Table 3. Selected structural data of compounds 17 ^a .

Compound	17a	17b	17c
R	Ph	Mes	t Bu
B1–P1	2.052(2)	2.085(2)	2.069(2)
P1–C1	1.835(2)	1.834(2)	1.827(2)
C1–C2	1.513(2)	1.509(3)	1.504(3)
C2–C3	1.334(3)	1.324(3)	1.321(3)
C3–C4	1.499(3)	1.497(3)	1.497(3)
B1–C4	1.649(2)	1.643(3)	1.649(3)
C1–P1–B1	104.7(1)	101.9(1)	98.3(1)
C4–B1–P1	101.9(1)	97.0(1)	103.1(1)
P1–B1–C4–C3	–49.9(2)	67.8(2)	25.9(2)
B1–P1–C1–C2	48.8(1)	17.8(2)	57.3(2)
∑P1CCC	317.1	316.4	317.2
∑B1CCC	338.2	332.8	326.4

^aBond lengths in Å, angles in deg.