Biomedical subjects

David M. Hoffman

Publications and source records attributed to David M. Hoffman.

4 recordsLinked to original sources

PubMed1999

Indium Fluoroalkoxide Compounds.

Reactions of indium amide complexes with fluorinated alcohols give indium fluoroalkoxide complexes. In[N-t-Bu(SiMe(3))](3) reacts with 3 equiv of (CF(3))Me(2)COH to give the homoleptic alkoxide dimer [In{&mgr;-OCMe(2)(CF(3))}{OCMe(2)(CF(3))}(2)](2), but reactions involving the more acidic alcohols (CF(3))(2)MeCOH and (CF(3))(2)CHOH yield products containing t-BuNH(2), which is derived from the amide ligands. Thus, In[N-t-Bu(SiMe(3))](3) reacts with (CF(3))(2)MeCOH to give In[OCMe(CF(3))(2)](3)(H(2)N-t-Bu) and with (CF(3))(2)CHOH to yield In[OCH(CF(3))(2)](3)(H(2)N-t-Bu)(3) and [H(3)N-t-Bu][In{OCH(CF(3))(2)}(4)(H(2)N-t-Bu)]. Reactions of (CF(3))(2)MeCOH and (CF(3))(2)CHOH with In(tmp)(3) (tmp = the anion derived from 2,2,6,6-tetramethylpiperidine) and In(NEt(2))(3) are less complicated. In(tmp)(3) reacts with 3 equiv of (CF(3))(2)CHOH to give In[OCH(CF(3))(2)](3)(Htmp) and with 4 equiv of (CF(3))(2)CHOH or (CF(3))(2)MeCOH to yield the salt compounds [H(2)tmp][In{OCR(CF(3))(2)}(4)] (R = H, Me). Trigonal bipyramidal [H(2)NEt(2)][In{OCH(CF(3))(2)}(4)(HNEt(2))] and octahedral mer-In[OCMe(CF(3))(2)](3)(py)(3) are isolated from reactions involving In(NEt(2))(3). Crystal structure determinations of [In{&mgr;-OCMe(2)(CF(3))}{OCMe(2)(CF(3))}(2)](2), [H(3)N-t-Bu][In{OCH(CF(3))(2)}(4)(H(2)N-t-Bu)].EtOEt, In[OCH(CF(3))(2)](3)(Htmp), [H(2)tmp][In{OCMe(CF(3))(2)}(4)], In[OCMe(CF(3))(2)](3)(py)(3), and [H(2)NEt(2)][In{OCH(CF(3))(2)}(4)(HNEt(2))] were carried out.

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PubMed1998

Synthesis of Indium Amide Compounds.

Indium trichloride reacts with 3 equiv of lithium amide in diethyl ether to give In(NRR')(3) (R = Ph or t-Bu, R' = SiMe(3); R = t-Bu, R' = SiHMe(2)) and with 3 or 4 equiv of LiNMe(SiMe(3)) to yield Li[In{NMe(SiMe(3))}(4)]. The chloride also reacts with LiNPh(2) in THF to give the salt Li[In(NPh(2))(3)Cl] and with LiNRR' in pyridine to yield the neutral adduct In(NRR')(3)(py) (R = R' = Ph; R = Me, R' = SiMe(3)). The volatile liquids In[N(t-Bu)(SiHMe(2))](3) and In[NMe(SiMe(3))](3)(py) react with p-Me(2)Npy to form the solid compounds In[N(t-Bu)(SiHMe(2))](3)(p-Me(2)Npy) and In[NMe(SiMe(3))](3)(p-Me(2)Npy), respectively. X-ray crystallographic studies show that In(NPh(2))(3)(py), In[N(t-Bu)(SiHMe(2))](3)(p-Me(2)Npy), and the ether adduct of In[NPh(SiMe(3))](3) contain nearly planar In(amide)(3) fragments. Crystallographic studies also show that the anion in the salt [Li(THF)(4)][In(NPh(2))(3)Cl] is nearly tetrahedral and in [Li(p-Me(2)Npy)][In{NMe(SiMe(3))}(4)] the tetrahedral-like anion is bound to the Li cation via two amide nitrogens. The Li in the latter structure is also bonded to p-Me(2)Npy, resulting in a planar three-coordinate geometry for Li. Crystal data are the following. C(31)H(52)N(3)OSi(3)In at -50 degrees C: P2(1)/n (monoclinic), a = 11.003(2) Å, b = 18.678(3) Å, c = 17.618(3) Å, beta = 95.42(1) degrees, and Z = 4. C(41)H(35)N(4)In.C(7)H(8) at -50 degrees C: P&onemacr; (triclinic), a = 10.112(2) Å, b = 12.786(3) Å, c = 15.870(5) Å, alpha = 87.42(2) degrees, beta = 74.95(2) degrees, gamma = 78.15(2) degrees, and Z = 2. C(25)H(58)N(5)Si(3)In at -50 degrees C: P2(1)/c (monoclinic), a = 9.797(3) Å, b = 18.203(6) Å, c = 19.592(5) Å, beta = 100.27(2) degrees, and Z = 4. C(52)H(62)ClInLiN(3)O(4) at 23 degrees C: P2(1)/n (monoclinic), a = 16.076(2) Å, b = 17.185(2) Å, c = 18.447(3) Å, beta = 97.41(1) degrees, and Z = 4. C(23)H(58)InLiN(6)Si(4) at 23 degrees C: P&onemacr; (triclinic), a = 15.792(3) Å, b = 16.345(3) Å, c = 16.678(3) Å, alpha = 62.69(1) degrees, beta = 81.00(1) degrees, gamma = 86.94(1) degrees, and Z = 4.

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PubMed1997

Synthesis of Homoleptic Neopentoxide and Hydrido-Neopentoxide Trirhenium(III) Clusters.

The purpose of this study was to synthesize Re(3)(&mgr;-OCH(2)CMe(3))(3)(OCH(2)CMe(3))(6) and to determine if it could serve as a source of Re(3)(&mgr;-OCH(2)CMe(3))(3)(H)(OCH(2)CMe(3))(5) by analogy to Re(3)(&mgr;-O-i-Pr)(3)(O-i-Pr)(6), a previously reported cluster that exists in solution as an equilibrium mixture with Re(3)(&mgr;-O-i-Pr)(3)(H)(O-i-Pr)(5) and acetone. The halide Re(3)(&mgr;-Cl)(3)Cl(6)(THF)(3) reacts at room temperature in THF with 9 equiv of NaOCH(2)CMe(3) to give Re(3)(&mgr;-OCH(2)CMe(3))(3)(OCH(2)CMe(3))(6). An X-ray crystallographic study shows that the core of the homoleptic cluster has virtual D(3h) symmetry, which is consistent with solution NMR data. In refluxing THF, Re(3)(&mgr;-Cl)(3)Cl(6)(THF)(3) reacts with 10 equiv of NaOCH(2)CMe(3) to give [Na(THF)(2)][Re(3)(&mgr;-OCH(2)CMe(3))(3)(H)(OCH(2)CMe(3))(6)]. The same anionic hydride cluster is also produced when Re(3)(&mgr;-OCH(2)CMe(3))(3)(OCH(2)CMe(3))(6) reacts with excess NaOCH(2)CMe(3) in hot THF. Spectroscopic and X-ray crystallographic data show that [Re(3)(&mgr;-OCH(2)CMe(3))(3)(H)(OCH(2)CMe(3))(6)](-) has virtual C(s)() core symmetry with a terminal hydride and two terminal alkoxides located at the unique rhenium atom. The hydride and one of the alkoxides have a trans-H-Re-OR arrangement, and in the solid state structure the terminal alkoxide ligands at the unique rhenium atom interact with [Na(THF)(2)](+). It is proposed [Na(THF)(2)][Re(3)(&mgr;-OCH(2)CMe(3))(3)(H)(OCH(2)CMe(3))(6)] forms when Re(3)(&mgr;-OCH(2)CMe(3))(3)(H)(OCH(2)CMe(3))(5) or its pivaldehyde adduct, which is generated by neopentoxide beta-hydrogen elimination from Re(3)(&mgr;-OCH(2)CMe(3))(3)(OCH(2)CMe(3))(6), is trapped by NaOCH(2)CMe(3). Crystal data are as follows. C(45)H(99)O(9)Re(3) at -50 degrees C: Pbca (orthorhombic); a = 19.570(2), b = 28.192(3), c = 21.203(3) Å; Z = 8. Na(+)[C(45)H(100)O(9)Re(3)](-).2C(4)H(8)O at -50 degrees C: P&onemacr; (triclinic); a = 13.040(2), b = 14.716(2), c = 19.653(4) Å; alpha = 92.38(1), beta = 92.30(1), gamma = 113.42(1) degrees; Z = 2.

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PubMed1996

Synthesis and Structural Characterization of Tantalum(IV) Amido Compounds.

Tantalum(IV) amido complexes have been synthesized from Ta(V) precursors. Ta(N(SiMe(3))(2))(2)Cl(3) reacts with Na/Hg to give Ta(N(SiMe(3))(2))(2)Cl(2), and Ta(NEt(2))(2)Cl(3) reacts with LiNPh(2) and Na/Hg to yield Ta(NPh(2))(2)(NEt(2))(2). Ta(N(SiMe(3))(2))(2)Ph(2) is prepared by reacting Ta(N(SiMe(3))(2))(2)Cl(2) with LiPh. Attempts to prepare other organometallic derivatives failed to yield clean products. X-ray crystallographic studies show that Ta(N(SiMe(3))(2))(2)Cl(2), Ta(N(SiMe(3))(2))(2)Ph(2), and Ta(NPh(2))(2)(NEt(2))(2) have distorted tetrahedral geometries.

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