Beiträge zur Chemie des Phosphors. 159. Über die Reaktion des Diphosphaborirans (t-BuP)2BN(i-Pr)2 mit Kalium bzw. Kaliumnaphthalid

Contributions to the Chemistry of Phosphorus. 159. On the Reaction of the Diphosphaborirane (t-BuP)₂BN(i-Pr)₂ with Potassium or Potassium Naphthalenide The reaction of (t-BuP)₂BN(i-Pr)₂ with potassium or K-naphthalenide in tetrahydrofuran leads to K(t-Bu)P? ;BN(i-Pr)₂? P(t-Bu)K ( 1 ) via P? ;P bond cleavage of the three-membered ring skeleton. Above ? 78°C 1 changes into the asymmetric compound K(t-Bu)P? ;P(t-Bu)? BHN(i-Pr)₂ ( 2 ). In dimethoxyethane additionally the monometallated diphosphaborirane K(t-Bu)P₂BN(i-Pr)₂ ( 3 ) is formed. 1 and 3 , which could be isolated free from other phosphorus containing compounds, as well as the corresponding silylphosphanes Me₃Si(t-Bu)P? ;BN(i-Pr)₂? ;P(t-Bu)SiMe ₃ ( 4 ) and Me₃Si(t-Bu)P₂BN(i-Pr)₂ ( 5 ) were characterized by NMR spectroscopy. Protolysis of 3 or 5 leads to a decomposition of the three-membered ring skeleton with formation of H(t-Bu)P? ;PH₂.     

Beiträge zur Chemie des Phosphors. 144. Synthese und Eigenschaften des Hexaphospha-3-germaspiro[2.4]heptans (t-BuP)2Ge(t-BuP)4

Contributions to the Chemistry of Phosphorus. 144. Synthesis and Properties of the Hexaphospha-3-germaspiro[2.4]heptane (t-BuP)₂Ge(t-BuP)₄ The cyclocondensation of K(t-Bu)P? P(t-Bu)K with germanium tetrachloride in the molar ratio of 2:1 yields the novel spirocyclic compound 1,2,4,5,6,7-hexa-tert-butyl-1,2,4,5,6,7-hexaphospha-3-germaspiro[2.4]heptane, (t-BuP)₂Ge(t-BuP)₄ ( 1 ). Besides considerable amounts of (t-BuP)₄ are formed and occasionally some (t-BuP)₃ can be found. 1 could be isolated in the pure state and has been NMR-spectroscopically characterized as a spirocyclic compound with a P₂GeP₄ skeleton.     

Beiträge zur Chemie des Phosphors. 101. Synthese und Eigenschaften von Diphosphaboriranen (t-BuP)2BNR2 und (t-BuP)2BNR1R2

Contributions to the Chemistry of Phosphorus. 101 Synthesis and Properties of Diphosphaboriranes (t-BuP)₂BNR₂ and (t-BuP)₂BNR¹R² The reaction of K(t-Bu)P? P(t-Bu)K with diorganylaminodichloroboranes under suitable conditions leads to the new 1,2-di-tert-butyl-3-diorganylamino-1,2,3-diphosphaboriranes (-1,2-diphospha-3-boracyclopropanes) (t-BuP)₂BNR₂ ( 2 , 7 ) and (t-BuP)₂BNR¹R² ( 3 — 6 ), respectively. The P₂B three-membered heterocycles 2 — 5 can be isolated in good yields. They are relatively stable against dimerization to the corresponding phosphorus boron six-membered ring compounds with opposite boron atoms. The rate of dimerization depends on steric and electronic influences of the substituents at the three-membered ring. All NMR spectroscopic results are only consistent with a structure in which the B and N atoms show planar coordination and are connected by a partial double bond.     

Beiträge zur Chemie des Phosphors. 129. Synthese und Eigenschaften der Phospha-germa-cyclobutane (t-BuP)2(GePh2)2 und (t-BuP)3GePh2

Contributions to the Chemistry of Phosphorus. 129. Synthesis and Properties of the Phospha-germa-cyclobutanes (t-BuP)₂(GePh₂)₂ and (t-BuP)₃GePh₂ The phospha-germa-cyclobutanes 1,2-di-tert-butyl-3,3,4,4-tetraphenyl-1,2-diphospha-3,4-digerma-cyclob utane, (t-BuP)₂(GePh₂)₂ ( 1 ), and 1,2,3-tri-tert-butyl-4,4-diphenyl-1,2,3-tri-phospha-4-germa-cyclobutan e, (t-BuP)₃GePh₂ ( 2 ), are obtained as main-products of the cyclocondensation of K(t-Bu)P? P(t-Bu)K with Ph₂GeCl₂ under certain reaction conditions. 1 and 2 could be isolated in the pure state and were clearly characterized as the first four-membered P₂Ge₂ and P₃Ge heterocycles, respectively.     

Beiträge zur Chemie des Phosphors. Synthese und Eigenschaften des 1,2-Diphospha-3,4-diboretans (t-BuP)2(BNMe2)2

Contributions tot he Chemistry of Phosphorus. 148. Synthesis and Properties of the 1,2-Diphospha-3,4-diboretane (t-BuP)₂(BNMe₂)₂ The first 1, 2-diphospha-3,4-diboretane (1,2-diphospha-3, 4-diboracyclobutane) (t-BuP)₂(BNMe₂)(1) was prepared by [2+2] cyclocondensation of K(t-Bu)P? P(t-Bu)K with Cl(Me₂N)B? B(NMe₂)Cl. 1 could be isolated in the pure state and was NMR spectroscopically characterized as a compound with a planar P₂ B₂ ring skeleton.     

Beiträge zur Chemie des Phosphors. 152. Funktionalisierte Cyclotriphosphane des Typs (t-BuP)2PX (X = K,SiMe3, SnMe3, Cl,Br, PCl2, P(t-Bu)Cl,P(t-Bu)I)

Contributions to the Chemistry of Phosphorus. 152. Functionalized Cyclotriphosphanes of the Type (t-BuP)₂PX (X = K, SiMe₃, SnMe₃, Cl, Br, PCl₂, P(t-Bu)Cl, P(t-Bu)I) Functionalized cyclotriphosphanes of the type (t-BuP)₂PX with electropositive or electronegative substituents X have been prepared on various synthetic routes: KP(t-BuP)₂ ( 1 ) can be obtained in 50–55 per cent purity by reacting (t-BuP)₄ or (t-BuP)₃ with potassium. Reaction of 1 with Me₃SiCl or Me₃SnCl leads to the cyclotriphosphanes (t-BuP)₂PSiMe₃ ( 2 ) and (t-BuP)₂PSnMe₃ ( 3 ), respectively; the cyclocondensation of Cl(t-Bu)P? P(t-Bu)Cl with P(SnMe₃)₃, however, is more convenient for the preparation of 3 . In a similar way the halogenated compounds (t-BuP)₂PCl ( 4 ) and (t-BuP)₂PBr ( 5 ) can be obtained from Me₃Sn(t-Bu)P? P(t-Bu)SnMe₃ ( 6 ) and PX₃ (X = Cl, Br). The phosphino-substituted cyclotriphosphanes (t-BuP)₂P? PCl₂ ( 7 ), (t-BuP)₂P? P(t-Bu)Cl ( 8 ), and (t-BuP)₂P? P(t-Bu)I ( 9 ) are accessible by the reaction of 3 with PCl₃ and t-BuPX₂ (X = Cl, I), respectively. 2–9 could be obtained free from phosphorus-containing by-products and were ³¹P-NMR spectroscopically characterized as compounds with a cyclic P₃ skeleton.     

Beiträge zur Chemie des Phosphors. 128. Synthese des Diphosphastanna-cyclopropans (t-BuP)2Sn(t-Bu)2

Contributions to the Chemistry of Phosphorus. 128. Synthesis of the Diphosphastanna-cyclopropane (t-BuP)₂Sn(t-Bu)₂ The first three-membered P₂Sn heterocycle, 1,2,3,3-tetra-tert-butyl-1,2,3-diphosphastanna-cyclopropane (1,2,3,3-tetra-tert-butyl-1,2,3-diphosphastannirane) ( 1 ), has been synthesized by [2+1] cyclocondensation of K(t-Bu)P—P(t-Bu)K with (t-Bu)₂SnCl₂. 1 is stable at room temperature. Besides, (t-BuP)₂[Sn(t-Bu)₂]₂ ( 2 ), (t-BuP)₄Sn(t-Bu)₂ ( 3 ), and (t-BuP)₄ are formed. In the reaction with Et₂SnCl₂, the six-membered ring compound [(t-BuP)₂SnEt₂]₂ ( 4 ) is the main-product; the four- and five-membered cyclostannaphosphanes (t-BuP)₃SnEt₂ ( 5 ) and (t-BuP)₃(SnEt₂)₂ ( 6 ) are also formed. 1 could be isolated in the pure state and has been unambiguously characterized as a three-membered heterocycle with a P₂Sn skeleton. The ³¹P-NMR parameters of the other new cyclostannaphosphanes 2–6 are reported.     

Beiträge zur Chemie des Phosphors. 123. Synthese und Eigenschaften der Diphosphagermirane (t-BuP)2GePh2 und (t-BuP)2GeEt2

Contributions to the Chemistry of Phosphorus. 123. Synthesis and Properties of the Diphosphagermiranes (t-BuP)₂GePh₂ and (t-BuP)₂GeEt₂ The first three-membered P₂Ge heterocycles, 1,2-di-tert-butyl-3, 3-diphenyl-1, 2, 3-diphosphagermirane, (t-BuP)₂GePh₂ (1) , and 1, 2-di-tert-butyl-3, 3-diethyl-1, 2, 3-diphosphagermirane, (t-BuP)₂GeEt₂ (2) , were synthesized by [2+1] cyclocondensation reactions of K(t-Bu)P—P(t-Bu)K with diphenylgermanium dichloride and diethylgermanium dichloride, respectively. The four-, five-, and six-membered cyclogermaphosphanes (t-BuP)₂(GePh₂)₂ (3) , (t-BuP)₃GeR₂ ( 6 R = Ph; 7 R = Et), (t-BuP)₄GePh₂ (5) and (t-BuP)₄(GePh₂)₂ (4) as well as (t-BuP)₄ are formed as by-products. The diphosphagermiranes 1 and 2 could be isolated in 93 and 100% purity, respectively, and were unambiguously characterized as compounds with a cyclic P₂Ge skeleton. The ³¹P-NMR parameters of the cyclogermaphosphanes 3—7 are reported.     

Beiträge zur Chemie des Phosphors. 106. Synthese und Eigenschaften des Diphosphacyclopropans (t-BuP)2CHMe

Contributions to the Chemistry of Phosphorus. 106. Synthesis and Properties of the Diphosphacyclopropane (t-BuP)₂CHMe The new 1,2-di-tert-butyl-3-methyl-1,2-diphosphacyclopropane (1,2-di-tert-butyl-3-methyl-diphosphirane), (t-BuP)₂CHMe ( 1 ), is obtained by reacting K(t-Bu)P? P(t-Bu)K with 1,1-dichloroethane under suitable conditions. 1 can be isolated by high vacuum distillation and is stable for months when stored under inert gas at room temperature. Particularly, no dimerization to the corresponding 1,2,4,5-tetraphosphacyclohexane takes place. The NMR parameters indicate an increase of the exocyclic bond angles compared to (t-BuP)₂CH₂. The signs of all CP coupling constants have been determined by spin tickling experiments. The ²J(CCP)-coupling of the methyl group at the ring carbon depends strongly on the dihedral angle.     

Beiträge zur Chemie des Phosphors. 134. Über die Triphosphane H(t-BuP)3H,Li(t-BuP)3Li und Me3Si(t-BuP)3SiMe3

Contributions to the Chemistry of Phosphorus. 134. On the Triphosphanes H(t-BuP)₃H' Li(t-BuP)₃Li, and Me₃Si(t-BuP)₃SiMe₃ The reaction of 1,3-diiodo-1,2,3-tri-tert-butyltriphosphane, I(t-BuP)₃I, with lithium aluminium hydride leads to 1,2,3-tri-tert-butyltriphosphane, H(t-BuP)₃H ( 1 ). 1 reacts with n-butyllithium to 1,3-dilithium-1,2,3-tri-tert-butyltriphosphide, Li(t-BuP)₃Li ( 2 ), which reacts further with trimethylchlorosilane yielding 1,3-bis(trimethylsilyl)-1,2,3-tri-tert-butyltriphosphane, Me₃Si(t-BuP)₃SiMe₃ ( 3 ). The triphosphanes 1, 2 and 3 could be isolated in a pure state. In solution 1 forms the threo, threo and the threo,erythro configurated diastereomers 1a and 1b in a ratio of about 2:1. 3 predominantly exists in form of the threo,erythro configurated diastereomer 3b by steric reasons.     

Beiträge zur Chemie des Phosphors. 142. P6(t-Bu)5H – das erste Cyclotetraphosphan mit P2-Seitenkette

Contributions to the Chemistry of Phosphorus. 142. P₆(t-Bu)₅H – the First Cyclotetraphosphane with a P₂ Side Chain The thermolysis of 1, 2-di-tert-butyldiphosphane, H(t-Bu)P? P(t-Bu)H, leads to formation of the hitherto unknown hexaphosphane P₆(t-Bu)₅H ( 1 ). In the first instance the iso-P₅H₅ derivative P₅(t-Bu)₄H [3] is formed, which reacts further with H₂(t-BuP)₂ or H₂(t-BuP)₃ yielding 1 . Compound 1 has been isolated in the pure state and structurally characterized as 1-(1,2-di-tert-butyldiphosphino)-2, 3, 4-tri-tert-butyl-cyclotetraphosphane, i. e. as a four-membered ring compound with a P₂ side chain. Due to the chirality of the P atoms in the side chain, 1 exists as a mixture of two configurational isomers, the threo-and the erythro-form.     

Beiträge zur Strukturchemie phosphorhaltiger Ketten und Ringe. 7. Die Kristall- und Molekülstruktur des Diphosphagermetans (t-BuP)2(GePh2)2

Structural Chemistry of Phosphorus Containing Chains and Rings. 7. Molecular and Crystal Structure of the Diphosphagermetane (t-BuP)₂(GePh₂)₂ The compound 1,2-di-tert-butyl-3,3,4,4-tetraphenyl-diphospha-3,4-digerma-cyclobutan, (t-BuP)₂(GePh₂)₂, crystallizes monoclinically in the space group P2₁/c with a = 996.8 pm, b = 1337.3 pm, c = 2403.4 pm, β = 92.66° and Z = 4 formula units. The main structural feature is a non-planar four-membered ring. The (average) bond lengths are d(Ge? Ge) = 242.1 pm, d(Ge? P) = 234.0 pm, d(P? P) = 221.6 pm, d(Ge? C) = 194.9 pm, d(P? C) = 188.tyl4 pm, d(C? C)_Ph = 136.l5 pm, d(C? C)_t-Bu = 151.8 pm, d(C? H)_Ph = 91 pm, d(C? H)_t-Bu ? 95 pm. The geometry of the substituents phenyl and tert-butyl is quite normal.     

Beiträge zur Chemie des Phosphors. 138. P5(t-Bu)4H – das erste Derivat von iso-P5H5

Contributions to the Chemistry of Phosphorus. 138. P₅(t-Bu)₄H — the First Derivative of iso-P₅H₅ The thermolysis of 1,2-di-tert-butyldiphosphane, H(t-Bu)P? P(t-Bu)H, yields under suitable conditions the compound P₅(t-Bu)₄H ( 1 ) as the main product. Besides, the tert-butylphosphanes t-BuPH₂, P₆(t-Bu)₅H ( 2 ), H₂(t-BuP)₃, and (t-BuP)₄ are formed. 1 has been isolated in the pure state and structurally characterized as 1-(tert-butylphosphino)-2,3,4-tri-tert-butyl-cyclotetraphosphane. Hence, compound 1 is a derivative of iso-P₅H₅ with a branched phosphorus skeleton built up by a four-membered ring and a phosphorus side chain.     

Exploring organic reactions using simple cyclodiphosphazanes

Phosphine-activated reactions of alkynes/alkenes/allenes as well as the Mitsunobu reaction involve a rich phosphorus chemistry. With the aid of simple cyclodiphosphazanes, characterization of many compounds analogous to the proposed intermediates in such reactions has been accomplished. Use of a cyclodiphosphazane in Pd-catalyzed N-arylation reactions is highlighted. Results on molecular non-stoichiometry in phosphorus compounds and on the use of chiral phosphorus systems are discussed. Synthesis of allenylphosphoramides involving a cyclodiphosphazane is also described. X-ray structures of the new compounds [(t-BuNH)(PhCH₂CH(CN)CH₂-)P(μ-N-t-Bu)₂P(NH-t-Bu)]⁺[HCO₃]⁻ (13), [(t-BuNH)P(μ-N-t-Bu)₂P(N-t-Bu)-C(CH₂)CH(C₆H₄-4-Me)-P(O)(OCH₂CMe₂CH₂O)] (18), [(i-PrNH)P(μ-N-t-Bu)₂P(N-i-Pr)-N(CO₂-i-Pr)-NH(CO₂-i-Pr)] (24), [(S)-(2-OH-1-C₁₀H₆-1′-C₁₀H₆-2′-O-P(O)(NH-t-Bu)₂] (36) and [(t-BuNH)(O)P(μ-N-t-Bu)₂P(O)(CHCCMe₂)] (40) are also reported.     

Darstellung und Kristallstruktur von trans-(Ph4As)2[OsCl2(NCS)(SCN)], Schwingungsspektren und Normalkoordinatenanalyse

Preparation and Crystal Structure of trans-(Ph₄As)₂[OsCl₂(NCS) (SCN) ], Vibrational Spectra and Normal Coordinate Analysis By treatment of trans-[OsCl₂I₄]^2? with (SCN)₂ in dichloromethane a mixture of different linkage isomers is formed, from which trans-[OsCl₂(NCS)(SCN)]^2? has been isolated by ion exchange chromatography on diethylaminoethyl cellulose. The X-Ray structure determination on a single crystal of trans-(Ph₄As)₂[OsCl₂(NCS)(SCN)] (triclinic, space group P 1 , a = 12.505(5), b = 12.056(5), c = 19.833(5) Å, α = 108.047(5)°, β = 91.964(5)°, γ = 117.048(5)°, Z = 2) reveals that two cis-positioned Thiocyanate(N) groups are coordinated with Os? N? C angles of 172.1° and 173.0° and two cis-positioned Thiocyanate(S) groups are coordinated with Os? S? C angles of 106.9° and 108.7°. Using the molecular parameters of the X-Ray determination the low temperature (10 K) IR and Raman spectra of the (n-Bu₄N) salt of the linkage isomer are assigned by a normal coordinate analysis based on a modified valence force field. The valence force constants are f_d(OsN) = 1.63 and f_d(OsS) = 1.30 mdyn/Å. Taking into account the trans influence a good agreement between observed and calculated frequencies is achieved.     

Beiträge zur Strukturchemie phosphorhaltiger Ketten und Ringe. 1. Die KristallStruktur des Diphosphasilirans (t-BuP)2SiPh2

Structural Chemistry of Phosphorus-containing Chains and Rings. 1. Crystal Structure of the Diphosphasilirane (t-BuP)₂SiPh₂ The three-membered P₂Si-heterocycle 1, 2-di-tert-butyl-3, 3-diphenyl-1, 2, 3-diphosphasilirane (t-BuP)₂SiPh₂ crystallizes monoclinic in the space group P2₁ with a = 1041.2 pm, b = 882.3 pm, c = 1158.1 pm, β = 91.33° and Z = 2 formula units. A special structural feature is the regular triangle built up by two P and one Si. Therefore the endocyclic bond angle at Si is as low as 60°. The average bond lengths are P? P = 222.6 pm, P? Si = 222.5 pm, P? C = 190.8 pm, Si? C = 186.6 pm, (C? C )ph = 139.0 pm, ( C? C )_t-Bu = 151.7 pm. The geometry of the substituents phenyl and tert-butyl is quite normal, the last ones are slightly disordered.     

Beiträge zur Chemie des Phosphors. 104. Synthese und Eigenschaften von 1,3-Dihalogen-1,2,3-tritert-butyltriphosphanen (t-BuP)3X2, X = Cl,Br, I

Contributions to the Chemistry of Phosphorus. 104. Synthesis and Properties of 1,3-Dihalogen-1,2,3-tri-tert-butyltriphosphanes (t-BuP)₃X₂, X = Cl, Br, I The halogenating ring-cleavage of tri-tert-butyl-cyclotriphosphane, (t-BuP)₃, by iodine, bromine or phosphorus(V)bromide as well as phosphorus(V)chloride leads to the first 1,3-dihalogen-1,2,3-triorganyltriphosphanes (t-BuP)₃I₂ ( 1 ), (t-BuP)₃Br₂ ( 2 ), and (t-BuP)₃Cl₂ ( 3 ). The 1,2-dihalogen-1,2-di-tert-butyldiphosphanes (t-BuP)₂I₂ ( 4 ), (t-BuP)₂Br₂ ( 6 ), and (t-BuP)₂Cl₂ ( 9 ) as well as the dihalogen-tert-butylphosphanes t-BuPI₂ ( 5 ), t-BuPBr₂ ( 7 ), and t-BuPCl₂ ( 10 ) are formed as by-products. Moreover, the reaction of (t-BuP)₃ with PBr₅ leads to 1-bromo-2,3,4-tri-tert-butyl-cyclo-tetraphosphane, (t-BuP)₃(PBr) ( 8 ). The compounds 1 and 3 could be isolated in a pure state and were characterized in all details. 3 is a reMarkably stable open-chain triphosphane.     

Crystallization of poly(α-methyl-α-N-propyl-β-propiolactones) prepared from homogeneous and heterogeneous initiators

Half-crystallization times t_½, enthalpies of fusion ΔH, melting temperatures T_f glass transition temperatures T_g x-ray patterns, and morphologies were obtained for nine samples of poly(α-methyl-α-n-propyl-β-propiolactones) prepared from different homogeneous or heterogeneous initiators. The bulk of the results indicates that all samples can be classified into two categories: Polymers A having t_½?, 100 min, ΔH ? 26 J/g, T ? 376 K, T_g ? 275 K, and Polymers B having t_½ ? 10 min, ΔH ? 14.5 J/g T ? 425 K and T_g ? 271 K. Polymers A were prepared with homogeneous initiators while polymers B were polymerized with heterogeneous intiators. The difference in crystallization behavior between polymers A and polymers B is certainly due to a difference in microstructure, brought about by the initiators, which has been qualitatively observed by NMR.     

Silaheterocyklen. III. Erzeugung und Reaktivität von Di-tbutyl-Neopentylsilaethen,BuSiCHCH2But

Silaheterocycles. III. Synthesis and Reactivity of Di-^tbutylneopentylsilaethene, Bu Si?CHCH₂Bu^t The three di-^tbutylvinylsilanes BuSi(X)CH?CH₂ (X = H 5 , X = F 9 , X = Cl 22 ) are prepared by the reaction of their SiCl precursors with vinyl lithium. In the treatment with LiBu^t the first step is the generation of the α-lithio compound BuSi(X)CH(Li)CH₂Bu^t, the following reactions are governed by the nature of the substituent X and the reaction conditions (solvent, concentration, temperature). For X = H 2,3-LiH elimination leads to BuSi(H)CH?CHBu^t ( 7 ), with X = F or Cl Si?C formation by 1,2-LiX elimination competes with intermolecular Si-C-coupling producing BuSi(H)CH(SiBuCH?CHBu^t)CH₂Bu^t ( 13 ) as the main product. BuSi?CHCH₂Bu^t ( 1 ) probably coordinates to LiBu^t and reacts to yield BuSiCH?CHBu^t ( 3 ) and 7 , forms tetrabutyl-dineopentyl-1,3-disilacyclobutane 2 by cyclodimerization and 13 by addition of BuSi(X)CH(Li)CH₂Bu^t.     

Beiträge zur Strukturchemie phosphorhaltiger Ketten und Ringe. 2. Die Kristall- und Molekülstruktur des Diphosphaborirans (t-BuP)2BNEt2

Structural Chemistry of Phosphorus-containing Chains and Rings. 2. Crystal and Molecular Structure of the Diphosphaborirane (t-BuP)₂BNEt₂ The three-membered P₂B-heterocycles 1,2-di-tert-butyl-3-diethylamino-1,2,3-diphosphaborirane, (t-BuP)₂BNEt₂, crystallizes triclinic in the space group P1 with a = 935.5 pm, b = 985.4 pm, c = 987.4 pm,α = 81.55°, β = 89.40°, γ =69.07°, and Z = 2 formula units. The main structural feature is a short B? N-bond length (138.2 pm) inside a plane P₂BN-group. The endocyclic bond angles are 54.0° on phosphorus and 72.0° on boron. The (average) bond lengths are P? P = 222.5 pm, P? C = 189.5 pm, P? B = 189.3 pm, B? N = 138.2 pm, N? C = 147.2 pm, C? C = 152.6 pm, and C? H = 98 pm. The geometry of the substituents ethyl and tert-butyl is quite normal.