
reduced to N unique data (Rint 0 046 (4)) after absorption
correction ((2) Gaussian, (4) empirical (‘SADABS’)). N o with
I > 3 (I ) were considered ‘observed’ and used in full-matrix
least-squares re nement (anisotropic displacement parameters
(
1-3,5-Di-t-butylpyrazolato)trimethyltin(IV) (3)
3,5-Di-t-butylpyrazole (1 48 g, 8 2 mmol) was treated with
a diethyl ether solution (30 ml) of potassium hydride (0 33 g,
8 2 mmol) at room temperature. Gas evolution was observed
and a pale yellow solution formed. SnMe3Cl (1 00 g, 8 4 mmol)
was added causing formation of a white precipitate. The reaction
mixture was stirred for 12 h after which time the diethyl ether
was removed under vacuum yielding a white solid which was
extracted with light petroleum (50 ml). The light petroleum
solution was concentrated and cooled to 20 C, and a orded
large colourless crystals of (3) (yield 75%), m.p. 30 C (Found:
C, 49 5; H, 8 2; N, 8 5.
8 2; N, 8 2%). I.r. absorption: 1527m, 1418w, 1361s, 1307m,
1250m, 1224w, 1205m, 1113w, 1081m, 1043w, 1019w, 993m,
786vs, 724s, 632w, 534s, 514m, 464m cm
for the non-hydrogen atoms, (x, y, z, U iso
)
constrained at
H
estimates) after structure solution by conventional methods;
statistical weights were employed throughout. An Accessory
Publication, consisting of anisotropic displacement parameters,
hydrogen atom parameters, bond distances and angles, and
lists of structure factors, is available (until 31 December 2004)
from the Australian Journal of Chemistry, P.O. Box 1139,
Collingwood, Vic. 3066.
C14H28N2Sn requires C, 49 0; H,
1
.
Raman lines
(liquid sample): 1527m, 1042w, 1025w, 993w, 927w, 823m,
565w, 537m, 514vs, 260w, 220w, 163m cm
(C6D6) 0 42, s, JH,
1 38, s, 18H, But; 6 16, s, 1H, H 4. 119Sn n.m.r. (0 06
1
.
1H n.m.r.
58 Hz, 9H, Me;
Sn
2
2
Crystal/Re nement Data
55 Hz, JH,
119
117
Sn
M
(1).
C
33H57AlN6, M 564 83. Trigonal, space group P 3
(C31i, No. 147), a 14 4582(4), c 10 4065(2) A, V 1883 92(7)
in PhMe/10% C6D6) 72 1 (
26 Hz). Mass spectrum
1/2
m/z: 344 (10%, (120Sn)M+), 329 (70, (120Sn)(M Me)+),
A3. Dc(Z = 2) 0 996 g cm 3; F(000) 620.
0 081 mm
;
1
Mo
299 (40, (120Sn)(M 3Me)+), 180 (35, But2pzH+), 165 (100,
specimen: 0 25 by 0 25 by 0 25 mm.
13872, N 3510, N o 2598; R 0 067, Rw 0 097.
2
60 0 ; N tot
max
(
120SnMe3)+), 150 (30, (120SnMe2)+), 135 (30, (120SnMe)+),
120 (10, 120Sn+), 57 (90, But+). Vapour pressure P
=
(2).
C18H20N2Sn, M 383 08. Orthorhombic, space group
3
Pcan (D21h4 , No. 60 (variant)), a 10 4372(9), b 15 223(4), c
22 455(3) A, V 3568(1) A3. Dc(Z = 8) 1 426 g cm 3; F(000)
6 33 10
Pa (298 K).
(
1-3,5-Di-t-butylpyrazolato)triphenylgermanium(IV) (4)
3,5-Di-t-butylpyrazole (0 36 g, 2 0 mmol) was treated with
1536.
1 43 mm 1; specimen: 0 36 by 0 44 by 0 20 mm;
Mo
Tmin,max 0 61, 0 75. 2
Rw 0 052.
50 ; N 3558, N o 1845; R 0 042,
max
a thf solution (30 ml) of potassium hydride (0 08 g, 2 0 mmol)
at room temperature. Gas evolution was observed and a
pale yellow solution formed. Ph3GeBr (0 77 g, 2 0 mmol)
was added, causing formation of a white precipitate. The
reaction mixture was stirred for 2 h after which time the thf
was removed under vacuum yielding a white solid which was
extracted with light petroleum (50 ml). The light petroleum
solution was concentrated and cooled to 20 C and a orded
u y colourless crystals of (4) (yield 49%), m.p. 135 C (Found:
(4).
C29H34GeN2, M 483 20. Orthorhombic, space group
P 212121 (D24, No. 19), a 8 2525(8), b 10 680(1), c 28 895(3) A,
V 2546 6(7) A3. Dc(Z = 4) 1 260 g cm 3; F(000) 1016.
122 1 mm 1; specimen: 0 55 by 0 25 by 0 15 mm; ‘T’min,max
Mo
0 46, 0 86.
2
58 ; N tot 28148, N 3661, N o 3461; R
max
0 035, Rw 0 043 (preferred chirality; xabs = 0 01(1)).
Acknowledgments
C, 73 1; H, 7 2; N, 5 7.
C29H34GeN2 requires C, 72 1; H,
7 1; N, 5 8%). I.r. absorption: 1530m, 1433s, 1364s, 1298m,
We are grateful to the Australian Research Council
for nancial support and for an Australian Postgraduate
Award (E.E.D.).
1248m, 1225w, 1200m, 1188m, 1120w, 1113w, 1092s, 1027m,
1
993s, 920w, 797vs, 744vs, 697vs, 676vs, 633w cm
.
1H n.m.r.
(C4D8O) (298 K) 1 04 and 1 28, vbr s (coalescence at 303
K, 1 15, br s), 18H, But; 6 10, s, 1H, H 4; 7 37, m, 9H, m- and
p-H; 7 60, dd, 6H, o-H; (328 K) 1 15, s, 18H, But; 6 08, s, 1H,
H 4; 7 35, m, 9H, m- and p-H; 7 59, dd, 6H, o-H (a spectrum of
(4) in C7D8 at 298 K was similar to that in C4D8O at the same
temperature). Mass spectrum: m/z 484 (20%, (74Ge)M+), 469
(10, (74Ge)(M Me)+), 442 (40, (74Ge)(M But)+2CH3)+),
427 (20, (74Ge)(M But)+), 305 (100, (74GePh3)+), 227 (40,
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