Organogermanium compound

Organogermanium compounds are organometallic compounds containing a carbon to germanium or hydrogen to germanium chemical bond. Organogermanium chemistry is the corresponding chemical science.^[1] Germanium shares group 14 in the periodic table with silicon, tin and lead and not surprisingly the chemistry of organogermanium is in between that of organosilicon compounds and organotin compounds.

The main reason why the organogermanium is of limited synthetic value are the costs of germanium compounds. On the other hand germanium is advocated as a non-toxic alternative to many toxic organotin reagents and compounds like tetramethylgermanium and tetraethylgermanium are used in the microelectronics industry as precursors for germanium dioxide chemical vapor deposition.

The first organogermanium compound, tetraethylgermane, was synthesised by Winkler in 1887, by the reaction of germanium tetrachloride with diethylzinc.^[2] The organogermanium compound bis (2-Carboxyethylgermanium)sesquioxide was first reported in 1966.^[3]

1 Organogermanes
2 Germanium hydrides
3 Other germanium compounds
4 External links
5 See also
6 References

Organogermanes

Organogermanes of the type R₄Ge with alkyl (R) groups are accessed through the cheapest available germanium precursor germanium tetrachloride and alkyl nucleophiles. The following trends are observed going down the carbon group: The nucleophilicity increases Si<Ge<Sn as well as the hyperconjugation effect known as the beta-silicon effect Si<Ge<<Sn. Where the Si-C bond is mainly ionic and the Sn-C bond is mainly radical, bonds with germanium are in between.

Just as with silicon the nucleophilicity of allyl germanes is high due to the intrinsic polarization of the bond (difference in electronegativity 2.55 − 2.01 = 0.54) and the combined stabilizing effect on the α-carbonion by the allyl group and the germanium atom. The germanium pendant of the Sakurai reaction was discovered in 1986:

The carbonyl group in this reaction is activated with boron trifluoride.

Germanium hydrides

Isobutylgermane (IBGe) (Me₂CHCH₂)GeH₃ is the organogermanium hydride that is a high vapor pressure liquid germanium source for MOVPE. Isobutylgermane is currently investigated as safer and less hazardous alternative to toxic germane gas in microelectonic applications.

Tris(trimethylsilyl)germanium hydride (Me₃Si)₃GeH has been investigated as a non-toxic alternative to many tin hydrides such as tributyltinhydride.

Other germanium compounds

Many germanium reactive intermediates are known: germylenes (carbene pendants), germyl free radicals, germynes (carbyne pendants). Digermynnes only exist for extremely bulky substituents. Unlike alkynes, the C-Ge-Ge-C core of these distannynes are nonlinear, although they are planar. The Ge-Ge distance is 2.22 Å, and the Ge-Ge-C angles are 131°. Such compounds are prepared by reduction of bulky arylgermanium(II) halides.^[4]

As with silicon and contrasting with carbon, compounds containing Ge=C (germenes) and Ge=Ge (digermylenes) double bonds are rare. One example is the bulky derivatives of germanabenzene, an analogue of benzene.

External links

Tetramethylgermanium Datasheet commercial supplier
Tetraethylgermanium Datasheet commercial supplier
Tris(trimethylsilyl)germanium hydride Datasheet commercial supplier

CH				He
CLi	CBe	CB	CC	CN	CO	CF	Ne
CNa	CMg	CAl	CSi	CP	CS	CCl	CAr
CK	CCa	CSc	CTi	CV	CCr	CMn	CFe	CCo	CNi	CCu	CZn	CGa	CGe	CAs	CSe	CBr	CKr
CRb	CSr	CY	CZr	CNb	CMo	CTc	CRu	CRh	CPd	CAg	CCd	CIn	CSn	CSb	CTe	CI	CXe
CCs	CBa		CHf	CTa	CW	CRe	COs	CIr	CPt	CAu	CHg	CTl	CPb	CBi	CPo	CAt	Rn
Fr	Ra	Rf	Db	Sg	Bh	Hs	Mt	Ds	Rg	Cn	Uut	Uuq	Uup	Uuh	Uus	Uuo
	↓
	CLa	CCe	CPr	CNd	CPm	CSm	CEu	CGd	CTb	CDy	CHo	CEr	CTm	CYb	CLu
	Ac	Th	Pa	CU	Np	Pu	Am	Cm	Bk	Cf	Es	Fm	Md	No	Lr

**Chemical bonds to carbon**
Core organic chemistry	Many uses in chemistry
Academic research, but no widespread use	Bond unknown / not assessed

References

^ Main Group Metals in Organic Synthesis, Hisashi Yamamoto (Editor), Koichiro Oshima (Editor) ISBN 3-527-30508-4 2004
^ Winkler, Clemens (1887). "Mittheilungen über des Germanium. Zweite Abhandlung". J. Prak. Chemie 36: 177–209. doi:10.1002/prac.18870360119. http://gallica.bnf.fr/ark:/12148/bpt6k90799n/f183.table. Retrieved 2008-08-20.
^ "Bis(2-carboxyethylgermanium(IV) sesquioxide". http://www.germaniumsesquioxide.com/Pages/History%20Germanium%20Sesquioxide.html.
^ Philip P. Power "Bonding and Reactivity of Heavier Group 14 Element Alkyne Analogues" Organometallics 2007, volume 26, pp 4362–4372. doi:10.1021/om700365p

CH																	He
CLi	CBe											CB	CC	CN	CO	CF	Ne
CNa	CMg											CAl	CSi	CP	CS	CCl	CAr
CK	CCa	CSc	CTi	CV	CCr	CMn	CFe	CCo	CNi	CCu	CZn	CGa	CGe	CAs	CSe	CBr	CKr
CRb	CSr	CY	CZr	CNb	CMo	CTc	CRu	CRh	CPd	CAg	CCd	CIn	CSn	CSb	CTe	CI	CXe
CCs	CBa		CHf	CTa	CW	CRe	COs	CIr	CPt	CAu	CHg	CTl	CPb	CBi	CPo	CAt	Rn
Fr	Ra		Rf	Db	Sg	Bh	Hs	Mt	Ds	Rg	Cn	Uut	Uuq	Uup	Uuh	Uus	Uuo
		↓
		CLa	CCe	CPr	CNd	CPm	CSm	CEu	CGd	CTb	CDy	CHo	CEr	CTm	CYb	CLu
		Ac	Th	Pa	CU	Np	Pu	Am	Cm	Bk	Cf	Es	Fm	Md	No	Lr

CH																	He
CLi	CBe											CB	CC	CN	CO	CF	Ne
CNa	CMg											CAl	CSi	CP	CS	CCl	CAr
CK	CCa	CSc	CTi	CV	CCr	CMn	CFe	CCo	CNi	CCu	CZn	CGa	CGe	CAs	CSe	CBr	CKr
CRb	CSr	CY	CZr	CNb	CMo	CTc	CRu	CRh	CPd	CAg	CCd	CIn	CSn	CSb	CTe	CI	CXe
CCs	CBa		CHf	CTa	CW	CRe	COs	CIr	CPt	CAu	CHg	CTl	CPb	CBi	CPo	CAt	Rn
Fr	Ra		Rf	Db	Sg	Bh	Hs	Mt	Ds	Rg	Cn	Uut	Uuq	Uup	Uuh	Uus	Uuo
		↓
		CLa	CCe	CPr	CNd	CPm	CSm	CEu	CGd	CTb	CDy	CHo	CEr	CTm	CYb	CLu
		Ac	Th	Pa	CU	Np	Pu	Am	Cm	Bk	Cf	Es	Fm	Md	No	Lr