Table 1. Selected bond lengths (Å) and angles (°), and tetrahedral characters (THC) (%).

Compound		B–S bond lengths/Å		Σ(C–B–C)/°	THC/%
cis-1a		B1–S1	2.161(1)	350.2	31.1
		B2–S2	2.161(1)	350.2	31.1
cis-1ba	A	B1–S1	2.181(2)	350.6	29.8
		B2–S2	2.231(3)	353.4	21.0
	B	B1–S1	2.146(3)	351.0	28.6
		B2–S2	2.381(3)	354.4	17.8
trans-2a		B1–S1/B2–S2	2.228(4)	353.5	20.7
trans-2b		B1–S1/B2–S2	2.289(2)	355.1	15.6

^a cis-1b contains two crystallographically independent molecules A and B in the unit cell.