trans‐Chloro­(methyl)­bis­(tri­cyclo­hexyl­phosphine)­platinum(II)

The crystal structure of the title compound, [PtCl(CH₃)(C₁₈H₃₃P)₂], is isostructural with various platinum(II) and palladium(II) complexes containing two bulky tri­cyclo­hexyl­phosphine ligands in a trans orientation. The Pt atom resides on an inversion centre, resulting in a 50% statistical disorder in the chloro and methyl positions. The most significant geometrical parameters are Pt—P 2.3431 (8), Pt—­Cl 2.440 (4) and Pt—C1 2.179 (13) Å, and P—Pt—P 180, P—Pt—Cl 89.15 (12) and 90.85 (12), and C—Pt—Cl 172.7 (5)°. The effective and Tolman cone angles for the tricyclohexylphosphine ligands were calculated as 160 and 162°, respectively.     

Structural change in a series of protonated layered perovskite compounds, HLnTiO4 (Ln=La, Nd and Y)

A deuterated n=1 Ruddlesden-Popper compound, DLnTiO₄ (HLnTiO₄, Ln=La, Nd and Y), was prepared by an ion-exchange reaction of Na⁺ ions in NaLnTiO₄ with D⁺ ions, and its structure was analyzed by Rietveld method using powder neutron diffraction data. The structure analyses showed that DLaTiO₄ and DNdTiO₄ crystallized in the space group P4/nmm with a=3.7232(1) and c=12.3088(1) Å, and a=3.7039(1) and c=12.0883(1) Å, respectively. On the other hand, DYTiO₄ crystallized in the space group P2₁/c with a=11.460(1), b=5.2920(4), c=5.3628(5) Å and β=90.441(9)°. The loaded protons were found to statistically occupy the sites around an apical oxygen of TiO₆ octahedron in the interlayer of these compounds, rather than Na atom sites in NaLnTiO₄.     

An Asymmetric Contrastive Loss for Handling Imbalanced Datasets

Contrastive learning is a representation learning method performed by contrasting a sample to other similar samples so that they are brought closely together, forming clusters in the feature space. The learning process is typically conducted using a two-stage training architecture, and it utilizes the contrastive loss (CL) for its feature learning. Contrastive learning has been shown to be quite successful in handling imbalanced datasets, in which some classes are overrepresented while some others are underrepresented. However, previous studies have not specifically modified CL for imbalanced datasets. In this work, we introduce an asymmetric version of CL, referred to as ACL, in order to directly address the problem of class imbalance. In addition, we propose the asymmetric focal contrastive loss (AFCL) as a further generalization of both ACL and focal contrastive loss (FCL). The results on the imbalanced FMNIST and ISIC 2018 datasets show that the AFCL is capable of outperforming the CL and FCL in terms of both weighted and unweighted classification accuracies.     

trans‐Di­iodo­bis(1,3,5‐tri­aza‐7‐phosphaadamantane)­platinum(II)

The crystal structure of the title compound, trans‐[PtI₂(C₆H₁₂N₃P)₂], describes one of the few platinum(II) complexes containing two of the water‐soluble 1,3,5‐tri­aza‐7‐phosphaadamantane ligands reported to date. The complex crystallizes on an inversion centre with the most important bond lengths and angles being Pt—P 2.3128 (12) Å, Pt—I 2.6022 (6) Å, P—Pt—I 90.94 (3)° and P′—Pt—I 89.06 (3)°.     

Synthesis and crystal structure of a palladium dimer containing ferrocenyldiphenylphosphine, trans-[Pd(μ-Cl)(CH3)(PPh2Fc)]2

The chloro-bridged dimeric complex, trans-[Pd(-Cl)(CH₃)(PPh₂Fc)]₂, was prepared by reaction of [Pd(Cl)(CH₃)(COD)] (COD = cis,cis-1,5-cyclooctadiene) with 1 equivalent of PPh₂Fc (PPh₂Fc = ferrocenyldiphenylphosphine) in acetone medium. The complex was characterized by ¹H and ³¹P NMR spectroscopy and a single crystal X-ray diffraction study revealed a trans geometry. The compound crystallizes in the triclinic space group P1, a = 11.476(2) Å, b = 14.059(3) Å, c = 14.658(3) Å and = 82.34(3)°, = 75.09(3)°, and = 68.48(3)° with Z = 2. Most important geometrical parameters include bond lengths Pd(1)–P(1) 2.2165(10), Pd(2)–P(2) 2.2290(10), Pd(1)–C(1) 2.157(3), Pd(2)–C(2) 2.079(4), Pd(1)–Cl(1) 2.4329(13), Pd(1)–Cl(2) 2.4106(11), Pd(2)–Cl(1) 2.4169(10), and Pd(2)–Cl(2) 2.4414(13) Å and bond angles P(1)–Pd(1)–C(1) 87.47(8), P(1)–Pd(1)–Cl(2) 176.88(4), C(1)–Pd(1)–Cl(1) 173.93(7), P(2)–Pd(2)–C(2) 89.03(11), P(2)–Pd(2)–Cl(1) 174.18(4), and C(2)–Pd(2)–Cl(2) 173.50(11)°. The effective and Tolman cone angles for P(1) were calculated as 170 and 167° and that for P(2) as 179 and 177°, respectively.     

trans‐Carbonyliodotris(triphenylstibine‐κSb)rhodium(I)

The crystal structure of the title compound, [RhI(C₁₈H₁₅Sb)₃(CO)], represents a rare example of a crystallographically characterized five‐coordinate Rh^I–SbPh₃ complex. The compound crystallizes with the I—Rh—CO core on a threefold rotation axis, with three crystallographically equivalent tri­phenyl­stibine ligands. Selected geometric parameters are: Rh—I = 2.7159 (8), Rh—Sb = 2.5962 (4), Rh—C_CO = 1.825 (6) and C_CO—O 1.153 (6) Å, and Sb—Rh—I = 89.374 (10) and Sb—Rh—C_CO = 90.626 (10)°. The cone angle of the SbPh₃ ligand was determined as 137°, according to the Tolman model.     

trans‐Carbonylchloridobis(ferrocenyldiphenylphosphane‐κP)rhodium(I) dichloromethane monosolvate and trans‐carbonylchloridobis(ferrocenyldiphenylphosphane‐κP)iridium(I) dichloromethane monosolvate

The isomorphous crystal structures of the title compounds, [Fe₂M(C₅H₅)₂(C₁₇H₁₄P)Cl(CO)]·CH₂Cl₂ or trans‐[MCl(CO)(PPh₂Fc)₂]·CH₂Cl₂ (M = Rh or Ir, and Fc is ferrocenyl), are reported. The data collection for M = Rh was performed at 293 (2) K, while the M = Ir data were collected at 160 (2) K. The compounds crystallize with two independent half‐molecules in the asymmetric unit, both occupying inversion centres, and are accompanied by a single dichloromethane molecule on a general position. Due to the symmetry, there is 0.50/0.50 disorder present in the chloride and carbonyl positions. One molecule in each structure also has a second type of disorder in the chloride and carbonyl positions, which was refined over another two positions of equal distribution. The steric impact of the bulky PPh₂Fc ligands was evaluated using the Tolman cone‐angle model, resulting in an average value of 172° for the four molecules in both structures.