Article
Inorganic Chemistry, Vol. 49, No. 23, 2010 10799
to lower processing temperatures impacting a number of
advanced ceramic systems. Additionally, it is of interest to
understand how the cations and their associated chemistry
affect the final nanomaterial properties. To meaningfully
accomplish this goal, it is critical to have similar shaped
precursors for a group to minimize the variables in the re-
action process. Unfortunately, this uniformity is not com-
mon for metal alkoxides (M(OR)x).9-11
Since these initial reports, no additional homoleptic ONep
Group 4 structures have been disseminated.9-11
2TiðORÞ4 þ 8HONep f ½Tiðμ -ONepÞðONepÞ3ꢀ2 þ 8HOR
ð1Þ
2MðOButÞ4 þ 8HONep
One of the most useful alkoxide ligands that we have
found12-32 for materials synthesis is the neo-pentoxide
(OCH2C(CH3)3 or ONep) moiety. The ONep ligand is at-
tractive since it often yields compounds with reduced olig-
omerization and thus higher solubility and/or volatility, low
decomposition temperatures with low C retention, minimal
side reactions, and ease of crystallization, critical for identi-
fication of M(OR)x. Over a decade ago, the synthesis of
[Ti(μ-ONep)(ONep)3]2 (1) from the alcoholysis of Ti(OPri)4
(where OPri = OCH(CH3)2) with 4 equiv HONep in toluene
(eq 1) was reported.33 Subsequently, extensive investigations
of 1 for both chemical and materials production have been
reported.12-31 Our previous attempts to extend this chemistry
to Zr resulted only in partial substitution or oxo formation.31
f f½Hꢀ½ðμ -ONepÞ M2ðONepÞ ðOButÞꢀg þ 7HOBut
3
5
M ¼ Zr, Hf
ð2Þ
Recently, interest in generating the homoleptic ONep
congeners led to the study of the tert-butoxide (OC(CH3)3
or OBut) derivatives as shown in eq 2. The products were
eventually characterized as {[H][(μ-ONep)3M2(ONep)5-
(OBut)]} M = Zr (2) and Hf(3) with a proton disordered over
the entire molecule. The surprisingly similar dinuclear struc-
ture types observed for these congeners (1-3) allows for a
comparative investigation of the influence of the metal cation
on the final ceramic materials’ properties under low, neutral,
and high pH conditions following established solvothermal
(SOLVO) routes.33 The characterization of the starting ma-
terials (1-3), the pyridine adducts {[Ti(μ-ONep)(ONep)3]2-
(μ-py) [(1a), 2a, and 3a], and hydrolysis products [Ti6(μ3-
O)7(μ-O)(μ-ONep)2(ONep)6]2 [(1b), 2a, 3a], and the final
nanomaterials generated by these unusual similarly shaped
group 4 precursors are reported.
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(11) Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge
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Experimental Section
All compoundsdescribed belowwere handledunderan argon
atmosphere with rigorous exclusion of air and water using
standard Schlenk line and glovebox techniques. All solvents
were stored under argon and used as received (Aldrich) in Sure/
Seal bottles, including toluene (tol) and pyridine (py). The
following chemicals were used as received (Aldrich and Alfa
Aesar): M(OBut)4 (M = Ti, Zr, Hf) and H-ONep. Ti(OPri)4
was freshly distilled prior to use. Compound 1 was prepared
according to literature procedures33 and from the reaction of
Ti(OBut)4 with 4.5 HONep in toluene.
FT-IR data were obtained on a Bruker Vector 22 Instru-
ment using KBr pellets under an atmosphere of flowing
nitrogen. Elemental analysis was performed on a Perkin-
Elmer 2400 CHN-S/O Elemental Analyzer. All NMR sam-
ples were prepared from dried crystalline materials that were
handled and stored under an argon atmosphere and redis-
solved in deuterated chloroform (CDCl3). Spectra were col-
lected on a Bruker DRX 400 MHz NMR spectrometer under
standard experimental conditions (1H spectra 4-s recycle
delay at 16 scans; 13C Spectra were obtained with a 10 s delay
and 4k scans).
{[H][(μ-ONep)3Zr2(ONep)5(OBut)]} (2). To a stirring solu-
tion of Zr(OBut)4 (1.00 g, 2.61 mmol), in ∼10 mL of toluene,
H-ONep (1.03 g, 11.7 mmol), was added. After 12 h, a pre-
cipitate was present, the reaction was heated until clear and set
aside until crystals formed. Yield 92.7% (1.15 g). FTIR (KBr
Pellet, cm-1) 3440(br, m), 2954(s), 2908(s), 2867(w), 1651(w),
1478(m), 1395(m), 1363(m), 1261(w), 1194(s), 1135(s), 1111(s),
1017(s), 1017(w), 904(w), 800(w), 751(w), 630(m), 580(w),
533(w), 457(m). 1H NMR (400.1 MHz, CDCl3) δ 3.98 (14.0H,
s, OCH2C(CH3)3), 1.32 (5.8H, s, OC(CH3)3), 1.07 (62.6H, s,
OCH2C(CH3)3). 13C (100.1 MHz, CDCl3) δ 80.1 (OCH2C(CH3)3),
33.6 (OC(CH3)3), 32.8 (OCH2C(CH3)3), 27.0 (OCH2C(CH3)3).
Elemental Analysis C44H98O9Zr2 (MW = 953.69): calc’d 55.41, %
C; 10.36, %H. Found 55.58, %C; 10.64, %H.
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