Novel molybdenum and tungsten carbonyl compounds containing the bidentate chelating thiomethoxymethyl group and tridentate chelating gallate ligands: crystal and molecular structures of [Me2Ga(N2C3H3)(OCH2CH2NMe2)]Mo(CO)2(η2-CH2SMe) and [Me2Ga(N2C5H7)(OCH2CH2NMe2)]Mo(CO)2(η2-CH2SMe)

1980 ◽  
Vol 58 (11) ◽  
pp. 1080-1090 ◽  
Author(s):  
Kenneth S. Chong ◽  
Steven J. Rettig ◽  
Alan Storr ◽  
James Trotter
Keyword(s):  
Physical Properties ◽  
Least Squares ◽  
Carbonyl Compounds ◽  
Molecular Structures ◽  
Full Matrix ◽  
Space Group ◽  
Bond Lengths ◽  
Crystal And Molecular Structures ◽  
Tungsten Carbonyl ◽  
And Tungsten

Details of the synthesis and physical properties of novel molybdenum and tungsten carbonyl compounds containing the bidentate chelating thiomethoxymethyl group and tridentate chelating gallate ligands are described. Crystals of [Me2Ga(N2C3H3)(OCH2CH2NMe2)]Mo(CO)2(η2-CH2SMe) are triclinic, a = 8.144(1), b = 9.150(1), c = 13.731(1) Å, α = 96.155(6), β = 98.83(1), γ = 108.73(1) °, Z = 2, space group [Formula: see text] and crystals of [Me2Ga(N2C5H7)(OCH2CH2NMe2)]Mo(CO)2(η2-CH2SMe) are monoclinic, a = 8.1754(7), b = 15.074(1), c = 16.708(1) Å, β = 94.365(6) °, Z = 4, space group P21/c. The structures were solved by Patterson and Fourier syntheses and were refined by full-matrix least-squares procedures to final R values of 0.021 and 0.033 for 3679 and 4362 reflections with I ≥ 3σ(I) respectively. The Mo atoms in both structures are best described as heptacoordinate with bidentate η2-CH2SMe ligands. Important bond lengths (corrected for libration) are: Mo—S, 2.4750(6), Mo—C(S), 2.202(3), Mo—O, 2.248(2), Mo—N(pyrazolyl), 2.192(2), Mo—N(amino), 2.394(2), Mo—C(O), 1.903(3) and 1.957(3), Ga—O, 1.912(2), Ga—N, 2.020(2), and Ga—C, 1.962(4) and 1.969(4) Å for [Me2Ga(N2C3H3)(OCH2CH2NMe2)]Mo(CO)2(η2-CH2SMe); corresponding distances for [Me2Ga(N2C5H7)(OCH2CH2NMe2)]Mo(CO)2(η2-CH2SMe) are 2.4906(8), 2.211(3), 2.263(2), 2.205(2), 2.403(3), 1.906(3), 1.958(3), 1.918(2), 2.014(3), 1.963(4), and 1.966(4) Å.

Structural studies of organoboron compounds. XVI. Preparation and crystal and molecular structures of 4,4-dimethyl-2,5,5-triphenyl-1,3-dioxa-4-azonia-2-bora-5-boratacyclopentane and 4,4,5,5-tetramethyl-2,2-diphenyl-1,3-dioxa-4-azonia-2-boratacyclopentane

1984 ◽  
Vol 62 (5) ◽  
pp. 838-844 ◽  
Author(s):  
W. Kliegel ◽  
H.-W. Motzkus ◽  
Steven J. Rettig ◽  
James Trotter
Keyword(s):  
Physical Properties ◽  
Least Squares ◽  
Steric Hindrance ◽  
Direct Methods ◽  
Structural Features ◽  
Molecular Structures ◽  
Structural Studies ◽  
Full Matrix ◽  
Space Group ◽  
Crystal And Molecular Structures

Details of the synthesis, physical properties, and molecular structures of 4,4-dimethyl-2,5,5-triphenyl-1,3-dioxa-4-azonia-2-bora-5-boratacyclopentane, 4, and 4,4,5,5-tetramethyl-2,2-diphenyl-1,3-dioxa-4-azonia-2-boratacyclopentane, 5, are reported. Crystals of 4 are triclinic, a = 9.841(2), b = 14.722(3), c = 6.6701(12) Å, α = 86.79(1), β = 102.95(1), γ = 93.89(1)°, Z = 2, space group [Formula: see text]; and those of 5 are monoclinic, a = 14.9164(12), b = 6.4732(3), c = 18.2248(15) Å, β = 117.263(3)°, Z = 4, space group Cc. Both structures were solved by direct methods and were refined by full-matrix least-squares procedures to final R values of 0.032 and 0.035 for 1456 and 1649 observed reflections, respectively. Molecules of 4 contain non-planar BOBON rings with an unusually long N(sp3)—B(sp3) distance of 1.728(3) Å and in 5 there is a long N(sp3)—C(sp3) bond of 1.591(3) Å. These structural features are ascribed to steric hindrance.

Crystal and molecular structures of 2,2,4,4,6,8,8-heptamethyl-6-methylamino-1,3,5-triaza-2,4,6,8(PV)-tetraphosphorin and 2,2,4,4,6,8,8-heptamethyl-6-methylamino-7-benzoyl-1,3,5-triaza-2,4,6,8(PV)-tetraphosphorin

1978 ◽  
Vol 56 (22) ◽  
pp. 2833-2843 ◽  
Author(s):  
Harry P. Calhoun ◽  
Richard T. Oakley ◽  
Norman L. Paddock ◽  
Steven J. Rettig ◽  
James Trotter
Keyword(s):  
Least Squares ◽  
Direct Methods ◽  
Molecular Structures ◽  
Full Matrix ◽  
Space Group ◽  
Bond Lengths ◽  
Crystal And Molecular Structures ◽  
Out Of Plane ◽  
The Mean

Crystals of 2,2,4,4,6,8,8-heptamethyl-6-methylamino-1,3,5-triaza-2,4,6,8(PV)-tetraphosphorin are monoclinic, a = 11.639(4), b = 11.957(7), c = 12.114(4) Å, β = 94.07(2) °, Z = 4, space group P21/n. The structure was solved by direct methods and was refined by full-matrix least-squares procedures to R = 0.032 and Rw of 0.041 for 2012 reflections with I ≥ 3σ(I). Crystals of 2,2,4,4,6,8,8-heptamethyl-6-methylamino-7-benzoyl-1,3,5-triaza-2,4,6,8(PV)-tetraphosphorin are triclinic, a = 15.513(1), b = 8.422(1), c = 8.933(1) Å, α = 89.24(1), β = 100.18(1), γ = 107.30(1) °, Z = 2, space group [Formula: see text]. The structure was solved by Patterson and Fourier syntheses and was refined to a final R of 0.041 and Rw of 0.044 for 3654 reflections with I ≥ 3σ(I). The eight-membered P4N3C rings in both structures hâve 'tub' conformations. The mean bond lengths (corrected for libration) are: P—N(endo), 1.609(9), P—N(exo), 1.679(2), P—C(endo), 1.717(2), and P—C(exo), 1.815(8) Å for Me7(MeNH)P4N3CH and 1.595(4), 1.655(2), 1.763(4), and 1.804(5) Å respectively for Me7(MeNH)P4N3CC(O)Ph. The near-equivalence of the endocyclic P—N bond lengths in the azaphosphorins is discussed in terms of opposing changes in the in-plane and out-of-plane Π-systems.

Structural studies of organoboron compounds. XXXII. 5,5-Difluoro-2,2-pentamethylene-1,4,6-trioxa-3a-azonia-5-borata-1,2,3,4,5,6-hexahydrobenzo[h]azulene and 2,2-pentamethylene-5,5-diphenyl-1,4,6-trioxa-3a-azonia-5-borata-1,2,3,4,5,6-hexahydrobenzo[h]azulene

1988 ◽  
Vol 66 (10) ◽  
pp. 2621-2630 ◽  
Author(s):  
Wolfgang Kliegel ◽  
Mahmood Tajerbashi ◽  
Steven J. Rettig ◽  
James Trotter
Keyword(s):  
Solid State ◽  
Physical Properties ◽  
Least Squares ◽  
Crystal Structures ◽  
Direct Methods ◽  
Structural Studies ◽  
Full Matrix ◽  
Space Group ◽  
Bond Lengths ◽  
Conformational Isomers

Details of the syntheses, physical properties, and crystal structures of the title compounds are reported. Crystals of 5,5-difluoro-2,2-pentamethylene-1,4,6-trioxa-3a-azonia-5-borata-1,2,3,4,5,6-hexahydrobenzo[h]azulene are triclinic, a = 6.1576(3), b = 11.2651(3), c = 10.8118(3) Å, α = 109.747(3), β = 105.807(4), γ = 92.976(4)°, Z = 2, space group [Formula: see text], and those of 2,2-pentamethylene-5,5-diphenyl-1,4,6-trioxa-3a-azonia-5-borata-1,2,3,4,5,6-hexahydrobenzo[h]azulene are monoclinic, a = 9.8549(6), b = 10.9242(6), c = 41.263(2) Å, β = 92.717(6)°, Z = 8, space group P21/n. Both structures were solved by direct methods and were refined by full-matrix least-squares procedures to R = 0.045 and 0.042 for 2344 and 4248 reflections with I ≥ 3σ(I), respectively. The molecules were both found to possess a seven-membered chelate structure, the O,O-chelatїng ligand being strongly bound to the X2B moiety. Two conformational isomers of the X = Ph compound were found in the solid state. The 2-oxazoline N-oxide moieties present in both compounds are the first to be structurally characterized. Important mean libration-corrected bond lengths are: O—B = 1.491 and F—B = 1.387 Å for X = F; O—B = 1.511 and C—B = 1.620 Å for X = Ph.

Aromatic aldonitrones of 2-(hydroxyamino)benzyl alcohol and their cyclic isomers. Crystal and molecular structures of a 1-hydroxy-1,2-dihydro-4H-3,1-benzoxazine, a boron chelate, and its parent nitrone ligand

1998 ◽  
Vol 76 (4) ◽  
pp. 389-399 ◽  
Author(s):  
Wolfgang Kliegel ◽  
Jörg Metge ◽  
Steven J Rettig ◽  
James Trotter
Keyword(s):  
Least Squares ◽  
Benzyl Alcohol ◽  
Crystal Structures ◽  
Direct Methods ◽  
Molecular Structures ◽  
Full Matrix ◽  
Space Group ◽  
Crystal And Molecular Structures ◽  
Independent Molecules ◽  
Boron Chelate

The synthesis of a series of C-aryl-N-[2-(hydroxymethyl)phenyl]nitrones, 5 (that can also exist under certain conditions as isomeric 1-hydroxy-2-aryl-1,2-dihydro-4H-3,1-benzoxazines, 8), via 2-(hydroxyamino)benzyl alcohol, 4, and their subsequent reactions with oxybis(diphenylborane), (Ph2B)2O, leading to the 5-(arylmethylene)-7,7-diphenyl-6,8-dioxa- 5-azonia-7-borata-5H-6,7,8,9-tetrahydrobenzocyclo- heptenes 6 are described. Crystals of 1-hydroxy-2- (4-methoxyphenyl)- 1,2-dihydro-4H-3,1-benzoxazine, 8b, are monoclinic, a = 9.379(2), b = 10.699(2), c = 12.9392(7) Å, β = 99.916(2)°, Z = 4 (two independent molecules), space group Pa; those of C-[4-(dimethylamino)phenyl]-N-[(2-hydroxymethyl)phenyl]nitrone, 5c, are monoclinic, a = 7.687(1), b = 7.891(1), c = 11.5053(9) Å, β = 92.781(9)°, Z = 2, space group P21; and those of 5-[4-(dimethylamino)phenylmethylene]-7,7-diphenyl-6,8-dioxa-5-azonia-7-borata-5H-6,7,8,9- tetrahydro-benzocycloheptene, 6a, are monoclinic, a = 10.771(1), b = 13.1057(9), c = 16.8724(7) Å, β = 90.005(5)°, Z = 4, space group P21/n. The structures were solved by direct methods and refined by full-matrix least-squares procedures to R(F2) = 0.120 (Rw(F2) = 0.135) for all 3149 reflections (R(F) = 0.071, Rw(F) = 0.063 for 1500 reflections with I >3 σ (I)) for 8b and R(F) = 0.035 and 0.036 (Rw(F) = 0.031 and 0.038) for 1071 and 3594 reflections with I >3 σ (I), respectively, for 5c and 6a. Compound 8b is the first structurally characterized 1-hydroxy-1,2-dihydro-4H-3,1-benzoxazine derivative and 6a features a relatively rare seven-membered boron-containing heterocycle.Key words: C-aryl-N-[2-(hydroxymethyl)phenyl]nitrones, 1-hydroxy-2-aryl-1,2-dihydro-4H-3,1-benzoxazines, organoboron compounds, crystal structures

Structural studies of organoboron compounds. XV. Crystal and molecular structures of (3-aminopropanolato)diphenylboron, (2-N,N-dimethylaminoethanolato)diphenylboron, and (2-N,N-dimethylaminoethanolato)diphenylboron – diphenylborinic acid (1:1)

1983 ◽  
Vol 61 (10) ◽  
pp. 2334-2340 ◽  
Author(s):  
Steven J. Rettig ◽  
James Trotter
Keyword(s):  
Least Squares ◽  
Boron Atom ◽  
Direct Methods ◽  
Molecular Structures ◽  
Structural Studies ◽  
Organoboron Compounds ◽  
Full Matrix ◽  
Space Group ◽  
Crystal And Molecular Structures

Crystals of (3-aminopropanolato)diphenylboron are monoclinic, a = 9.6717(13). b = 9.8867(6), c = 14.452(2) Å, β = 99.500(7)°, Z = 4, space group P21/n: those of (2-N,N-dimethylaminoethanolato)diphenylboron are monoclinic, a = 7.0721(4), b = 16.8829(4), c = 12.0975(8) Å, β = 97.875(3)°, Z = 4, space group Cc; and those of (2-N,N-dimethylaminoethanolato)diphenylboron – diphenylborinic acid (1:1) are monoclinic. a = 11.3231(10). b = 19.3190(12). c = 12.2451(11) Å, β = 109.321(4)°, Z = 4, space group P21/n. All three structures were solved by direct methods and were refined by full-matrix least-squares procedures to final R values of 0.038. 0.031, and 0.040 for 1522, 1649, and 2420 reflections with I ≥ 3σ(I) respectively. Each structure contains a tetrahedrally coordinated boron atom. The libration-corrected B—O, B—N, and mean B—C distances are: 1.481(2), 1.643(3), and 1.623(3) Å for (3-aminopropanolato)diphenylboron; 1.476(2), 1.691 (2), and 1.625(7) Å for (2-N,N-dimethylaminoethanolato)diphenylboron. The Ph2BOH molecule contains a trigonal-planar boron atom with B—O = 1.354(3) Å and mean B—C = 1.572(3) Å.

The Crystal and Molecular Structures of the 3,5-Dimethylpyrazolylgallium dimethyl dimer, [Me2Ga·N2C5H7]2, and the Hydroxy-bridged Species, [Me2Ga(OH)(N2C5H7)GaMe2·2N2C5H8]

1975 ◽  
Vol 53 (19) ◽  
pp. 2944-2954 ◽  
Author(s):  
David F. Rendle ◽  
Alan Storr ◽  
James Trotter
Keyword(s):  
Least Squares ◽  
Membered Ring ◽  
Molecular Structures ◽  
Methyl Groups ◽  
Central Feature ◽  
Fourier Methods ◽  
Full Matrix ◽  
Space Group ◽  
Crystal And Molecular Structures ◽  
The Mean

Crystals of the 3,5-dimethylpyrazolylgallium dimethyl dimer [Me2Ga·N2C5H7]2 (1a) are monoclinic, a = 8.660(3), b = 13.776(1), c = 8.443(2) Å, β = 112.45(2)°, Z = 2, space group P21/c, and crystals of the hydroxy-bridged species [Me2Ga(OH)(N2C5H7)GaMe2·2N2C5H8] (1b) are monoclinic, a = 28.778(3), b = 9.098(3), c = 20.222(2) Å, β = 100.72(1)°, Z = 8, space group C2/c. Both structures were solved by Patterson and Fourier methods and were refined by full-matrix least-squares methods to final R values of 0.071 and 0.045 for 1443 and 2746 reflections with I ≥ 3σ(I) respectively. Molecules of 1a lie on crystallographic centers of symmetry, the central Ga—(N—N)2—Ga ring being almost planar as a result of steric interactions between gallium-methyl groups and those on the 'pyrazolyl' rings. The mean Ga—N and Ga—C distances are 1.993 Å and 1.962 Å respectively. Compound 1b was formed by the attack of moisture on the strained dimer 1a. The central feature is a five-membered Ga2N2O ring, with two 3,5-dimethylpyrazoie molecules hydrogen-bonded to it (N—H … O, O—H … N, 2.851 and 2.892 Å) and to each other (N—H … N, 2.907 Å). The five-membered ring adopts a slightly distorted envelope conformation, the angle between the Ga2N2 and N2O moieties being 13.9°. The mean Ga—N and Ga—O distances are 1.989 and 1.934 Å respectively.

Structural studies of organoboron compounds. XII. Crystal and molecular structures of (acetylacetonato)diphenylboron and (tropolonato)diphenylboron

1982 ◽  
Vol 60 (23) ◽  
pp. 2957-2964 ◽  
Author(s):  
Steven J. Rettig ◽  
James Trotter
Keyword(s):  
Least Squares ◽  
Chelate Ring ◽  
Direct Methods ◽  
Molecular Structures ◽  
Structural Studies ◽  
Organoboron Compounds ◽  
Full Matrix ◽  
Space Group ◽  
Crystal And Molecular Structures ◽  
The Mean

There are two crystalline modifications of (acetylacetonato)diphenylboron: triclinic, a = 8.3557(8), b = 9.3519(8), c = 9.6103(9) Å, α = 96.094(5), β = 94.904(6), γ = 93.489(6)°, Z = 2, space group [Formula: see text], and monoclinic, a = 11.6329(11), b = 17.1628, c = 7.6542(6) Å, β = 97.669(4)°, Z = 4, space group P21/c. Crystals of (tropolonato)diphenylboron are monoclinic, a = 12.1596(5), b = 10.2614(4), c = 12.4883(6) Å, β = 100.965(2)°, Z = 4, space group P21/c. All three structures were solved by direct methods and were refined by full-matrix least-squares procedures to R values of 0.046, 0.041, and 0.035 for 2465, 2124, and 1722 reflections with I ≥ 3σ(I) respectively. Each structure consists of discrete molecules containing tetrahedrally coordinated boron atoms, both the acetylacetonato and tropolonato moieties being delocalized and symmetric. The chelate rings in both forms of (acetylacetonato)-diphenylboron have distorted B-envelope conformations while the chelate ring in (tropolonato)diphenylboron is essentially planar. The mean B—O and B—C distances (corrected for libration) are: 1.543(4) and 1.605(4) Å in triclinic, 1.533(3) and 1.607(4) Å in monoclinic (acetylacetonato)diphenylboron, and 1.555(11) and 1.605(6) Å in (tropolonato)diphenylboron.

Structural studies of organoboron compounds. XVIII. Crystal and molecular structures of 2,2-diphenyl-1,3-dioxa-3a-azonia-2-borataindan and 4-cyclohexyl-6-methyl-2,2-diphenyl-1,3-dioxa-3a-azonia-2-borataindan

1983 ◽  
Vol 61 (11) ◽  
pp. 2493-2499 ◽  
Author(s):  
W. Kliegel ◽  
D. Nanninga ◽  
Steven J. Rettig ◽  
James Trotter
Keyword(s):  
Least Squares ◽  
Direct Methods ◽  
Coordination Complexes ◽  
Molecular Structures ◽  
Structural Studies ◽  
Full Matrix ◽  
Space Group ◽  
Crystal And Molecular Structures ◽  
Anionic Ligand ◽  
Oxide Crystals

The crystal structures of 2,2-diphenyl-1,3-dioxa-3a-azonia-2-borataindan, 6a, and 4-cyclohexyl-6-methyl-2,2-diphenyl-1,3-dioxa-3a-azonia-2-borataindan, 6b, reported here represent the first crystallographic examples of coordination complexes of the anionic ligand derived from 2-hydroxypyridine N-oxide. Crystals of 6a are monoclinic, a = 11.5210(13), b = 10.2860(8), c = 12.7354(15) Å, β = 101.878(5)°, Z = 4, space group P21/c; and those of 6b are monoclinic, a = 8.5047(8), b = 15.6603(14), c = 16.0501(18) Å, β = 104.776(5)°, Z = 4, space group P21/n. Both structures were solved by direct methods and were refined by full-matrix least-squares procedures to final R values of 0.039 and 0.042 for 1440 and 1750 reflections with I ≥ 3σ(I), respectively. Both molecules feature tetrahedrally coordinated boron atoms incorporated into five-membered OBOCN chelate rings which have B-envelope conformations. The observed molecular geometries indicate that the ligand may be classed as a hybrid of the 2-hydroxypyridine N-oxide and 1-hydroxy-2-pyridinone tautomers of the parent alcohol. Important bond lengths (corrected for libration) are: O—B = 1.557(3)−1.580(3), mean C—B = 1.600(4), C—O = 1.316(3), and N—O = 1.389(3) Å.

Structural studies of organoboron compounds. XXI. Crystal and molecular structures of 3-(phenylmethylidene)-4-methyl-1-phenyl-2,6,7-trioxa-3-azonia-1-boratabicyclo-[2.2.2]octane and N-(4-nitrophenylmethylidene)-5-methyl-2-phenyl-1,3-dioxa-2-bora-5-cyclohexaneamine N-oxide

1985 ◽  
Vol 63 (2) ◽  
pp. 509-515 ◽  
Author(s):  
W. Kliegel ◽  
L. Preu ◽  
Steven J. Rettig ◽  
James Trotter
Keyword(s):  
Least Squares ◽  
Phenylboronic Acid ◽  
Direct Methods ◽  
Molecular Structures ◽  
Structural Studies ◽  
Full Matrix ◽  
Space Group ◽  
Condensation Products ◽  
Crystal And Molecular Structures ◽  
Bicyclic Structure

Crystals of 3-(phenylmethylidene)-4-methyl-1-phenyl-2,6,7-trioxa-3-azonia-1-boratabicyclo[2.2.2]octane are orthorhombic, a = 8.0732(7), b = 11.8499(10), c = 31.679(2) Å, Z = 8, space group Pbca, and those of N-(4-nitrophenylmethylidene)-5-methyl-2-phenyl-1,3-dioxa-2-bora-5-cyclohexaneamine N-oxide are monoclinic, a = 6.1873(6), b = 23.206(2), c = 11.3081(11) Å, β = 92.326(5)°, Z = 4, space group P21/n. Both structures were solved by direct methods and were refined by full-matrix least-squares procedures to final R values of 0.041 and 0.036 for 943 and 1679 reflections with I ≥ 3σ(I), respectively. Both compounds are condensation products of bis(hydroxyalkyl)nitrones and phenylboronic acid. 3-(Phenyl-methylidene)-4-methyl-1-phenyl-2,6,7-trioxa-3-azonia-1-boratabicyclo[2.2.2]octane was found to possess a bicyclic structure resulting from intramolecular O → B coordination (O—B = 1.604(7) Å) and is the first such bicyclic boron compound to be structurally characterized. In N-(4-nitrophenylmethylidene)-5-methyl-2-phenyl-1,3-dioxa-2-bora-5-cyclohexaneamine N-oxide, which has weakened nitrone basicity, the O → B interaction does not occur, resulting in a monocyclic system incorporating a trigonal planar boron atom.

Synthesis and Crystal and Molecular Structures of the N,N-Dimethylethanol-aminogallane and N,N-Dimethylethanolaminogallium Dimethyl Dimers

1975 ◽  
Vol 53 (1) ◽  
pp. 58-66 ◽  
Author(s):  
Steven J. Rettig ◽  
Alan Storr ◽  
James Trotter
Keyword(s):  
Least Squares ◽  
Molecular Structures ◽  
Methyl Groups ◽  
Steric Interactions ◽  
Full Matrix ◽  
Space Group ◽  
Trigonal Bipyramidal Geometry ◽  
Crystal And Molecular Structures ◽  
Trigonal Bipyramidal ◽  
Distorted Trigonal Bipyramidal

Crystals of the N,N-dimethylethanolaminogallane dimer 1a are monoclinic, a = 8.540(1), b = 7.0433(7), c = 12.227(6) Å, β = 92.94(3)°, Z = 2, space group P21/c and crystals of the N,N-dimethylethanolaminogallium dimethyl dimer 1b are orthorhombic, a = 15.608(3), b = 11.655(2), c = 10.266(2) Å, Z = 4, space group Pccn. Both structures were determined by Patterson and Fourier syntheses and were refined by full-matrix least-squares procedures to final R values of 0.039 and 0.053 for 1062 and 1155 reflections with 1 ≥ 3σ(I) respectively. Both structures feature well-separated centrosymmetric dimeric units occurring via the formation of four-membered Ga2O2 rings. The five-coordinate gallium atoms have distorted trigonal bipyramidal geometry. Steric interactions between methyl groups in 1b are believed responsible for the lengthening of the axial Ga—N distance from 2.279(3) in 1a to 2.471(4) Å in 1b. Other bond distances are: for 1a; Ga—O (axial), 2.053(3), Ga—O, 1.911(3), Ga—H, 1.50(7) and 1.73(5), O—C, 1.369(5), N—C, 1.466 – 1.485(6), C—C, 1.512(7), and mean C—H, 1.05; for 1b; Ga—O (axial), 2.078(3), Ga—O, 1.913(3), Ga—C, 1.936(6) and 1.948(7), O—C, 1.382(7), N—C, 1.452–1.482(7−8), C—C, 1.516(9), and mean C—H, 1.01 Å.

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